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PROGRAM AND ABSTRACTS

47TH ANNUAL INTERNATIONAL ARCTIC WORKSHOP

March 23-25, 2017 Buffalo, New York

Sponsored and Hosted by: University at Buffalo Center for GeoHazards Studies College of Arts and Sciences Department of Geology The RENEW Institute

Organizing Committee: Jason Briner Barbara Catalano Beata Csatho Avriel Schweinsberg Elizabeth Thomas Greg Valentine

Introduction

Overview and history The 47th Annual International Arctic Workshop will be held March 23-25, 2017, on the campus of the University of Buffalo. The meeting is sponsored and hosted by the University at Buffalo, Center for GeoHazard Studies, College of Arts and Sciences, Department of Geology, and the RENEW Institute. This workshop has grown out of a series of informal annual meetings started by John T. Andrews and sponsored by INSTAAR and other academic institutions worldwide.

2017 Theme “Polar Climate and Sea Level: Past, Present & Future”

Website https://geohazards.buffalo.edu/aw2017

Check-In / Registration Please check in or register on (1) Wednesday evening at the Icebreaker/Reception between 5:00 – 7:00 pm in the Davis Hall Atrium (UB North Campus), or (2) Thursday morning between 8:00 – 8:45 am in the Davis Hall Atrium. At registration those who have ordered a print version will also receive their printed high-resolution volume.

Davis Hall Davis Hall is located between Putnam Way and White Road on the UB North Campus. Davis Hall is directly north of Jarvis Hall and east of Ketter Hall. To view an interactive map of North Campus, please visit this webpage: https://www.buffalo.edu/home/visiting- ub/CampusMaps/maps.html

Wi-Fi Wireless internet access is available (“UB_Connect”).

Posters At registration you will receive information on where to set up your poster. Please put it up as early as possible on the day that you are presenting, and leave it up as late as possible. There will be two poster sessions; one on each day of the workshop.

Presentation Files (e.g., PowerPoint) Please load your presentation onto our computer during Check-In/Registration on Thursday or Friday mornings between 8:00 – 8:55 am. Time during breaks is limited.

Arctic Workshop 2017 Program Summary

Wednesday March 22 5:00-7:00 Evening Reception, Check-in & Davis Hall Atrium Registration

Thursday March 23 8:00-8:45 Check-in & Registration Davis Hall Atrium Load presentations onto computer, put up posters 8:45-9:00 Welcome & Introduction Davis Hall 101 9:00 Baffin Bay/Greenland Paleoclimate 1 talks Davis Hall 101 10:30 30 minute coffee break Davis Hall Atrium 11:00 Baffin Bay/Greenland Paleoclimate 2 talks Davis Hall 101 12:00 Lunch buffet provided Davis Hall Atrium 1:00 Poster Session 1 Davis Hall Atrium 2:30 Posters and coffee Davis Hall Atrium 3:00 Arctic Paleoclimate talks Davis Hall 101 4:00 Invited talk: Isla Castañeda Davis Hall 101 5:00 Happy Hour Davis Hall Atrium 5:30 Keynote Talk by Eric Steig Davis Hall 101 6:30 Banquet Dinner Davis Hall Atrium

Friday March 24 8:55-9:00 Welcome & Introduction Davis Hall 101 9:00 Glacier Dynamics 1 talks Davis Hall 101 10:30 30 minute coffee break Davis Hall Atrium 11:00 Glacier Dynamics 2 talks Davis Hall 101 12:00 Lunch buffet provided Davis Hall Atrium 1:00 Poster Session 2 Davis Hall Atrium 2:30 Posters and coffee Davis Hall Atrium 3:00 Alaska Paleoclimate talks Davis Hall 101 4:00 Invited talk: Gifford Miller Davis Hall 101 5:00 Happy Hour Davis Hall Atrium

Saturday March 25 9:00-2:00 Niagara Falls field trip followed by Big Ditch Depart from Spot Brewery Coffee, Williamsville

Program Details

PM - Wednesday March 22 5:00-7:00 Evening Reception, Check-in & Registration Davis Hall Atrium Snacks and drinks will be served, including beer and wine.

AM - Thursday March 23 8:00-8:45 Check-in & Registration Davis Hall Atrium Load presentations onto computer, put up posters

8:45-9:00 Welcome & Introduction Davis Hall 101 Jason Briner, Chair of Organizing Committee

1. Baffin Bay/Greenland Paleoclimate 1 - Talks Chair: Gifford Miller 9:00 HOLOCENE CLIMATE AND OCEAN CONDITIONS IN THE EASTERN CANADIAN ARCTIC AND GREENLAND: LAND-SEA LINKAGES Anne de Vernal, Estelle Allan, Bianca Fréchette, Claude Hillaire-Marcel 9:15 THE EARLY HOLOCENE GLACIATION IN BAFFIN BAY PROJECT: INITIAL RESULTS Nicolás Young, Gifford Miller, Jason Briner, Joerg Schaefer, Sarah Crump, Alia Lesnek, Simon Pendleton 9:30 ICE, LAKES & CLIMATE: EXPLORING THE COMPLEXITIES OF PROGLACIAL-THRESHOLD LAKE SEDIMENTARY RECORDS FROM WESTERN GREENLAND Heidi Roop, Jason Briner, Nicolás Young 9:45 LATE-WISCONSINAN MAXIMUM EXTENT AND DECAY OF THE LAURENTIDE ICE SHEET ON THE NORTHEASTERN BAFFIN ISLAND CONTINENTAL SHELF Etienne Brouard and Patrick Lajeunesse

10:00 ICE CORE MEASUREMENTS OF 14CH4 SHOW NO EVIDENCE OF METHANE RELEASE FROM METHANE HYDRATES OR OLD PERMAFROST CARBON DURING A LARGE WARMING EVENT 11,600 YEARS AGO Vasilii Petrenko, Andrew Smith, Hinrich Schaefer, Katja Riedel, Edward Brook, Daniel Baggenstos, Christina Harth, Quan Hua, Christo Buizert, Adrian Schilt, Xavier Fain, Logan Mitchell, Thomas Bauska, Anais Orsi, Ray F. Weiss, Jeffrey P. Severinghaus

10:15 THE PROVENANCE OF GLACIAL MARINE SEDIMENTS IN BAFFIN BAY AND APPLICATION TO LATE QUATERNARY CHANGES IN ICE SHEET ACTIVITY John Andrews

10:30 COFFEE BREAK (Davis Hall Atrium)

2. Baffin Bay/Greenland Paleoclimate 2 - Talks Chair: Anne Jennings

11:00 TOWARDS MULTI-DECADAL TO MULTI-MILLENNIAL ICE CORE RECORDS FROM COASTAL WEST GREENLAND ICE CAPS Sarah Das, Matthew Osman, Luke Trusel, Joseph McConnell, Ben Smith, Matthew Evans, Karen Frey, Monica Arienzo, Nathan Chellman 11:15 DETAILED SEDIMENTOLOGICAL INVESTIGATIONS CHALLENGE OUR UNDERSTANDING OF DEPOSITION IN ARCTIC GLACIATED FJORDS Lena Håkansson and Maria Jensen 11:30 SALTMARSH RECORD OF POST LITTLE ICE AGE MASS BALANCE CHANGES IN SOUTHEAST GREENLAND Sarah Woodroffe, Natasha Barlow, Leanne Wake, Kristian Kjeldsen, Anders Bjork, Kurt Kjaer, Antony Long 11:45 A 400-YR WINTER TEMPERATURE RECONSTRUCTION FROM THE HIGH ARCTIC USING VARVED LAKE SEDIMENTS Benjamin Amann, Scott Lamoureux, Maxime Boreux

12:00 LUNCH BUFFET PROVIDED (Davis Hall Atrium)

PM - Thursday March 23 3. Poster Session 1 - 1:00-3:00 pm (Davis Hall Atrium) Chair: Carolyn Roberts 1 EVALUATING AND TESTING CLIMATE MODEL SIMULATIONS OF GREENLAND ICE SHEET SNOW AND FIRN DENSITIES P. Alexander, L. Koenig, M. Tedesco, P. Kuipers Munneke, X. Fettweis, S. Ligtenberg, B. Noël, M. van den Broeke, C. Miège 2 MODERN FORAMINIFERAL ASSEMBLAGES IN THE PETERMANN FJORD, NW GREENLAND Anne Jennings, Alan Mix, Maureen Walczak , Brendan Reilly, Joe Stoner, Maziet Cheseby 3 A HIGH-RESOLUTION HOLOCENE MARINE SEDIMENTOLOGICAL RECORD FROM POND INLET, NUNAVUT - IS THERE A PALEOSEISMICITY SIGNAL? Laura-Ann Broom, Calvin Campbell, John Gosse 4 RADIOACTIVE AND STABLE PALEOATMOSPHERIC METHANE ISOTOPES ACROSS THE OLDEST DRYAS-BØLLING TRANSITION FROM TAYLOR GLACIER, ANTARCTICA Michael Dyonisius, Vasilii Petrenko, Andrew Smith, Ben Hmiel, Quan Hua, Bin Yang, James Menking, Sarah Shackleton 5 HOLOCENE AND LAST INTERGLACIAL CLIMATE OF THE FAROE ISLANDS FROM SEDIMENTARY LEAF WAX HYDROGEN ISOTOPES Lorelei Curtin, William D’Andrea, Gregory de Wet, Raymond Bradley 6 A 40-YEAR RECORD OF NORTHERN HEMISPHERE ATMOSPHERIC CARBON MONOXIDE CONCENTRATION AND ISOTOPE RATIOS FROM THE FIRN AT GREENLAND SUMMIT Philip Place, Vasilii Petrenko, Isaac Vimont, Christo Buizert, Patricia Lang, Christina Harth, Ben Hmiel, James White 7 RECENT HYDROLOGICAL RESPONSE OF A GLACIERIZED WATERSHED TO HIGH ARCTIC WARMING, LINNÉVATNET, SVALBARD Michael Retelle, Noel Potter, Steve Roof, Al Werner 8 HYDROCLIMATE RESPONSE TO ABRUPT TEMPERATURE CHANGES DURING THE DEGLACIAL INTERVAL IN NORWAY AND RUSSIA Owen Cowling, Elizabeth Thomas, John-Inge Svendsen, Kristian Vasskog 9 PALEOENVIRONMENTAL RECONSTRUCTION FROM THE SEDIMENT RECORD OF THE VARVED PROGLACIAL LINNÉVATNET, SVALBARD, NORWEGIAN HIGH ARCTIC Gwenyth Williams and Michael Retelle 10 NEW CONSTRAINTS ON THE TIMING AND PATTERN OF DEGLACIATION IN THE HÚNAFLÓI BAY REGION OF NORTHWEST ICELAND USING COSMOGENIC 36CL DATING AND GEOMORPHIC MAPPING Amanda Houts, Joseph Licciardi, Sarah Principato, Susan Zimmerman, Robert Finkel

11 PROVENANCE, STRATIGRAPHY, AND CHRONOLOGY OF HOLOCENE TEPHRA ARCHIVED IN LAKE SEDIMENT FROM VESTFIRÐIR (NW), ICELAND David Harning, Thorvaldur Thórdarson, Kate Zalzal, Áslaug Geirsdóttir, Gifford Miller 12 LATE SEASON HIGH-SEDIMENTATION EVENTS AND ANNUAL SEGMENT FLUX IN SEDIMENT FLUX IN A SEDIMENT TRAP RECORD FORM LINNÉVATNET, SVALBARD Noel Potter and Michael Retelle 13 UNDERSTANDING THE PRODUCTION AND RETENTION OF IN SITU COSMOGENIC 14C IN POLAR FIRN Ben Hmiel, Vasilii Petrenko, Michael Dyonisius, Andrew Smith, J. Schmitt, Christo Buizert, Philip Place, Christina Harth, R. Beaudette, Quan Hua, Bin Yang, Isaac Vimont, M. Kalk, R.F Weiss, J.P. Severinghaus, Ed Brook, James White 14 LATE WISCONSINAN GLACIAL DYNAMICS IN BROUGHTON TROUGH AND MERCHANT’S BAY, CENTRAL-EASTERN BAFFIN ISLAND Pierre-Olivier Couette, Patrick Lajeunesse, Etienne Brouard 15 RECONSTRUCTING THE QUEBEC-LABRADOR SECTOR OF THE LAURENTIDE ICE SHEET FROM NEW SURFICIAL GEOLOGY MAPS, TILL PROVENANCE, AND DETRITAL 10BE DATA Jessey M. Rice, Martin A. Ross, Roger C. Paulen 16 PROGLACIAL LAKE SEDIMENT RECORDS OF HOLOCENE MOUNTAIN GLACIER CHANGE ON THE NUUSSUAQ PENINSULA, WEST GREENLAND: INITIAL RESULTS Avriel Schweinsberg, Jason Briner, Joseph Licciardi, Ole Bennike 17 GLACIAL HISTORY AND GEOMORPHOLOGY OF TRYGGHAMNA, WESTERN SPITSBERGEN Nína Aradóttir, Ólafur Ingólfsson, Anders Schomacker, Lena Håkansson, Riko Noormets 18 CONSTRAINTS ON WESTERN GREENLAND ICE SHEET EXTENT DURING THE MIDDLE HOLOCENE FROM PROGLACIAL THRESHOLD LAKES Alia Lesnek, Jason Briner, Heidi Roop, Allison Cluett, Elizabeth Thomas, Nicolás Young 19 LAKE WATER ISOTOPIC VARIABILITY IN WESTERN GREENLAND: IMPLICATIONS FOR PALEOHYDROLOGICAL STUDIES Allison Cluett and Elizabeth Thomas 20 NEW COSMOGENIC RADIONUCLIDE DATA CONSTRAIN THE FREQUENCY OF DISAPPEARANCE OF THE GREENLAND AND LAURENTIDE ICE SHEETS THROUGH THE FULL QUATERNARY Gifford Miller, Simon Pendleton, Joerg Schaefer, Nicolas Young, Jason Briner, Adrien Gilbert, Gwenn Flowers

2:30 TREATS AND POSTERS

4. Arctic Paleoclimate - Talks Chair: Elizabeth Thomas

3:00 SOIL DEPOSITS RECORD HOLOCENE CLIMATE AND LANDSCAPE DISTURBANCE IN THE HIGHLANDS OF ICELAND Darren Larsen, Dervla Meegan Kumar, Áslaug Geirsdóttir, Gifford Miller 3:15 PLIO-PLEISTOCENE CIRCULATION AND SEA ICE HISTORY IN THE WESTERN ARCTIC OCEAN, BASED ON A NORTHWIND RIDGE SEDIMENT RECORD Geoffrey Dipre, Leonid Polyak, Joe Ortiz, Emma Oti, Anton Kuznetsov 3:30 DEGLACIAL – HOLOCENE PALEOCEANOGRAPHY OF HERALD CANYON, CHUKCHI SEA Christof Pearce, Matt O’Regan, Jayne Rattray, David Hutchinson, Igor Semiletov, Martin Jakobsson 3:45 INVESTIGATING GLACIAL- INTERGLACIAL ENVIRONMENTAL CHANGES DURING THE MID- TO LATE- PLEISTOCENE: A BIOGEOCHEMICAL RECORD FROM LAKE EL’GYGYTGYN, RUSSIA Helen Habicht, Isla Castañeda, Julie Brigham-Grette 4:00 THE BIG THAW: TRANSDISCIPLINARY EXPLORATIONS OF PROFOUND TRANSFORMATION THROUGHOUT THE ARCTIC DUE TO CLIMATE CHANGE Connolly, Kim Diana 5. Invited Talk: Isla Castañeda Chair: Elizabeth Thomas

4:15 MID- TO LATE-PLEISTOCENE TEMPERATURE AND ENVIRONMENTAL VARIABILITY AT LAKE EL'GYGYTGYN, FAR EAST RUSSIA Isla Castañeda, Helen Habicht, Molly Patterson, Gregory de Wet, Benjamin Keisling, Rob DeConto, Julie Brigham-Grette

5:00-5:30 HAPPY HOUR (Davis Hall Atrium)

5:30 Keynote Talk

“Paleoclimate data assimilation: the next frontier in getting the best science from ice core, sediment, and other high- resolution proxy data”

Eric Steig

Earth and Space Sciences University of Washington

Followed by the Workshop Banquet Dinner (provided)

AM - Friday March 24 8:30-8:55 Load presentations onto computer, take down Davis Hall Atrium posters, put up posters

8:55-9:00 Announcements Davis Hall 101 Jason Briner, Chair of Organizing Committee

6. Glacier Dynamics 1 - Talks Chair: Beata Csatho 9:00 RAPID THINNING AND ACCELERATION AT THE COLD-BASED VAVILOV ICE CAP, SEVERNAYA ZEMLYA, RUSSIA Michael Willis, Matthew Pritchard, Whyjay Zheng, William Durkin IV, Joan Ramage, Julian Dowdeswell, Toby Benham, Robin Bassford 9:15 MONITORING LAND-ICE ELEVATION CHANGES IN FRANZ JOSEF LAND USING REMOTE SENSING Whyjay Zheng, Matthew Pritchard, Michael Willis 9:30 A SEISMIC PERSPECTIVE ON THE EVOLUTION OF THE NW GREENLAND ICE SHEET Paul Knutz, Ulrik Gregersen, Karen Dybkjær, Emma Sheldon, John Hopper 9:45 EVIDENCE FOR THE DRAINAGE OF A SUPRAGLACIAL LAKE AS THE SOURCE OF SEISMIC WAVES RECORDED AT REGIONAL DISTANCE Erik Orantes, Patricia Kenyon, Patrick Alexander, Marco Tedesco 10:00 THE CONTRIBUTION OF TOPOGRAPHIC SHADOWING BY ICE ON THE ALBEDO VARIABILITY Sasha Leidman, Asa Rennermalm, Johnny Ryan, Dimitri Acosta 10:15 HYDRAULIC CONDUCTIVITY AS A PROXY FOR DRAINAGE SYSTEM CONNECTIVITY IN A SUBGLACIAL HYDROLOGY MODEL Jacob Downs, Jesse Johnson, Joel Harper, Toby Meierbachtol

10:30 COFFEE BREAK (Davis Hall Atrium)

7. Glacier Dynamics 2 (+ hazards) - Talks Chair: Jesse Johnson 11:00 LOCAL PROCESSES AND REGIONAL PATTERNS - INTERPRETING A MULTI-DECADAL ALTIMETRY RECORD OF GREENLAND ICE SHEET CHANGES Bea Csatho, Toni Schenk 11:15 DETAILED SURFACE ELEVATION RECONSTRUCTION OF HELHEIM GLACIER (1981-2016) Carolyn Roberts, Beata Csatho, Toni Schenk 11:30 COUPLED CHANGES IN THE CRYOSPHERE AND SOLID EARTH MEASURED BY SPACE GEODESY William Durkin IV and Matthew Pritchard 11:45 GEOLOGICAL HAZARD ASSESSMENT IN WESTERN BAFFIN BAY- APPROACHES AND PRELIMINARY RESULTS Calvin Campbell, Kimberley Jenner, Kevin MacKillop, David Piper, Meaghan MacQuarrie, Laura Broom

12:00 LUNCH BUFFET PROVIDED (Davis Hall Atrium)

PM - Friday March 24

8. Poster Session 2 - 1:00-3:00 pm (Davis Hall Atrium) Chair: Avy Schweinsberg 1 ON THE CONTRIBUTION OF BAFFIN BAY ICE COVER AND SEA SURFACE TEMPERATURES TO GREENLAND'S WEST COAST WARMING Thomas Ballinger, Edward Hanna, Richard Hall, Jeffery Miller, Mads Ribergaard, Jacob Høyer 2 FINAL DEGLACIATION AND MARINE INCURSION: A VIEW FROM WESTERN HUDSON BAY Samuel Kelley, M.S. Gauthier, M. Ross, T.J. Hodder 3 EARLY HOLOCENE GLACIER CHRONOLOGIES FROM BAFFIN ISLAND, ARCTIC CANADA Sarah Crump, Gifford Miller, Nicolás Young, Jason Briner, Simon Pendleton 4 A MID-LATE HOLOCENE MULTI-PROXY PALEOENVIRONMENTAL RECONSTRUCTION OF NORTHERN FINNMARK USING A SEDIMENT CORE FROM THE ISLAND OF INGØY, NORWAY Claire Markonic, Michael Retelle, Alan Wanamaker 5 TESTING THE ICE COVER HISTORY OF PRESERVED LANDSCAPES ON BAFFIN ISLAND USING 14C Simon Pendleton, Gifford Miller, Nathaniel Lifton, Robert Anderson 6 DETERMINING AND INTERPRETING DETAILED ICE SURFACE ELEVATION CHANGES OF THE GLACIERS IN UPERNAVIK ISSTRØM, NORTHWEST GREENLAND, 1981-2014 Lindsay Wendler, Beata Csatho, Toni Schenk 7 CHANGES IN LAKE ICE PHENOLOGY AT LINNÉVATNET, A FRESH WATER LAKE IN THE HIGH ARCTIC OF SVALBARD Lea Maria Frederiksen 8 IMPLICATIONS FOR INTERPRETING LEAF WAX PALEOCLIMATE PROXIES IN ECOSYSTEMS WITH STRONG SEASONAL CYCLES USING OBSERVED SEASONAL TRENDS OF ENVIRONMENTAL WATER AND SEDIMENTARY LEAF WAX HYDROGEN ISOTOPES IN CENTRAL NEW YORK Megan Corcoran, Elizabeth Thomas, David Boutt 9 A HIGH-RESOLUTION APPROACH TO EVALUATE THE OCCURRENCE OF VARVED SEDIMENTS IN LAKE WALKER, QUÉBEC NORTH SHORE, USING IMAGE ANALYSIS AND X-RAY MICROFLUORESCENCE Obinna Nzekwe, Pierre Francus, Guillaume St-Onge, Patrick Lajeunesse, David Fortin, Antoine Gagnon-Poiré, Edouard Philippe

10 SURFACE STATUS ACROSS SCALES - EVALUATING TEMPORAL AND SPATIAL PATTERNS IN FREEZE/THAW CYCLES Helena Bergstedt and Annett Bartsch 11 DEVELOPMENT OF AN INTENSIVE HYDROLOGICAL MONITORING PROGRAM TO EVALUATE VULNERABILITY OF MACKENZIE DELTA REGION LAKES TO CLIMATE CHANGE Evan Wilcox, Philip Marsh, Branden Walker, Philip Mann 12 CLIMATE VARIATIONS OF THE COAST OF LABRADOR, 1750-1950 : A DISCURSIVE APPROACH Marie-Michèle Ouellet-Bernier, Anne de Vernal, Daniel Chartier 13 CENTENNIAL SCALE VARIATIONS OF SEA-SURFACE IN THE DISKO BUGT, WEST GREENLAND Estelle Allan, Anne de Vernal, Mads Faurschou Knudsen, Matthias Moros, Sofia Ribeiro, Marie-Michèle Ouellet-Bernier, Henry Maryse 14 MARINE EVIDENCE FOR COLLAPSES OF THE ARCTIC SECTOR OF THE LAURENTIDE ICE SHEET IN THE WESTERN ARCTIC OCEAN DURING THE LAST GLACIAL CYCLE Kenta Suzuki, Masanobu Yamamoto, Tomohisa Irino, Seung-II Nam, Leonid Polyak, Takayuki Omori, Toshiro Yamanaka 15 GEOGRAPHIC VARIATION OF CIRQUES ON ICELAND: FACTORS INFLUENCING CIRQUE MORPHOLOGY Heather Ipsen, Sarah Principato, Rachael Grube, Jessica Lee 16 MODELING THE EVOLUTION OF SUPRAGLACIAL RIVER NETWORKS OVER SOUTHWEST GREENLAND Rohi Muthyala and Asa Rennermalm 17 ONE THOUSAND YEARS OF NORTH ATLANTIC SEA-SURFACE VARIABILITY PORTRAYED IN AN ARRAY OF PAN-ARCTIC ICE CORE METHANESULFONIC ACID (MSA) RECORDS Matthew Osman, Sarah Das, Luke Trusel, Joseph McConnell, Matthew Evans 18 RECONSTRUCTING THE GLACIAL HISTORY OF MIDTRE LOVÉNBREEN, SVALBARD Erik Holmlund and Lena Håkansson

2:30 TREATS AND POSTERS

9. Alaska Paleoclimate - Talks Chair: Jason Briner

3:00 PALEOGENETIC SURVEY OF BROWN AND BLACK BEAR DIVERSITY IN PLEISTOCENE SOUTHEAST ALASKA Charlotte Lindqvist, Tianying Lan, Sandra Talbot, Joseph Cook, Timothy Heaton 3:15 THE LAST DEGLACIATION OF THE REVELATION MOUNTAINS, ALASKA: DISTINGUISHING BETWEEN GLOBAL AND REGIONAL CLIMATIC CONTROLS Joseph Tulenko, Jason Briner, Nicolás Young 3:30 A TEST OF INTRINSIC CLIMATE VARIABILITY AS THE CAUSE OF LATE HOLOCENE VALLEY GLACIER FLUCTUATIONS David Barclay, Brian Luckman, and Gregory Wiles 3:45 RECONSTRUCTING SOUTHEAST ALASKA’S RELATIVE SEA LEVEL HISTORY FROM RAISED SHELL-BEARING STRATA AND NARROWING THE TIMING OF THE RETREAT OF THE CORDILLERAN ICE SHEET FROM THE ARCHIPELAGO TO NEAR 13.700 CAL. BP James Baichtal, Risa Carlson, Jane Smith, Dennis Landwehr

10. Invited Talk: Gifford Miller Chair: Jason Briner

4:00 AN ARCTIC PERSPECTIVE ON CONTEMPORARY WARMING Gifford Miller

5:00 HAPPY HOUR Workshop photo & John Andrews toast

STUDENT PARTY – DETAILS TO BE ANNOUNCED. EVERYBODY ELSE – DINNER ON YOUR OWN!

END OF WORKSHOP

OPTIONAL FIELD TRIP TO NIAGARA FALLS DEPARTS 9 AM, SATURDAY, MARCH 25, FROM SPOT COFFEE IN WILLIAMSVILLE

EVALUATING AND TESTING CLIMATE MODEL SIMULATIONS OF GREENLAND ICE SHEET SNOW AND FIRN DENSITIES

Alexander, P.M.1, Koenig, L.S.2, Tedesco, M.3,1, Kuipers, P.4, Fettweis, X.5, Ligtenberg, S.R.M.4, Noël, B.4, van den Broeke, M.R.4, Miège, C.6

1NASA Goddard Institute for Space Studies, NY 2National Snow and Ice Data Center, Boulder, CO 3Lamont Doherty Earth Observatory, Columbia University 4Institute for Marine and Atmospheric Research, Utrecht, The Netherlands 5University of Liège, Liège, Belgium 6University of Utah

Simulations of ice sheet snow and firn densities are necessary for converting altimetry-derived ice sheet thickness change and radar-derived accumulation estimates into estimates of mass change. Simulated densities also influence the ice sheet surface mass and energy budget simulated by regional climate models (RCMs). Accurately modeling profiles of snow and firn density is therefore important for understanding changes in ice sheet mass, which play a key role in sea level change.We conduct a comparison between density estimates from the Modèle Atmosphérique Régionale (MAR) RCM (Fettweis et al., 2016), the IMAU firn densification model (IMAU FDM; Kuipers Munneke et al., 2015), and in situ measurements from the SUMup snow density dataset (Koenig et al., 2015) for the Greenland ice sheet (GrIS). The MAR RCM is forced at the lateral boundaries with ECMWF reanalysis outputs. The IMAU- FDM is forced with atmospheric forcing from the Regional Atmospheric Climate Model (RACMO2; Noël et al., 2016). Observed density profiles are compared with spatially and temporally coincident model profiles. In order to better understand the causes of discrepancies between models and measurements, profiles were separated into three groups: (1) areas with modeled sub-surface ice, (2) areas with less than 5 days of melt per year, and (3) areas with more than 5 days of melt per year (Figure 1). An offline version of the MAR surface model is used to conduct sensitivity experiments to determine the impact of various factors, including the initial fresh snow density, the rate of snow accumulation, and modeled liquid water retention capacity on simulated density profiles. Modeled root mean squared errors for the entire density profile revealed that the largest errors exist in low elevation areas with negative SMB or persistent melting (Figure 2). Average density profiles in the three groups mentioned above (Figure 3) indicate a good agreement between models and observations in areas of dry snow, and a poorer agreement in areas of melting, percolation, and refreezing. The largest inter-model differences are also seen in areas of meltwater percolation and refreezing; MAR is in better agreement with observed profiles. MAR densities also tend to be underestimated within the top meter of the snowpack. To better understand the sources of these discrepancies, additional comparisons were conducted at a test site (the FA13 site of Koenig et al., 2014)

18 where liquid water content estimates and temperature profiles were available. A comparison of temperature profiles reveals a fairly good agreement between both models and observations, with MAR overestimating and IMAU-FDM underestimating temperatures below a depth of ~3 m. According to model parameterizations, the IMAU-FDM retains less water in snow pore space than MAR, which may explain the slightly colder temperatures in the IMAU-FDM. MAR accumulation rate and density estimates indicate that the 15 m MAR snowpack is completely refreshed over a 10-year period spanning early 2004 through early 2014, when the density profile at FA13 was measured. Comparison between MAR and IMAU-FDM outputs over this period indicates a cumulative refreezing of ~5 kg m-2 in both models, but a higher accumulation rate of 15 kg m-2 in MAR vs. 10 kg m-2 for MAR. This discrepancy suggests that in this particular location, the inter-model difference can be explained at least in part by a lower accumulation rate in MAR. To test the influence of accumulation rate, initial snow density, and other factors on modeled density profiles, an offline version of the MAR surface model is being developed. Preliminary tests with this model suggest that initial snow density can significantly modulate the modeled density profile at the FA13 high accumulation site. Further tests are planned to examine the impact of altered atmospheric forcing on model outputs, including forcing the MAR offline model with atmospheric forcing from RACMO.

Fettweis, X., J. E. Box, C. Agosta, C. Amory, C. Kittel and H. Gallée, 2016, Reconstructions of the 1990-2015 Greenland ice sheet surface mass balance using the regional climate MAR model: The Cryosphere Discussions, doi:10.5194/tc-2016-268. Koenig, L. S. and the Surface mass balance and snow on sea ice working group (SUMup), July 2015, SUMup Snow Density Dataset, Greenbelt, MD, USA: NASA Goddard Space Flight Center, Digital Media. Koenig, L. S., C. Miège, R. R. Forster, and L. Brucker, 2014, Initial in situ measurements of perennial meltwater storage in the Greenland firn aquifer: Geophysical Research Letters, 41,81-85, doi:10.1002/2013GL05083. Kuipers-Munneke, P., S. R. M. Ligtenberg, B. P. Y. Noël, I. M. Howat, J. E. Box, E. Mosley Thompson, J. R. McConnell, K. Steffen, S. B. Das, and M. R. van den Broeke, 2015, Elevation change of the Greenland Ice Sheet due to surface mass balance and firn processes, 1960-2014: The Cryosphere, 9, 2009-2025, doi: 10.5194/tc-9-2009-2015. Noël, B., van de Berg, W. J., Machguth, H., Lhermitte, S., Howat, I., Fettweis, X., and van den Broeke, M. R., 2016, A daily, 1 km resolution data set of downscaled Greenland ice sheet surface mass balance (1958-2015): The Cryosphere, 9, 2361-2377, doi: 10.5194/tc-10- 2361-2016.

Figure 1. MAR average June-July-August density (g cm-3) for the top meter of snow, and locations of SUMup profiles (with colors indicating surface or subsurface conditions).

Figure 2. Root mean squared error (RMSE) in g/cm3 relative to observations for MAR (left) and the IMAU-FDM (right).

Figure 3. (a) Example density profile comparison for a single location where climate models simulate sub-surface ice. (b) Average modeled and measured profiles for locations where melt occurs on less than 5 days per year (where melt is defined as a liquid water content of 1.1% or more in the first meter of the snowpack. (c) Same as (b) for relatively wet locations.

CENTENNIAL SCALE VARIATIONS OF SEA-SURFACE IN THE DISKO BUGT, WEST GREENLAND

Allan, Estelle1, de Vernal, Anne1, Knudsen, Mads Faurschou2, Moros, Matthias3, Ribeiro, Sofia4, Ouellet-Bernier, Marie-Michèle1, Henry, Maryse1

1Centre de recherche en géochimie et géodynamique (Geotop), Université du Québec à Montréal, Canada 2Centre for Past Climate Studies, Department of Geoscience, Aarhus University, Denmark 3Leibniz Institute for Baltic Sea Research, Department of Marine Geology, Germany 4Department of Biology, University of Copenhagen, Denmark

The organic-walled cysts of dinoflagellates, dinocysts, as the reference databases for Arctic and subarctic areas allow for quantitative reconstruction of seasonal extent of sea ice cover. The dinocysts are well preserved in the sediment and they lived in a wide range of environmental conditions, from freshwater to fully marine and from equatorial to polar settings. Therefore, they are useful to illustrate the relationships between hydrographical parameters and productivity in surface waters. They can be used to reconstruct various parameters like sea-ice cover, sea-surface temperature, sea-surface salinity and productivity, using the modern analogue technique. A new update from the dinocyst database that includes 74 taxa and 1777 reference sites from the Northern Hemisphere will be used to reconstruct the sea surface variability from Disko Bugt, West Greenland, during the last 3600 years. The dinocyst assemblages dominated by Islandinium minutum, Brigantedinium spp., Islandinium? cezare and the cyst of Pentapharsodinium dalei indicates large seasonal gradients of temperature due to stratified surface waters. The application of the modern analogue technique to dinocyst assemblages shows centennial scale variation of sea-surface salinity and temperature in phase with the fluctuation of the δ18O in the Camp Century ice core, thus highlighting the importance of ocean/atmosphere exchanges on regional proxy-climate records. The seasonal sea ice cover records large amplitude variations, with a main change of regime at about 500 AD, from winter only sea ice of about 2 months/year to more unstable conditions marked by successive cooling pulses with up to 8 months/year of ice coverage. Until about 500 AD, a notable link between the sea-surface salinity and temperature with the solar activity are found. This may indicate a strong sun-climate relationship on sea ice area. Andresen, C.S. et al., 2010. Interaction between subsurface ocean waters and calving of the Jakobshavn Isbrae during the late Holocene. The Holocene 21, 211-224.

de Vernal, A. et al., 2013. Dinocyst based reconstructions of sea ice cover concentration during the Holocene in the Arctic Ocean, the northern North Atlantic Ocean and its adjacent seas. Quaternary Science Reviews 79, 111-121. Krawczyk, D.W. et al., 2013. Late-Holocene diatom derived seasonal variability in hydrological

conditions off Disko Bugt, west Greenland. Quaternary Science Reviews 67, 93-104. Lloyd, JM. et al., 2011. A 100 yr record of ocean temperature control on the stability of Jakobshavn Isbrae, West Greenland. Geology 39, 867-870. Moros, M. et al., 2016. Surface and subsurface multi-proxy reconstruction of middle to late Holocene palaeoceanographic changes in Disko Bugt, West Greenland. Quaternary Science Reviews 132, 146-160. Perner K. et al., 2011. Centennial scale benthic foraminiferal record of late Holocene oceanographic variability in Disko Bugt, West Greenland. Quaternary Science Reviews 30, 2815-2826. Ribeiro, S. et al., 2012. Climate variability in West Greenland during the past 1500 years: Evidence from a high-resolution marine palynological record from Disko Bay. Boreas 41, 68-83. Vinther, B.M. et al., 2009. Holocene thinning of the Greenland ice sheet. Nature 461, 385-388.

A 400-YR WINTER TEMPERATURE RECONSTRUCTION FROM THE HIGH ARCTIC USING VARVED LAKE SEDIMENTS

Amann, Benjamin1, Lamoureux, Scott F. 1, Boreux, Maxime P. 1

1Department of Geography and Planning, Queen's University, ON, Canada

Winter climate reconstructions have received relatively little attention as compared to the efforts to reconstruct past annual and summer temperature changes in the Arctic. As a result, seasonality is hardly considered in climate models, especially regarding the winter season. At the same time, it is increasingly recognized from instrumental data and climate modeling that the winter is the most sensitive season with regards to Arctic climate change (past, present and future). To target this specific season, recent studies have emerged using sediments from Arctic lakes, especially those characterised by a nival (snowmelt) catchment. Sediment transport and deposition in these lakes are primarily governed by the length and intensity of the snowmelt runoff, and indirectly by the preceding winter temperature and snowfall conditions. Nevertheless, very few well-calibrated quantitative records exist for the Arctic, which clearly limits the possibility to resolve large-scale patterns of winter climate change prior the instrumental period. Using the varve record from Chevalier Bay (unofficial name, Melville Island, Northwest Territories, Canada), we produce a well-calibrated quantitative record of winter temperature and snowfall conditions over the past c. 400 years. Chevalier Bay has a large catchment influenced by nival terrestrial processes, which leads to high sedimentation rates and annual sedimentary structures (varves). Using detailed microstratigraphic analysis from two sediment cores and supported by µ-XRF data, we separate the nival units (spring snowmelt) from the rainfall units (summer), and also identify subaqueous slumps. This is the cornerstone for the development of a reliable and precise chronology and a good proxy-climate calibration model. To test the sensitivity of our study site to climate variability, varve thickness for each seasonal phase (nival, rainfall, winter clay cap) was correlated with climate data for each individual month and 2-to-12- month windows. These tests were performed using temperature (mean) and precipitation (cumulative rainfall and snowfall) data from three meteorological stations and the CRU TS3.23 gridded dataset. Results reveal the best correlation between the thickness of the nival units and extended winter (November through March) temperature (r= 0.71, pc< 0.01, 5-yr filter) and snowfall (r= 0.65, pc< 0.01, 5-yr filter). From these results, we propose the following mechanism: higher spring sedimentation rates (i.e. thicker nival units) are associated with greater snowmelt runoff in spring, which is likely a consequence of warmer winter along with increased snowfall on the previous winter. Thus, we use the thickness of the nival units to predict winter temperature and snowfall back to CE 1670. We demonstrate that this winter reconstruction is representative for a large part of the western Canadian Arctic Archipelago, and captures most of the annual climate variability. These results are supported by: (i) the analysis of

23 spatial correlation within the instrumental period (1950 – 2010); and (ii) long-term agreement with other winter-weighted proxies and annual records published from this region of the Arctic. Through this comparison, we demonstrate that the indirect information stored in the winter temperature and winter snowfall conditions (pre-conditioning for the spring snowmelt season and most sediment transport) offers a unique opportunity to evaluate climate change in the Arctic. This record from Chevalier Bay holds great potential for model implementation to make comprehensive assessments of long-term regional changes in Arctic winter, and to constrain scenarios in the western Canadian Arctic region under future climate change.

THE PROVENANCE OF GLACIAL MARINE SEDIMENTS IN BAFFIN BAY AND APPLICATION TO LATE QUATERNARY CHANGES IN ICE SHEET ACTIVITY

Andrews, John T.1

1INSTAAR and Department of Geological Sciences, University of Colorado- Boulder

The provenance of glacial marine sediments can be determined by several different methods, including the radioisotopic ages (White et al., 2016) and mineralogy (Aksu, 1981; Andrews and Eberl, 2011). Over the last 4 decades attention in Baffin Bay has focused on the timing and significance of detrital carbonate units (BBDC events) (Aksu, 1981), which indicate intervals of significant ice stream collapse in the major channels leading into northern Baffin Bay (e.g. Smith, Lancaster, Jones Sounds. There were, however, significant ice streams draining the Greenland and Laurentide ice sheets, particularly on the east side of Baffin Bay where large trough mouth fans are evident along the West Greenland slope (Fig. 1A), but on the west side the Home Bay Ice Stream appears to be the only significant indication on ice streaming across Baffin Island from Foxe Basin and where the spread of detrital carbonate from the Foxe Basin outcrop is visible on imagery and on the ground (Tippett, 1985)---although not that evident in the 10 km spaced grid of geochemical data. In order to estimate the provenance of sediments recovered in cores from the shelves, slope, and deep-sea basin of Baffin Bay I have expanded the earlier work of Andrews and Eberl (Andrews and Eberl, 2011) from 86 to 239 surface samples (Fig. 1A). This was the result of adding two important data sets; the first are a series of grab samples from cruise HU70037- from the West Greenland shelf (Fig. 1C) and the second was a series of grab samples recovered during the S.A.F.E. HU82 and HU83 cruises into a series of Baffin Island fiords (Fig. 1D)(Syvitski and Schafer, 1985). In addition to the surface and downcore samples a series of bedrock and large IRD clasts were pulverized and scanned for mineralogy; this series included carbonate samples, early Tertiary basalt, Ordovician shales, Cretaceous mudstones and sandstones, highly weathered (saprolite) bedrock, and Archean and Proterozoic igneous and metamorphic rocks (Fig. 2). Baffin Bay glacial marine sediments can be considered as mixtures of these bedrock components and the unmixing program “SedUnMix” (Andrews and Eberl, 2012) is used to characterize the provenance of the surface samples, and the variations in Late Quaternary sediment sources in cores from the West Greenland slope and Baffin Island slope. Given the anti-clockwise circulation of surface currents in Baffin Bay (Fig. 1B) then we can expect some transport of West Greenland sediments onto the Baffin Is. shelf and slope, primarily through iceberg rafting. The results indicate a plume of carbonate-rich sediments extend southward from the Canadian High Arctic Channels along the Baffin Island shelf and slope, but does not extend eastward onto the West Greenland margin. A distinct trail of sediments with basalt-associations spreads northward on the West

Greenland shelf from the area of Disko Island. Most of the samples are dominated by high wt% of quartz and feldspar and represent erosion of the Precambrian shield rocks. A more detailed analysis was undertaken on the HU70037 and HU82/83 samples from the two shelves (Fig. 1). The identification of distinct source compositions on the West Greenland and Baffin Is. shelves is then used to identify downcore changes in sediment provenance---this is illustrated by data from HU2008029-0008, which was retrieved on the Davis Strait sill (Fig. 1A), and HU2013029-077 from the slope below Home Bay (Klein et al., 2016) (Fig. 1A). These results indicate that sediment delivery was marked by discrete pulses of specific sediment compositions implying regional variations in ice stream activity distinct in phasing from the BBDC events.

Aksu, A.E., 1981. Late Quaternary stratigraphy, paleoenvironmentology, and sedimentation history of Baffin Bay and Davis Strait. Dalhousie University, Halifax, N.S. Andrews, J.T., Eberl, D.D., 2011. Surface (sea floor) and near-surface (box core) sediment mineralogy in Baffin Bay as a key to sediment provenance and ice sheet variations. Canadian Journal of Earth Science 48, 1307-1328. Andrews, J.T., Eberl, D.D., 2012. Determination of sediment provenance by unmixing the mineralogy of source-area sediments: The ""SedUnMix"" program. Marine Geology 291, 24-33. Klein, A.J., Andrews, J.T., Jenner, K., Jennings, A.E., Campbell, D.C., 2016. Late Quaternary variations in sediment mineralogy and grain-size on the northern Baffin Island slope: insights into the glacial history of Baffin Bay. Geological Society of America Abstract vol. Syvitski, J.P.M., Schafer, C., 1985. Sedimentology of Arctic Fjords Experiment (S.A.F.E.) Project: Project Introduction. Arctic 38, 264-270. Tippett, C.R., 1985. Glacial dispersal train of Paleozoic erratics, central Baffin Island, N.W.T., Canada. Can. J. Earth Sci. 22, 1818-1826. White, L.F., Bailey, I., Foster, G.L., Allen, G., Kelley, S.P., Andrews, J.T., Hogan, K., Dowdeswell, J.A., Storey, C.D., 2016. Tracking the provenance of Greenland-sourced, Holocene aged, individual sand-sized ice-rafted debris using the Pb-isotope compositions of feldspars and Ar-40/Ar-39 ages of hornblendes. Earth and Planetary Science Letters 433, 192-203.

Figure 1. A) Surface sampling sites, B) surface currents, major present day ice streams, C) Samples from HU70037, D) Samples from the HU82 & HU83 S.A.F.E. expeditions.

Figure 2. Pie diagrams of the wt% of minerals from bedrock, last, or stream samples.

GLACIAL HISTORY AND GEOMORPHOLOGY OF TRYGGHAMNA, WESTERN SPITSBERGEN

Aradóttir, Nína1,2, Ingólfsson, Ólafur1,3, Schomacker, Anders2, Håkansson, Lena1, Noormets, Riko1

1Department of Arctic Geology, University Centre in Svalbard, Norway 2The Arctic University of Norway (UiT), Norway 3Faculty of Earth Sciences, University of Iceland, Reykjavík, Iceland

Glacier surges often produce diagnostic landform-sediment assemblages. Investigations of the margins of known surge-type glaciers can give insight into the interaction between climate fluctuations and glacier dynamics. Where historical and glaciological data is absent, landsystem models can be developed to identify antecedent surge events (Evans and Rea, 2003; Brynjólfsson, 2015). Recent work has demonstrated that different factors in the glacier’s environment affect the landform-sediment assemblage. Modified landsystem models have thus been developed for surge-type glaciers in different environments, both terrestrial and marine, to demonstrate the variability (Ottesen et al., 2008; Brynjólfsson et al., 2012, 2014; Schomacker et al., 2014; Brynjólfsson, 2015; Flink et al., 2015). As surge-type glaciers have a non-direct response to climate, it is important to identify paleo-surges in order to understand the reason for the advance of individual glaciers. This project investigates the geomorphological archives contained within the marine and terrestrial forefields of five glaciers located in Trygghamna, western Spitsbergen. The maximum Holocene extent of the glaciers on Svalbard is considered to be during the Little Ice Age (LIA). At that time the large glaciers at the head of Trygghamna coalesced and reached significantly further out in the fjord. Subsequent warming led to the termination of the LIA, around 1900s, and the glacier’s retreat. None of the investigated glaciers have previously been described as surge-type glaciers. High-resolution geomorphological mapping was conducted, both in the terrestrial and marine realms using aerial images (Norwegian Polar Institute, 2009) and bathymetric data set (Norwegian Hydrographic Service, 2000; 2007) (Figure 1). In addition, ice marginal reconstructions for the years 1909/1910, 1936, 1968, 1990, 2007 and 2016 based on historical maps, aerial and satellite images was produced (Figure 2). Crevasse squeeze ridges (CSRs), indicative of former surge activity, are present in the terrestrial forefields of Harriet- and Kjerulfbreen (Evans and Rea, 2003, Schomacker et al., 2014). The absence of CSRs in the other forefields can be a result of the differences in the environments and their preservation potential or because these glaciers have not surged in the past (Brynjólfsson et al., 2012, 2014; Brynjólfsson, 2015). While CSRs are absent in the marine setting, a set of sub-parallel transverse ridges, interpreted as retreat moraines, are present on the proximal side of the terminal moraine (Ottesen et al., 2008; Flink et al., 2015). These retreat moraines are not observed in the terrestrial setting, highlighting the differences in the landform

29 assemblages in the terrestrial and marine realms. A moraine marks the outermost extent of the glaciers in both setting, which reaches further out than the 1909/1910 margin. Reconstruction of ice margins indicates steady retreat since 1909/1910, suggesting that if a surge occurred it was prior to this. The landform assemblages documented in this investigation are compared to previously published landsystem models. This investigation highlights the contrast in landform assemblages between both divergent terrestrial environments and terrestrial and marine realms of the glacier forefields in Trygghamna. Studies reconstructing glacier dynamics should, where appropriate incorporate evidence from both marine and terrestrial geomorphological archives, because of their dynamic behavior in different environments.

Brynjólfsson, S., Ingólfsson, Ó., & Schomacker, A. 2012. Surge fingerprinting of cirque glaciers at the Tröllaskagi. Jökull, 62, p. 153–168. Brynjólfsson, S. 2015. Dynamics and Glacial History of the Drangajökull Ice Cap, North-west Iceland. Norwegian University of Science and Technology,Trondheim (Doctoral thesis, 233 pp). Brynjólfsson, S., Schomacker, A., & Ingólfsson, Ó. 2014. Geomorphology and the Little Ice Age extent of the Drangajökull ice cap, NW Iceland, with focus on its three surge-type outlets. Geomorphology, 213, p. 292–304. Evans, D. J. A., & Rea, B. R. 2003. Surging Glacier Landsystems. In D. J. A. Evans (Ed.), Glacial Landsystems (pp. 259–288). London: Arnold. Flink, A. E., Noormets, R., Kirchner, N., Benn, D. I., Luckman, A., & Lovell, H. 2015. The evolution of a submarine landform record following recent and multiple surges of Tunabreen glacier, Svalbard. Quaternary Science Reviews, 108, p. 37–50. Schomacker, A., & Kjær, K. H. 2007. Origin and de-icing of multiple generations of ice-cored moraines at Brúarjökull, Iceland. Boreas, 36, p. 411–425. Ottesen, D., Dowdeswell, J. A., Benn, D. I., Kristensen, L., Christiansen, H. H., Christensen, O., Hansen, L., Lebesbye, E., ., Forwick, M. & Vorren, T. O. 2008. Submarine landforms characteristic of glacier surges in two Spitsbergen fjords. Quaternary Science Reviews, 27(15–16), p. 1583–1599.

Figure 1. Geomorphological map of Trygghamna.

Figure 2. Ice marginal reconstructions of Trygghamna.

RECONSTRUCTING SOUTHEAST ALASKA’S RELATIVE SEA LEVEL HISTORY FROM RAISED SHELL-BEARING STRATA AND NARROWING THE TIMING OF THE RETREAT OF THE CORDILLERAN ICE SHEET FROM THE ARCHIPELAGO TO NEAR 13.700 CAL. BP

Baichtal, James F.1, Carlson, Risa J.2, Smith, Jane L.3, Landwehr, Dennis J. 1

1Tongass National Forest, Ketchikan, Alaska 99901 2Tongass National Forest, Thorne Bay, Alaska 99919 3Tongass National Forest, Petersburg, Alaska 99833

Uplifted marine sediments and terraces have long been observed and recorded throughout southeastern Alaska (Buddington and Chapin, 1929). Miller (1973) working near Juneau, Alaska characterized these facies naming these shell bearing strata as the Gastineau Channel Formation. They recognized these deposits as evidence of a marine transgression immediately post glacial on isostatically depressed lands. Mobley (1988) developed Holocene sea-level curves for Heceta and Prince of Wales islands based on a limited data. Mobley compared these deposits to those described by Clague et al. (1982). Mann and Hamilton (1995) recognized the marine transgression described by Mobley (1988) and a transgression of similar magnitude and duration in the Queen Charlotte Islands. Mann and Streveler (2008) characterized the glacial and relative sea level history of the Icy Strait region. Recent new data is expanding our understanding of the timing and complexity of the marine transgression following the Last Glacial Maximum (LGM). This data also defines the timing of the retreat of the Cordilleran Ice Sheet from the Archipelago. An extensive literature search and years of field reconnaissance and sample collection have resulted in a dataset of over 600 shell-bearing raised marine deposits throughout Southeast Alaska. It includes site location, elevation, and description when available, and over 300 radiocarbon dates beginning at ~48,000 Cal BP. Interpretation of this data gives insight on the timing and complexity of isostatic crustal adjustments that resulted from glaciation and deglaciation, eustatic sea level change, and subsequent tectonic uplift. From this data, preliminary relative sea level curves have been developed for much of Southeast Alaska allowing for modeling of the paleoshorelines through time. The modeling suggests a peripheral forebulge developed west of the ice front along the whole of the coast of Southeast Alaska expanding the area of previously modeled coastal refugia. This forebulge is believed to be similar in extent and timing as that described along the coastal margins of British Columbia (Josenhans et al., 1997, Hetherington et al., 2004). Evidence for this forebulge exists along the whole of the western submerged coast of southeastern Alaska. Terraces can be seen at -165 to -180 meters on recently acquired high resolution multibeam bathymetry images hinting at a minimum of a 45 to 60 meter forebulge on the outer shelf. Maar volcanoes, volcanic cones, and pāhoehoe lava can be seen at depths up to -160 meters in Alaska Department of Fish and Game video tapes from submersible dives.

To date, focused research defining the detailed timing of glaciation in southeastern Alaska is in its infancy. Through the years however several efforts have yielded results which shed light on the maximum LGM extent of the rate of deglaciation. Mann and Hamilton (1995) suggested that LGM glacier retreat was rapid due to iceberg caving and was complete by 13,500 YBP. They preface the southeastern Alaska discussions with ‘the glacial history is poorly understood”. During the LGM the Cordilleran glacier complex flowed westward from the crest of the coastal mountains to the coastal plain exposed by lower sea levels and crustal response to ice loading. The LGM glaciers coalesced with local alpine glaciers from the higher mountains. The exact extent of the LGM ice sheet in southeastern Alaska is poorly known because much of the evidence is now submerged due to postglacial sea level rise and the land’s response to deglaciation. Some of the now submerged lands west of the Alexander Archipelago were likely ice free. As NOAA and researchers collect multibeam bathymetry along the western shore, now submerged terminal moraines, drumlins, and post glacial rivers are brought to light. The above mentioned data set shows that Dixon Entrance deglaciated by 15,499 Cal BP (15,215– 15,795 Cal BP, 2 Sigma Calibration 95.4%). Glacier Bay deglaciated by 14,624 Cal BP (13,855– 15, 331Cal BP, 2 Sigma Calibration 95.4%). The remainder of Southeast Alaska deglaciated by a median age of 13,708 Cal BP (13,418 – 14,091 Cal BP, 2 Sigma Calibration 95.4%). This age range corresponds closely to the published dates for meltwater pulse 1a and a peak rate of sea level rise at ~13,800 Cal BP. During meltwater pulse 1A rising sea-level outpaced the isostatic rebound. By ~13,700 Cal BP all ice retreated from all of Southeast’s fiords, channels, and passages to the elevation of the highest shell occurrences. Likely there were isolated/stranded ice sheets on the islands and existing alpine glaciers. The large coastal rivers like the Taku, Stikine, Iskut, Unuk, and Nass River Valleys would have been fiords with tidewater glaciers in their valleys. Many of the largest islands such as Admiralty, Kupreanof, Kuiu, and Mitkof would have consisted of several smaller islands at that time. It is important to note that all of the highest shell-bearing strata, regardless of their present elevation, date to an average of ~13,700 Cal BP. In the vicinity of Juneau mainland, Douglas, and northern Admiralty Islands this is up to 191 meters above sea level. In the vicinity of Mitkof, Wrangell, and Etolin Islands this is near 65 meters above sea level. Near Revillagigedo Island shell- bearing strata are found up to 80 meters above sea level. A forebulge persisted along the coast until from 16,700 to 11,100 Cal BP. This implies that glacial ice was present on the mainland until the collapse of the forebulge. The marine reservoir correction for samples dating from 5,900 to 10,330 ¹⁴C YBP has been calculated to be ~700 ¹⁴C YBP (Baichtal and Schmuck, unpublished data). The marine reservoir correction is largely unconstrained in this region for samples dating to ≥11,000 ¹⁴C YBP; the above age assignment uses a correction of 1100 years for samples older than 11,000 ¹⁴C YBP.

Buddington, A.F., and Chapin, T., 1929, Geology and mineral deposits of southeastern Alaska:

U.S. Geological Survey Bulletin 800, 398 p. Clague, J.J., Harper, J.R., Hebda, R.J., & Howes, D.E., 1982, Late Quaternary sea levels and crustal movements, coastal British Columbia: Canadian Journal of Earth Sciences, 19, p. 597–618. Hetherington, R., Barrie, J. V., Reid, R.G.B., MacLeod, R., Smith, D.J., 2004. Late Paleogeography, glacially induced crustal displacement, and late Quaternary coastlines on the continental shelf of British Columbia, Canada: Quaternary Science Reviews 23, p. 295–318. Josenhans, H.W., Fedje, D.W., Pienitz, R., & Southon, J., 1997, Early humans and rapidly changing Holocene sea levels in the Queen Charlotte Islands—Hecate Strait, British Columbia, Canada: Science, 277, p. 71–74. Mann, D. H., Hamilton, T. D., 1995. Late Pleistocene and Holocene paleoenvironments of the North Pacific Coast: Quaternary Science Reviews 14, p. 449–471. Mann, D.H. and Streveler, G.P. 2008, Relative sea level history, isostasy, and glacial history in Icy Strait, Southeast Alaska: Quaternary Research 69, p. 201–216. Miller, R.D., 1973, Gastineau Channel Formation, a composite glaciomarine deposit near Juneau, Alaska: U.S. Geological Survey Bulletin 1394-C, p. C1–C20. Mobley, C.M., 1988, Holocene sea levels in Southeast Alaska: Preliminary results. Arctic, 41(4), p. 261–266.

Figure 1. Preliminary Sea Level Curves for Southeastern Alaska with Haida Gwaii Data (Josenhans, 1997; Hetherington et al., 2004) and Global Sea Level (Peltier and Fairbanks, 2006).

Figure 2. Minimum Timing of Deglaciation in Southeast Alaska Based on Ages of Shell-bearing Strata.

ON THE CONTRIBUTION OF BAFFIN BAY ICE COVER AND SEA SURFACE TEMPERATURES TO GREENLAND'S WEST COAST WARMING

Ballinger, Thomas J.1, Hanna, Edward2, Hall, Richard J.2, Miller, Jeffrey3, Ribergaard, Mads H.4, Høyer, Jacob L.4

1Department of Geography, Texas State University 2Department of Geography, University of Sheffield, Sheffield, UK 3Wyle Information Sciences, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA 4Danish Meteorological Institute, Copenhagen DK-2100, Denmark

Observed changes to sea ice formation and sea surface temperatures (SST) around Greenland since 1979 have coincided with autumn Greenland coastal surface air temperature (SAT) warming over the period. In this study, strong, statistically significant correlations are found between Baffin Bay SSTs, freeze onset, and air temperatures across the western and southernmost coastal regions, while weaker and fewer significant correlations are noted between east coast SATs and the SSTs and freeze conditions observed across marginal seas to the east of the island. SAT composites by extreme late freeze years reveal positive monthly SAT departures that often exceed one standard deviation from the 1981-2010 mean over the broad western coastal areas that exhibit a similar spatial pattern as the peak correlations. Statistical linkages between the timing of sea ice freeze-up, SSTs, and SATs appear physically related through increases in both Greenland Blocking Index conditions and meridional atmospheric circulation patterns during the modern sea ice monitoring era. Greater occurrence of upper-air, anticyclonic blocking patterns promotes poleward transport of warm air from lower latitudes and local warm air advection from thin, ice-covered portions of Baffin Bay onto the west flank of the island. This analysis provides an observational framework of coastal SAT links to SST and sea ice behaviors through regional atmospheric circulation changes. Ongoing research extends the aforementioned analyses back to the early 1850s by utilizing recently released global reanalysis and sea ice datasets.

A TEST OF INTRINSIC CLIMATE VARIABILITY AS THE CAUSE OF LATE HOLOCENE VALLEY GLACIER FLUCTUATIONS

Barclay, David J.1, Luckman, Brian H.2, Wiles, Gregory C.3

1SUNY Cortland 2University of Western Ontario 3The College of Wooster

Fluctuations of valley glacier termini are widely used as proxy records of climate change. However, analyses using simple glacier models (Roe and O’Neal, 2005; Roe, 2011) have suggested that significant advances and retreats of termini can result from intrinsic climate variability (specifically, from random year-to-year weather interacting with the memory of glacier systems). These effects may cause terminus fluctuations of several kilometers on multi-decadal to centennial timescales, can produce moraines in the landform record (Anderson et al., 2014), and can be expected to occur in the absence of actual shifts in the mean climate state. This poses a question for reconstructions of past climate change from moraines and other forefield data: how do we know that glacial deposits used to define events such as the Little Ice Age represent real shifts in climate and are not just the result of glacier fluctuations arising from intrinsic climate variability? One way to address this question is to focus on the synchronous behavior of termini. Consider two valley glaciers that are physically similar (i.e. similar length, area, slope, etc.). If they are close together in the same area then they will experience the same weather, will respond in the same way due to their geometries, and so their fluctuations due to intrinsic climate variability will be the same. In contrast, if they are far apart (i.e. many hundreds of kilometers) then they will experience different weather, their fluctuations due to intrinsic climate variability will be different, and so any synchronous advances or retreats of their termini must be a common response to the same climate forcing (i.e. hemispheric or global climate change). Here we apply this synchronous behavior test to late Holocene termini fluctuations in northwestern North America. We use valley glacier histories from two areas, coastal south-central Alaska and the Canadian Rockies, which are about 2000 km apart and on opposite sides of the North Pacific dipole. This means that weather, and thus any terminus fluctuations due to intrinsic climate variability, will be distinctly different in these two areas. Our data set is developed from several decades of research in the two areas (e.g. Luckman, 2000; Wiles et al., 2008; Barclay et al., 2013). We focus on forefields of valley glaciers that have well-defined termini and exclude data from tidewater-calving, surging, cirque, interrupted, and rock glaciers. All age control is high precision tree-ring dates or from direct observations of termini. Our first analysis is a visual comparison of time-distance diagrams for the four most complete forefield records spanning the past 1200 years (Tebenkof and Sheridan glaciers in Alaska, Robson and Peyto glaciers in Canada). These

38 diagrams combine tree-ring crossdates of first and last years of growth in forefield trees, qualitative descriptions of glacial sediments and landforms, and recent direct observations of ice margins to depict glacier length changes over time. The four forefields show essentially the same fluctuations; all four termini advanced in the 1200s-1300s CE, made more extensive advances in the 1600s- 1700s CE, had major re-advances in the 1800s CE, and made major retreats in the past 100 years that continue to the present. Our second analysis is a statistical comparison of moraine stabilization dates in the two areas. These dates record times when trees colonized abandoned morainal ridges as termini retreated from maxima. The moraine dates were split into data sets respectively for the two areas (32 Alaskan forefields, 29 Canadian forefields), grouped into 25-year bins for the 1501 CE-to- present period, and the Pearson correlation coefficient calculated; the result (r = 0.899, t = 8.71, p < 0.001) indicates that intervals of moraine stabilization have been coeval in these two areas. To test robustness of the calculation, the analysis was repeated for 5-, 15-, 35-, and 45-year bins and for all possible start dates of bins, with similar results. The third analysis is a statistical comparison of tree damage and death dates in the two areas. These dates record times when termini advanced into mature forefield forests and when outwash aggraded on and just beyond forefields. The happenstance of subfossil tree preservation and re-exposure on forefields means that these data under-sample the true number of glaciers that advanced, and so the data were reduced to nominal (binary) scales for analysis. Using 25-year bins and the 801 CE-to-present interval, the non-parametric phi coefficient of φ = 0.605 (χ2 = 15.1, p < 0.01) indicates that intervals of glacially caused tree damage and death in these two areas have been coeval. Repeating the analysis for 5-, 15-, 35-, and 45-year bins and for all possible start dates of bins shows that the result is robust. In both of the statistical tests the null hypothesis, that there is no relationship between times of moraine stabilization or forefield tree damage and death in the two areas, can be rejected at or above the 99% confidence level. Together with the visual coherence of the time-distance diagrams, these results support the interpretation that late Holocene fluctuations of valley glacier termini in coastal south-central Alaska and the Canadian Rockies have been synchronous at multi-decadal to centennial timescales. These major fluctuations are highly unlikely to be due to intrinsic climate variability; rather, these advances and retreats must represent a similar response of valley glaciers in these two areas to hemispheric or global climate change.

Anderson, L.S., Roe, G.H., and Anderson, R.S., 2014. The effects of interannual climate variability on the moraine record. Geology 42 (1): 55-58. Barclay, D.J., Yager, E.M., Graves, J., Kloczko, M., and Calkin, P.E., 2013. Late Holocene glacial history of the Copper River Delta, coastal south-central Alaska, and controls on valley glacier fluctuations. Quaternary Science Reviews 81: 74-89. Luckman, B.H., 2000. The Little Ice Age in the Canadian Rockies. Geomorphology 32: 357-384. Roe, G.H., 2011. What do glaciers tell us about climate variability and climate change? Journal of Glaciology 57 (203): 567-578. Roe, G.H. and O’Neal, M.A., 2005. The response of glaciers to intrinsic climate variability:

observations and models of late-Holocene variations in the Pacific Northwest. Journal of Glaciology 55 (193): 839-854. Wiles, G.C., Barclay, D.J., Calkin, P.E., and Lowell, T.V., 2008. Century to millennial-scale temperature variations for the last two thousand years indicated from glacial geologic records of Southern Alaska. Global and Planetary Change 60: 115-125.

Figure 1. A: Study areas in western North America. B: Subfossil tree stumps. The innermost annual ring is a minimum date for when the substrate became available for forest growth, the outermost annual ring dates when the tree died, and the enclosing glacigenic sediments indicate the relationship between tree death and advance of the terminus.

Figure 2. Data for the synchronous behavior test. A: time-distance diagrams; green bars are age spans of crossdated subfossil and living trees, circles are direct observations, and blue lines are ice margin positions of termini. B: moraine stabilization dates based on tree colonization. C: forefield tree damage and death dates due to outwash aggradation and glacier contact. 40

SURFACE STATUS ACROSS SCALES - EVALUATING TEMPORAL AND SPATIAL PATTERNS IN FREEZE/THAW CYCLES

Bergstedt, Helena1 and Bartsch, Annett2

1University Salzburg, Austria 2Zentralanstalt für Meteorologie und Geodynamik, Vienna, Austria

Permafrost and seasonally frozen ground cover large parts of the Earth’s surface and are an important factor in assessing environmental developments and possible changes in the Arctic. The Arctic freeze/thaw cycles of the ground surface are an annual phenomenon and drive hydrological and ecological processes. The change from frozen to thawed ground can be detected using microwave remote sensing. Algorithms designed for freeze/thaw information retrieval utilize a rapid change in the dielectric properties of the ground caused by the status change of water (e.g., Kimball et al., 2004). Microwave remote sensing has found many applications in environmental studies. In particular in the Arctic where optical remote sensing is limited by cloud cover and the absence of daylight during large parts of the year. In the past, studies focusing on permafrost environments have used different sensors with varying spatial and temporal resolution to retrieve surface status information. Active microwave remote sensing has been shown to be a suitable tool for freeze/thaw information retrieval (e.g., Rignot and Way, 1994; Zwieback et al., 2015). In this study, we compare two data products and consider terrain and landcover of permafrost regions as well as possible temporal dynamics. Both data sets used were produced within the ESA DUE Permafrost project. They were obtained using two different active microwave remote sensing platforms and while they operate at the same frequency (C-band), they differ in spatial and temporal resolution. The data set with high spatial resolution (1 km) covers selected regions and is based on data obtained by the Advanced Synthetic Aperture Radar (ASAR) sensor on-board the Envisat satellite and has a temporal resolution of one week. The second data set has a higher temporal resolution of up to one day, covers the circumpolar area and was created using data obtained by the Advanced Scatterometor (ASCAT) sensor on-board the Metop satellites. While this data set has a notably higher temporal resolution, it has a coarser spatial resolution of 25 km. The used products are based on different algorithms. The ASCAT product is based on an approach applying an empirical threshold- analysis algorithm to the backscatter data which is designed for global application (Naeimi et al., 2012). The retrieval of freeze/thaw information from Synthetic Aperture Radar (SAR) requires a different approach as demonstrated in Park et al. (2011). The SAR data set used in this study is based on a temporal edge detection approach. For this study we concentrate on the areas and time periods that are covered by both data sets. This limits the extent of the study area to the Laptev Sea Coast, the Yamal region, central Yakutia, Alaska North Slope and the

MacKenzie region. The overlapping time period is limited to 2007 to 2010. To investigate temporal and spatial differences between the two data products we assign the fraction of frozen ground in the SAR product to the ASCAT grid and transform it to daily time slices for comparison. We investigate temporal and spatial patterns in the agreement of the two data products. The number of acquisitions used in the single SAR maps (which is crucial for the accuracy of the product) are included in the assessment. Results show different patterns for spring and autumn which are assessed using ancillary information. Results are discussed with respect to the used wavelength (C-Band), noise (specifically an issue of the SAR product), the methods which have been used to produce the SAR and scatterometer products, and eventually the applicability of the coarse resolution data set in complex terrain.

Kimball, J.S., McDonald, K.C., Running, S.W., Frolking, S.E., 2004., Satellite radar remote sensing of seasonal growing seasons for boreal and subalpine evergreen forests: Remote Sensing of Environment, v. 90, p. 243–258. Naeimi, V., Paulik, C., Bartsch, A., Wagner, W., Kidd, R., Park, S.E., Elger, K., Bioke, J., 2012, ASCAT Surface State flag (SSF): Extracting information on surface freeze/thaw conditions from backscatter data using an empirical threshold analysis algorithm: IEEE Transactions on Geoscience and Remote Sensing, v. 50, p. 2566–2582. Park, S.E., Bartsch, A., Sabel, D., Wagner, W., Naeimi, V., Yamaguchi, Y., 2011, Monitoring freeze/thaw cycles using Envisat ASAR global mode: Remote Sensing of Environment, v. 115, p. 3457–3467. Rignot, E., Way, J.B., 1994, Monitoring freeze-thaw cycles along north-south Alaskan transects using ERS-1 SAR: Remote Sensing of Environment, v. 49, p.131–137. Zwieback, S., Paulik, C., Wagner, W., 2015, Frozen soil detection based on advanced scatterometer observations and air temperature data as part of soil moisture retrieval: Remote Sensing, v. 7, p. 3206-3231.

A HIGH-RESOLUTION HOLOCENE MARINE SEDIMENTOLOGICAL RECORD FROM POND INLET, NUNAVUT - IS THERE A PALEOSEISMICITY SIGNAL?

Broom, Laura-Ann1, Campbell, Calvin2, Gosse, John1

1Department of Earth Science, Dalhousie University; Geological Survey of Canada 2Bedford Institute of Oceanography, Dartmouth, Nova Scotia, B2Y 4A2, Canada

Baffin Bay is one of the most seismically active regions in Canada. The largest measured earthquake (Ms = 7.3) north of the Arctic Circle occurred in northern Baffin Bay in 1933. Despite this, the instrumental earthquake record is limited, and the geological record must be utilized to understand the paleoseismicity of the region. Pond Inlet, a fjord in northern Baffin Island, is located within this region of high seismicity and preserves high sedimentation rates since deglaciation during the Holocene (0.8 mm/a) (Figure 1). This gives it the potential to preserve a high resolution paleoseismic record for the region. The depositional processes responsible for the sedimentological record in Pond Inlet are not well understood and are likely influenced by the high seismicity of Baffin Bay as well as by climate fluctuations during the Holocene. Submarine geological and geophysical data have been recently collected from Pond Inlet including five piston cores, 3.5 kHz seismic reflection data, and high resolution multibeam bathymetry (Figure 2). These data reveal deposits interpreted to be mass transport deposits (MTDs) and turbidites which are hypothesized to be seismogenic (Figure 2). To test if these mass movement events are related to paleoseismicity or if climatic triggers are more likely, the MTDs and turbidites need to be characterized, correlated and dated. The MTDs and turbidites will be characterized based on their sedimentological and acoustic characteristics, and the sedimentology and grain size patterns of the deposits will be compared with each other and with other MTDs related to paleoseismicity. They will also be correlated throughout the study area and dated using relative and radiocarbon dating techniques to determine if deposition was synchronous throughout the basin. Timing of deposition will also be compared to known Arctic Holocene paleoclimate anomalies to determine if climate could be a likely trigger. If the MTDs and turbidites can be linked to paleoseismicity, then the recurrence of large earthquakes in northern Baffin Bay can be determined. This will lead better understanding the seismic risk to the Hamlet of Pond Inlet and to the improved assessment of the geological hazards in Baffin Bay.

LATE-WISCONSINAN MAXIMUM EXTENT AND DECAY OF THE LAURENTIDE ICE SHEET ON THE NORTHEASTERN BAFFIN ISLAND CONTINENTAL SHELF

Brouard, Etienne1 and Lajeunesse, Patrick2

1Centre d’études nordiques & Département de géographie, Université Laval, Québec, QC, Canada 2Centre Eau Terre Environnement, Institut national de la Recherche Scientifique (INRS-ETE), Québec, QC, Canada

Recent multibeam bathymetry and subbottom profiler data were collected during the 2015 and 2016 ArcticNet cruises aboard the CCGS Amundsen to investigate the pattern and dynamics of former ice-flow on the northeastern Baffin Shelf and in the Baffin Island fjords. Merged with bathymetric data from previous ArcticNet cruises (2003-2014) and seismic data collected during the last decades by the Geological Survey of Canada, the new dataset reveals glacial landforms indicating that the Laurentide Ice Sheet (LIS) extended to the continental shelf edge in three troughs (Pond Inlet Trough, Buchan Trough and Scott Trough) at the Last Glacial Maximum (LGM). On the inter-trough areas, perpendicular-to-ice-flow ridges interpreted as moraines suggest the LIS extended on the shelf, but it is unclear if it reached the shelf edge as no data covers the shelf edge in the inter-trough areas. In Pond Inlet, Buchan and Scott troughs, sets of highly elongated glacial bedforms (MSGLs, crag and tails, drumlins, streamlined medial moraines and lateral-shear moraines) provide evidence that ice streams operated in these routes during the LGM. The presence of medial shear moraines indicate that ice-streams were experiencing spatial variations in ice-flow velocities, probably reflecting the advection of ice from different tributaries (i.e., different fjords) and the presence of sticky spots. In Sam Ford Trough, the absence of glacial elongated bedforms and the presence of perpendicular to the trough ridges indicate that it was characterized by slower sheet-flow, much like inter-streams areas. The slow ice-flow in the trough is probably due to the advection of ice discharge from Sam Ford Fjord into the Scott Inlet Ice Stream. The ice-flow route from Sam Ford Fjord to Scott Inlet can be inferred from the northward orientation of glacial lineations and drumlins at the junction of Sam Ford Fjord and Hecla & Griper Trough. Grounding zone wedges and moraines are observed in the troughs and in the fjords, respectively. The location of these deposits suggests that the retreat of the LIS from the shelf edge to the fjords head has been marked by several periods of grounding-line stability. These results therefore indicate a more episodic retreat pattern than previously suggested (e.g., Praeg et al., 2007).

Praeg, D. B., MacLean, B., & Sonnichsen, S. (2007). Quaternary geology of the northeast Baffin Island continental shelf, Cape Aston to Buchan Gulf (70 to 72 N). Geological Survey of Canada, Open File 5409, 92.

GEOLOGICAL HAZARD ASSESSMENT IN WESTERN BAFFIN BAY- APPROACHES AND PRELIMINARY RESULTS

Campbell, Calvin1, Jenner, Kimberley1, MacKillop, Kevin1, Piper, David1 MacQuarrie, Meaghan1, Broom, Laura-Ann2

1Geological Survey of Canada 2Department of Earth Science, Dalhousie University

A predominantly coastal population, high seismicity, and competing demands for seabed usage have driven the need to understand marine geohazards, particularly seabed stability, in western Baffin Bay (Fig. 1). The vast extent of the bay currently makes it impractical to map the entire area in high resolution; therefore research must strike a balance between site-specific (process) and regional (mapping) studies. Since 2012, a research project has been underway to create a predictive geohazard framework for offshore Baffin Island. The approach integrates seabed morphology, shallow seismic stratigraphy, lithostratigraphy, and geotechnical parameters to delimit the extent of geohazards, their recurrence, trigger mechanisms, and likelihood of future events. Our results show that the Late Quaternary geology of the western Baffin Bay margin is dominated by trough mouth fans fed by 12 distinct transverse troughs. Fourteen piston cores, targeting a range of acoustic facies along the Baffin Island slope, were used to establish a Late Pleistocene and Holocene lithostratigraphic framework. Within this framework, a typical succession of lithofacies is correlatable along the margin. This succession includes basal glacigenic debris flows overlain by fine-grained turbidites and meltwater plume deposits, carbonate-rich ice-rafted debris, and hemipelagic sediments. Although the geophysical data shows evidence of shallow seabed failure (Fig. 2), sediment core data show that Holocene seabed failure is limited or absent, albeit data coverage is sparse in places. Advanced geotechnical analyses show the surficial sediments are characterized by 6 geotechnical units which are related to the lithostratigraphic framework (Fig. 3). The sediments are predominately normally consolidated to slightly under-consolidated lean clays. Slope stability analysis using the infinite slope method suggests that the sediments are statically stable at slope angles less than approximately 5°. In addition, pseudo-static analysis indicates that sediments are stable and require a ground acceleration coefficient >0.15. Several Atterberg tests reveal lithologic units that are potentially liquefiable. Research is ongoing to integrate the geotechnical results and the geological framework with the goal of delimiting areas where the potential for seabed failure is greatest.

Figure 1. Location map of Baffin Bay showing core locations (white circles) and sub-bottom profiler coverage (black lines) collected in 2013. White lines indicate high resolution seismic reflection profiles collected prior to the 2013 expedition. Bathymetric contour interval is 200 m.

Figure 2. Sparker seismic reflection profile from the western Baffin Bay margin showing evidence of slope failure. PC 077 and PC 079 are the location of core samples collected in 2013. Profile location is shown on Fig. 1.

Figure 3. Lithological and geotechnical plot for core 2013029-075 from the slope seaward of Qikiqtarjuaq. Core location is shown on Fig. 1.

MID- TO LATE-PLEISTOCENE TEMPERATURE AND ENVIRONMENTAL VARIABILITY AT LAKE EL'GYGYTGYN, FAR EAST RUSSIA

Castañeda, Isla S.1, Habicht, M. Helen1, Patterson, Molly O.1,2, de Wet, Greg A.1, Keisling, Benjamin A.1, DeConto, Rob1, Brigham-Grette, Julie1

1Department of Geosciences, University of Massachusetts Amherst 2Department of Geological Sciences & Environmental Studies, Binghamton University

The regional response of the high Arctic to past climate variability is little known beyond the brief time period (~120,000 years) covered by Greenland ice cores. In 2009, a 3.6 Ma sediment core was recovered from Lake El’gygytgyn (NE Russia), the largest and oldest unglaciated Arctic lake basin. These sediments offer a unique opportunity to examine Plio-Pleistocene high-latitude continental climate variability. Determining the magnitude of past Arctic temperature and precipitation variability is especially relevant to understanding the mechanisms and feedbacks contributing to arctic amplification. Here we present results of ongoing organic geochemical analyses of Lake El’gygytgyn sediments focusing on the Mid- to Late-Pleistocene. Despite the ultra-oligotrophic nature of Lake El'gygytgyn and the generally low sedimentary total organic carbon (TOC) content, we find abundant branched glycerol dialkyl glycerol tetraethers (brGDGTs) throughout the entire record (de Wet et al., 2016; Keisling et al., 2017) and abundant plant leaf waxes in portions of the record (Keisling et al., 2017). We use the methylation of branched tetraethers (MBT) to reconstruct past temperature (Weijers et al., 2007; De Jonge et al., 2014) and ratios of plant leaf waxes to examine vegetation variability within the Lake El’’gygytgyn catchment. In addition, a suite of algal biomarkers provides insights into past changes in primary productivity and organic matter preservation within the lake. We hypothesize that the majority of brGDGTs are produced in the lake during the brief summer period of ice free conditions and that MBT likely reflects a warm season temperature. Trends noted in the MBT record are in close agreement with pollen-based temperature estimates throughout the entire core and reveal a strong response to interglacial-glacial variability as well as local summer insolation (Figure 1). MBT temperature reconstructions indicate the terrestrial Arctic experienced both warm interglacials and mild glacial periods during the Mid-Pleistocene but transitioned to more extreme temperature fluctuations in the more recent part of the record. Plant leaf wax average chain lengths suggest that glacial intervals were marked by increased aridity, while interglacial periods were wetter at Lake El’gygytgyn. Overall, application of organic geochemical proxies to Lake El’gygytgyn sediments is a highly promising technique for examining environmental change in the continental Arctic, particularly when used in combination with inorganic and other biological (e.g. diatom assemblages, biogenic silica) proxies.

Cheng, H., Edwards, R.L., Sinha, A., Spötl, C., Yi, L., Chen, S., Kelly, M., Kathayat, G., Wang, X., Li, X. and Kong, X., 2016. The Asian monsoon over the past 640,000 years and ice age terminations. Nature, 534(7609), pp.640-646. De Jonge, C., Hopmans, E.C., Zell, C.I., Kim, J.H., Schouten, S. and Damsté, J.S.S., 2014. Occurrence and abundance of 6-methyl branched glycerol dialkyl glycerol tetraethers in soils: Implications for palaeoclimate reconstruction. Geochimica et Cosmochimica Acta, 141, pp.97-112. De Wet, G.A., Castañeda, I.S., DeConto, R.M. and Brigham-Grette, J., 2016. A high-resolution mid-Pleistocene temperature record from Arctic Lake El'gygytgyn: a 50 kyr super interglacial from MIS 33 to MIS 31? Earth and Planetary Science Letters, 436, pp.56-63. Keisling, B.A., Castañeda, I.S. and Brigham-Grette, J., 2017. Hydrological and temperature change in Arctic Siberia during the intensification of Northern Hemisphere Glaciation. Earth and Planetary Science Letters, 457, pp.136-148. Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A.C.M. and Levrard, B., 2004. A long term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428(1), pp.261-285. Lisiecki, L.E. and Raymo, M.E., 2005. A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography, 20. Sun, Q., Chu, G., Liu, M., Xie, M., Li, S., Ling, Y., Wang, X., Shi, L., Jia, G. and Lü, H., 2011. Distributions and temperature dependence of branched glycerol dialkyl glycerol tetraethers in recent lacustrine sediments from China and Nepal. Journal of Geophysical Research: Biogeosciences, 116(G1). Weijers, J.W., Schouten, S., van den Donker, J.C., Hopmans, E.C. and Damsté, J.S.S., 2007. Environmental controls on bacterial tetraether membrane lipid distribution in soils. Geochimica et Cosmochimica Acta, 71(3), pp.703-713.

Figure 1: Branched GDGT data from Lake El’gygytgyn compared to global and regional climate proxies. Note the break in the X-axis scale. From top to bottom: the global benthic oxygen isotope stack (Lisiecki and Raymo, 2005); Lake El’gygytgyn brGDGT temperature reconstruction (this study) plotted using the calibration of Sun et al. (2011). Dark blue represents samples from piston core LZ1024 and the light blue represents samples from drill core 5011-1. Summer insolation at 65°N is plotted in gray (Laskar et al., 2004) and at the bottom the oxygen isotope record from Sanbao Cave (Cheng et al., 2016) is plotted in green.

LAKE WATER ISOTOPIC VARIABILITY IN WESTERN GREENLAND: IMPLICATIONS FOR PALEOHYDROLOGICAL STUDIES

Cluett, Allison A.1 and Thomas, Elizabeth K.1

1Department of Geology, University at Buffalo

Arctic precipitation is projected to increase by over 50% within the century, tightly coupled to a decrease of sea ice in the Arctic Ocean, and potentially offsetting mass loss of the Greenland Ice Sheet (GrIS) (Bintanja & Selten, 2014; Kopec et al., 2016; Thomas et al., 2016). These changes signify profound modification of the Arctic hydrological cycle, intricately linked with the cryosphere. However, the relationship between hydrological and cryosphere variability is poorly constrained in the long-term due to a scarcity of high-resolution hydroclimate records from the Arctic (Briner et al., 2016). Paleoclimate proxies of lake water isotopes, such as hydrogen isotopes of mid-chain sedimentary n- alkanes and n-alkanoic acids, may provide long-term records of hydroclimate (as in Rach et al., 2014). However, lake water isotopes are sensitive to both regional hydroclimate and local hydrology. To analyze spatial trends in the isotopic variability of modern surface lake waters, we present measurements of the hydrogen and oxygen isotopes (δD and δ18O) from 92 lakes across an aridity gradient in Western Greenland. Samples were collected from clusters of lakes distributed across approximately 180 km between the coast (humid) and ice sheet (arid), from 66.73ºN to 67.45ºN. We pair isotope measurements with remotely-sensed catchment parameters including lake surface area, catchment area, and residence time from the recently released 2m-resolution ArcticDEM. We observe distinct isotopic differences between proglacial lakes and non-glacial lakes. While proglacial lake waters plot close to the global meteoric water line (GMWL), non-glacial lake waters plot on or below the GMWL, indicating increased sensitivity to evaporative enrichment. Local evaporation lines calculated from six groups of clustered lakes range from 3.7 to 4.9, generally increasing coastward. Preliminary analysis suggests that the strength of the evaporative signal is dependent on the amount of through-flow, and the greatest sensitivity to evaporation occurs in small lakes under arid conditions. These results underscore the importance of considering local hydrological setting in interpreting paleohydrological records for regional hydroclimate.

Bintanja, R., & Selten, F. M., 2014, Future increases in Arctic precipitation linked to local evaporation and sea-ice retreat: Nature, v. 509, p. 479–482. Briner, J. P., McKay, N. P., Axford, Y., Bennike, O., Bradley, R. S., de Vernal, A., Fisher, D., Francus, P., Fréchette, B., Gajewski, K., Jennings, A., Kaufman, D.S., Miller, G., Rouston, C., and Wagner, B., 2016, Holocene climate change in Arctic Canada and Greenland: Quaternary Science Reviews, v. 147, p. 340–364. Kopec, B. G., Feng, X., Michael, F. A., & Posmentier, E. S., 2016, Influence of sea ice on Arctic precipitation: Proceedings of the National Academy of Sciences, v. 113, p. 46–51. Rach, O., Brauer, A., Wilkes, H., & Sachse, D., 2014, Delayed hydrological response to Greenland cooling at the onset of the Younger Dryas in western Europe: Nature Geoscience, v. 7, p. 109–112.

Thomas, E. K., Briner, J. P., Ryan-Henry, J. J., & Huang, Y., 2016, A major increase in winter snowfall during the middle Holocene on western Greenland caused by reduced sea ice in Baffin Bay and the Labrador Sea: Geophysical Research Letters, v. 43, p. 5302-5308.

THE BIG THAW: TRANSDISCIPLINARY EXPLORATIONS OF PROFOUND TRANSFORMATION THROUGHOUT THE ARCTIC DUE TO CLIMATE CHANGE

Connolly, Kim Diana1

1University at Buffalo School of Law

As climate change catalyzes global transformation worldwide, the Arctic is facing profound change across systems in multiple and extreme ways. In 2013, a group of academics and experts convened at a University at Buffalo conference entitled The Big Thaw to discuss this reality. The conference discourse led to papers which were edited and sent to print as a resulting book, compiling diverse expert contemplations of climate change across various Arctic systems. Offering complimentary perspectives, The Big Thaw aims to provide readers both further insight into information they may already have, while also offering new information delivered from unique perspectives that may suggest new ways to contemplate our thawing world.

To begin discussing this book, I want to start with “the end,” - the concluding chapter of The Big Thaw. That chapter commences with a discussion of video of composer-pianist Ludovico Einaudi performing his original piece, “Elegy for the Arctic,” on a raft floating in front of a glacier amidst drift ice in the Arctic.1 As editors we thought this dramatic and timely opening would help contextualize the multi-layered book that comes before, featuring multiple voices engaged in thinking through climate change and it impact on Arctic life of all types, Arctic culture, and Arctic governance. A collage of perspectives and analyses creates harmony and cacophony, hope and despair, emerging climate commitment and frighteningly inadequate climate governance institutions. There is hope that it is not quite time for an elegy yet.

The first part of the book explores multiple efforts to better document and understand the intricate and manifold dynamics of climate change – its causal patterns, its physical and social effects. The next part of the book touches on a sampling of the many policy and governance initiatives being mounted to address the multifarious challenges of climate change. These include a cacophony of actions by national and international institutions – all with their severe limitations and contradictions. It asks whether we can both find and foster sufficient shared understanding to carry out concerted action to respond effectively to climate change.

National regulation and international cooperation for climate protection have been painfully slow to develop. Even ambitious governmental statements of commitment have rarely been matched by effective action – often out of fear that difficult and expensive emissions reductions in one country would quickly be obliterated by opportunistic increases in others. After more than three decades of ponderously slow, clearly inadequate progress, the “Paris Agreement” negotiated

52 in December 2015 initially seemed to have stepped up the pace, ambition, and level of participation in the intergovernmental system.

The Paris Agreement may offer some cause for hope for the Arctic – or at least mitigate some despair. Agreed to by virtually every country in the world, it commits signatories to the goal of “holding the increase in global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C.”2 Almost every country in the world (195 of them) agreed on the terms of the Paris Agreement. It will become formally binding when 55 countries representing 55 percent of global emissions have signed and ratified the agreement.3 As this book went to press the Agreement had 191 signatories. Sixty-one countries had ratified, accounting for slightly less than 48% of global GHG emissions.4

Just as US ratification was critical to reaching the Paris Agreement threshold, so continued US support for climate action will be critical to its eventual success. Former President Obama made climate change action a major part of his agenda. In ratifying the Agreement the US submitted an NDC promising to cut emissions by 26 to 28 percent by 2025 as compared to 2005 levels.5 The US also officially made climate change a top priority of its two-year (2015-2017) chairmanship of the Arctic Council, a high-level organization of eight countries with arctic territories and six native groups that inhabit the region.6 Negotiations with Canada and Mexico have yielded a joint commitment to produce half of the continent’s electricity from non-emitting sources, including hydropower, wind, solar and energy efficiency, by 2025.7

Meanwhile, Arctic temperatures continue to increase, with 2015 temperatures as much as 3°C above long term averages.8 Arctic glaciers continue to retreat. Arctic sea ice continues to disappear, now lasting three to nine weeks less than it did in 1979.9 Taking advantage, a cruise ship recently completed the first ever luxury cruise through the Northwest Passage.10 Arctic shorelines erode more quickly every year. Arctic permafrost continues to melt. And so on.

The Big Thaw book offers a collected moment to stop and think about collectively moving forward in the modern climate change era.

1 Einaudi, Ludovicoeinaudi. "Ludovico Einaudi - "Elegy for the Arctic" - Official Live (Greenpeace)." YouTube. January 20, 2016. Accessed October 10, 2016. https://www.youtube.com/watch?v=2DLnhdnSUVs. 2 Article 2.1.a. While the 2° goal may be achievable with extraordinary effort, the 1.5°, insisted upon most urgently by low lying island countries, seems nearly impossible. The COP Decision includes a request that the IPCC undertake assessment of possible 1.5° pathways. COP21 Decision paragraph 21. https://unfccc.int/resource/docs/2015/cop21/eng/l09.pdf 3 Paris. United Nations Agreement on Climate Change. http://unfccc.int/paris_agreement/items/9485.php. Article 21.1

4 United Nations Framework Convention on Climate Change. "From the UN System." United Nations Framework Convention on Climate Change: Paris Agreement - Status of Ratification. Accessed October 10, 2016. http://unfccc.int/2860.php. 5 Chemnick, Jean. "U.S. and China Formally Commit to Paris Climate Accord." Scientific American. September 06, 2016. Accessed October 10, 2016. https://www.scientificamerican.com/article/u-s-and-china-formally-commit-to-paris-climate- accord/. 6 It is worth noting that climate change is the third of three priorities, the first two being economic development and safety and security; "U.S. Chairmanship of the Arctic Council." U.S. Department of State. Accessed October 10, 2016. http://www.state.gov/e/oes/ocns/opa/arc/uschair/. 7 Eilperin, Juliet, and Brady Dennis. "U.S., Canada and Mexico Vow to Get Half Their Electricity from Clean Power by 2025." Washington Post. June 27, 2016. Accessed October 10, 2016. https://www.washingtonpost.com/news/energy-environment/wp/2016/06/27/u-s-canada-and- mexico-to-pledge-to-source-half-their-overall-electricity-with-clean-power-by- 2025/?utm_term=.c20c2aef734f. 8 Milman, Oliver. "Record High Arctic Temperatures in 2015 Having 'profound Effects' on Region." The Guardian. December 15, 2015. Accessed October 10, 2016. https://www.theguardian.com/world/2015/dec/15/arctic-noaa-report-record-high-temperatures- diminishing-sea-ice. 9 Harvey, Chelsea. "Every Single Part of the Arctic Is Becoming Worse for Polar Bears." Washington Post. September 4, 2016. Accessed October 10, 2016. https://www.washingtonpost.com/news/energy-environment/wp/2016/09/14/every-single-part-of- the-arctic-is-becoming-worse-for-polar-bears/?utm_term=.fb7723b82a25. 10 Revkin, Andrew C. "Arctic Climate Change Revealed in a Luxury Cruise and Haunting Wreck." Dot Earth, September 23, 2016. Accessed October 10, 2016. http://dotearth.blogs.nytimes.com/2016/09/23/arctic-change-revealed-in-a-luxury-cruise-and-a- haunting-wreck/.

MPLICATIONS FOR INTERPRETING LEAF WAX PALEOCLIMATE PROXIES IN ECOSYSTEMS WITH STRONG SEASONAL CYCLES USING OBSERVED SEASONAL TRENDS OF ENVIRONMENTAL WATER AND SEDIMENTARY LEAF WAX HYDROGEN ISOTOPES IN CENTRAL NEW YORK

Corcoran, Megan C.1, Thomas, Elizabeth K.1, Boutt, David2

1Department of Geology, University at Buffalo 2Department of Geosciences, University of Massachusetts-Amherst

Hydrogen isotope ratios, δ2H, in leaf waxes are used as a proxy to reconstruct past climate. Leaf waxes are n-alkyl lipids produced by plants as a protective coating on their leaves. Environmental water δ2H is reflected in δ2H- wax, allowing for past climate to be determined from these compound-specific isotopes. However, there are still many details of this proxy that are unknown, such as seasonal signals contained in leaf waxes preserved in sediment archives. This study aims to understand the relationship between climate, environmental water δ2H and sedimentary δ2H-wax throughout the growing season. Precipitation, lake water, and lake sediment samples were collected at regular intervals throughout the year at a site in Central New York. Water and sediments samples were collected weekly using sediment traps deployed both near the surface and near the bottom of the studied lake. Daily precipitation samples were collected in close proximity to the lake. A Picarro L2130-i water isotope analyzer with an instrumental precision of 0.51 ‰ for δ2H-H2O and 0.08 ‰ for δ18O-H2O was used to measure δ2H and δ18O of lake and precipitation water samples. The δ2H of n-alkyl lipids was determined using gas chromatography-pyrolysis-isotope ratio mass spectrometry. Precipitation and lake water δ2H change seasonally due to changing lake water evaporation, temperature and precipitation source and transport history. Trends in δ2H-wax will also be presented and compared to year round environmental water δ2H. This comparison will elucidate the seasonal signal that is preserved in sedimentary leaf waxes under current climate conditions. Once these current seasonality trends are fully determined, they can be used to provide more precise interpretations of δ2Hwax records of past climate.

LATE WISCONSINAN GLACIAL DYNAMICS IN BROUGHTON TROUGH AND MERCHANT’S BAY, CENTRAL-EASTERN BAFFIN ISLAND

Couette, Pierre-Olivier1, Lajeunesse, Patrick2, Brouard, Etienne1

1Centre d’études nordiques & Département de géographie, Université Laval, Québec, QC, Canada 2Institut national de la recherche scientifique, Centre Eau Terre Environnement (INRS-ETE), Québec, QC, Canada

The maximal extent of the Laurentide Ice Sheet (LIS) in eastern Baffin Island is still controversial as different glaciation models have been proposed during the last decades ranging from a single-domed ice sheet extending beyond the shelf break to an ice sheet margin that barely reached the head of the fjords. (Gilbert, 1982; Dyke and Prest, 1987; Fulton, 1989; Miller et al., 2002; Margold et al., 2015). Late Wisconsinan spatial and temporal variability of glacial fluctuations on the eastern Baffin Island coast and shelf make it difficult to have a reliable reconstruction of the ice margin (Dyke et al., 2003; Briner et al., 2007). High- resolution swath bathymetry and seismic data in fjords and troughs, such as Broughton Trough and Merchant’s Bay, would improve existing models of extent and retreat of the formerly marine-based LIS margin in this region (De Angelis and Kleman, 2007; Margold et al., 2015). Here we use high-resolution swath bathymetry combined with seismic profiles and sediment cores collected during recent and past oceanographic expeditions to: (1) trace the extent of the LIS margin on central-eastern Baffin Island shelf during the Last Glacial Maximum; (2) reconstruct the dynamics and variations of ice-flow in the region; and (3) identify possible periods of stillstands and/or readvances from the early phase of deglaciation to the complete retreat of the LIS from the fjords. The preliminary geomorphological mapping of these sectors include glacial landforms such as crag-and-tails, drumlins and mega- scale glacial lineations (MSGLs) that indicate corridors of fast-flowing ice (i.e., ice streams). At the mouth of Merchant’s Bay, these ice-flow landforms are intersected by a grounding-zone wedge (GZW) constructed during a major phase of ice margin stabilisation. A lateral moraine observed seaward from this GZW indicates that ice margin reached a position farther on the shelf at some time during the Quaternary. The swath bathymetry data in Broughton Trough also shows an extensive area of MSGLs associated with an ice stream. Future work in the area during the summer of 2017 will provide additional data in order to complete the analysis and reconstruct palaeo-ice dynamics in the two sectors of central-eastern Baffin Island.

Briner, J.P., Overeem, I., Miller, G.H., Finkel, R.C., 2007, The deglaciation of Clyde Inlet, northeastern Baffin Island, Arctic Canada: Journal of Quaternary Science, v. 22, p. 223– 232. De Angelis, H., Kleman, J., 2007, Palaeo-ice streams in the Foxe/Baffin sector of the Laurentide Ice Sheet: Quaternary Science Reviews, v. 26, p. 1313–1331. Dyke, A.S., Prest, V.K., 1987, Late Wisconsinan and Holocene History of the Laurentide Ice Sheet: Géographie physique et Quaternaire, v. 41, no. 2, p. 237-263. 56

Dyke AS, Moore A, Robinson L., 2003, Deglaciation of North America: Geological Survey of Canada, Open File 1574. Fulton, R.J., 1989, Quaternary Geology of Canada and Greenland: Geological survey of Canada, 839 p. Gilbert, R., 1982, The Broughton Trough on the continental shelf of eastern Baffin Island, Northwest Territories: Canadian Journal of Earth Sciences, v. 19, p. 1599-1607. Margold, M., Stokes, C. R., Clark, C. D., 2015, Ice streams in the Laurentide Ice Sheet: Identification, characteristics and comparison to modern ice sheets: Earth-Science Reviews, v. 143, p. 117-146. Miller, G.H., Wolfe, A.P., Steig, E.J., Sauer, P.E., Kaplan, M.R., Briner, J.P., 2002, The Goldilocks dilemma: big ice, little ice, or ‘‘just-right’’ ice: Quaternary Science Reviews, v. 22, p. 33– 48.

Figure 1. Location of the study area on Baffin Island, Nunavut, Canada.

HYDROCLIMATE RESPONSE TO ABRUPT TEMPERATURE CHANGES DURING THE DEGLACIAL INTERVAL IN NORWAY AND RUSSIA

Cowling, Owen1, Thomas, Elizabeth K.1, Svendsen, John-Inge2, Vasskog, Kristian2

1Department of Geology, University at Buffalo 2Department of Earth Science, University of Bergen, Norway

There were rapid changes in global climate during the deglacial interval (21-11.7 ka), and these changes were pronounced in high latitudes (Serreze and Barry, 2011). Rapid changes in Northern Hemisphere temperature can influence the distribution of moisture over Greenland and Central Europe, and moisture changes lag behind temperature by as much as 200 years (Rach et al., 2014; Muschitiello et al., 2015). Deglacial changes in terrestrial hydroclimate throughout high latitudes are quantified only at a few sites, creating a gap in mechanistic understanding of the moisture response to climate change. This project will address the hypothesis that hydroclimate changes in Europe lag behind changes in Arctic temperature, indicated in Greenland ice core d18O records, by up to 200 years. This hypothesis will be tested by creating high- resolution d2H records from lake sediments in southwestern coastal Norway covering the deglacial interval, focusing on the Younger Dryas (12.7-11.7 ka), in order to determine the timing of hydrological changes. Lake sediments from Kringlemyr, a bog in southwestern Norway, were extracted and sent to University at Buffalo for leaf wax d2H analysis. The current resolution of the Kringlemyr d2H record is ~140 years between samples, although additional sample processing may increase it to ~70-year time-steps. The record from Kringlemyr can be directly compared to leaf wax d2H records from Hässeldala Port in Southern Sweden and Meerfelder Maar in central Germany, both of which span the Younger Dryas (Rach et al., 2014; Muschitiello et al., 2015). Preliminary d2H results indicate that climate in southwestern coastal Norway cooled and dried at the onset of the Younger Dryas, but the timing of those changes at Kringlemyr may be earlier than at either Meerfelder Maar or Hässeldala Port. This suggests that there is spatial variability in the response of regional hydroclimate to temperature changes, but the exact cause of that variability is not yet determined.

Muschitiello, F., Pausata, F.S.R., Watson, J.E., Smittenberg, R.H., Salih, A.A.M., Brooks, S.J., Whitehouse, N.J., Karlatou-Charalampopoulou, A., and Wohlfarth, B., 2015, Fennoscandian freshwater control on Greenland hydroclimate shifts at the onset of the Younger Dryas: Nature Communications, v. 6, p. 8939, doi: 10.1038/ncomms9939. Rach, O., Brauer, A., Wilkes, H., and Sachse, D., 2014, Delayed hydrological response to Greenland cooling at the onset of the Younger Dryas in western Europe: Nature Geoscience, v. 7, p. 109–112, doi: 10.1038/ngeo2053. Serreze, M.C., and Barry, R.G., 2011, Processes and impacts of Arctic amplification: A research synthesis: Global and Planetary Change, v. 77, p. 85–96, doi: 10.1016/j.gloplacha.2011.03.004.

EARLY HOLOCENE GLACIER CHRONOLOGIES FROM BAFFIN ISLAND, ARCTIC CANADA

Crump, Sarah E.1, Miller, Gifford H.1, Young, Nicolás E.2, Briner, Jason P.3, Pendleton, Simon L.1

1INSTAAR, University of Colorado–Boulder 2Lamont-Doherty Earth Observatory, Columbia University 3Department of Geology, University at Buffalo

Peak summer insolation in the high northern latitudes during the early Holocene resulted in a general pattern of ice retreat across the Arctic. However, this trend was interrupted by centennial-scale cooling events, including the 8.2 and 9.3 ka events, which resulted in ice expansion in some settings. In order to test whether these and other Early Holocene cooling events resulted in synchronous glacier advances across the Baffin Bay region, we are developing cosmogenic 10Be chronologies for a suite of prominent post-LGM, pre-Neoglacial moraines on eastern Baffin Island and West Greenland. Here, we present 14C dates on moraine-dammed lakes and preliminary 10Be ages from three such moraine complexes on eastern Baffin Island, informally named Sulung, Narmak, and Narpaing moraines. We compare these chronologies with other glacial records in the region to assess the degree to which early Holocene glaciers responded in concert to cooling across the North Atlantic region, and we explore the site-specific factors that may help explain the formation and preservation of early Holocene moraines in select settings.

LOCAL PROCESSES AND REGIONAL PATTERNS - INTERPRETING A MULTI-DECADAL ALTIMETRY RECORD OF GREENLAND ICE SHEET CHANGES

Csatho, Beata1 and Schenk, Toni1

1Department of Geology, University at Buffalo

Rapid warming has caused a dramatic decrease of ice in the Artic region during last few decades. Sea ice extent rapidly declined; glaciers sped up, thinned and retreated, and permafrost warmed up and thinned. Arctic warming is further amplified as surface temperature increases due to the melt of the protective snow and ice cover. The Greenland Ice Sheet (GrIS) has lost an average ~250 Gt/yr ice annually, equivalent to 0.7 mm/yr sea-level rise, since 2003 (Csatho et al., 2014). This presentation provides a comprehensive update of Greenland Ice Sheet (GrIS) surface elevation changes and mass losses from the laser altimetry record, obtained using our Surface Elevation And Change detection (SERAC) approach (Schenk and Csatho, 2012). We have developed SERAC to derive information from laser altimetry data, particularly time series of elevation changes and their partitioning into changes caused by surface processes and ice dynamics. This partition allows direct investigation of ice dynamic processes that is much needed for improving the predictive power of ice sheet models. Our latest reconstruction of GrIS surface elevation changes consists of ~130,000 ice-sheet elevation change time series, spanning 1993-2016, derived from satellite laser altimetry data acquired by NASA’s Ice, Cloud and land Elevation Satellite mission, airborne laser observations obtained by Airborne Topographic Mapper (ATM) and the Land, Vegetation and Ice Sensor (LVIS). This work provides a major upgrade of the results presented in our latest study (Csatho et al., 2014), by extending the temporal coverage and by including local ice caps and glaciers. The results reveal significant spatial and temporal variations of dynamic mass loss and widespread intermittent thinning, indicating the complexity of ice sheet response to climate forcing. To investigate the regional and local controls of ice dynamics, we examined thickness change time series near outlet glacier grounding lines. We show that changes are consistent with one or more episodes of dynamic thinning propagating upstream from the glacier terminus. The spatial pattern of the onset, duration, and termination of these dynamic thinning events suggest a regional control, such as warming ocean and air temperatures. Previous results suggested a northward propagation of ice sheet thinning, possibly caused by increasing air and ocean temperatures (Khan et al., 2014; Mouginot et al., 2014). However, we detected a simultaneous onset of increasing dynamic thinning in 2000 on several outlet glaciers in W, SW and NE Greenland (e.g., Jakobshavn Isbræ, Kangerlussuaq Glacier, Zachariæ Isstrøm), when run-off also increased (van den Broeke et al., 2016). This finding has important implications for identifying the processes responsible for observed changes. However, the

60 significant local variations in dynamic thickness change patterns suggest that, regardless of the forcing responsible for initial glacier acceleration and thinning, the response of individual glaciers is modulated by local conditions.

Csatho, B. M., Schenk, A. F., van der Veen, C. J., Babonis, G., Duncan, K., Rezvanbehbahani, S., et al. (2014). Laser altimetry reveals complex pattern of Greenland Ice Sheet dynamics. Proceedings of the National Academy of Sciences, 111(52), 18478–18483. http://doi.org/10.1073/pnas.1411680112. Khan, S. A., Kjær, K. H., Bevis, M., Bamber, J. L., Wahr, J., Kjeldsen, K. K., et al. (2014). Sustained mass loss of the northeast Greenland ice sheet triggered by regional warming. Nature Climate Change, 4(4), 292–299. http://doi.org/10.1038/nclimate2161. Mouginot, J., Rignot, E., Scheuchl, B., FENTY, I., Khazendar, A., Morlighem, M., et al. (2015). Fast retreat of Zachariæ Isstrøm, northeast Greenland. Science, 350(6266), 1357–1361. http://doi.org/10.1126/science.aac7111. Schenk, T., & Csatho, B. (2012). A New Methodology for Detecting Ice Sheet Surface Elevation Changes From Laser Altimetry Data. Geoscience and Remote Sensing, IEEE Transactions on, 50(9), 3302–3316. van den Broeke, M. R., Enderlin, E. M., Howat, I. M., Kuipers Munneke, P., Noël, B. P. Y., Van De Berg, W. J., et al. (2016). On the recent contribution of the Greenland ice sheet to sea level change. The Cryosphere, 10(5), 1933–1946. http://doi.org/10.5194/tc-10-1933- 2016.

HOLOCENE AND LAST INTERGLACIAL CLIMATE OF THE FAROE ISLANDS FROM SEDIMENTARY LEAF WAX HYDROGEN ISOTOPES

Curtin, Lorelei1, D’Andrea, William1, de Wet, Gregory2, Bradley, Raymond2

1Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 2Department of Geosciences, University of Massachusetts-Amherst

The climate of the North Atlantic region is extremely sensitive to changes in ocean and atmospheric circulation, which impact local terrestrial environments. Understanding past natural variability in North Atlantic climate provides important context for modern climate change, and records of abrupt changes are important for evaluating climate models. Here, we present Holocene and Eemian hydrogen isotope (dD) records from leaf waxes preserved in lacustrine sediments from the North Atlantic Faroe Islands and interpret them as a proxy for temperature and hydroclimate variability. In addition to helping constrain the timing and amplitude of climate evolution during each of these interglacial periods, the data can be used to directly compare Eemian and Holocene climate using the same proxy from the same terrestrial location. Of the leaf waxes measured, the dD values of long-chain and mid-chain n-alkanes showed two different signals, which we interpret to represent leaf water dD values and lake water dD values, respectively. The dD values for long-chain and mid-chain fatty acids were most similar to the mid-chain n-alkanes, and likely represent a mixture of terrestrial and aquatic sources. The Holocene data reveal a sudden decrease in the ddD value of precipitation at 8,500 cal yr BP that is potentially related to the 8.2 ky event reported from Greenland ice cores. The observed isotopic shift is much greater than models predict (LeGrande and Schmidt, 2008), and is equivalent to a cooling of 2.7 to 5°C if possible changes in moisture source are disregarded. By the same measure, our snapshot of the last interglacial was, on average, 1.3 to 1.9°C warmer than the Holocene. Leaf wax-inferred dD values of precipitation over the remainder of the Holocene (after 8,000 cal yr BP) are relatively stable and remain ~13 ‰ lower than values in the earliest Holocene. Inferred lake water dD values decreased slowly over the Holocene, suggesting a gradual transition to a wetter climate. At ~2,000 cal yr BP there was a significant change in the distribution of leaf waxes that suggests a transition from shrubland to grassland, but which pre-dates the pollen evidence for this transition (Hannon and Bradshaw, 2000, Hannon et al., 2001).

Hannon, G.E., and Bradshaw, R.H.W., 2000, Impacts and timing of the first human settlement on vegetation of the Faroe Islands: Quaternary Research, v. 54, no. 3, p. 404–413. Hannon, G.E., Wastega, S., Bradshaw, E., and Bradshaw, R.H.W., 2001, Human impact and landscape degradation on the Faroe Islands: v. 139, p. 129–139. LeGrande, A.N., and Schmidt, G.A., 2008, Ensemble, water isotope-enabled, coupled general circulation modeling insights into the 8.2 ka event: Paleoceanography, v. 23, no. 3, p. 1– 19.

TOWARDS MULTI-DECADAL TO MULTI-MILLENNIAL ICE CORE RECORDS FROM COASTAL WEST GREENLAND ICE CAPS

Das, Sarah B.1, Osman, Matthew B.2, Trusel, Luke D.3, McConnell, Joseph R.4, Smith, Ben E.5, Evans, Matthew J.6, Frey, Karen E.7, Arienzo, Monica4, Chellman, Nathan4

1Woods Hole Oceanographic Institution, Woods Hole, MA 2MIT/WHOI Joint Program, Woods Hole, MA 3Rowan University, Glassboro, NJ 4Desert Research Institute, Reno, NV 5University of Washington, Seattle, WA 6Wheaton College, Norton, MA, USA 7Clark University, Worcester MA

The Arctic region, and Greenland in particular, is undergoing dramatic change as characterized by atmospheric warming, decreasing sea ice, shifting ocean circulation patterns, and rapid ice sheet mass loss, but longer records are needed to put these changes into context. Ice core records from the Greenland ice sheet have yielded invaluable insight into past climate change both regionally and globally, and provided important constraints on past surface mass balance more directly, but these ice cores are most often from the interior ice sheet accumulation zone, at high altitude and hundreds of kilometers from the coast. Coastal ice caps, situated around the margins of Greenland, have the potential to provide novel high-resolution records of local and regional maritime climate and sea surface conditions, as well as contemporaneous glaciological changes (such as accumulation and surface melt history). But obtaining these records is extremely challenging. Most of these ice caps are unexplored, and thus their thickness, age, stratigraphy, and utility as sites of new and unique paleoclimate records is largely unknown. Access is severely limited due to their high altitude, steep relief, small surface area, and inclement weather. Furthermore, their relatively low elevation and marine moderated climate can contribute to significant surface melting and degradation of the ice stratigraphy. We recently targeted areas near the Disko Bay region of central west Greenland where maritime ice caps are prevalent but unsampled, as potential sites for new multi- decadal to multi-millennial ice core records. In 2014 & 2015 we identified two promising ice caps, one on Disko Island (1250 m. asl) and one on Nuussuaq Peninsula (1980 m. asl) based on airborne and ground-based geophysical observations and physical and glaciochemical stratigraphy from shallow firn cores. In spring 2015 we collected ice cores at both sites using the Badger- Eclipse electromechanical drill, transported by a medley of small fixed wing and helicopter aircraft, and working out of small tent camps. On Disko ice cap, despite high accumulation rates and ice thickness of ~250 meters, drilling was halted twice due to the encounter of liquid water at depths ranging from 18-20 meters, limiting the depth of the final core to 21 m, providing a multi-decadal record (1980-2015.) On Nuussuaq Peninsula, we collected 138 m ice core,

63 almost to bedrock, representing a ~2500 year record. The ice cores were subsequently analyzed using a continuous flow analysis system (CFA). Age- depth profiles and accumulation histories were determined by combining annual layer counting and an ice flow thinning model, both constrained by glaciochemical tie points to other well-dated Greenland ice core records (e.g. volcanic horizons and continuous heavy metal records). Here we will briefly provide an overview of the project and the new sites, and the novel dating methodology, and describe the latest stratigraphic, isotopic and glaciochemical results. We will also provide a particular focus on new regional climatological insight gained from our records during three climatically sensitive time periods: the late 20th & early 21st century; the Little Ice Age; and the Medieval Climate Anomaly.

HOLOCENE CLIMATE AND OCEAN CONDITIONS IN THE EASTERN CANADIAN ARCTIC AND GREENLAND : LAND-SEA LINKAGES

de Vernal, Anne1, Allan, Estelle1, Fréchette, Bianca1, Hillaire-Marcel, Claude1

1Centre de recherche en géochimie et géodynamique (GEOTOP), Université du Québec à Montréal, Canada

There is often a hiatus between the land-based climate reconstructions and paleoceanographical data. The reconstructed parameters are not the same (e.g. surface air temperature vs. sea-surface temperature) and the spatial (local to regional) and temporal dimensions (seasonal, annual to multi-decadal) of proxy-data are often inconsistent, thus preventing direct correlation of time series and often leading to uncertainties in multi-site, multi-proxy compilations. Here, we explore the land-sea relationships in the eastern Canadian Arctic-Baffin Bay- Labrador Sea-western Greenland based on the examination of different climate- related information from marine cores (dinocysts) collected nearshore vs. offshore, ice cores (isotopes), fjord and lake data (pollen). The combined information tends to indicate that the seasonal contrast of temperatures seems to be a very important parameter. Whereas it is often attenuated offshore, it is generally easy to reconstruct nearshore, where water stratification is usually stronger. The confrontation of data also shows a relationship between ice core data and sea-ice cover and/or sea-surface salinity, suggesting that air-sea exchanges in basins surrounding ice sheets play a significant role with respect to their isotopic signal. On the whole, combined onshore-offshore data consistently suggest a two-step shift towards optimal summer and winter conditions the circum Baffin Bay and northern Labrador Sea at 7.5 and 6 ka BP. These delayed optimal conditions compared to other locations seem to result from ice-meltwater discharges maintaining low salinity conditions in marine surface waters and thus a strong seasonality from winter to summer.

PLIO-PLEISTOCENE CIRCULATION AND SEA ICE HISTORY IN THE WESTERN ARCTIC OCEAN, BASED ON A NORTHWIND RIDGE SEDIMENT RECORD

Dipre, Geoffrey1, Polyak, Leonid1, Ortiz, Joe2, Oti, Emma1, Kuznetsov, Anton3

1Byrd Polar and Climate Research Center, The Ohio State University 2Kent State University 3IGGD, Russian Academy of Sciences

The Arctic Ocean is projected to be seasonally ice-free within the next couple of decades, resulting in major climatic and hydrographic changes. Understanding the trajectory and effects of the rapid ice loss requires knowledge of paleo sea ice conditions on time scales longer than historical observations. The time period after the development of modern Arctic geography (opening of the Bering Strait) at ca. 5-6 Ma but before the onset of major Northern Hemisphere glaciations (~0.8-0.7 Ma), corresponding to Pliocene and early Pleistocene, may represent the closest analogs for the near-future Arctic Ocean conditions. However, there is a lack of Arctic records extending back through the Pliocene, due to low sedimentation rates, problems with age control, and widespread dissolution of biogenic content. Here we present an investigation of sediment core HLY0503-03JPC (JPC3), raised from top of the Northwind Ridge, in the center of the Beaufort Gyre circulation system of the western Arctic Ocean. Based on strontium isotope ages, this sedimentary record dates to ~5 Ma and contains uniquely preserved calcareous microfossils back to ~3.2 Ma. Based on a nearby core from the Northwind Ridge, Polyak et al. (2013) reconstructed sea ice conditions for the last estimated ~1.5 Ma through the use of paleobiologic proxies, such as benthic foraminifers and ostracodes. It was concluded that the early Pleistocene was predominantly seasonally ice-free, with the transition to mostly perennial sea ice occurring ca 0.8 Ma. We further these results through the investigation of stratigraphically longer core JPC3, which dates back through the Pliocene. Initial assemblage data for the early Pleistocene to late Pliocene show that phytodetritus species related to seasonal sea-ice cover constitute the dominant foraminiferal group, indicating persistent reduced-ice conditions. We supplement the paleobiologic data with physical (grain size, X-ray tomography) and chemical (XRF) proxies, to gain more insights into circulation and sediment transport processes. Based on these proxies, we identify three major stratigraphic divisions representing early to mid-Pleistocene, early Pleistocene, and Pliocene. Overall changes through time are interpreted as increasing sea-ice and glaciation controlled environments, and decreasing current activity. Further investigation is needed to determine the mechanisms driving these changes, especially for the early Pleistocene and Pliocene.

L. Polyak, K.M. Best, K.A. Crawford, E.A.Council & G. St-Onge (2013). Quaternary history of sea ice in the western Arctic Ocean based on foraminifera. Quaternary Science Reviews, 79, p. 145-156.

HYDRAULIC CONDUCTIVITY AS A PROXY FOR DRAINAGE SYSTEM CONNECTIVITY IN A SUBGLACIAL HYDROLOGY MODEL

Downs, Jacob1, Johnson, Jesse1, Harper, Joel1, Meierbachtol, Toby1

1Geosciences, University of Montana

The link between subglacial hydrology and basal sliding has prompted work on basal hydrology models with water pressure and storage as prognostic variables. We find that a commonly used model of distributed drainage through linked cavities under- predicts winter water pressure when compared to borehole observations from Isunnguata Sermia in Western Central Greenland. Possible causes for this discrepancy including unrealistic model inputs or unconstrained parameters are investigated through a series of modeling experiments on both synthetic and realistic ice sheet geometries. We find that conductivity acts as a proxy for the connectivity of the linked cavity system and should therefore change seasonally. Model experiments also suggest that trends in winter sliding velocity are more closely related to winter water storage rather than pressure.

Schoof, C., Hewitt, I.J. and Werder, M.A. (2012) ‘Flotation and free surface flow in a model for subglacial drainage. Part 1. Distributed drainage’, Journal of Fluid Mechanics, 702, pp. 126–156. doi: 10.1017/jfm.2012.165. Wright, P. J., J. T. Harper, N. F. Humphrey, and T. W. Meierbachtol (2016), Measured basal water pressure variability of the western Greenland Ice Sheet: Implications for hydraulic potential, J. Geophys. Res. Earth Surf., 121, 1134–1147, doi:10.1002/2016JF003819.

Figure 1. Model inputs for a model run on Isunnguata Sermia.

Figure 2. Decline in modeled winter pressure in Isunnguata Sermia with fixed conductivity.

COUPLED CHANGES IN THE CRYOSPHERE AND SOLID EARTH MEASURED BY SPACE GEODESY

Durkin IV, William J. 1 and Pritchard, Matthew E. 1

1Department of Earth and Atmospheric Sciences, Cornell University

Southeast Alaska is host to some of the world’s highest rates of Glacial Isostatic Adjustment (GIA) uplift and understanding the spatial patterns of GIA deformation is important for constraining the region’s deglaciation history and Earth rheology, but can be difficult to measure due to the remote, vast, and mountainous nature of the region. We present spatially comprehensive maps of ice elevation change rates using digital elevation map (DEM) time series to constrain the elastic contribution to GIA and make the first attempts to measure crustal deformation using Interferometric Synthetic Aperture Radar (InSAR) time series in southeast Alaska. Southeast Alaska is a tectonically complex region that is currently experiencing among the most rapid Glacial Isostatic Adjustment (GIA) uplift rates in the world (>30 mm/yr; Larsen et al., 2005; Sato et al., 2011). GIA deformation is the composite of an immediate elastic response to changes in ice mass on the scale of individual glaciers and the viscoelastic flow of the mantle in response to deglaciation on the scale of ice fields and ice sheets. In southeast Alaska, GIA uplift is largely driven by viscoelastic deformation with uplift rates as high as 20- 35 mm/yr due to low asthenospheric viscosity (~4x10 18 Pa s) and widespread deglaciation following the end of the Little Ice Age ~ 1750 - 1900 A.D. (Larsen et al., 2005). Present day rates of ice mass loss in the larger Gulf of Alaska region (65 ± 11 Gt/yr) are the highest in the world outside of Greenland and Antarctica and drive elastic uplift at rates on the order of ~10 mm/yr while also providing significant contributions to non-steric sea level rise (e.g., Arendt et al., 2013; Gardner et al., 2013; Sato et al., 2011). The spatial patterns of GIA deformation rates can be used to provide constraints on the Gulf of Alaska’s history of deglaciation and constrain the region’s rheology (including lithospheric elastic thickness and upper mantle viscosity) -- which can be elusive to other geophysical techniques. The elastic component of deformation can be modelled using observed ice thinning rates (dh/dt) and an assumed ice density (e.g., Farrell, 1972; Larsen et al., 2005; Melkonian et al., 2014). Once the elastic component is inferred, it can be removed from the total deformation observed to estimate the viscoelastic component. Because ice thinning rates can change in magnitude and in spatial pattern over time, it is important to have dh/dt results that are coeval with uplift observations to correctly model the elastic deformation component. Sato et al. (2011) demonstrated the importance of this by comparing the effect of using different present-day ice thinning models when solving for the mantle viscosity of southeast Alaska. The GPS uplift observations have a mean epoch of 2004, while the two present-day ice thinning models, UAF05 (Arendt et al., 2002) and UAF07 (Larsen et al., 2005), have mean epochs in the mid-1970's and mid-

1980's, respectively. Sato et al. (2011) found that due to a decadal increase in ice thinning rates, the modeled elastic uplift rates of UAF07 vs. UAF05 increased by a factor of 2-3 and changed their spatial patterns. The authors continued to show that the larger elastic uplift rates allowed for less of the observed uplift to be attributed to viscoelastic deformation, resulting in a mantle viscosity ~2.5 times larger than previously estimated (Larsen et al., 2005). However, since the UAF08 model has a mean epoch that is ~ 20 years earlier than that of the GPS observations, it is plausible that the modelled elastic uplift does not accurately represent what is measured by the GPS. Jin et al. (2017) addressed this by estimating ice thinning rates using ICESat altimetry centered in time around the year 2006. Although dh/dt derived from ICESat altimetry has comprehensive coverage of the entire glaciated region of the Gulf of Alaska and is coeval with the GPS observations, the spacing between ICESat altimetry tracks is on the scale of 100’s of km and cannot resolve changes in ice elevation on the scale of individual glaciers. Thinning rates can vary dramatically between neighboring glaciers, and the coarse spacing of the altimetry tracks has the potential to under represent the elastic component of deformation in the GPS observations. Similarly, while GPS has proven to be an invaluable tool for measuring GIA uplift, as it is capable of millimeter scale precision and high temporal resolution, the vast, remote and glaciated nature of the Gulf of Alaska region creates a logistical impediment that can make it costly to deploy dense GPS observations. We address these issues simultaneously by developing high resolution maps of dh/dt and crustal deformation that will provide spatially comprehensive coverage of southeast Alaska. Ice elevation change rates are measured using a time series of digital elevation maps (DEMs) constructed from high resolution satellite stereo imagery, and GIA crustal deformation is measured using interferometric synthetic aperture radar (InSAR) integrated with available GPS. InSAR has been used to measure GIA deformation in Iceland (Auriac et al., 2013) and elastic uplift following glacial unloading in Greenland (Liu et al., 2011), however it has heretofore not been used to measure GIA deformation in Alaska. InSAR in southeast Alaska is difficult due to the region’s mountainous topography, dense vegetation, and coastal environment, all of which increase the likelihood of incoherence between SAR image pairs over time. However, since the recent launch of the Sentinel-1 satellite constellation, SAR imagery is collected over Alaska at repeat periods of 6-, 12-, and 24-days. Using this newly available data, we are able to produce coherent interferograms using image pairs with up to 24-day repeat periods. In this presentation, we illustrate how this approach can be used to improve previous studies of GIA in southeast Alaska and show preliminary results of our InSAR time series. Ice elevation change rates are estimated using a time series of DEMs that are horizontally and vertically coregistered to the off-ice pixels in a reference DEM. After stacking the DEMs, dh/dt is calculated by applying a linear regression at each pixel in which each elevation value is weighted by the uncertainty of its DEM. In this presentation, we use the dh/dt results of Melkonian et al., (2012,

2014, 2016) that were derived from Advanced Spaceborne Thermal Emission and Reflection (ASTER), WorldView, and Shuttle Radar Topography Mission (SRTM) DEMs spanning the years 2000-2010/2013/2014 and on average are centered in time around the year 2006 (Figure 1). By assuming a density of the material lost or gained that is dependent on the equilibrium line altitude (eg., Melkonian et al., 2014), we convert volume change rates into mass change rates. Ice mass loss rates are discretized as a collection of disks 1km in diameter and used with the Regional ElAstic Rebound calculator (REAR; Melini et al., 2015) to calculate elastic uplift rates (Figure 2). REAR calculates the elastic deformation rates by convolving the ice loads with Green’s functions and assuming the Earth to be a solid, isotropic, non-rotating sphere (e.g., Farrell, 1972) with internal elastic properties constrained seismologically (e.g., PREM, Dziewonski et al., 1981; Larsen et al., 2005; Sato et al., 2011). We find that since the mid-1980’s, dh/dt has both changed in spatial pattern and increased in magnitude. In some places, thinning rates are as high as 20 m/yr, roughly twice as high as the largest thinning rates in the mid-1980’s. Similarly, peak elastic uplift rates range between 10-20 mm/yr, greatest around regions of rapid ice thinning and as much as twice as high as previously estimated elastic uplift rates. The larger rates of elastic uplift imply that a smaller percentage of the total uplift rate measured by GPS can be attributed to viscoelastic deformation, suggesting that the asthenospheric viscosity in southeast Alaska may be higher than previously estimated. Interferograms are processed with the InSAR Scientific Computing Environment (ISCE; Rosen et al., 2012 ) using C-band imagery collected by the Sentinel-1 satellite constellation. We are able to obtain coherent interferograms using summer-time 24-day image pairs (Figure 3). Atmospheric water vapor is a source of phase delays and interferometric artifacts due to the coastal setting and high topographic relief of the region. Compared to the GIA deformation signal, the atmospheric phase delay is highly variable in time, and by stacking intereferograms and taking the average deformation rate at each pixel we strengthen the signal-to-noise ratio. We will attempt to further reduce the atmospheric noise by applying phase corrections based on North American Regional Reanalysis (NARR; Mesinger et al., 2006) weather models. Deformation measured with InSAR will be checked for consistency with trends in historic GPS measurements at well-studied sites (e.g., Larsen et al., 2005, Elliott et al., 2010). InSAR will possibly measure even larger rates than the GPS as it can observe crustal deformation up to the edge of the glaciers, where the greatest elastic response to glacier mass change.

Arendt et al., Science 297.5580 (2002): 382-386. Arendt, et al., Journal of Glaciology 59.217 (2013): 913-924. Auriac, et al., Journal of Geophysical Research: Solid Earth 118.4 (2013): 1331-1344. Dziewonski and Anderson, Physics of the earth and planetary interiors 25.4 (1981): 297-356. Elliott et al., Journal of Geophysical Research: Solid Earth 115.B9 (2010). Farrell, Reviews of Geophysics 10.3 (1972): 761-797. Gardner et al., Science 340.6134 (2013): 852-857. Jin et al., Journal of Geophysical Research: Earth Surface (2017). Larsen et al., Earth and Planetary Science Letters 237.3 (2005): 548-560.

Larsen et al., Journal of Geophysical Research: Earth Surface 112.F1 (2007). Liu et al. Geophysical Journal International 188.3 (2012): 994-1006. Melini, Daniele, et al. "a Regional ElAstic Rebound calculator." (2015). Melkonian et al., AGU Fall Meeting Abstracts. Vol.1. 2012. Melkonian et al., Journal of Glaciology 60.222 (2014): 743-760. Melkonian et al., Frontiers in Earth Science 4 (2016): 89. Mesinger et al., Bulletin of the American Meteorological Society 87.3 (2006): 343-360. Sato et al., Tectonophysics 511.3 (2011): 79-88.

Figure 1. Ice elevation change rates for Glacier Bay derived from weighted linear regression of DEM time series. Mass change rates are estimated by assuming a density dependence on the equilibrium line altitude (e.g., Melkonian et al., 2014) and expressed as the aggregate mass loss rate of each ice field.

Figure 2. Elastic uplift modelled using dh/dt as input into the REAR toolkit. Black dots mark the locations of GPS observations (Sato et al. 2011).

Figure 3. Interferogram made from a 24-day Sentinel-1 image pair shows coherent phase up to the edge of the glaciers (shown in grey), where elastic uplift is expected to be greatest. No measurements are possible in the water areas shown in black.

RADIOACTIVE AND STABLE PALEOATMOSPHERIC METHANE ISOTOPES ACROSS THE OLDEST DRYAS-BØLLING TRANSITION FROM TAYLOR GLACIER, ANTARCTICA

Dyonisius, Michael1, Petrenko, Vasilii V.1, Smith, Andrew M.2, Hmiel, Ben1, Hua, Quan2, Yang, Bin2, Menking, James A.3, Shackleton, Sarah4

1Earth and Environmental Sciences, University of Rochester 2Australian Nuclear Science Technology Organization (ANSTO) 3College of Earth, Ocean, and Atmospheric Sciences (CEOAS), Oregon State University 4Scripps Institution of Oceanography, University of California San Diego

Methane (CH4) is the 2nd most important greenhouse gas in the atmosphere, with 84 times GWP (Global Warming Potential) of CO2 on the 20- year timescale. Understanding how the natural CH4 budget has changed in the past is important to help us constrain how CH4 budget will change in the future under anthropogenic global warming. CH4 isotopes (Δ14CH4, δ13C-CH4, δD- CH4) can be used to fingerprint the CH4 sources. We collected six large volume (~1000kg) samples of ancient ice from Taylor Glacier across the Oldest Dryas- Bølling transition for Δ14CH4, δ13C-CH4, and δD-CH4 analysis. Among the CH4 isotopes, Δ14CH4 is unique in its ability to unambiguously distinguish old (e.g. geologic emission/marine clathrates) vs. modern (e.g. tropical and boreal wetlands) CH4 sources. Taylor Glacier, Antarctica (77°44′S, 162°10′E) is one of the outlet glaciers from the East Antarctic Ice Sheet that terminates on land. In blue ice margin sites like Taylor Glacier old ice is brought up to the surface, allowing easy access and nearly unlimited amount of sample size. Our research group has identified a surface transect that spans the entire Last Deglaciation up to the early Holocene (≈20-8ka). For each samples ~1000 kg of ice cores from 10-15m deep were drilled & retrieved using the 9.5 inch diameter Blue Ice Drill (BID) made by Ice Drilling Designs & Operations (Kuhl et al., 2014). The ice was then loaded into a 670L aluminum-melting tank & melted under vacuum in the field. The liberated air was then transferred into a 35L electropolished stainless steel canister and shipped back to the US for further processing (Petrenko et al., 2016). Back in University of Rochester the CH4 in the air samples was cryogenically separated, oxidized into CO2, and then flame-sealed in a quarter inch Pyrex glass tube (Petrenko et al., 2008). The flame-sealed glass tubes were then shipped to Australian Nuclear Science Organization (ANSTO) where they were graphitized using the ANSTO “conventional” furnace (Hua et al., 2004) and then measured for 14C on the ANSTO, ANTARES AMS machine (Fink et al., 2004). Part of the air extracted was also subsampled into 2.5L NOAA style glass flasks and shipped to University of Bern for δ13C-CH47 and δD-CH48 analyses. A preliminary age scale was constructed by value matching the CH4 concentration of the samples onto the WAIS Divide continuous CH4 age scale.

Our preliminary 14CH4 data strongly suggest that the CH4 increase during the OD-BØ transition was caused by increased CH4 emissions from wetlands rather than CH4 emissions from marine clathrates or old permafrost carbon.

Baggenstos, D. (Ph.D Thesis) UC San Diego, California (2015).. Kuhl, T. W. et al. Ann. Glaciol. 55, 1–6 (2014). Petrenko, V. V. et al. Geochim. Cosmochim. Acta 177, 62–77 (2016). Petrenko, V. V. et al. Radiocarbon, 50, 53-73 (2008). Hua, Q., et al. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 223–224, 284–292 (2004). Fink, D. et al. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 223–224, 109–115 (2004). Fischer, H. et al. Nature 452, 864–867 (2008). Bock, M., et al. Atmos Meas Tech 7, 1999–2012 (2014). Reimer, P. J. et al. Radiocarbon 55, 1869–1887 (2013). Möller, L. et al. Nat. Geosci. 6, 885–890 (2013). Brook, E.J. et al. Boulder, Colorado USA: NSIDC (2015).

Figure 1. Δ14CH4, δ13C-CH4, δD-CH4 and CH4 measured in Taylor Glacier samples (blue markers, error bars represent 1-σ uncertainty) plotted against INTCAL139, EDML δ13C- CH410,EDML δD-CH4 (Bock et al. unpublished data) and WAIS Divide continuous CH411 respectively. The Taylor Glacier Δ14CH4 data has only undergone preliminary corrections for in- situ 14CH4 production. The Taylor Glacier δ13C-CH4 and δD-CH4 data have not been corrected for firn column gravitational and diffusive fractionation.

Figure 2. Enlarged version of the Δ14CH4 and CH4 measured in Taylor Glacier samples (blue marker, error bars represent 1-σ uncertainty) for the OD-BØ transition. The solid green line on the top plot is the INTACL13 data, which represent the paleoatmospheric 14CO2 at the time; dashed yellow and purple line represent the hypothetical line where the Δ14CH4 should plot if the OD-BØ CH4 if the global fossil CH4 were 10% and 20% of the global CH4 source.

CHANGES IN LAKE ICE PHENOLOGY AT LINNÉVATNET, A FRESH WATER LAKE IN THE HIGH ARCTIC OF SVALBARD

Frederiksen, Lea Maria1,2

1Department of Geosciences, University of Copenhagen, Denmark 2Department of Arctic Geology, University Centre in Svalbard, Norway

Clear signs of changes in the cryosphere are emerging due to global temperature changes. Also in the lake ice phenology, changes have been seen. According to both Leppäranta (2015) and Weyhenmeyer et al. (2011), lake ice phenology is a good climatic indicator because it is driven directly by climate, are globally available and long time records exist (Leppäranta 2015; Weyhenmeyer et al. 2011). This project focuses on the changes in ice phenology on Lake Linné, a freshwater lake in the high Arctic of Svalbard. Based on the data in this report a tendency towards a shorter ice season over the past 13 years is evident (-1.32 days year-1). In contrast to other studies, this project shows that especially the freeze-up date happens later in the year. This seems to be due to the fact that the first day with negative temperatures happens later in the season. But not only does the temperatures appears to affect the changes in freeze- and break-up dates, but also factors like wind and precipitation.

Leppäranta, M. 2015, Freezing of Lakes and the Evolution of their Ice Cover: Springer, UK. Weyhenmeyer, G. A., Livingstone, D. M., Meili, M., Jensen, O., Benson, B. & Magnuson, J. J. 2011, Large geographical differences in the sensitivity of ice-covered lakes and rivers in the Northern Hemisphere to temperature changes: Global Change Biology, v. 17, p. 268- 275.

Figure 1. Number of ice days in the ice seasons 2004-2016.

Figure 2. Graph over the first day with negative average temperature after break-up and dates for freeze-up for the years 2003-2015.

INVESTIGATING GLACIAL- INTERGLACIAL ENVIRONMENTAL CHANGES DURING THE MID- TO LATE- PLEISTOCENE: A BIOGEOCHEMICAL RECORD FROM LAKE EL’GYGYTGYN, RUSSIA

Habicht, Helen1, Castañeda, Isla S. 1, and Brigham-Grette, Julie1

1Department of Geosciences, University of Massachusetts-Amherst

Lake El’gygytgyn, Chukotka, NE Russia is a meteorite impact crater located 100 km north of the Arctic Circle. The crater was formed 3.6 Ma and has remained unglaciated since its formation, thus providing the longest continuous record of Arctic paleoclimate. The mid- to late- Pleistocene is characterized by strong alternations between warm interglacial climate conditions and cold glacial climates. Here, we present a record of environmental and climatic changes in the Arctic using terrestrial and aquatic organic biomarkers spanning Marine Isotope Stages (MIS) 8-19 (288- 800 ka), with a particular focus on MIS 11. This combination of biomarkers to allows us to present a robust record of lacustrine ecosystem sensitivity to climate change. MIS 11 is described as a “super interglacial” at Lake El’gygytgyn, with pollen data suggesting summer temperatures of ~15 oC (Melles et al., 2012). Strong warming is also recorded in the branched glycerol dialkyl glycerol tetraether record during MIS 11 (Habicht et al., in prep). Studies of pollen in the Lake El’gygytgyn core indicate the lake catchment area was forested during MIS 11, which is notable because today the lake is surrounded by tundra and the treeline lies 150 km to the south (Lozhkin et al., 2007). In contrast, the landscape was dominated by herbaceous taxa during glacial periods MIS 12 and 10 (Lozhkin and Anderson, 2013; Melles et al., 2012). In this study, terrestrial vegetation changes are inferred through analysis of plant leaf wax n-alkane distributions and concentrations of arborinol. The distribution of these compounds throughout the study interval indicates that terrestrial vegetation is highly impacted by climatic changes associated with glacial- interglacial cycles. We also examine aquatic biomarkers to explore how primary production varied during Pleistocene glacial-interglacial cycles. Previous studies have noted that organic matter preserved in Lake El’gygytgyn sediments is primarily of terrestrial origin (D’Anjou et al., 2013; Holland et al., 2013), but periods of enhanced aquatic productivity are also present. Increased aquatic productivity has been observed during MIS 11 (D’Anjou et al., 2013; Snyder et al., 2012) but also during some glacial periods (Holland et al., 2013; Snyder et al., 2012). Additionally, bulk geochemical data including Si/Ti and %TOC, which are both commonly used as primary production proxies, indicate significant variability in productivity throughout the record (Melles et al., 2012). We examine biomarkers indicative of dinoflagellates (dinosterol) and eustigmatophyte algae (C28, C30, and C32 1, 15 n-alkyl diols), as well as short- chain n-alkanes (C19, C21, and C23) as a general aquatic productivity biomarker, and identify periods of increased aquatic productivity across the study interval. Overall our results indicate both the vegetation surrounding Lake El’gygytgyn and primary

80 production within the lake experienced dramatic changes during Pleistocene climatic cycles.

D’Anjou, R.M., Wei, J.H., Castañeda, I.S., Brigham-Grette, J., Petsch, S.T., Finkelstein, D.B., 2013. High-latitude environmental change during MIS 9 and 11: biogeochemical evidence from Lake El’gygytgyn, Far East Russia. Clim. Past 9, 567–581. doi:10.5194/cp-9-567- 2013 Holland, A.R., Petsch, S.T., Castañeda, I.S., Wilkie, K.M., Burns, S.J., Brigham-Grette, J., 2013. A biomarker record of Lake El’gygytgyn, Far East Russian Arctic: investigating sources of organic matter and carbon cycling during marine isotope stages 1–3. Clim. Past 9, 243–260. doi:10.5194/cp-9-243-2013 Lozhkin, A.V., Anderson, P.M., 2013. Vegetation responses to interglacial warming in the Arctic: examples from Lake El’gygytgyn, Far East Russian Arctic. Clim. Past 9, 1211–1219. doi:10.5194/cp-9-1211-2013 Lozhkin, A.V., Anderson, P.M., Matrosova, T.V., Minyuk, P.S., 2007. The pollen record from El’gygytgyn Lake: implications for vegetation and climate histories of northern Chukotka since the late middle Pleistocene. J. Paleolimnol. 37, 135–153. doi:10.1007/s10933-006- 9018-5 Melles, M., Brigham-Grette, J., Minyuk, P.S., Nowaczyk, N.R., Wennrich, V., DeConto, R.M., Anderson, P.M., Andreev, A.A., Coletti, A., Cook, T.L., Haltia-Hovi, E., Kukkonen, M., Lozhkin, A.V., Rosen, P., Tarasov, P., Vogel, H., Wagner, B., 2012. 2.8 Million Years of Arctic Climate Change from Lake El’gygytgyn, NE Russia. Science 337, 315–320. doi:10.1126/science.1222135

DETAILED SEDIMENTOLOGICAL INVESTIGATIONS CHALLENGE OUR UNDERSTANDING OF DEPOSITION IN ARCTIC GLACIATED FJORDS

Håkansson, Lena1 and Jensen, Maria1

1Department of Arctic Geology, University Centre in Svalbard, Norway

Svalbard and the Barents Sea shelf have repeatedly been covered by large ice sheets during the Pleistocene. Most of the evidence for this comes from the marine record, but there are a hand-full of sites where the evidence for multiple glacier advances on Svalbard have been preserved in the terrestrial stratigraphic record; one of them being the coastal sections at Kapp Ekholm situated in the central parts of Svalbard (Fig.1). During the 1960’s-1990’s several studies investigated the stratigraphy at Kapp Ekholm. The study of Mangerud and Svendsen (1992) identified four diamict beds which were interpreted as subglacial till interlayered by sorted sediments suggested to have been deposited during a falling relative sea level. Thus, Kapp Ekholm became the only locality on Svalbard with evidence of four successive glaciations and intervening marine intervals and therefore came to form the backbone of the glaciation curve for the western margin of the Barents Sea Ice sheet (Mangerud et al 1998). However, the coastal sections at this site are dissected by several gullies making correlation challenging and the discontinuous lateral distribution of the deposits has given rise to discussion on the stratigraphy. Now, 25 years have passed but the study by Mangerud and Svendsen (1992) still stands as the key reference for the stratigraphy and paleoenvironmental reconstruction of the Kapp Ekholm. In this time our knowledge about Arctic depositional environments, glacial sedimentology and the dynamics of the Barents Sea Ice Sheet has advanced considerably. In the present study we take a modern approach to test whether or not the stratigraphy and the paleoenvironmental interpretations need to be revised. Here we use a systematic approach to describing the sedimentology and internal geometry by applying architectural element analysis. Architectural element analysis was originally developed for describing the internal geometry of sorted clastic sedimentary deposits (Miall, 1985, 1988). The method emphasises the description of lithological assemblages by defining their bounding surfaces; bounding surface hierarchy is assigned based on the degree of environmental change represented at each facies contact. Architectural elements are packages of genetically related sediments and they are bounded by 4th order or higher rank surfaces (Miall, 1988; Boyce and Eyles 2000). In addition we use facies analysis, clast morphology and fabric analysis. We identify eight different architectural elements named descriptively based on dominant lithofacies and geometry (mud horizon, massive sand lens, coarse-grained lens, diamict sheet, loosely compacted diamict sheet, silty diamict sheet and diamict lenses 1-3). These act as the basic building blocks of the sedimentary succession and are identified repeatedly throughout the sections. Our investigations together with new IRSL ages (Eccleshall et al 2016) confirm the stratigraphy originally presented by Mangerud and Svendsen (1992) and does not change the

82 implications for the glaciation curve suggesting that the Kapp Ekholm deposits represent two glacial/interglacial cycles. However, it revises the paleoenvironmental interpretations and emphasises how Arctic Quaternary deposits often represent a much more fragmented time window than traditionally assumed. We suggest that the entire sedimentary succession was deposited during relative sea levels higher than present. The analyses of the diamict sheet and diamict lense elements indicate that these are to a large extent made up by ice proximal glaciomarine deposits with only thin horizons subglacial sediments. Our results suggest that the glacigenic sediments at Kapp Ekholm were deposited at times when the glaciers in the fjord were only slightly more extensive than at present (see modern ice margins in Fig. 1B), most likely during the final retreat phase of large-scale glaciations (Landvik et al 2013). The sedimentary succession represented by our mud horizon-, massive sand lens- and coarse grained lens elements has previously been interpreted as evidence for continuous deposition during a falling relative sea level. Instead, we sugget that these architectural elements were deposited during a relatively short time. The massive sand lenses elements are interpreted as fans deposited by sediment gravity flows emanating from the mouth of sediment-laden creeks. The coarse grained lenses are interpreted to represent spit propagation over the sandy fans, building up to the beach. Modern coastal environments in Svalbard are characterised by high sediment supply and highly dynamic patterns, and migration of spits and fans takes place on a m/yr scale.

Boyce, J.I., Eyles, N., 2000: Architectural element analysis applied to glacial deposits. Internal geometry of a late Pleistocene till sheet, Ontario, Canada: Geological Society of America Bulletin, v. 112, p. 98-118. Eccleshall, S., Hormes, A., Hovland, A., Preusser, F., 2016: Constraining the chronology of Pleistocene glaciations on Svalbard. Kapp Ekholm re-visited: Boreas, v. 45, p 790-803 Landvik, J., Alexanderson, H., Henriksen, M., Ingolfsson, O., 2013: Landscape imprints of changing glacial regimes during ice-sheet build-up and decay: a conceptual model from Svalbard. Quaternary Science Reviews, v. 92, p. 258-268 . Mangerud, J., Svendsen, J.I., 1992: The last interglacial-glacial period on Spitsbergen, Svalbard. Quaternary Science Reviews, v. 11, p. 633-664 Mangerud, J. Dokken, T., Hebbeln, D., Heggen, B., Ingolfsson, O., Landvik, J., Mejdahl, V. Svendsen, J.I., Vorren, T.O., 1998: Fluctuations of the Svalbard–Barents Sea Ice Sheet during the last 150,000 years. Quaternary Science Reviews, v. 17, p. 11–42. Miall, A.D., 1985: Architectural-element analysis: A new method of facies analysis applied to fluvial deposits. Earth-Science Reviews, v. 22, p. 261-308. Miall, A.D., 1988: Architectural elements and bounding surfaces in fluvial deposits: anatomy of the Kayenta Fm. (Lower Jurassic), southwest Colorado. Sedimentary Geology, v. 55, p. 233-262.

Figure 1. Map showing the Svalbard archipelago. The dark blue line marks the NW Barents Sea shelf break and the ice marginal position during the Last Glacial Maximum (LGM), and earlier glaciations. The Kapp Ekholm site is marked with a red star. B: The location of the Kapp Ekholm site is marked with a white star.

PROVENANCE, STRATIGRAPHY, AND CHRONOLOGY OF HOLOCENE TEPHRA ARCHIVED IN LAKE SEDIMENT FROM VESTFIRÐIR (NW), ICELAND

Harning, David J.1, Thórdarson, Thorvaldur2, Zalzal, Kate1,2, Geirsdóttir, Áslaug2, Miller, Gifford H.1

1INSTAAR and Department of Geological Sciences, University of Colorado- Boulder 2Faculty of Earth Sciences, University of Iceland, Reykjavík, Iceland

Tephrochronology facilitates the interpretation and cross comparison of terrestrial and marine paleoclimate records in and around Iceland. The Holocene tephra record on the Vestfirðir peninsula, NW Iceland, has until now been poorly known. Based on major elemental chemistry, we present a holistic tephra stratigraphy and chronology comprised of 20 tephra units from four lakes located on northeastern Vestfirðir. Key tephra of known age include the 10 ka Grímsvötn tephra layer series, the renamed Hekla VF (originally “AlB-1”), Hekla T, Hekla 4?, Hekla B, Snæfellsjökull-1, Landnám and Hekla 1693. Inconsistencies of tephra preservation between lake records suggest that variable ash plume trajectories and/or glacier/ice covered lakes were potential processes controlling tephra distribution throughout the Holocene. The northernmost lake, Skorarvatn, archives three tephra layers consistent with the 10 ka Grímsvötn tephra layer series and correlative to the well-known Saksunarvatn tephra. Radiocarbon- dated macrofossils bounding Skorarvatn’s upper and basal tephra layers in the 10 ka series suggest that they were produced by three large, successive phreatoplinian eruptions from Grímsvötn over ~240 years. The 10 ka Grímsvötn tephra series has already been shown to be useful in constraining early Holocene limits of the local ice cap, Drangajökull. The composite Vestfirðir tephra stratigraphy and chronology presented here will allow better age control and correlation of climate changes in the northern North Atlantic region.

UNDERSTANDING THE PRODUCTION AND RETENTION OF IN SITU COSMOGENIC 14C IN POLAR FIRN

Hmiel, Benjamin1, Petrenko, V.V. 1, Dyonisius, M. 1, Smith, A.M.2, Schmitt, J.3, Buizert, C.4, Place, P.F1, Harth, C.5, Beaudette, R.5, Hua, Q.2, Yang, B.2, Vimont, I.6, Kalk, M.4, Weiss, R.F5, Severinghaus, J.P.5, Brook, E.J.4, White, J.W.C.5

1Department of Earth and Environmental Sciences, University of Rochester 2Australian Nuclear Science and Technology Organization, Australia 3Oeschger Centre for Climate Change Research, University of Bern, Switzerland 4College of Earth, Ocean and Atmospheric Sciences, Oregon State University 5Scripps Institution of Oceanography, University of California San Diego 6INSTAAR and Department of Geological Sciences, University of Colorado- Boulder

Radiocarbon in CO2, CO and CH4 trapped in polar ice is of interest for dating of ice cores, studies of past solar activity and cosmic ray flux, as well as studies of the paleoatmospheric CH4 budget. The major difficulty with interpreting 14C measurements in ice cores stems from the fact that the measured 14C represents a combination of trapped paleoatmospheric 14C and 14C that is produced within the firn and ice lattice by secondary cosmic ray particles. This in situ cosmogenic 14C component in ice is at present poorly understood. Prior ice core 14C studies show conflicting results with regard to the retention of in situ cosmogenic 14C in polar firn and partitioning of this 14C among CO2, CO and CH4. Our study aims to comprehensively characterize the 14C of CO2, CO, and CH4 in both the air and the ice matrix throughout the firn column at Summit, Greenland. We will present preliminary measurements of 14C in Summit firn air and the firn matrix, along with initial interpretations with regard to in situ cosmogenic 14C retention. Preliminary results from firn air indicate a 14CO increase with depth in the lock-in zone resulting from in situ production by muons, as well as a lock-in zone 14CO2 bomb peak originating from nuclear testing in the late 1950s and early 1960s. A decrease in 14CH4 with depth is observed in the lock-in zone that is in agreement with observations of increasing atmospheric 14CH4 over the past several decades. We observe that only a small fraction of in-situ produced 14CO, 14CH4 and 14CO2 is retained in the firn matrix. Additionally, we describe progress in the development of a field-portable sublimation apparatus for extraction of CO2 from firn and ice for 14C measurements.

RECONSTRUCTING THE GLACIAL HISTORY OF MIDTRE LOVÉNBREEN, SVALBARD

Holmlund, Erik S.1 and Håkansson, Lena2

1Department of Physical Geography, Stockholm University 2Department of Arctic Geology, University Centre in Svalbard, Norway

The archipelago of Svalbard is covered by about 60% in ice (Hagen, et al., 2003), and its glaciers with their proglacial environments are widely used in historical climate reconstructions. But many glaciers in Svalbard exert a so called surge-type behaviour (Hagen, et al., 2003; Farnsworth, et al., 2016), having a cyclical advance and retreat of a glacier’s terminus that cannot be directly connected to climate change (Hagen, et al., 2003). This process obstructs the ease of reconstruction as some of these glaciers’ changes are not only related to climate and topography, which sets Svalbard apart from most other locations. The surge-type behaviour is not yet perfectly understood and there is an ongoing debate on how many surge-type glaciers there are in Svalbard, and which might have surged in the past. In this study, drone imagery has been used to map the geomorphology of the forefield of Midtre Lovénbreen in Svalbard, see Figure 1. The mapping produced an orthophoto with a resolution of 8 cm/pixel, see Figure 2, as well as a digital elevation model. In addition, we have used documented observations of terminus positions (Norsk Polarinstitutt), mass balance records (WGMS, 2016), orthophotos from Norsk Polarinstitutt, satellite imagery from the Landsat program, and old photographs to reconstruct the glacial history of Midtre Lovénbreen since the end of the Little Ice Age (LIA). Here we present evidence for three glacier advances, within the two past centuries, at an interval of ca 50 years; the oldest occurred near the end of the LIA, the second is represented by a large transverse ridge which formed between 1948 and 1962, and the youngest occurred between 1994 and 1998. Many landforms indicating the glacier’s historical thermal regime were identified, filling most criteria of what is being thought to enable a surge-type behaviour (Ingólfsson, et al., 2016). These landforms include flutes, elongated landforms and drumlinoids, and a terminal moraine with a steep distal edge preceded by a hummocky gentle inner slope with frequent dead ice hollows, see Figure 3. Concertina eskers have previously been identified (Hansen, 2003) and they were also identified in this study. They are particularly of interest, since they are used as key landforms for identifying surge-type glaciers (Ingólfsson, et al., 2016). A surge-type behaviour for Midtre Lovénbreen in Svalbard has been suggested for many years, but is not widely supported due to previous lack of enough evidence. This study tests the hypothesis that Midtre Lovénbreen is a surge-type glacier, based on this newly collected material. Midtre Lovénbreen is the most studied glacier in Svalbard (e.g. Hagen, et al., 1993, Bennet & Evans, 2010), and the landsystem model for small polythermal glaciers (Glasser & Hambrey, 2003). The glacier is widely agreed

87 upon to not be a surge-type glacier, even though some key landforms exist (Hansen, 2003). Thus, Midtre Lovénbreen challenges the methods of identifying surge-type glaciers, making it an interesting subject of research. The use of this glacier as a reference could also be questioned if it is proven to exert a surge- type behaviour.

Bennet, D. I., Evans, D. J. (2010). Glaciers & Glaciation 2nd Edition. London: Hodder Arnold Publication. Farnsworth, W., Ingólfsson, Ó., Retelle, M., & Schomacker, A. (2016). Over 400 previously undocumented Svalbard surge-type glaciers identified. Geomorphology, 264, 52-60. Hagen, J. O., Kohler, J., Kjetil, M., & Winther, J.-G. (2003). Glaciers in Svalbard: mass balance, runoff and freshwater flux. Polar Research, 22(2), 145-159. Hagen, J. O., Liestøl, O., Roland, E., & Jørgensen, T. (1993). Svalbard, Glacier atlas of Svalbard and Jan Mayen. Oslo: Norsk Polarinstitutt. Hamberg, A. (1932). Struktur und bewegungs vorgänge im Gletschereise. Naturwissenschaftlige untersuchungen des Sarekgebirges in SchwedischLappland, III(1), 69-129. Hansen, S. (2003). From surge-type to non-surge type glacier behaviour: Midtre Lovénbreen, Svalbard. Annals of Glaciology 36, 97-102. Johnson, M. D. (2016). Glacial geological studies of surge-type glaciers in Iceland — Research status and future challenges. Earth-Science Reviews 152, 37-69. Norsk Polarinstitutt. (2016). Retrieved from http://www.npolar.no. World Glacier Monitoring Service. (2016). Retrieved from http://wgms.ch/

Figure 1. Midtre Lovénbreen in Kongsfjorden, Svalbard, 11 September 2016. By Erik S. Holmlund.

Figure 2. Produced orthophoto with a resolution of 8 cm/pixel.

Figure 3. Geomorphological map of the Midtre Lovénbreen forefield.

NEW CONSTRAINTS ON THE TIMING AND PATTERN OF DEGLACIATION IN THE HÚNAFLÓI BAY REGION OF NORTHWEST ICELAND USING COSMOGENIC 36CL DATING AND GEOMORPHIC MAPPING

Houts, Amanda N.1, Licciardi, Joseph M.1, Principato, Sarah M.2, Zimmerman, Susan H.3, Finkel, Robert C.3

1Department of Earth Sciences, University of New Hampshire 2Department of Environmental Studies, Gettysburg College 3Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory

Understanding the evolution and timing of changes in ice sheet geometry and extent in Iceland during the Last Glacial Maximum (LGM) and subsequent deglaciation continues to stimulate much active research. Though many previous studies have advanced our knowledge of Icelandic ice sheet history preserved in marine and terrestrial settings (e.g., Andrews et al., 2000; Norðdahl et al., 2008), the timing of ice margin retreat remains largely unknown in several key regions. Recently published 36Cl surface exposure ages of bedrock surfaces and moraines in the West Fjords (Brynjólfsson et al., 2015) contribute important progress in establishing more precise age control of ice recession in northwest Iceland. In another recent study, the spatial pattern and style of deglaciation in northern Iceland have been revealed through geomorphic mapping and GIS analyses of glacial landforms (Principato et al., 2016). Additional insight comes from updated numerical modeling reconstructions, which now provide a series of glaciologically plausible Icelandic ice sheet configurations from the LGM through the last deglaciation (Patton et al., 2017). However, the optimization of ice sheet model simulations relies on critical comparisons with the available empirical record of glacial-geologic evidence and chronological control, which remains relatively limited and sparsely distributed throughout Iceland. Our investigation is motivated by the need for more accurate constraints on the deglacial history in northern Iceland, where dated terrestrial records of ice margin retreat are particularly scarce. Here we present a suite of 36Cl exposure ages on glacially scoured bedrock and erratics as well as striation measurements from the Húnaflói Bay region that elucidate the chronology and pattern of ice sheet margin retreat in northern Iceland during the last deglaciation. Results indicate that the ice margin retreated to positions inside the present-day coastline near Húnaflói Bay between 10.2-8.5 ka. Dated ice margin positions reported here are combined with ice sheet surface profiles derived from previously dated tuyas in the northern volcanic zone (Licciardi et al., 2007), and reveal a broad and consistent pattern of ice surface thinning and margin retreat across northern Iceland from ~11-10 ka. The orientations of ice flow indicators measured in this study align with streamlined landforms in three valleys south of Húnaflói Bay, supporting the presence of paleo-ice stream activity in northern Iceland which may have provided a facilitating mechanism for ice to reach the shelf-slope break

(Principato et al., 2016). The timing of ice margin retreat in northern Iceland is concurrent with documented periods of rapid glacier recession in both Greenland (Young et al., 2013) and Norway (Briner et al., 2014; Stroeven et al., 2016), suggesting a common driver of deglaciation in the circum-North Atlantic region that may have involved perturbations in ocean circulation and attendant changes in temperature. The improved terrestrial chronology of glacial thinning, retreat, and ice stream activity in this region will inform future glaciological modeling studies in Iceland (e.g., Patton et al., 2017).

Andrews, JT et al. 2000, The N and W Iceland Shelf: Insights into Last Glacial Maximum ice extent and deglaciation based on acoustic stratigraphy and basal radiocarbon AMS dates: Quat. Sci. Rev. 19,619–19,631. Briner, JP et al. 2014, A 10Be chronology of south-western Scandinavian Ice Sheet history during the Lateglacial period: J. Quat. Sci. 29: 370–380. Brynjólfsson, S et al. 2015, Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajökull region, northwest Iceland: Quat. Sci. Rev. 126, 140–157. Licciardi, JM et al. 2007, Glacial and volcanic history of Icelandic table mountains from cosmogenic 3He exposure ages: Quat. Sci. Rev. 26, 1529–1546. Norðdahl, H et al. 2008, Late Weichselian and Holocene environmental history of Iceland: Jökull 58, 343–364. Patton, H et al. 2017, The configuration, sensitivity and rapid retreat of the Late Weichselian Icelandic ice sheet: Earth-Sci. Rev. 166, 223–245. Principato, SM et al. 2016, Using GIS and streamlined landforms to interpret palaeo-ice flow in northern Iceland: Boreas 45, 470–482. Stroeven, AP et al. 2016, Deglaciation of Fennoscandia: Quat. Sci. Rev. 147, 91–121. Young, NE et al. 2013, Age of the Fjord Stade moraines in the Disko Bugt region, western Greenland, and the 9.3 and 8.2 ka cooling events: Quat. Sci. Rev. 60, 76–90.

GEOGRAPHIC VARIATION OF CIRQUES ON ICELAND: FACTORS INFLUENCING CIRQUE MORPHOLOGY

Ipsen, Heather A.1, Principato, Sarah M.2, Grube, Rachael E.2, Lee, Jessica F.3

1Department of Earth Sciences, Syracuse University 2Department of Environmental Studies, Gettysburg College 3Department of Geological Sciences, University of Delaware

Cirques are one of the most common glacial landforms in alpine settings. They also provide important paleoclimate information (e.g. Meierding 1984; Evans 2006). The purpose of this study is to fill in gaps in the climate record of Iceland by conducting a quantitative analysis of cirques in three regions in Iceland: Tröllaskagi, the East Fjords, and Vestfirðir. Iceland, located in the center of the North Atlantic Ocean, contains many small glaciers, in addition to large ice caps. The glaciers on Iceland are particularly sensitive to variations in oceanic and atmospheric circulation (Andresen et al. 2005; Geirsdóttir et al., 2009; Ólafsdóttir et al. 2010). Iceland thus provides an excellent case study to examine factors influencing glacial landforms such as cirques. Our study identifies at least 483 cirques using Google Earth and the National Land Survey of Iceland Map Viewer. We use ArcGIS to measure length, width, aspect, latitude and distance to coastline of each cirque. A slope raster is constructed from the first derivative of the Digital Elevation Model (DEM) of the study area in order to determine the location of the headwall, cirque floor, and toewall of each cirque. Paleo-equilibrium-line altitudes (ELAs) of paleo-cirque glaciers are calculated using the altitude-ratio method, the cirque floor method, and a minimum point method (e.g. Meierding 1982; Porter 2001; Principato and Lee 2014). We compute average aspect using an inverse tangent function based on lines constructed for the altitude-ratio method. The mean paleo-ELA values in Tröllaskagi, the East Fjords, and Vestfirðir are approximately 788 m, 643 m, and 408 m, respectively. Interpolation maps of ELA distributions in all three regions demonstrate a positive relationship between paleo-ELA and distance to coastline. There is a negative relationship between paleo-ELA and latitude in Tröllaskagi and Vestfirðir, but no relationship exists in the East Fjords. The modal orientation of the cirques in Tröllaskagi and Vestfirðir is northeast, while the orientation of cirques in the East Fjords is north. Paleo- wind reconstructions for the LGM show that modal aspect aligns opposite prevailing wind directions in each of the three regions (Bush and Philander 1999). Cirque length is similar in Tröllaskagi and the East Fjords, but cirques are approximately 200 m shorter in Vestfirðir. Cirque widths are similar in all three regions. Comparisons with a global dataset of cirque analyses compiled by Barr and Spagnolo (2015) show that cirques in Iceland are generally smaller and more circular in shape than cirques in other regions of the world. However, cirques on Iceland are particularly comparable to those in Kamchatka, Russia, likely due to similarities in study site characteristics (e.g. influence of ocean currents and location on a volcanically active island).

Our results are significant because they reiterate the idea that access to a moisture source is key in determining ELA elevation (Principato and Lee 2014; Barr and Spagnolo 2015). Cirque aspect is influenced by wind direction, and cirque size and shape depends on bedrock structure. The difference in cirque morphometry on Iceland and globally is indicative of the importance of specific local weather conditions in dictating the formation and characteristics of glacial landforms. As previous research has shown (e.g. Barr and Spagnolo 2015; Delmas et al. 2015), this study also demonstrates that cirques are complex landforms that cannot likely be explained by a single definitive relationship between their formation processes and structure.

Andresen, C. S., et al. 2005: Holocene climate variability at multidecadal time scales detected by sedimentological indicators in a shelf core NW off Iceland. Marine Geology v. 214, p. 323–338. Barr, I., Spagnolo, M., 2015. Understanding controls on cirque floor altitudes: Insights from Kamchatka. Geomorphology, v. 248, p. 1–13. Bush, A., Philander, G., 1999. The climate of the Last Glacial Maximum: Results from a coupled atmosphere-ocean general circulation model. Journal of Geophysical Research, v. 104, p. 24509 –24525. Delmas, M. et al. 2015. A critical appraisal of allometric growth among alpine cirques based on multivariate statistics and spatial analysis. Geomorphology, v. 228, p. 637–652. Geirsdóttir, A., et al. 2009. Holocene and latest Pleistocene climate and glacier fluctuations in Iceland. Quaternary Science Reviews, v. 28, 2107–2118. Meierding, T. C. 1982: Late Pleistocene glacial equilibrium-line altitudes in the Colorado Front Range: a comparison of methods. Quaternary Research v. 18, p. 289–310. Ólafsdóttir, S., et al. 2010: Holocene variability of the North Atlantic Irminger current on the south- and northwest shelf of Iceland. Marine Micropaleontology v. 77, p. 101–118. Porter, S. C. 2001: Snowline depression in the tropics during the Last Glaciation. Quaternary Science Reviews v. 20, p. 1067–1091. Principato, S.M., Lee, J.F., 2014. GIS analysis of cirques on Vestfirðir, northwest Iceland: implications for palaeoclimate. Boreas, v. 43, p. 807–817.

MODERN FORAMINIFERAL ASSEMBLAGES IN THE PETERMANN FJORD, NW GREENLAND

Jennings, Anne1, Mix, Alan2, Walczak, Maureen2, Reilly, Brendan2, Stoner, Joe2, Cheseby, Maziet2

1INSTAAR and Department of Geological Sciences, University of Colorado- Boulder 2College of Earth, Ocean, and Atmospheric Sciences (CEOAS), Oregon State University

The Petermann Glacier, northwest Greenland, is one of only 4 remaining Greenland Ice Sheet outlet-glaciers terminating with a floating ice tongue. Large calving events in 2010 and 2012 reduced the length of the Petermann ice tongue by c. 25 km, allowing exploration of newly uncovered seafloor during the Petermann 2015 Expedition with the Swedish icebreaker Oden. A team from the British Antarctic Survey successfully collected sediment cores from beneath the ice tongue at sites 15 and 25 km from the grounding line of the Petermann Glacier. Samples of the upper 1 to 2 cm of the seafloor sediments were taken from the two sub ice-tongue cores and from 12 multicore sites in the Petermann Fjord and adjoining Hall Basin to document modern foraminiferal assemglages. We explore the differences and similarities in the modern foraminiferal assemblages from these sites to gain a better understanding of the environmental preferences of the species and as a basis for interpreting the foraminiferal assemblage analysis underway in several sediment cores. The core-top samples were sealed in vials with a mixture of buffered alcohol and a biological stain (Rose Bengal) so that specimens living at the time of collection could be identified. Samples were sieved at 63 µm, stored in a buffered alcohol and water solution and counted wet to preserve delicate calcareous and agglutinated tests. Analyses so far have revealed 49 calcareous and 26 agglutinated benthic species. The greatest diversity and faunal abundance is in the outer shelf site and the least diversity and abundance is in the sub ice tongue site closest to the grounding line. Living fauna ranged between 10 and 34% and in many samples the living fauna is found embedded in organic material. The sub ice tongue sites had more agglutinated than calcareous fauna. The fauna of the middle to outer fjord sites were comprised of 80% or more calcareous species. The most common calcareous species are Stetsonia horvathi, Epistominella arctica, Elphidium excavatum f clavata, and Cassidulina neoteretis. S. horvathi, a tiny species that has been associated with perennial sea ice in the Arctic Ocean, is common in the fjord and beneath the ice tongue. Epistominella arctica, another tiny species, is rare under the ice shelf, and becomes more common with distance away from the ice margin. It exceeds S. horvathi in abundance on the shelf. E. excavatum, a species associated with turbid meltwater and unstable conditions is dominant (up to 50%) in the middle to outer fjord. C. neoteretis, a species associated with stratified water column and chilled Atlantic Water is

95 found in every sample except the most grounding line proximal site; it is common in the outer fjord and the shelf. The sub-ice shelf sites are dominated by agglutinated species Textularia earlandi, Trochammina quadriloba and Rhizammina algaeformis, a tubular species with very low preservation potential. These three species occur in much lower percentages at sites beyond the ice shelf. Nonionella iridea and Ceratobulimina arctica occur in all sites, but only tiny specimens of these species are found beneath the ice shelf.

FINAL DEGLACIATION AND MARINE INCURSION: A VIEW FROM WESTERN HUDSON BAY

Kelley, S.E.1, Gauthier, M.S.2, Ross, M.1, Hodder, T.J.2

1Department of Earth and Environmental Sciences, University of Waterloo 2Manitoba Geological Survey

The final deglaciation of Hudson Bay was a major early-mid Holocene event, marked by catastrophic drainage of Lake Agassiz/Ojibway, rapid collapse of ice over the bay, and marine incursion by the Tyrrell Sea. The timing of deglaciation is still uncertain, owing to a paucity of field data. Evidence from marine sediment cores track the initial retreat of the Laurentide Ice Sheet (LIS) margin from western Hudson Strait by 9.7 ± 0.1 cal ka (Laymon, 1992), with the initial deglaciation of Hudson Bay prior to 8.7 ± 0.1 cal ka near Coats Island (Andrews and Falconer, 1969). Terrestrial evidence corroborates this timing of deglaciation, with ice remaining longer on the Fox Peninsula of Baffin Island, until at least 8.5 ± 0.1 cal ka (Utting et al., 2016) and at least 8.3 ± 0.1 ca ka (Ross et al., 2012) on Southampton Island. Chronology for the deglaciation of inner Hudson Bay comes from minimum limiting ages ringing the bay, indicating deglaciation and marine inundation by 8.3 ± 0.3 cal ka or possibly as early as 8.6 ± 0.3 cal ka from the eastern margin of the bay (Lajeunesse and Allard, 2003) and as early as 8.6 ± 0.4 cal ka from western Hudson Bay. To the south and west, glacial Lakes Agassiz and Ojibway coalesced during the early Holocene ringing the southern margin of the Hudson Bay Sector of the LIS, and catastrophically draining at ~8.2 ka. The influx of freshwater to the North Atlantic attributed to have caused the 8.2 ka event registered in Greenland ice cores. Model simulations suggest the severity and duration of the 8.2 ka event may also be tied to freshwater input from the collapse of the LIS over Hudson Bay, adding another piece to this climatic puzzle (Wagner et al., 2013). Regardless of cause, the cryosphere response to this climatic event is recorded in the moraine records on Greenland and Baffin Island (Young et al. 2012). Here we present radiocarbon and stratigraphic evidence from western Hudson Bay, in the Hudson Bay Lowlands, for glacial lake drainage, local deglaciation, and marine incursion. Local stratigraphy in the area records the presence of glaciolacustrine sediments conformably overlain by glaciomarine sediments, with a few localities with till overlying glaciolacustrine sands, providing evidence of late-stage advances of the LIS. We document the presence of freshwater molluscs at 8.1 ± 0.07 cal ka and 8.0 ± 0.04 cal ka, indicating marine and ice-free conditions. Conversely, numerous radiocarbon ages from the same region and similar elevation place marine incursion at ~8.1 cal ka, possibly as early as 8.5 cal ka. We note that these ages are similar to the published 8.3 ± 0.1 cal ka age obtained from Southampton Island, and 8.3 ± 0.3 cal ka age from eastern Hudson Bay, indicating rapid collapse of ice within Hudson Bay, a concept supported by marine geomorphologic evidence. The chronostratigraphic framework from our

97 work on the western margin of Hudson Bay provides a perspective on the dynamic nature of the LIS during the early- to mid-Holocene and the speed at which the center of the LIS collapsed. This allows for a view of a possible paleo- analog to the future condition of modern ice sheets with beds that are isostatically depressed below sea level.

Andrews, J.T., Falconer, G., 1969. Late glacial and postglacial history and emergence of the Ottawa Islands, Hudson Bay, Northwest Territories: evidence on the deglaciation of Hudson Bay. Can. J. Earth Sci. 6, 1263-1276. Lajeunesse, P. and Allard, M., 2003. The Nastapoka drift belt, eastern Hudson Bay: implications of a stillstand of the Quebec Labrador ice margin in the Tyrrell Sea at 8 ka BP. Canadian Journal of Earth Sciences. 40, 65-76. Laymon, C.A., 1992. Glacial geology of western Hudson Strait, Canada, with reference to Laurentide Ice Sheet dynamics. Geol. Soc. Am. Bull. 104, 1169-1177. Ross, M., Utting, D. J., Lajeunesse, P. Kosar, K. G. A., 2012. Early Holocene deglaciation of northern Hudson Bay and Foxe Channel constrained by new radiocarbon ages and marine reservoir correction. Quaternary Research. 78, 82–94. Utting, D. J., Gosse, J. C., Kelley, S. E., Vickers, K. J., Ward, B. C., Trommelen, M. S., 2016. Advance, deglacial and sea-level chronology for Foxe Peninsula, Baffin Island, Nunavut. Boreas. 45, 439-454. Wagner, A.J., Morrill, C., Otto-Bliesner, B.L., Rosenbloom, N. and Watkins, K.R., 2013. Model support for forcing of the 8.2 ka event by meltwater from the Hudson Bay ice dome. Climate dynamics, 41, 2855-2873. Young, N.E., Briner, J.P., Rood, D.H. and Finkel, R.C., 2012. Glacier extent during the Younger Dryas and 8.2-ka event on Baffin Island, Arctic Canada. Science, 337, 1330-1333.

A SEISMIC PERSPECTIVE ON THE EVOLUTION OF THE NW GREENLAND ICE SHEET

Knutz, Paul C.1, Gregersen, Ulrik1, Dybkjær, Karen1, Sheldon, Emma1, Hopper, John R. 1

1Geological Survey of Denmark and Greenland, Denmark

Seismic mapping has been carried out within the Neogene-Quaternary interval of the NW Greenland shelf margin using a regional seismic data grid (TGS, 2007-2010). The study reveals geomorphic surfaces and depositional features that illustrate the transition from a marine setting dominated by contour currents to onset of shelf edge progradation related to drainage of the northern Greenland Ice Sheet into Baffin Bay (Knutz et al., 2015). This glacial drainage, mainly through fast-flowing ice streams, has produced large sedimentary accumulations referred to as the Melville Bugt and Upernavik trough-mouth fans (TMF) (Fig. 1). Seismic mapping and imaging of these TMF systems allows spatial depositional patterns to be resolved, that result from advance and retreat phases of the northern Greenland Ice Sheet since the onset of shelf-based glaciation. The TMF’s are constructed by sequentially organized prograding depositional units, bounded by glacial erosion surfaces that extend into steeply dipping clinoforms on the outer margin (Fig. 2). South of the main trough, the erosion surfaces that separate each of the prograding units are onlapped by laterally continuous strata that may represent marine interglacial deposits. By mapping the glacial unconformities and their continuation into the basin 11 prograding units have been identified. Thickness maps reveal the depositional history of the TMF’s from linear shelf edge advances to development of the recent trough mouth depocentres. The Melville Bugt TMF is subject to an IODP drilling proposal, aimed at understanding causes and mechanisms that govern the dynamics and long-term evolution of the Greenland Ice Sheet. This presentation will provide an overview of the seismic stratigraphy and chronological constraints from regional seismic well-ties, and discuss the implications for Greenland Ice Sheet evolution.

Knutz, P.C., Hopper, J.R., Gregersen, U., Nielsen, T., Japsen, P., 2015, A contourite drift system on the Baffin Bay-West Greenland margin linking Pliocene Arctic warming to poleward ocean circulation: Geology, v. 43, p. 907-910.

Figure 1. Topology of the Melville Bugt and Upernavik trough-mouth fans on the NW Greenland - Baffin Bay margin.

Figure 2. Seismic section with key horizons that define the prograding units of the Melville Bugt trough-mouth fan. Pre-fan deposits showing contourite features (between b1 and c1) are probably of Pliocene age. Seismic profile courtesy of TGS.

100

SOIL DEPOSITS RECORD HOLOCENE CLIMATE AND LANDSCAPE DISTURBANCE IN THE HIGHLANDS OF ICELAND

Larsen, Darren1, Kumar, Dervla M.2, Geirsdóttir, Áslaug3, Miller, Gifford4

1Department of Geology, Occidental College 2Department of Geology and Environmental Science, University of Pittsburgh 3Department of Earth Sciences, University of Iceland 4INSTAAR and Department of Geological Sciences, University of Colorado- Boulder

Paleoclimate investigations from Iceland reflect high-magnitude Holocene climate changes that greatly exceeded the Arctic average, emphasizing the sensitivity of terrestrial environments in the North Atlantic region to shifts in oceanic and atmospheric circulation. A suite of climate records derived from Icelandic lake sediments describe a pattern of early Holocene warmth followed by persistent gradual cooling that was interrupted by a series of abrupt cold excursion events. Icelandic lake records are often securely-dated, continuous in nature, and contain multiple climate, environmental, and glacier indicators that can be analyzed at high temporal resolution. However, despite their importance, these climate datasets are seldom quantitative in measure. Here, we explore the potential for generating quantitative reconstructions of Holocene climate in Iceland using the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soil deposits. BrGDGTs are bacterial membrane-spanning lipids that are present in a wide array of terrestrial environments, including soils, peat bogs, and lakes. There are fifteen primary compounds that vary in the degree of methylation (4-6 methyl groups) and cyclization (0-2 cyclopentane moieties) of the alkyl chains. In soils, changes in the methylation and cyclization of brGDGTs have been empirically related to mean annual air temperature (MAT) and soil pH. Moreover, a recent advance in the LC/MS analysis of brGDGTs revealed the existence of structural isomers with methyl groups at the C6 position rather than C5. The separate quantification of the brGDGT isomers has since improved the MAT calibrations, in addition to providing valuable insights into the relationship between brGDGT-producers, their membrane lipids, and the environment. We excavated soil stratigraphic sections in the Hvítárnes region (~450 m a.s.l.), central Icelandic highlands. Mean annual and summer (JJA) temperature and precipitation measured nearby at Hveravellir (~640 m a.s.l.) are 0.9°C, 6.4°C, and 730 mm, respectively (1966 to 2003 reference period). Similar to much of the central highlands, large portions of the regional landscape are covered by barren volcanic deserts reflecting active soil erosion and desertification processes. However, relict soil accumulations are present in isolated pockets and near streams and wetlands. These soils are typically andosols and are dominated by inputs of eolian and volcanic material. Soil profiles in this study range in thickness from ~1.9 m to >5.2 m, and contain a series of diagnostic tephra layers from volcanic eruptions of known age. The tephrostratigraphy in the Hvítárnes region is well established from soil and lake

101 sequences, including the nearby Hvítárvatn lake record. Prominent tephra deposits identified in the soil profiles provide a secure chronologic framework and confirm generally continuous accumulation during the past ~10ka. Coupled and abrupt increases in grain size and accumulation rates after ~1300 AD are observed at each site and document the initiation of prevalent soil erosion during recent times. Five soil profiles were sampled and analyzed for bulk organic matter properties (e.g. TOC, 13C, C:N) and brGDGT distributions. BrGDGT-derived paleotemperatures were calculated for various intervals during the Holocene using multiple published transfer functions. Emerging results are promising and demonstrate a temperature history that resembles that inferred by Icelandic lake sediment proxy records. In addition, reconstructed temperatures for the uppermost soil samples are well aligned with a previous brGDGT calibration study in Iceland. A temperature estimate of ~6.4°C for the near-surface of one soil profile suggests brGDGT distributions track changes in summer or growing season temperatures in the central highlands. Variability in absolute temperature estimates between sites indicate local environmental factors may influence brGDGT distributions. However, inter-site variability is within the range of uncertainty inherent to the calibrations. The soil profile with the most complete Holocene temperature reconstruction contains a maximum amplitude of summer temperature variation of ~3.5°C and is in close agreement to independent estimates derived from lake sediments and model simulations.

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THE CONTRIBUTION OF TOPOGRAPHIC SHADOWING BY ICE ON THE ALBEDO VARIABILITY

Leidman, Sasha1, Rennermalm, Asa1, Ryan, Johnny2, Acosta, Dimitri3

1Department of Earth and Planetary Sciences, Rutgers University 2Department of Geography and Earth Science, University of Aberystwyth, UK 3Environmental Protection Agency

Accurately predicting global sea level rise requires more refined surface mass balance (SMB) models of the Greenland Ice Sheet (GrIS). SMB models energy balance calculations are generally based off of course resolution satellite albedo values which ignore the substantial spatial heterogeneity observed within the ablation zone. Surface topography casting shadows on the landscape is potentially a large cause of the spatial variability of absorbed incoming solar radiation. The lower ablation zone of the GrIS shows extensive meso-scale surface topography caused by fracturing, supraglacial drainage features, and large-scale bed deformation (Ryan et al., 2016). This topography can reduce the total absorption of radiation and potentially shadow out depressions in the ice that generally have low albedo from sediment accumulation. This could result in a negative feedback loop for melting. The extent of this effect is not well understood and may cause deviations from expected albedo values based off large-scale topographic gradients. To address this, a catchment along the ice edge near Kangerlussuaq in southwest Greenland was mapped via a fixed-wing unmanned aerial drone mounted with a camera and GPS. Flight lines covered a 6 x 1.5km area (Fig. 1). The imagery was analyzed using Structure from Motion (SFM) software to create a 40cm resolution digital elevation model (DEM) and georeferenced ortho- mosaic. A python based shadowing model calculated the total amount of radiation hitting the ice surface for each pixel. A correlation matrix was then used to determine the significance of solar radiation on RGB albedo values and the importance of solar radiation mapping compared to more easily obtainable geographic parameters including aspect, slope, and an average hillshade. Solar radiation was then compared with other secondary influences on albedo such as crevassing, river networks and sediment sources. The analysis will quantify the degree of covariability between albedo and measurable parameters that contribute to its variability including shadowing, ice geometry, and the abundance of low albedo features. The analysis shows that radiation absorption (Fig. 1) is extremely spatially heterogeneous and accounts for as much as 54% of the total measured ablation rate of the ice. Shadowing also decreased the average exposure time to direct radiation within the study area to 35.7% of the year suggesting that modeled calculations of melt rates based off flat topography assumptions could be substantially overestimated in areas of crevasses and extensive river networks. This might partially explain the disparity between model outputs of stream flow and in situ measurements observed by Smith (2016). Solar radiation is well

103 correlated with reflectance and radiation exposure is fairly well correlated with relatively thin crevasses emphasizing the importance of fine scale shadow mapping for surface mass balance models. This research offers a tool for refining our understanding of the processes that dictate the albedo of the Greenland Ice Sheet and a way of more accurately predicting the impacts of surface features and warming climates on runoff.

Ryan, J. C., Hubbard, A., Stibal, M., Box, J. E., & Project, S., 2016, Attribution of Greenland’s ablating ice surfaces on ice sheet albedo using unmanned aerial systems: The Cryosphere Disc., v. 9, p.1–23. Smith, L. C., 2016, Surface water hydrology and the Greenland Ice Sheet: AGU Nye Lecture.

Figure 1. Calculated radiation values for the study area from a DEM based shadow model. Radiation values average 2.1x109 ± 3.2x108 J/m2 or 8.39m of melting based on density measurements of the weathering crust.

104

CONSTRAINTS ON WESTERN GREENLAND ICE SHEET EXTENT DURING THE MIDDLE HOLOCENE FROM PROGLACIAL THRESHOLD LAKES

Lesnek, Alia J.1, Briner, Jason P.1, Roop, Heidi A.2, Cluett, Allison A.1, Thomas, Elizabeth K.1, Young, Nicolás E.3

1Department of Geology, University at Buffalo 2Climate Impacts Group, University of Washington 3Lamont-Doherty Earth Observatory, Columbia University

With ~7 m sea level equivalent, the Greenland Ice Sheet (GrIS) is the largest ice mass in the Northern Hemisphere and is a key component of the Arctic climate system. Research on the GrIS has focused on predicting its response to projected climate warming, but there remain large uncertainties surrounding the ice sheet’s future behavior, including its potential contribution to 21st century sea level rise. Records of GrIS change that extend beyond the relatively brief instrumental period can place empirical constraints on the timing and magnitude of ice sheet response to warmer-than-present climates, and are vital to reducing uncertainties in predictions of future GrIS change and global sea level rise. The Holocene Thermal Maximum (HTM; Kaufman et al., 2004) is the most recent period when temperatures were warmer than present, and consequently it offers an exceptional opportunity to assess the response of the GrIS to a warmer climate. The spatial and temporal expression of the HTM, however, was not uniform across Greenland (Briner et al., 2016), and little is known about the magnitude of ice retreat within its present extent during this interval. A great deal of this uncertainty stems from difficulties in locating physical records of ice margin change during periods when the GrIS was smaller than today, as this evidence now lies below the ice sheet. However, detailed and precise histories of GrIS change during the HTM can be obtained from proglacial threshold lakes (Briner et al., 2010). Here, we reconstruct the timing and magnitude of GrIS retreat behind its present position in the Kangerlussuaq region of western Greenland by (1) 14C dating sedimentological transitions in five proglacial threshold lakes, (2) determining how far the lake drainage basins extend under the GrIS using sub-ice topographic data (Morlighem et al., 2014), and (3) analyzing down-core geochemical data from one proglacial threshold lake. Macrofossil 14C ages (n=5) collected from the basal contact between minerogenic and organic sediment units in the five study lakes range from 5,430 ± 460 cal yr BP to 6,370 ± 60 cal yr BP. In four of the study lakes [informally named Baby Loon Lake, Four Hare Lake, Lake Constance, and Lake Lucy (Young and Briner, 2015)] the transition between minerogenic and organic sediment is interpreted as the GrIS retreating out of the lake’s drainage basin. Sub-ice topography indicates that the drainage basins of these four lakes extend between ~0.5 and 3 km behind the modern ice margin, which, together with our 14C chronology, places a minimum limit on the magnitude of GrIS retreat during the middle Holocene.

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Tasersuaq (~312 m above sea level) is the largest and southernmost of our study lakes. This proglacial lake lies ~7 km south of Søndre Strømfjord and is fed by a land-terminating portion of the GrIS margin ~90 km to the southeast. Based on reconstructions of regional glacial history from 10Be exposure dating, Tasersuaq itself was most likely deglaciated between 8 and 7 ka (Carlson et al., 2014; Winsor et al., 2015). The turquoise color of Tasersuaq’s water indicates that our coring sites currently receive silt-laden meltwater from the GrIS, yet visual inspection and geochemical proxies (e.g., density, magnetic susceptibility, Si, and Ti) measured in multiple cores show that the sediment does not possess the commonly observed minerogenic “cap” atop the middle Holocene organic sediment unit. The absence of this cap suggests that the GrIS has remained within Tasersuaq’s drainage basin, which extends ~6 km behind the present-day ice margin, ever since ice retreated from the lake itself. This record from Tasersuaq is, to our knowledge, one of the few maximum constraints on middle Holocene GrIS retreat obtained from empirical data. The data presented here are in agreement with other constraints on the timing of GrIS retreat within its present extent (e.g., Carlson et al., 2014), and future work will focus on improving our 14C chronologies in each lake, as well as integrating these data with new 10Be exposure ages from nearby perched boulders and bedrock.

Briner, J. P., et al.., 2016, Holocene climate change in Arctic Canada and Greenland: Quaternary Science Reviews, v. 147, p. 340-364. Briner, J. P., Stewart, H. A. M., Young, N. E., Philipps, W., and Losee, S., 2010, Using proglacial threshold lakes to constrain fluctuations of the Jakobshavn Isbræ ice margin, western Greenland, during the Holocene: Quaternary Science Reviews, v. 29, no. 27–28, p. 3861- 3874. Carlson, A. E., Winsor, K., Ullman, D. J., Brook, E. J., Rood, D. H., Axford, Y., LeGrande, A. N., Anslow, F. S., and Sinclair, G., 2014, Earliest Holocene south Greenland ice sheet retreat within its late Holocene extent: Geophysical Research Letters, v. 41, no. 15, p. 5514- 5521. Kaufman, D. S., et al.., 2004, Holocene thermal maximum in the western Arctic (0–180°W): Quaternary Science Reviews, v. 23, no. 5–6, p. 529-560. Morlighem, M., Rignot, E., Mouginot, J., Seroussi, H., and Larour, E., 2014, Deeply incised submarine glacial valleys beneath the Greenland ice sheet: Nature Geoscience, v. 7, no. 6. Winsor, K., Carlson, A. E., Caffee, M. W., and Rood, D. H., 2015, Rapid last-deglacial thinning and retreat of the marine-terminating southwestern Greenland ice sheet: Earth and Planetary Science Letters, v. 426, p. 1-12. Young, N. E., and Briner, J. P., 2015, Holocene evolution of the western Greenland Ice Sheet: Assessing geophysical ice-sheet models with geological reconstructions of ice-margin change: Quaternary Science Reviews, v. 114, p. 1-17.

106

PALEOGENETIC SURVEY OF BROWN AND BLACK BEAR DIVERSITY IN PLEISTOCENE SOUTHEAST ALASKA

Lindqvist, Charlotte1, Lan, Tianying1, Talbot, Sandra L.2, Cook, Joseph3, Heaton, Timothy4

1Department of Biological Sciences, University at Buffalo 2U.S. Geological Survey, Alaska Science Center 3University of New Mexico, Museum of Southwestern Biology and Department of Biology 4Department of Earth Sciences, University of South Dakota

During the peak of the Last Glacial Maximum (LGM), ice sheets divided the Old and New Worlds, extensively curbing biotic exchange across the Bering Land Bridge for thousands of years. Geological and biological evidence have suggested, however, that refugia along the North Pacific Coast may have played crucial roles as “stepping stones” for movements of species between the Old and New Worlds, forming an early postglacial corridor for the recolonization of North America. Building on an unparalleled vertebrate bone collection excavated from limestone caves in Southeast (SE) Alaska we are performing paleogenetic analyses of brown and American black bears that occupied SE Alaska during the late Wisconsin glaciation and into the Holocene. We aim to directly test if bears occupied these caves at the peak of the LGM, if the same bear populations inhabited this region continuously for the last 50,000 years, or if they were recolonized following the LGM, and if they contributed to postglacial (modern) mainland populations. We have screened numerous bear specimens from the Alexander Archipelago and produced both incomplete and complete mitochondrial genome sequences. Many fossil specimens that were presumed to be brown bear based on morphology are clearly diagnosed as black bear based on genetic data, demonstrating that morphology alone can be insufficient in species diagnosis. Furthermore, affinities to several contemporary matrilineal genetic lineages, and possibly also extinct lineages, have been found among these specimens. For example, pre-LGM black bear specimens have a phylogenetic affinity to both contemporary coastal and continental lineages, suggesting that both these lineages were present in the archipelago prior to the LGM. The contemporary brown bear lineages on the Admiralty, Baranof, and Chichagof islands were apparently more widespread in the archipelago 10- 12,000 years ago. This research will have broad significance toward understanding past and present black and brown bear diversity and for assessing the impact of late Pleistocene climate change on their diversification and historical biogeography of the region.

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A MID-LATE HOLOCENE MULTI-PROXY PALEOENVIRONMENTAL RECONSTRUCTION OF NORTHERN FINNMARK USING A SEDIMENT CORE FROM THE ISLAND OF INGØY, NORWAY

Markonic, Claire1, Retelle, Michael1,2, Wanamaker, Alan3

1Department of Arctic Sciences, Bates College 2Department of Arctic Geology, University Centre in Svalbard, Norway 3Department of Geological and Atmospheric Sciences, Iowa State University

The extreme climate variability of the Arctic has stimulated an increase in scientific research focusing on various feedback mechanisms that enhance the phenomenon now referred to as Arctic amplification (Serreze and Barry, 2011). For example, an increase in the circulation of Atlantic Water (AW) into the northern latitudes, entering the Arctic along the coast of Norway as well as through Fram Strait, has been observed over recent decades. The North Atlantic Current (NAC) serves as the main transporter of warm water into the Arctic Ocean, as it is an extenuation of the Gulf Stream, and an unprecedented heat flux as well as an increase in volume of AW has been recorded in the Arctic (Hald et al., 2011; Polyakov et al., 2013; Spielhagen et al., 2011). Effects of this trend include a reduction in the ice extent of the Polar Ice Cap, which was reported to have reached a record low on September 16th, 2012 based on the satellite image record of the National Snow and Ice Data Center (NSIDC) that extends back to 1979. For accurate predictions to be made regarding the response of the Arctic to current and future fluctuations in climate, a compilation of high-resolution marine and terrestrial paleoenvironmetal records encompassing the entire region must be compiled. This study aims to shed light on the environmental conditions of northern Finnmark, developed using a muti-proxy analysis of a 65 cm sediment core recovered from an isolation basin on the island of Ingøy, Norway at 71ºN latitude (Figure 1). The island is located within a dynamic region of the North Atlantic as three major ocean current systems are observed off of the northern coast of Norway. These include the North Atlantic Current (NAC), the Arctic Current and the Norwegian Coastal Current (NCC), which propagate and mix within the Barents Sea. Due to its unique hydrographic location, the climate of Ingøy has been greatly influenced by ocean current systems and associated feedback mechanisms. Through a multi-proxy analysis the geochemical, physical, and biological conditions of the area spanning over 6000 cal yrs BP were reconstructed. Downcore elemental profiles were obtained using an ITRAX XRF core scanner at 500µm resolution, while carbon and nitrogen isotope analysis, percent loss on ignition and grain size analysis was performed at 1 cm resolution. Magnetic susceptibility as well as measurements of chlorophyll were obtained at half cm and 1 cm resolution respectively. An age-depth model was created using AMS radiocarbon dates obtained from four terrestrial macrofossils of woody vegetation discovered downcore. The identification of a cesium-137 peak produced as a

108 result of radioactive fallout and lead-210 dating were used to strengthen the age- depth model and provide an estimated sedimentation rate. Figure 2 shows the combined results of ITRAX XRF, grain size, magnetic susceptibility and loss on ignition analyses. Distinct stratigraphic variations are observed throughout the predominantly organic rich (>40% OM) gyttja. The majority of the sediment falls within the silt/clay fraction (<63µm) while interruptions in deposition are observed as fine-grained sand layers and mica- rich deposits (<2mm >62µm). Isotope analysis displays delta 13C values less than -25‰, and atomic C/N ratios greater than 18, which indicate a terrestrial source of sedimentary organic matter. Chlorophyll and isotope data will be used to reconstruct paleoproductivity, which will be compared to the sedimentation rate and changes in source material entering the basin. Broader climate signals preserved within the sediment will be investigated including solar forcings and the 1500 year Holocene climate cycles discovered by Bond et. al. (2001). The determination of correlations between multiple proxy records will serve to strengthen the chronological constraints of major climate events and reduce uncertainty in the reconstruction of past environmental conditions of northern Norway.

Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M.N., Showers, W., Hoffmann, S., Lotti-Bond, R., Hajdas, I. and Bonani, G., 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science, 294(5549), pp.2130-2136. Hald, M., Salomonsen, G. R., Husum, K., and Wilson, L. J., 2011, A 2000 year record of Atlantic Water temperature variability from the Malangen Fjord, northeastern North Atlantic: The Holocene, v. 21, no. 7, p. 1049-1059. Polyakov, I. V., Bhatt, U. S., Walsh, J. E., Abrahamsen, E. P., Pnyushkov, A. V., and Wassmann, P. F., 2013, Recent oceanic changes in the Arctic in the context of long-term observations: Ecological Applications, v. 23, no. 8, p. 1745-1764. Serreze, M. C., and Barry, R. G., 2011, Processes and impacts of Arctic amplification: A research synthesis: Global and Planetary Change, v. 77, no. 1–2, p. 85-96. Spielhagen, R. F., Werner, K., Sørensen, S. A., Zamelczyk, K., Kandiano, E., Budeus, G., Husum, K., Marchitto, T. M., and Hald, M., 2011, Enhanced Modern Heat Transfer to the Arctic by Warm Atlantic Water: Science, v. 331, no. 6016, p. 450.

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Figure 1. A regional map of the North Atlantic Ocean that includes an outline of the study area in black. B. An inset map of the island of Ingøy, which includes a star over the isolation basin from which Core #1 was recovered.

Figure 2. A comparison of the downcore elemental profiles obtained through ITRAX XRF analysis, grain size, magnetic susceptibility, and percent loss on ignition analyses performed on Core #1. A high-resolution image of the core is presented adjacent to the symbolized visual stratigraphy.

110

AN ARCTIC PERSPECTIVE ON CONTEMPORARY WARMING

Miller, Gifford H.1

1INSTAAR and Department of Geological Sciences, University of Colorado- Boulder

The instrumental record shows planetary warming from ~1970 to 2016 of ~1°C, while coeval trends in the Arctic are 2 to 3 times larger, in response to strong positive feedbacks in both summer and winter unique to polar regions. However, the degree of “Arctic Amplification” and the extent to which recent Arctic warming is anomalous with respect to natural climate variability remain difficult to evaluate because of the limited temporal and spatial coverage of the instrumental record within the Arctic, and the presence of multi-decadal temperature trends that may be related to internal modes of climate system variability. Placing the recent warming in a longer perspective requires secure reconstructions of past summer temperatures. To achieve that goal, we need secure paleotemperature proxies that can extend the instrumental record much farther into the past. The dimensions of ice caps in the Canadian Arctic are almost wholly determined by summer temperature; as summer temperatures have risen, ice caps have been receding. We exploit the unusual character of cold-based ice caps which act as preservation rather than erosive agents, entombing the landscape when ice cap expand, and re-exposing their preserved ancient landscapes as ice recedes. Radiocarbon dates on rooted plants revealed as ice-margins recede document the last time each site was ice-free. We determined the radiocarbon ages on 223 samples of rooted tundra vegetation collected the year of their exposure by ice recession over a 1000 km transect in the Eastern Canadian Arctic, with smaller datasets from West Greenland, Iceland and Svalbard. The dates demonstrate that average summer temperatures of the most recent decades have been higher than any century in at least 5000 years throughout the North Atlantic Arctic, and in more than 50,000 years (likely since the Last Interglaciation ~120,000 years ago) in the Canadian Arctic. The Canadian sites span the peak warmth of the early Holocene, when solar energy in summer was 9% greater than at present, providing compelling evidence that recent anthropogenic contributions to the atmosphere have now resulted in summer warming well outside the range of natural climate variability. Although the most dramatic current warming is in the Arctic, the impacts of a warmer Arctic are already being felt at lower latitudes, directly through a rising sea level and indirectly through changes in atmospheric circulation.

111

NEW COSMOGENIC RADIONUCLIDE DATA CONSTRAIN THE FREQUENCY OF DISAPPEARANCE OF THE GREENLAND AND LAURENTIDE ICE SHEETS THROUGH THE FULL QUATERNARY

Miller, Gifford, Pendleton, Simon, Schaefer, Joerg, Young, Nicolás Briner, Jason, Gilbert, Adrien and Flowers, Gwenn

The inherent stability of both the Laurentide and Greenland ice sheets (LIS, GIS) through the Quaternary (past 2.6 Ma) has long been debated. Two recent papers report cosmogenic radionuclide (CRN) data from the most likely final residual points of both ice sheets. Schaefer et al. (Nature, 2016) measured 10Be and 26Al through 1.5 m of a bedrock core recovered from the base of the GISP2 core site at Summit, Greenland. Their data indicate that the GIS was not as persistent as previously thought and records only 1.1 Ma of cumulative burial, and a total duration of exposure that likely occurred over several brief interglacial intervals. A second paper by Gilbert et al. (GRL, 2017) reports 14C, 10Be, and 26Al concentrations in bedrock and erratics at the margin of the Barnes Ice Cap (BIC), the final vestige of the LIS. Their data indicate that previous LIS deglaciations occurred with a similar spatial pattern as the last deglaciation. Furthermore, their data suggest that LIS deglaciation resulted in a residual ice cap similar to or smaller than the current BIC during only two brief previous interglacials, with remnant CRN inventories from long pre-glacial exposure. They speculate that the two pre-Holocene ice-free intervals were likely to have been during MIS 5e and MIS 11. Can the results and interpretations of these two papers be resolved without violating known constraints? There are fundamental differences between the behaviors of these two ice sheets during the last deglaciation. The LIS almost entirely collapsed and withdrew asymmetrically to its ancestral home on the central plateau of Baffin Island, whereas the GIS retracted only slightly and nearly symmetrically. Yet, at the center of Greenland, there is more exposure and less burial than beneath the center of the Laurentide, which mostly did not survive the current interglacial. The GIS is centered on a mountain-constrained interior lowland, with modest troughs through which ice was delivered to the sea, whereas the central LIS had multiple large channels through which ice could be even more efficiently delivered to the ocean. The change in the beat of glacial cycles associated with the mid- Pleistocene transition (MPT) may provide some explanation. Prior to the MPT, glacials may have been too brief to build such a thick ice sheet as at present, and lacking the ice-elevation feedback the GIS was more vulnerable to interglacial warmth. Also, the pre-MPT interglacials may have been too brief to melt the residual LIS from central Baffin Is, which is colder than adjacent Greenland. The GIS may have grown much larger during post-MPT glacials, making it less likely that central Greenland was deglaciated during interglacials. Preservation of remnant LIS on central Baffin Island, on the other hand, may have been aided by interglacial moisture availability.

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MODELING THE EVOLUTION OF SUPRAGLACIAL RIVER NETWORKS OVER SOUTHWEST GREENLAND

Muthyala, Rohi1 and Rennermalm, Asa1

1Department of Geography, Rutgers University

Supraglacial river networks are the most efficient conduits for evacuation of meltwater produced on Greenland Ice Sheet (GrIS). These rivers are dominant features in both ablation and proglacial zones of Greenland, and have large carrying capacities for the fast transport of meltwater. Supraglacial lakes formed through these river networks drain into the ice sheet, sometimes even reach the bed via moulins. This process influences the ice dynamics and subglacial drainage development system, and further enhances basal lubrication. Modeling of these river networks and lakes helps us to estimate the total runoff that enters into the icesheet via moulins. Recent observations show a significant surface melt increase over the GrIS, efficient supraglacial drainage network, and an increased discharge from outlet glaciers. However, these observation-based studies are not always representative for long-term variations given the important year to year variations observed in the annual mass balance. Large uncertainties remain in observation-based studies due to the sparseness in time and/or space; continued monitoring is needed to identify any significant future changes on the GrIS. Therefore, we designed a model that can route the meltwater, generated from a regional climate model RACMO 2.3, through the supraglacial river networks based on Digital Elevation Model (DEM) topography. We used a single- flow direction algorithm to route surface meltwater based on surface elevation, where the amount of meltwater in each cell weighted downstream flow accumulation (Schwanghart and Kuhn, 2010; Schwanghart and Scherler, 2014). We also intend to evaluate the model based on hourly surface runoff measurements we obtained from field in 2015 over a 63 km2 catchment on the top of ice sheet called Behar basin.

Schwanghart, W., and Kuhn, N.J., 2010, TopoToolbox: A set of Matlab functions for topographic analysis: Environmental Modelling & Software, 25(6), pp.770-781. Schwanghart, W., and Scherler, D., 2014, Short Communication: TopoToolbox 2-MATLAB-based software for topographic analysis and modeling in Earth surface sciences: Earth Surface Dynamics, 2(1), p.1.

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A HIGH-RESOLUTION APPROACH TO EVALUATE THE OCCURRENCE OF VARVED SEDIMENTS IN LAKE WALKER, QUÉBEC NORTH SHORE, USING IMAGE ANALYSIS AND X-RAY MICROFLUORESCENCE

Nzekwe, Obinna1, Francus, Pierre1,6, St-Onge, Guillaume2,6, Lajeunesse, Patrick1,3, Fortin, David5, Gagnon-Poiré, Antoine1, Philippe, Edouard2,6

1 Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, Québec, Canada 2Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, Canada, & Canada Research Chair in Marine Geology 3Centre d’études nordiques, Département de géographie, Université Laval 4Institut de Physique de Globe de Paris, France 5School of Earth Sciences and Environmental Sustainability, Northern Arizona University 6Geotop Research Center, Montreal, Canada

On the Québec North Shore, in the southeastern Canadian Shield (eastern Canada), three lakes (lakes Pentecôte, Walker and Pasteur) were studied for the possible occurrence of laminated sediments. Facies analysis using CT-scan images and thin-sections of short sediment cores sampled along transects show that lakes Pentecôte, Walker and Pasteur contain bioturbated, laminated and partially laminated sediments in relatively high proportions, respectively. It has been demonstrated that of the three studied lakes, Lake Walker is characterized by morphological factors (such as higher relative depth, mean depth, maximum depth, critical boundary and topographic exposure) that favour the preservation of sediment laminae. However, the existence of an annual rhythmicity has not been confirmed. Hence, the objectives of this study are to: (1) establish a depth-age model based on 14C dating of a ∼8 m composite section from Lake Walker, and (2) to conduct a microfacies analysis of the laminated sediments from that lake in order to confirm whether they are indeed varved. The methodology includes image analysis of thin-sections supported by high-resolution X-ray microfluroescence and CT-scan data. Based on a lamination visibility index established from CT-scan images Lake Walker contains varved and non-varved intervals, with a basal age of 7060 ± 25 14C BP (7904 ± 31 14C calBP) that marks the transition between the underlying glacial sediments and the overlying (annually) laminated sequence. This research aims determine if Lake Walker is a promising site for varve-based paleoenvironmental reconstructions.

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EVIDENCE FOR THE DRAINAGE OF A SUPRAGLACIAL LAKE AS THE SOURCE OF SEISMIC WAVES RECORDED AT REGIONAL DISTANCE

Orantes, Erik J.1,3, Kenyon, Patricia M.3,4, Alexander, Patrick M.5, Tedesco, Marco2,5

1NOAA-CREST 2Lamont-Doherty Earth Observatory, Columbia University 3Department of Geology, University at Buffalo 4Department of Earth and Atmospheric Science, City College of New York 5NASA Goddard Institute for Space Studies, NY

Surface melting during the summer leads to the formation of lakes on the Greenland Ice Sheet surface, known as supraglacial lakes. Some of these lakes drain through cracks in their beds and release the water into the ice sheet. Previous studies suggest that some of the water reaches the bedrock, enabling basal sliding, which could potentially increase glacial discharge (Sundal et al., 2009). Das et al. (2008) showed that supraglacial lake drainage can be accompanied by seismic activity, but little work has been done on the regional detection of such waves. The present study analyzes seismic data for the period coincident with the drainage of a supraglacial lake, an event that was documented by a team of researchers (Tedesco, et al., 2013). The study uses all available high frequency seismic data from the Greenland Ice Sheet Monitoring Network (GLISN) for the time around the onset of sudden drainage on June 19, 2011. Linear trends from a plot of seismic arrival times vs. distance from the lake location indicate seismic wave velocities of 292 and 378 m/s. These velocities are too slow for waves to be traveling through either rock or solid ice. Our current hypothesis is that they are traveling in a low-velocity channel of till underneath the ice. This would be consistent with the low attenuation required for the propagation of high frequency energy over regional distances. This research is relevant because it has become increasingly important to study how the surface- to-base interaction affects ice sheet discharge and therefore, sea level rise.

Alexander, P. M., Tedesco, M., Fettweis, X., van de Wal, R. S. W., Smeets, C. J. P. P., & van den Broeke, M. R. (2014). Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000–2013). The Cryosphere, 8(6), 2293–2312. http://doi.org/10.5194/tc-8-2293-2014 Chu, V. W. (2014). Greenland ice sheet hydrology: A review. Progress in Physical Geography, 38(1), 19–54. http://doi.org/10.1177/0309133313507075 Clarke, G. K. C. (1987, August 10). Subglacial Till: A Physical Framework for Its Properties and Processes. Journal of Geophysical Research: Solid Earth. Das, S. B., Joughin, I., Behn, M. D., Howat, I. M., King, M. A., Lizarralde, D., & Bhatia, M. P. (2008). Fracture Propagation to the Base of the Greenland Ice Sheet During Supraglacial Lake Drainage. Science, 320(5877), 778–781. http://doi.org/10.1126/science.1153360 Dow, C. F., Hubbard, A., Booth, A. D., Doyle, S. H., Gusmeroli, A., & Kulessa, Y. B. (2013). Seismic evidence of mechanically weak sediments underlying Russell Glacier, West Greenland. Annals of Glaciology, 54(64), 135–141. http://doi.org/10.3189/2013AoG64A032 Ekstrom, G., Nettles, M., & Abers, G. A. (2003). Glacial Earthquakes. Science, 302(5645), 622

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624. http://doi.org/10.1126/science.1088057 Irvine-Fynn, T. D. L., Hodson, A. J., Moorman, B. J., Vatne, G., & Hubbard, A. L. (2011). POLYTHERMAL GLACIER HYDROLOGY: A REVIEW. Reviews of Geophysics, 49(4). http://doi.org/10.1029/2010RG000350

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ONE THOUSAND YEARS OF NORTH ATLANTIC SEA-SURFACE VARIABILITY PORTRAYED IN AN ARRAY OF PAN-ARCTIC ICE CORE METHANESULFONIC ACID (MSA) RECORDS

Osman, Matthew1, Das, Sarah B.2, Trusel, Luke D.3, McConnell, Joseph R.4, Evans, Matthew J.5

1Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Sciences and Engineering 2Department of Geology and Geophysics, Woods Hole Oceanographic Institution 3Department of Geology, Rowan University 4Division of Hydrological Sciences, Desert Research Institute, University of Nevada 5Department of Chemistry, Wheaton College

Regional variations in sea-surface conditions at high latitudes, including changes in sea-surface temperatures (SST) and sea ice concentrations (SIC), are now well-known to modulate ice sheet mass balance and outlet glacier dynamics (Nöel et al., 2014). Whereas direct observations of these feedbacks are largely limited to the past few decades, ice core chemical records can extend our understanding of ocean-ice coupling well beyond the satellite era. One impurity species deposited in polar ice and snow, methanesulfonic acid (MSA), appears to be traced solely to spring-summertime phytoplankton blooms occurring at or near the sea ice margin and, as such, appears uniquely suited to analyses of past sea surface conditions. Here, we present an array of methanesulfonic acid (MSA) records from ten annually resolved Arctic ice cores (including two previously unpublished records) spanning the past 1000 years, and covering a broad geographic area within the pan-Arctic region (the Greenland Ice Sheet, the Canadian Arctic, and Svalbard). Long-term, Langrangian back-trajectories are employed in order to derive probabilistic spatial estimates of the maritime source regions of airmasses arriving at each site, suggesting a primary MSA source attribution deriving from the south- southeast Greenland coast and into the Nordic sea region. Notably, analysis of the MSA array reveals two modes of variance common amongst records. The first is a distinctive ~200 year decline in MSA concentrations into the present. This trend is similar to that observed in the anomalous, centennial-scale cooling of SST’s within the subpolar gyre region of the North Atlantic (Rahmstorf et al., 2015), where spatial correlations of the MSA array to historical SST reanalyses also show the highest significant correlations (p < 0.001; n = 154 years). The second mode suggests decadal-scale trends similar to previously published SIC reconstructions from the pan-Arctic region (Kinnard et al., 2011). These results suggest that the pan-Arctic MSA signal may retain important information on both SIC and SST variability. As such, our records may have implications for novel, ice-core based delineations of past sea-surface variability and coupled ocean-ice feedbacks in the North Atlantic.

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Nöel, B., et al., 2014, Sensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR, The Cryosphere, 8, 1871–1883. Kinnard C., et al., 2011 Reconstructed changes in Arctic sea ice over the last 1,450 years, Nature, Vol. 479, 509-512. Rahmstorf, S. et al., 2015, Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation, Nature Climate Change, Vol. 5, 475-480.

Figure 1. The standardized and 10-year low pass filtered stack of 10 pan-Arctic MSA records incorporated in this study.

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CLIMATE VARIATIONS OF THE COAST OF LABRADOR, 1750-1950: A DISCURSIVE APPROACH

Ouellet-Bernier, Marie-Michèle1, de Vernal, Anne1, Chartier, Daniel1

1Université du Québec à Montréal

Sea-ice cover plays an important role in Arctic and Subarctic communities. Communication, transportation and hunting depend on the sea-ice extend and duration. The relationship between human and sea-ice, together with cold, snow and light phenomena contributes to build the figure of winter. Discursive sources are a medium (a proxy) to communicate the representations of winter, it could tell on climate and weather-related extreme events. Discursive sources are analysed to reconstruct the sea-ice cover and the atmospheric temperature of the Labrador coast from 1750 to 1950 (A.D.). Despite the small subarctic human population, this research can rely on a variety of sources. Moravian missionaries have a long history of instrumental meteorological observations (Demarée and Ogilvie, 2008). In addition, explorer and trader journals, Inuit short stories, novels and many other narratives are providing valuable climate representations. The “Year Without a Summer” (1816) a Northern Hemisphere cooling consequence of the Tambora volcanic eruption in 1815, is highlighted in many narratives. From the Moravian Periodical Accounts, in late September 1816, the Mission ship was twice forced back by ice on its journey to Nain. Neither it could reach Nain the following summer due to the presence of ice (Newell, 1983). Other climate anomalies are represented such as the “Great Dry Fog” in 1783 (Stothers, 1996). This multidisciplinary research aims to use a new approach to reconstruct weather conditions with a monthly to a yearly resolution, which will contribute to fill the gap between the long-paleoclimatological records of the Labrador coast area (with decadal to centennial temporal resolution) and instrumental records (monthly to annual, but dating back only to 1927; Environment Canada, 2015).

Demarée, G. R., & Ogilvie, A. E. (2008). The Moravian missionaries at the Labrador coast and their centuries-long contribution to instrumental meteorological observations. Climatic change, 91(3-4), 423-450. Environment Canada. (2015). Monthly Data Report for 1927, Nain, Newfoundland, [Online database], http://climate.weather.gc.ca/index_e.html. Newell, J. P. (1983). Preliminary analysis of sea-ice conditions in the Labrador Sea during the nineteenth century. National Museums of Canada. Stothers, R. B. (1996). The great dry fog of 1783. Climatic change, 32(1), 79-89.

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DEGLACIAL – HOLOCENE PALEOCEANOGRAPHY OF HERALD CANYON, CHUKCHI SEA

Pearce, Christof1,2, O’Regan, Matt1, Rattray, Jayne1, Hutchinson, David1, Semiletov, Igor3, Jakobsson, Martin1

1Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University 2Department of Geoscience, Aarhus University 3Tomsk National Research Polytechnic University, Russia

The Herald Canyon is a local depression across the Chukchi Sea shelf, and acts as one of the main pathways for Pacific Water to the Arctic Ocean after entering through the narrow and shallow Bering Strait. We analyzed sediment samples of two piston cores from Herald Canyon, collected during the 2014 SWERUS-C3 Arctic Ocean Expedition. Core 2-PC1 from the shallow (57 mwd) flank contains the late Holocene at high resolution (> 2m/kyr), while Core 4-PC1 from the central canyon (120 mwd) extends back in time to ~13 ka. The lower part of 4-PC1 contains an abrupt increase in biogenic silica and a carbon isotopic shift towards more marine values, which are interpreted as the signal of the Beringia Land Bridge flooding and water exchange through the Bering Strait (Jakobsson et al., 2017). This major oceanic event is dated to ~11ka and thus occurs in the very early Holocene, contrary to most previous earlier estimates suggesting a Younger Dryas age for the opening of the gateway. The chronology of Core 2-PC1 is based on 17 radiocarbon dates and the 3.6 ka Aniakchak CFE II tephra, which is used as an absolute age marker to calculate the marine radiocarbon reservoir age (Pearce et al., 2016). The core site lies at the present day seasonal sea ice minimum edge, and is thus an ideal location for the reconstruction of past sea ice variability. Analysis of sea ice biomarkers and phytosterols indicate stable sea ice conditions throughout the entire late Holocene, which ends with an abrupt increase of phytoplankton sterols in the very top of both sediment sequences. This large shift is interpreted as a community turnover in primary producers from sea ice to open water biota and indicates that the ongoing rapid ice retreat observed in recent decades was unprecedented during the last 4000 years.

Jakobsson, M., Pearce, C., Cronin, T. M., Backman, J., Anderson, L. G., Barrientos, N., Björk, G., Coxall, H., de Boer, A., Mayer, L. A., Mörth, C.-M., Nilsson, J., Rattray, J. E., Stranne, C., Semilietov, I. and O’Regan, M.: Post-glacial flooding of the Beringia Land Bridge dated to 11,000 cal yrs BP based on new geophysical and sediment records, Climate of the Past Discussions, 2017, 1–22, doi:10.5194/cp-2017-11, 2017. Pearce, C., Varhelyi, A., Wastegård, S., Muschitiello, F., Barrientos, N., O’Regan, M., Cronin, T., Gemery, L., Semiletov, I., Backman, J. and Jakobsson, M.: The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea, Climate of the Past Discussions, 2016, 1–24, doi:10.5194/cp-2016-112, 2016.

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TESTING THE ICE COVER HISTORY OF PRESERVED LANDSCAPES ON BAFFIN ISLAND USING 14C

Pendleton, Simon L.1, Miller, Gifford H.1, Lifton, Nathaniel2, Anderson, Robert S.1

1INSTAAR and Department of Geological Sciences, University of Colorado- Boulder 2Department of Earth, Atmospheric, and Planetary Sciences and Department of Physics and Astronomy, Purdue University

Significant warming over recent decades at high latitudes is leading to marked ice loss and an overall decline of the Arctic cryosphere. Continued shrinkage of the cryosphere is expected to have far reaching and as yet unknown impacts within and beyond the Arctic, necessitating a better understanding of the consequences of these changes. Investigation and characterization of past glacial fluctuations provide important analogs and context for current and future Arctic cryosphere trends. Here we apply two dating techniques, both utilizing radiocarbon (14C), to investigate preserved landscapes and assess ice coverage since the last interglaciation (LIG) on Baffin Island. Recent ice margin retreat on Baffin Island is exposing preserved land surfaces from beneath cold-based, non-erosive ice. These land surfaces contain in situ dead vegetation preserved in growth position, whose 14C age most likely represents the timing of most recent ice advance over those locations. Building on the work of Miller et al. (2013), vegetation from the margins of 27 retreating ice caps on Cumberland Peninsula yield 14C concentrations at or beyond the range of the radiocarbon method, suggesting continuous ice coverage at these locations for more than ~40 ka. Paleoclimate records indicate that prior to ~40 ka, the last warm time similar to present was during the LIG, which ended ~120 ka (Andersen et al., 2004); we have therefore suggested that these surfaces have been buried by ice for ~120 ka. We test whether these sites were deglaciated and exposed for significant periods during earlier Holocene warm times and subsequently re-covered by ice during Late Holocene cooling, by determining the in situ cosmogenic 14C concentration of boulders and bedrock being exposed alongside the 14C- depleted vegetation. If these locations had been covered by ice since the LIG, inherited cosmogenic 14C would have decayed away. Spallation production of 14C is negligible under six meters or more of ice, but muogenic production would continue even under thicker ice. Modeling of both muogenic and spallogenic 14C production under varying ice coverage histories suggests that some recently deglaciated surfaces on Baffin Island have most likely been ice covered since the LIG, reinforcing our earlier conclusions that the current century is likely warmer than any century since the LIG. However, modeling also indicates that Holocene exposure is possible at some locations, though not necessary. It is possible that the dynamics and underlying physics of ice bodies on Cumberland Peninsula play a role in the non-uniformity of in situ 14C inventories on preserved landscapes. However, the number of locations with 14C-depleted vegetation and

121 low in situ 14C inventories reinforces the hypothesis that some recently exposed land surfaces have been ice covered since the LIG.

Andersen KK, Azuma N, Barnola JM, et al. (2004) High-resolution record of Northern Hemisphere climate extending into the last interglacial period. Nature 431(7005): 147–151. Miller GH, Lehman SJ, Refsnider KA, et al. (2013) Unprecedented recent summer warmth in Arctic Canada. Geophysical Research Letters 40(21): 5745–5751.

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ICE CORE MEASUREMENTS OF 14CH4 SHOW NO EVIDENCE OF METHANE RELEASE FROM METHANE HYDRATES OR OLD PERMAFROST CARBON DURING A LARGE WARMING EVENT 11,600 YEARS AGO

Petrenko, Vasilii V.1, Smith, Andrew M., Schaefer2, Hinrich, Riedel3, Katja, Brook, Edward4, Baggenstos, Daniel5, Harth, Christina5, Hua, Quan2, Buizert, Christo4, Schilt4, Adrian, Fain, Xavier7, Mitchell, Logan8, Bauska, Thomas9, Orsi, Anais10, Weiss, Ray F.5, Severinghaus, Jeffrey P.5

1Department of Earth and Environmental Sciences, University of Rochester, 2Australian Nuclear Science and Technology Organization (ANSTO), Austrailia 3National Institute of Water and Atmospheric Research Ltd (NIWA), New Zealand 4College of Earth, Ocean and Atmospheric Sciences, Oregon State University 5Scripps Institution of Oceanography, University of California 6University of Berne, Physics Institute, Switzerland 7University Grenoble Alpes/ CNRS, Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE), France 8Department of Atmospheric Sciences, University of Utah 9Department of Earth Sciences, University of Cambridge, UK 10CB2 3EQ Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, France

Thawing permafrost and marine methane hydrate destabilization have been proposed as large sources of methane to the atmosphere in response to both past and future warming. We present measurements of 14C of paleoatmospheric CH4 over the Younger Dryas – Preboreal (YD – PB) abrupt warming event (≈11,600 years ago) from ancient ice outcropping at Taylor Glacier, Antarctica. The YD – PB event was associated with a ≈ 50% increase in atmospheric CH4 concentrations. 14C can unambiguously identify CH4 emissions from “old carbon” sources, such as permafrost and CH4 hydrates. The only prior study of paleoatmospheric 14CH4 (from Greenland ice) suggested that wetlands were the main driver of the YD - PB CH4 increase, but the results were weakened by an unexpected and poorly understood 14CH4 component from in situ cosmogenic production directly in near-surface ice. In this new study, we have been able to accurately characterize and correct for the cosmogenic 14CH4 component. All samples from before, during and after the abrupt warming and associated CH4 increase yielded 14CH4 values that are consistent with 14C of atmospheric CO2 at that time, indicating a purely contemporaneous methane source. These new measurements rule out the possibility of large CH4 releases to the atmosphere from methane hydrates or old permafrost carbon in response to the large and rapid YD - PB warming, and confirm that wetlands were the main driver of the CH4 increase.

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A 40-YEAR RECORD OF NORTHERN HEMISPHERE ATMOSPHERIC CARBON MONOXIDE CONCENTRATION AND ISOTOPE RATIOS FROM THE FIRN AT GREENLAND SUMMIT

Place, Philip F.1, Petrenko, Vasilii1, Vimont, Isaac J.2, Buizert, Christo3, Lang, Patricia M.4, Harth, Christina5, Hmiel, Benjamin1, White, James W. C.2

1 Department of Earth and Environmental Sciences, University of Rochester 2INSTAAR and Department of Geological Sciences, University of Colorado- Boulder 3College of Earth, Ocean, and Atmospheric Sciences, Oregon State University 4National Oceanic and Atmospheric Administration, Global Monitoring Division, Earth System Research Laboratory 5Scripps Institution of Oceanography, University of California San Diego

Carbon Monoxide (CO) is an important atmospheric trace gas that affects the oxidative capacity of the atmosphere and contributes indirectly to climate forcing by being a major sink of tropospheric OH. A good understanding of the past atmospheric CO budget is therefore important for climate models attempting to characterize recent changes in the atmosphere. Previous work at NEEM, Greenland provided the first reconstructions of the Arctic atmospheric history of CO concentration and stable isotope ratios (δC18O and δ13CO) from firn air, dating into the 1950s. In this new study, firn air was sampled from eighteen depth levels through the firn column at Summit, Greenland (in May 2013), yielding a second, independent record of Arctic CO concentration and isotopic ratios. Carbon monoxide stable isotope ratios were analyzed, on replicate samples, using a newly developed system with improved precision allowing for a more robust reconstruction. The new CO concentration and stable isotope results overall confirm the earlier findings from NEEM, with a CO concentration peak around the 1970s and higher δC18O and δ13CO values associated with peak CO. Future work will extend the atmospheric reconstruction of CO by measuring part of the Greenland ice core record (recently collected in June 2015). Firn gas modeling and interpretation of the data are in progress.

Battle et al., 1996. Atmospheric gas concentrations over the past century measured in air from firn at the South Pole: Nature, 383, 231-235. Mak, J.E., Yang, W.B., 1998. Technique for analysis of air samples for C-13 and O-18 in carbon monoxide via continuous-flow isotope ratio mass spectrometry: Analytical Chemistry, 70, 5159-5161. Petrenko, V.V. et al., 2013. A 60 yr record of atmospheric carbon monoxide reconstructed from Greenland firn air: Atmospheric Chemistry and Physics, 13, 7567-7585. Wang et al., 2012. The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950: implications for the CO budget: Atmospheric Chemistry and Physics, 12, 4365-4377.

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LATE SEASON HIGH-SEDIMENTATION EVENTS AND ANNUAL SEGMENT FLUX IN SEDIMENT FLUX IN A SEDIMENT TRAP RECORD FORM LINNÉVATNET, SVALBARD

Potter, Noel L.1 and Retelle, Michael J.1

1Department of Geology, Bates College

Linnévatnet is a proglacial lake in the high Arctic, on the western coast of Spitsbergen, Svalbard, Norway. Svalbard’s climate is warm for its high latitude, with a mean annual air temperature of around -6°C for much of the 20th century (Humlum, 2002), which increased by as much as 2.5°C from 2001-2015 (Isaksen, et al., 2016) and is expected to continue to increase in the coming years (Førland, et al., 2011). The annually laminated sedimentary record in Linnévatnet has yielded high-resolution climate records extending back at least 1,000 years (e.g. Mangerud and Svendsen, 1990). Analysis of sedimentary records from Linnévatnet is an important component of understanding late- Holocene changes to the high Arctic climate of Svalbard, particularly as the warming trend of the 20th and 21st centuries has affected the Arctic disproportionately (Serreze and Francis, 2006). Of particular recent interest is the potential for increased sedimentation, especially during the fall “shoulder season,” after the major spring melt but before the winter freeze (Nowack and Hodson, 2013). Given the longer and more intense melt season brought about by a warming climate, overall sedimentation may increase, and a large portion of that increase may be due to shoulder season storms falling as rain more often than as snow during the time of year when the greatest portion of the ground surface is thawed (Retelle, et al., 2015). This study utilizes the annual sediment trap record for the 2015-’16 accumulation year in order to document the effects of such late-season events on sedimentation in Linnévatnet. Sediment traps have been deployed in Linnévatnet since 2003, with additional environmental monitoring equipment such as weather stations, time- lapse cameras, and an intervalometer, which records the timing of sediment deposition. Sediment traps are placed at varying depths throughout the water column on six moorings around the lake, in water depths from 5 to 35 m. Moorings are placed in an attempt to cover important zones within the lake. Several moorings form a proximal-to-distal transect from the lake’s primary inlet and sediment source, through a small eastern sub-basin, and into its main basin. Two moorings west of the main inlet gather sediment in a small western sub- basin and on the bathymetric ridge which separates the eastern and western sub-basins (Figure 1). Studies of modern sedimentation patterns in the lake allow for better understanding and interpretation of sedimentary records of past climate. Analyses of downcore trends in magnetic susceptibility and grain size were performed at 0.5 cm or intervals. ITRAX XRF profiles of elemental composition were measured at 0.5 mm intervals downcore on the sediment trap cores. Data from these analyses are used in conjunction with data from an

125 intervalometer, weather stations, and other monitoring equipment to understand the sediment year in detail. The intervalometer record revealed that sedimentation from the period of September 11-12, 2015 accounted for roughly 70% of the annual sedimentation at the intervalometer. This heavy influence from a late-season storm event stands in contrast with the classic model of annually varved lake sediments, in which a nival pulse of spring snowmelt is responsible for the greatest portion of sedimentation (Zolitschka, et al., 2015). While signatures of a nival pulse are present here, the warming Arctic climate may be driving an increasing prevalence of sediment related to late or “shoulder season” storm events in lake sediment climate records (Nowack and Hodson, 2013). Downcore profiles of grain size and Ca, Zr, Fe, and K content show distinct patterns differentiating sediment associated with the September rainstorm from that associated with the nival pulse. Based on these elemental signatures and grain size analyses, sediment from the September rainstorm did not reach the western sub-basin, and was deposited in varying amounts across the eastern and main basins, perhaps representing transportation in an irregular plume or plumes. By contrast, signatures of the nival pulse were seen in all sediment traps, with some minor variations in composition by location, likely associated with variations in bedrock composition across Linnédalen, the valley in which Linnévatnet sits. With 70% of the year’s sediment associated with the September rainstorm, the characteristics distinguishing this sediment from that associated with the nival pulse had a significant influence on Linnévatnet’s sedimentation for the year. If indeed shoulder season rainstorms are to become more and more prevalent, it could drastically alter the usual sedimentation patterns of Arctic lakes such as Linnévatnet.

Førland, E., Benestad, R., Hanssen-Bauer, I., Haugen, J.E., Skaugen, T.E., 2011, Temperature and Precipitation Development at Svalbard 1900-2100: Advances in Meteorology, v. 2011, 14 p. Humlum, O., 2002, Modelling late 20th century precipitation in Nordenskiold Land, Svalbard, by geographic means: Norsk Geogra sk Tidsskrift-Norwegian Journal of Geography, v. 56, p. 96-103. Isaksen, K., Nordli, Ø., Førland, E. J., Łupikasza, E., Eastwood, S., and Niedzwiedsz, T., 2016, Recent warming on Spitsbergen – Influence of atmospheric circulation and sea ice cover: Journal of Geophysical Research: Atmospheres, v. 121, p. 11,913-11,931. Mangerud, J., Svendsen, J.I., 1990, Deglaciation chronology inferred from marine sediments in a proglacial lake basin, western Spitsbergen, Svalbard: Boreas, v. 19, p. 249-272. Nowak, A., and Hodson, A., 2013, Hydrological response of a High-Arctic catchment to changing climate over the past 35 years: a case study of Bayelva watershed, Svalbard: Polar Research, v. 32, no. 0. Retelle, M., McCabe, C., Roof, S., Walther, T., and Werner, A., 2015, Hydroclimatic controls on laminated sediment formation in Linnévatnet, Svalbard: poster, American Geophysical Union Fall Meeting, San Francisco, CA. Serreze, M., and Francis, J. A., 2006, The Arctic on the fast track of change: Weather, v. 61, no. 3, p. 65-69.

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Figure 1. Location of Linnédalen on Svalbard (A, toposvalbard.npolar.no), location of Linnévatnet in Linnédalen (B, toposvalbard.npolar.no), and locations of moorings within Linnévatnet (C, after Svendsen, et al., 1989).

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Figure 2. From left to right, grain size, Zr, Ca, K, and Fe profiles downcore from sediment trap C4. Of note are the two distinct peaks in grain size, representing a September rainstorm and the spring nival pulse, respectively, and the high Ca content unique to the nival pulse.

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RECENT HYDROLOGICAL RESPONSE OF A GLACIERIZED WATERSHED TO HIGH ARCTIC WARMING, LINNÉVATNET, SVALBARD

Retelle, Michael1,2, Potter, Noel L.1, Roof, Steve3, Werner, Al4

1Department of Geology, Bates College 2Department of Arctic Geology, University Centre in Svalbard, Norway 3Department of Geology, Hampshire College 4Department of Geology, Mt. Holyoke College

Over the past three decades surface temperatures in the arctic have warmed twice as fast as the Northern Hemisphere average and climate models predict that this arctic amplification will continue to produce accelerated and amplified warming through the 21st Century (Serreze and Barry, 2011). In the Svalbard archipelago, major impacts include the loss of winter sea ice since 2006 (Muckenhuber et al., 2016; Nilsen et al., 2016), accelerated retreat of alpine glaciers and ice caps (Kohler et al. 2007) and a major shift in the annual precipitation regime. The recent warming has occurred in all seasons in Svalbard with greatest temperature increases in the winter season associated with warm sea surface temperatures due to the lack of sea ice cover (Nordli et al, 2016). In Svalbard heavy rainfall occurs in all seasons due to cyclonic storms that track northeastward from the North Atlantic (Nordli et al., 2016). Most recently, significant rainfall events occurred in October and November 2016, the warmest and wettest months on record for Longyearbyen (Svalbardposten, 2016) and rivers flowed in the Longyearbyen area following a warm storm in early February 2017. During the October 2016 event, intensive rainfall triggered debris flows in the valleys close to the town center in Longyearbyen (Christiansen et al, 2016) and many avalanches occurred in the interior plateau regions nearby. A major question is how anomalous are late season events in the long term? Are there periods in the past 1,000 years where sedimentation is similar to the current warm arctic scenario or are we experiencing a “new normal”? The annually laminated lacustrine sediment record in proglacial Linnévatnet, Svalbard provides a long term and high resolution record of hydro-climatic variability in the Norwegian high arctic. Sediment cores recovered from the lake in recent years span the past ca.1,000 years with varves that vary in thickness and structure in response to the amount and timing of sediment delivered by glacifluvial and nival sources. Monitoring watershed and climatological processes allows a more direct interpretation of annual varve sedimentation in recent years and thus will provide the basis for more accurately interpreting the longer term laminated lacustrine record. For the past 13 years, monitoring of the glacial-fluvial- lacustrine system has been facilitated using a network of instrumentation including time lapse cameras, automated weather stations, and moorings in the lake that are equipped with sediment traps, temperature loggers and ctd’s. Shorter term hydrological measurements, glacier mass balance measurements and sediment transport studies in the rivers and lake have been undertaken in summer field campaigns.

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Two general modes of hydro-climatic modes have been observed that drive lacustrine sedimentation: (1) peak discharge and sedimentation occurring during spring and early summer snow melt, and (2) peak discharge that occurs during late summer and fall as a result of late season rain storms. From 2004 to 2010 spring nival processes were the dominant hydro-climatic mode, however the late season mode was dominant in 4 of the last 5 years (2011, 2013, 2014, and 2015). The late or “shoulder season” precipitation events (Nowak and Hodson 2013) occur when thawed active layer sediments are mobilized and residual sediment in stream channels produced heavy sediment loads that exceeded the early season sediment delivery. In the two most recent years the majority of the annual sediment accumulation was comprised of sediment accumulated in the shoulder season. Over 40% of the annual sediment was deposited from a late August precipitation event in 2013 (McCabe 2016) while 70% of the annual accumulation occurred in a 36 hour rain event in September 2015 (Potter, 2017). These intense late summer and early fall rainfall events occurred when thawed active layer sediments were mobilized and residual sediment in stream channels, produced heavy sediment loads that exceeded the early season sediment delivery. Continued monitoring efforts will provide insights to the significance of these late season events and how they relate to regional climatological and oceanographic variability in this high arctic setting.

Christiansen, H., Farnsworth, W., Gilbert, G., Hancock, H., Humlum, O., O’Neill, B., Prokop, A., and Strand, A., 2016, Report on the 14-15 October mass movement event in the Longyearbyen area, unpublished report, University Centre in Svalbard 18 p. McCabe 2016 High Resolution XRF Sediment Analysis of Late Season Precipitation Events in a High Arctic Glaciated Watershed: Svalbard, Norway, unpublished B.Sc. Thesis, Bates College, Lewiston, Maine. Kohler, J., James, T. D., Murray, T., Nuth, C., Brandt, O., Barrand, N. E., & Luckman, A. (2007). Acceleration in thinning rate on western Svalbard glaciers. Geophysical Research Letters, volume 34, no. 18. Muckenhuber, S., Nilsen, F., Korosov, A. and Sandven, S., 2016. Sea ice cover in Isfjorden and Hornsund, Svalbard (2000–2014) from remote sensing data. The Cryosphere, 10(1), pp.149-158. Nilsen, F., Skogseth, R., Vaardal-Lunde, J. and Inall, M., 2016. A Simple Shelf Circulation Model: Intrusion of Atlantic Water on the West Spitsbergen Shelf. Journal of Physical Oceanography, 46(4), pp.1209-1230. Nowak, A., and Hodson, A., 2013, Hydrological response of a high arctic catchment to changing climate over 35 years: a case study of Bayelva watershed, Svalbard, Polar research, volume 32, p. 1-16. Serreze, M. and Barry, R.G, 2011, Processes and impacts of arctic amplification: a research synthesis, Global and Planetary Change, volume 7, p. 85–96.

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RECONSTRUCTING THE QUEBEC-LABRADOR SECTOR OF THE LAURENTIDE ICE SHEET FROM NEW SURFICIAL GEOLOGY MAPS, TILL PROVENANCE, AND DETRITAL 10BE DATA.

Rice, J.M.1, Ross, M.A.1, Paulen, R.C.2

1Earth and Environmental Sciences, University of Waterloo 2Geological Survey of Canada

Throughout the last glaciation, northeastern North America was covered by the Quebec-Labrador sector of the Laurentide Ice Sheet (LIS); a dynamic ice- dispersal center which persisted until the final stages of the LIS, when it became one of the last remnants of continental ice to disappear around 6.5 ka (Occhietti et al., 2011). Therefore, the Quebec-Labrador sector had an important influence on the late Pleistocene climate, specifically through its rapid release of ice and ice-dammed proglacial lakes into Ungava Bay and the North Atlantic. However, detail regarding the inception, migration, and disappearance of this ice center and its importance in glacial lake drainage is poorly understood. Understanding of the resultant glacial landscape within the George Plateau of the Canadian Shield is further complicated by the lack of Quaternary stratigraphy and preserved organic material suitable for radiocarbon dating, which could be used to constrain ice marginal retreat. A comprehensive understanding of the evolution of the Quebec-Labrador ice center could provide an important historical analogue when forecasting future long-term changes to current large scale continental ice sheets. Specifically, what role did the Quebec-Labrador ice sheet play in iceberg discharge through Ungava Bay into the Hudson Strait, and what is the record of proglacial lake drainage into the North Atlantic during deglaciation. To fully understand the evolution of the Quebec-Labrador ice sector, regional surficial mapping at the previously interpreted geographical location of the ice center was undertaken. Till samples collected from this region were analyzed for clast provenance, indicator mineral content, and geochemical abundances to obtain insights into glacial sediment dispersal patterns, resulting from changing ice flow and basal thermal regimes. Ice flow azimuths and relative chronology were established through large scale (oriented landforms) and outcrop scale ice flow indicator measurements. To constrain the deglacial phase of the ice sheet, four samples were collected for optically stimulated luminescence (OSL) dating of proglacial lacustrine beaches and twelve samples collected for 10Be surface exposure dating from glacially eroded bedrock and erratics. An additional ten till samples were collected for 10Be inventory to test the erosional vigor associated with subglacial conditions that should exist under our hypothesized subglacial conditions, following methodology established by Staiger et al. (2006) and Ross et al. (2015). The calculated 10Be abundances will be used as a quantitative test to assess the subglacial regime within, as previous studies have indicated correlations between regions of little glacial erosion with higher abundances of 10Be, reflecting high preglacial inheritance, and regions of high glacial erosion with low abundances of 10Be (Ross et al., 2015). Our work

131 has established a minimum of four glacial ice flows: 1) northeast across the entire study area, with ice-flow originating in the Quebec highlands (Veillette et al.1999), 2) a radial flow from the buildup of the Quebec-Labrador sector of the LIS, 3) radial flow following a dynamic westward adjustment of the dispersal center including the ice stream corridors established during deglaciation, and 4) deglacial flow with local topographic controls. Preliminary 10Be abundance results from till samples suggest a change from more sluggish colder based ice in the east to warmer, more highly erosive ice in the west. These results provide insights into the subglacial conditions related to the landscape evolution, as well as generate empirical based data that could be used to constrain glacial/climate models (cf. Stokes et al., 2015). With empirical based data to better confine such models, an improved conceptual understanding of how this large ice mass behaved during deglaciation, its effects on proglacial lake draining, and how it fed ice calving margins can be more accurately understood. From this framework, an increased understanding of how large ice evolve, migrate, and demise will be developed.

Occhietti, S., Parent, M., Lajeunesse, P., Robert, F., and Govare, É. 2011. Late Pleistocene-Early Holocene Decay of the Laurentide Ice Sheet in Québec-Labrador. Developments in Quaternary Science, v. 15, p. 601-630. Ross, M.A., Johnson, C.K., Gosse, J.C., Tremblay, T., Hodder, T.J., Grunski, E.C., and Pell, J. 2015. Detrital cosmogenic 10Be of till from contrasting landscapes on Hall Peninsula, Baffin Island: Investigating the relationship among multiple proxies of glacial dynamics. (Abstract) Geological Society of America Abstracts with Programs, v. 46, p. 63. Stainger, J.W., Gosse, J., Little, E.C., Utting, D.J., Finkel, R., Johnson, J.V., and Fastook, J. 2006. Glacial erosion and sediment dispersal from detrital cosmogenic nuclide analysis of till. Quaternary Geochronology, v. 1, p. 29-42. Stokes C.R., Tarasov, L., Blomdin, R., Cronin, T.M., Fisher, T.G., Gyllencreutz, R., Hättestrand, C., Heyman, J., Hindmarsh, R.C., Hughes, A.L., Jakobsson, M. 2015. On the reconstruction of palaeo-ice sheets: recent advances and future challenges. Quaternary Science Reviews. v. 125, p.15-49. Veillette, J.J., Dyke, A.S., and Roy, M. 1999. Ice-flow evolution of the Labrador Sector of the Laurentide Ice Sheet: a review, with new evidence from northern Quebec. Quaternary Science Reviews, v. 18, p 993-1019.

132

DETAILED SURFACE ELEVATION RECONSTRUCTION OF HELHEIM GLACIER (1981-2016)

Roberts, Carolyn1, Csatho, Beata1, Schenk, Toni1

1Department of Geology, University at Buffalo

As revealed by satellite data, Greenland Ice Sheet (GrIS) mass loss has increased since the late 1990s (Rignot et al., 2011). During 2005-2010, the GrIS was losing mass at a rate of 263 ± 30 Gt/yr, corresponding to 0.73 mm/yr of average global sea level rise (Shepard et al., 2012). In 2005, the mass loss in southeast Greenland contributed to more than half of the total mass loss for the entire ice sheet (Rignot and Kanagaratnam, 2006). A significant contributor to southeast GrIS mass loss, Helheim Glacier, is comprised of five separate tributaries joining several km upglacier from the terminus and has had a complex elevation change history (Khan et al., 2014). Between 1981 and 1998, the ice surface thickened ~2.5m/yr, up to the Little Ice Age elevation limit (above the elevation of the trimline). After 1998, the surface began thinning ~8.4 m/yr, and by 2003, Helheim Glacier was the same thickness it had been in 1981. Between 2003 and 2005, Helheim thinned dramatically (over 30 m/yr). In late 2005, there was a notably abrupt cessation in thinning, followed by thickening (~10-20 m) in 2006. The thinning-thickening behavior has yet to be fully understood. Moreover, during 2003-2006, near- synchronous behavior was observed at other outlet glaciers in the southeast (e.g., Koge Bugt C, A.P. Bernstorff glaciers), suggestive of a common forcing mechanism, or mechanisms. To better understand this complex elevation behavior, highly accurate elevation records are required at glacier-scale (tens of km2). While the elevation record for Helheim Glacier is rich temporally, the spatial coverage for high resolution laser altimetry data is sparse. Here we reconstruct the 1981-2016 elevation history of Helheim Glacier by employing the Surface Elevation Reconstruction and Change detection (SERAC) method (Schenk et al., 2014; Schenk and Csatho, 2012). Digital Elevation Models (DEMs) derived from stereo imagery are corrected using laser altimetry point data from 40 locations around Helheim Glacier. The corrected DEMs show a restablization period occurred during 2007-2012, characterized by minor elevation changes along- and across-flow. The DEMs also reveal dissimilar amounts of elevation change by tributary during 2005-2006, with the most dynamic elevation changes occurring on the widest, fastest-flowing tributary of Helheim Glacier.

Csatho, B., Schenk, A., van der Veen, C. J., Babonis, G., Duncan, K., Rezvanbehbahani, S., van den Broeke, M., Simonsen, S., Nagarajan, S., and J. van Angelen, 2014, Laser altimetry reveals complex pattern of Greenland Ice Sheet dynamics: Proceedings of the National Academy of Sciences, v. 111, p. 18478–18483. Khan, S. A., Kjeldsen, K. K., Kjær, K. H., Bevan, S., Luckman, A., Aschwanden, A., Bjørk, A. A., Korsgaard, N. J., Box, J. E., van den Broeke, M., van Dam, T. M., and A. Fitzner, 2014, Glacier dynamics at Helheim and Kangerlussuaq glaciers, southeast Greenland, since the Little Ice Age: The Cryosphere, v. 8, p. 1497–1507.

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Rignot, E., and P., Kanagaratnam, 2006, Changes in the velocity structure of the Greenland Ice Sheet: Science, v. 311, p. 986–990. Rignot, E., Velicogna, I., van den Broeke, M., Monaghan, A., and J. Lenaerts, 2011, Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise: Geophysical Research Letters, v. 38, p. L05503. Schenk, T., Csatho, B., van der Veen, C., and D. McCormick, 2014, Fusion of multi-sensor surface elevation data for improved characterization of rapidly changing outlet glaciers in Greenland: Remote Sensing of Environment, v. 149, p. 239–251. Schenk, T., and B. Csathó, 2012, A new methodology for detecting ice sheet surface elevation changes from laser altimetry data: IEEE Transactions on Geoscience and Remote Sensing, v. 50, p. 3302–3316. Shepherd, A., et al., 2012, A reconciled estimate of ice-sheet mass balance: Science, v. 338, p. 1183–1189.

134

ICE, LAKES & CLIMATE: EXPLORING THE COMPLEXITIES OF PROGLACIAL-THRESHOLD LAKE SEDIMENTARY RECORDS FROM WESTERN GREENLAND

Roop, Heidi A.1, Briner, Jason P.2, Young, Nicolás E.3

1Earth and Space Sciences, University of Washington 2Department of Geology, University at Buffalo 3Lamont-Doherty Earth Observatory, Columbia University

Sedimentary records recovered from proglacial-threshold lakes in Greenland can offer important insights into the ice margin history of the Greenland Ice Sheet (GrIS), particularly during warmer-than-present climates like the mid-Holocene. These proglacial-threshold lakes contain a characteristically ‘simple’ stratigraphy of minerogenic overlain by organic sediments, which is broadly indicative of the presence (minerogenic) or absence (organic) of the GrIS within a lake catchment. By exploiting this stratigraphy and dating the contacts between minerogenic and organic units we can place age constraints on the timing of GrIS margin growth and retreat. However, many of these sequences contain additional valuable information: investigation of more ‘complex’ sedimentary characteristics of these sequences (e.g. event layers), allow for consideration of other factors such as climate and depositional dynamics which are important for interpreting records from these lakes. Here we present two sedimentary records from Lake Lucy and Lake Constance (informal names), adjacent proglacial-threshold lakes in the Kangerlussuaq region of western Greenland. These sites currently receive silt- laden meltwater from Insunnguata Sermia and are characterized by a sharp mid- Holocene minerogenic-to-organic transition dated to 6050 ± 126 cal yr BP. However, an upper sequence of alternating minerogenic and organic units (starting at 1765 ± 45 cal yr BP) points to a more complicated relationship between the traditional “ice-in vs. ice-out” interpretation during the late Holocene. We will discuss mechanisms for this complicated stratigraphy including a dynamic GrIS margin, internal lake depositional dynamics and local jökulhlaups. We are in the process of extracting detailed records of the dynamics between lacustrine sedimentation and ice-sheet margin change and will explore additional interpretive frameworks that may be useful for expanding the utility and application of proglacial-threshold lakes as tools for reconstructing the timing, magnitude and characteristics of ice-sheet margin variability.

135

PROGLACIAL LAKE SEDIMENT RECORDS OF HOLOCENE MOUNTAIN GLACIER CHANGE ON THE NUUSSUAQ PENINSULA, WEST GREENLAND: INITIAL RESULTS

Schweinsberg, Avriel D.1, Briner, Jason P.1, Licciardi, Joseph M.2, Bennike, Ole3

1Department of Geology, University at Buffalo 2Department of Earth Sciences, University of New Hampshire 3Geological Survey of Denmark and Greenland

Mountain glaciers provide important paleoclimate records because they respond sensitively to climate change. Moreover, local glaciers that exist in the peripheral regions of Greenland may preserve a more detailed record of past glacier variability than the Greenland Ice Sheet (GrIS), which may have exhibited longer response times as it has been influenced by ice sheet dynamics (Kelly and Lowell, 2009). In contrast to extensive research on GrIS margin fluctuations during the Holocene (e.g., Briner et al., 2016), very few records constrain the timing and magnitude of mountain glaciation, thus the history of local glaciers in Greenland is relatively unknown (Kelly and Lowell, 2009). At present, three studies of local ice caps in East Greenland (Lowell et al., 2013; Levy et al., 2014; Balascio et al., 2015) and one investigation in West Greenland (Schweinsberg et al., in press) provide continuous records of local glacier changes during the Holocene. Here we present the first results from our summer 2016 field work where we collected seven sediment cores from two proglacial lakes on eastern Nuussuaq, West Greenland: Labrador Lake (informal name; 70.194 °N, 50.493 °W, 251 meters above sea level) and Saqqap Tasersua (70.196 °N, 51.500 °W, 245 meters above sea level). We present a preliminary lake sediment record from 246 cm-long core 16SAQ-B1 recovered from 10.8 meters water depth in a small embayment in the easternmost part of Saqqap Tasersua. We focus on utilizing proglacial lake sediments as records of glacier size, which relies on the assumption that large glaciers produce more minerogenic material and meltwater than small glaciers (Balascio et al., 2015). We interpret the relative proportions of organic matter versus inorganic clastic material to reflect the waxing and waning of ice; clastic sediment amount increases (and/or organic matter production decreases) during periods of glacier advance, and vice versa. We use radiocarbon-dated sediments from Saqqap Tasersua to reconstruct the timing of advance and retreat of local glaciers within the catchment. At present, four radiocarbon ages of macrofossils define a preliminary age model for 16SAQ-B1, and records of glacier change are developed from fluctuations in physical properties (magnetic susceptibility, gamma density) and inorganic geochemical analyses acquired using GEOTEK and Itrax nondestructive core scanners, respectively. The lowermost radiocarbon-dated sample from 16SAQ-B1 gives an age of 8880±50 cal yr BP (95 cm above the base of the core), and if extrapolated suggests the lake sediments from Saqqap Tasersua preserve a record of

136 mountain glaciation for almost the entire Holocene. A sharp decrease in mineral input from the base of the core to ~10 cal kyr BP reflects deglaciation, which is followed by relatively low levels of mineral input until ~4.5 cal yr BP. The prevalence of relatively low mineral input to the lake during the early to middle Holocene is interrupted by two intervals of increased mineral input from ~7.0-6.3 cal kyr BP and ~5.4-5.2 cal kyr BP. We suggest that the relatively low amount of mineral-rich sediment in the lake until ~4.5 cal kyr BP reflects restricted glaciers during a warmer/drier climate that characterizes the early to middle Holocene in western Greenland (Briner et al., 2016). The younger of the two episodes of increased mineral-rich sediment input may reflect a brief period of glacier advance recognized to the east in Sikuiui Lake at ~5.7 cal kyr BP (Schweinsberg et al., in press). Mineral sediment input gradually increases starting at ~4.5 cal kyr BP in Saqqap Tasersua, which we interpret as the onset of Neoglaciation in the catchment. This is coincident with the start of Neoglacial cooling and glacier expansion documented in local glacier records across West Greenland (Schweinsberg et al., in press), and from nearby records of the GrIS (Briner et al., 2016). Similar to the record of mountain glacier change reconstructed from Sikuiui Lake sediments (Schweinsberg et al., in press), periods of enhanced glacier activity, indicated by intervals of increased mineral input to the lake, punctuate the general trend of increasing glacier growth throughout the past ~4,500 years at ~3.5, ~1.4, and ~0.4 cal kyr BP. These intervals of glacier advance are correlative to ice cap expansion phases documented across West Greenland, suggesting that mountain glaciers throughout in this region were responding synchronously to a common climate forcing. Although our initial results from Saqqap Tasersua reveal several phases of glacier expansion throughout the Holocene, the estimated timing and magnitude of these intervals will likely change with refinements to the age model. Ongoing work includes obtaining additional radiocarbon ages to better constrain the age model for 16SAQ-B1 and for the sediment cores from Labrador Lake, as well as using Principal Component Analysis to detect the leading patterns of variability and to better identify the environmental factors that drive the fluctuations preserved in the lake sediment data. Additionally, we plan to supplement these lake records with cosmogenic 10Be surface-exposure dating of erratic boulders to further constrain the timing of deglaciation of the area, and of late Holocene moraines for direct age control on mountain glacier fluctuations in this region.

Balascio, N.L., D’Andrea, W.J., and Bradley, R.S., 2015, Glacier response to North Atlantic climate variability during the Holocene: Climate of the Past, v. 11, p. 2009–2036, doi:10.5194/cpd-11-2009-2015. Briner, J.P., et al., 2016, Holocene climate change in Arctic Canada and Greenland: Quaternary Science Reviews, v. 147, p. 340–364, doi:10.1016/j.quascirev.2016.02.010. Kelly, M.A., and Lowell, T.V., 2009, Fluctuations of local glaciers in Greenland during latest Pleistocene and Holocene time: Quaternary Science Reviews, v. 28, p. 2088–2106, doi:10.1016/j.quascirev.2008.12.008. Levy, L.B., Kelly, M.A., Lowell, T.V., Hall, B.L., Hempel, L.A., Honsaker, W.M., Lusas, A.R.,

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Howley, J.A., and Axford, Y.L., 2014, Holocene fluctuations of Bregne ice cap, Scoresby Sund, east Greenland: A proxy for climate along the Greenland Ice Sheet margin: Quaternary Science Reviews, v. 92, p. 357–368, doi:10.1016/j.quascirev.2013.06.024. Lowell, T.V., Hall, B.L., Kelly, M.A., Bennike, O., Lusas, A.R., Honsaker, W., Smith, C.A., Levy, L.B., Travis, S., and Denton, G.H., 2013, Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland: Quaternary Science Reviews, v. 63, p. 128–140, doi:10.1016/j.quascirev.2012.11.012. Schweinsberg, A.D., Briner, J.P., Miller, G.H., Bennike, O., and Thomas, E.K., 2017, Local glaciation in West Greenland linked to North Atlantic Ocean circulation during the Holocene, Geology, v. 45, 195-198, doi:10.1130/G38114.1.

138

MARINE EVIDENCE FOR COLLAPSES OF THE ARCTIC SECTOR OF THE LAURENTIDE ICE SHEET IN THE WESTERN ARCTIC OCEAN DURING THE LAST GLACIAL CYCLE

Suzuki, Kenta1, Yamamoto, Masanobu1, Irino, Tomohisa1, Nam, Seung-Il2, Polyak, Leonid3, Omori, Takayuki4, Yamanaka, Toshiro5

1Division of Earth System Science, Hokkaido University, Japan 2Korea Polar Research Institute (KOPRI), Korea 3School of Earth Sciences, Ohio State University 4Department of Earth and Planetary Science, University of Tokyo, Japan 5Department of Earth Sciences, Okayama University, Japan

The last glacial stage was characterized by a marked sequence of abrupt warming and cooling cycles on millennial-scale, such as the Dansgaard- Oeschger (DO) cycles. The Heinrich events (HE) are a potential trigger of the abrupt warming, however the DO cycles were not always associated with the HE. The rate of cooling were variable, and the factors controlling the rates remains poorly understood. One way to answer these questions is by reconstructing icebergs discharges into the western Arctic Ocean. In this study, we develop the sediment stratigraphy for the Chukchi margin, western Arctic Ocean, during the last ca. ~80,000 years and reconstruct sediment provenance and transportation processes. We discuss iceberg discharge events from the Laurentide ice sheet and their potential influence on glacial millennial climate changes. For this purpose, we use six sediment cores retrieved on the RV “Araon” cruises in 2011- 2012 and the Healy–Oden Trans-Arctic Expedition (HOTRAX) in 2005. Proxies analyzed include ice-rafted debris (IRD) contents, mineral composition, grain size distribution, color, organic carbon, total nitrogen and total sulfur contents, stable carbon isotope ratios of organic matter, and glycerol dialkyl glycerol tetraethers (GDGT) composition. The age model is constrained by radiocarbon ages and correlation to earlier developed stratigraphies. Dolomite-rich layers were recognized at ca. 9ka, 10ka, 11 ka, 42-35 ka, 45 ka, and 76 ka, respectively. Sedimentological properties suggest that these sediments were derived from the Canadian Arctic Archipelago by iceberg rafting. Their deposition occurred when the sea level was 40-80 m lower than today. We suppose that the northern edge of the Laurentide ice sheet reached the Arctic continental margin, and the calving of icebergs was not obstructed by ice in the Arctic Ocean (ice shelf or very thick sea ice) during these periods. The deposition of dolomite-rich layers at 9 ka and 45 ka seems to be consistent with H0 and H5 events, respectively, that lasted longer than other interstadials. We speculate that the large collapses of the Laurentide ice sheet delayed build-up of Laurentide ice sheet and subsequent cooling. No evidence of iceberg discharge into the western Arctic Ocean during ca. 53-11 ka indicates that the interstadials 4 to 1 were possibly unrelated to collapses of the Arctic sector of the Laurentide ice sheet. A kaolinite-rich layer was found in sediments of the last deglaciation,

139 possibly indicating deposition related to the collapse of an ice dam and freshwater discharge event.

140

THE LAST DEGLACIATION OF THE REVELATION MOUNTAINS, ALASKA: DISTINGUISHING BETWEEN GLOBAL AND REGIONAL CLIMATIC CONTROLS

Tulenko, Joseph P.1, Briner, Jason P.1, Young, Nicolás E.2

1Department of Geology, University at Buffalo 2Lamont-Doherty Earth Observatory, Columbia University

Global mean sea level is expected to rise by as much as 45 cm by the end of the 21st century. While many factors contribute to sea level rise, meltwater from glaciers and ice caps is predicted to contribute the most in this century since both are particularly sensitive to climate change. Studying past alpine glacier behavior provides valuable insight into the fate of current and future alpine glaciers as climate continues to change. Mounting improvements to the 10Be dating technique make it a precise and accurate dating tool for dating past glacier change, especially in regions where the use of other dating methods is limited. Motivation for this work is a recent synthesis of alpine glacier chronologies that pointed to globally synchronous glacier retreat forced by rising atmospheric CO2 (ca. 18 ka) following the LGM (Shakun et al., 2015). However, they found that greenhouse gas forcing does not fully explain why some of the glaciers they compiled initiated retreat earlier than ca. 18 ka. Moreover, the study centers on glacier records from the mid-low latitudes. In order to address the global pattern, we wonder if alpine glaciers in the Arctic behaved similarly. Alaska provides a rare opportunity to study alpine-style glaciation in the Arctic during and following the LGM since ice sheets covered only a small portion of the state at that time. However, there are no published high-resolution records of glacier recession from a single valley in Alaska (Kaufman et al., 2011). For this project, we return to an area surveyed by Briner et al. (2005) – they noted an exceptional moraine sequence with large granite boulders. They dated 4 boulders on the outermost late Wisconsin moraine, averaging 20.4 ± 0.7 ka (re-calculated here with updated production rates). Here, we present 22 new 10Be exposure ages used to constrain glacier retreat following the LGM in the Swift River Valley, which drains the Revelation Mountains in the western Alaska Range. The ages are from large granitic moraine boulders deposited on left-lateral LGM and recessional moraines. We dated boulders from 3 prominent moraines in the sequence. Ages from the LGM moraine average 21.0 ± 0.5 ka (n=4; 2 outliers excluded). Ages inboard of the LGM limit and on the first recessional moraine average 19.9 ± 1.0 ka (n=6; 4 outliers excluded). Finally, ages on the innermost recessional moraine that we sampled average 17.7 ± 0.5 ka (n=4; 2 outliers excluded). While there are occurrences of statistical outliers, such as older ages that suggest significant inheritance and younger ages that suggest post-depositional disruption, a majority of the ages cluster well. Moraine mapping of the site shows that the glacier had retreated in length by approximately 40% of its LGM extent when it deposited the ~17.7 ka recessional moraine. The chronology indicates significant

141 retreat prior to global CO2 rise. We suggest that glacier recession was initiated by orbital forcing, which was perhaps modulated by polar amplification.

Briner, J. P., D. S. Kaufman, W. F. Manley, R. C. Finkel and M. W. Caffee 2005. Cosmogenic exposure dating of late Pleistocene moraine stabilization in Alaska. Bulletin of the Geological Society of America. Vol 117 Issue 7-8. pp. 1108-1120. 10.1130/B25649.1 Kaufman, D.S., Young, N.E., Briner, J.P., and Manley, W.F. 2011. Alaska PaleoGlacier Atlas version 2. in Ehlers, J., and Gibbard, P.L., eds., Quaternary Glaciations - Extent and Chronology: North America. Developments in Quaternary Science. Shakun, J. D., Clark, C. U., He, F., Lifton, N. A., Liu, Z. & Otto-Bliesner, B. L. 2015. Regional and global forcing of glacier retreat during the last glaciation. Nature Communications. 10.1038/ncomms9059

142

DETERMINING AND INTERPRETING DETAILED ICE SURFACE ELEVATION CHANGES OF THE GLACIERS IN UPERNAVIK ISSTRØM, NORTHWEST GREENLAND, 1981-2014

Wendler, Lindsay1, Csatho, Beata1, Schenk, Toni1

1Department of Geology, University at Buffalo

The several distinct glaciers of Upernavik Isstrøm, which drain a portion of the northwest margin of the Greenland Ice Sheet (GrIS), exhibit variable thinning, retreat, and velocity behaviors, despite being in such close proximity, draining into the same fjord, and experiencing similar climatic conditions. The goal of this study was to reconstruct, in as much detail as possible, a 1985-2014 surface elevation change history for each Upernavik glacier. Surface elevation datasets used in these reconstructions included laser altimetry data collected by several NASA systems (ATM, LVIS, ICESat) and digital elevation models (DEMs) derived from various sources (1985 aerial photographs; ASTER, SPOT, and Worldview-1 and 2 satellite stereo imagery). The Surface Elevation Reconstruction and Change detection (SERAC) program was used to combine the data and correct the DEMs for use in final reconstructions. The spatiotemporal pattern of ice surface change was analyzed and compared with other data sets, such as bed elevation, changes in ice surface velocity, effective pressure, SMB anomalies, runoff, as well as marginal retreat derived from satellite imagery corresponding to the ASTER DEMs, to investigate possible forcings that may have influenced the variable behavior of the glaciers. Improved surface elevation change histories for Upernavik glaciers 1, 2, 3, and 5 were produced that are the most detailed and accurate to date. Our results contradict the previously held hypothesis that the rapid thinning and retreat of glacier 1 was initiated by the break-up of its long-lived floating tongue, resulting in a reduction of backstress. We detected rapid thinning and retreat of the previously grounded front between 2006 and 2008, indicating that rapid thinning was due to increasing velocity as the glacier surface approached the height of flotation and effective pressure decreased toward zero. Finally, our results show a period of large thinning on glacier 2 between 2010 and 2011 with a relatively stable front position, suggesting a loss of lateral drag as the glacier calving front retreated from a pair of flanking outcrops.

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DEVELOPMENT OF AN INTENSIVE HYDROLOGICAL MONITORING PROGRAM TO EVALUATE VULNERABILITY OF MACKENZIE DELTA REGION LAKES TO CLIMATE CHANGE

Wilcox, Evan1, Marsh, Philip1, Walker, Branden1, Mann, Philip1

1Cold Regions Research Centre, Wilfrid Laurier University

The Arctic is experiencing faster warming than any other region warming, leading to hydrological impacts to its nival systems (Vaughan et al., 2013). At Trail Valley Creek in the Mackenzie Delta region (68.75°N, 133.5°W), the yearly average temperature of the past thirty years has been 2.3°C warmer than the previous thirty years (Figure 1). Many small thermokarst lakes in other regions of continuous permafrost have experienced dynamic changes: some growing in size or draining through thermokarst processes, others desiccating after evaporation overcomes inflow (Marsh and Neumann, 2001; Smith et al., 2005; Turner et al., 2014). The period and rate of evaporation is increasing as ice-free periods become longer and lakes become warmer, leaving them vulnerable to desiccate in low-snowfall years (Bouchard et al., 2013). More thaw slumps are developing in the region in coordination with the warming climate; an indication of increasing permafrost instability (Lantz and Kokelj, 2008). Both thermokarst and hydrological processes are affected by changes in climate which influences the lakes of this region. It is largely unknown how much yearly excess runoff thermokarst lakes receive to maintain a consistent water level, or how basin characteristics such as size, vegetation cover, and slope affect runoff inputs. Therefore, components of lake water inputs and outputs must be quantified to determine the risk of lakes in this region to desiccate as the climate changes. The monitoring program is comprised of eight lakes instrumented with water level recorders, and two lake basins instrumented and surveyed to capture full daily water balances. RBR pressure loggers were installed in eight lakes surrounding Trail Valley Creek research station (68.75°N, 133.5°W) in May 2016, and will be maintained for the remainder of the study. These lakes represent differences in lake size and shape, and also basin size, topography and vegetation cover. Initial water level data from one lake suggests a large portion of snowmelt runoff is quickly discharged, and does not fully recharge the lake (Figure 2). Newly developed methods using an unmanned aerial system (UAS) will be validated with conventional MagnaProbe and snow tube density measurements to estimate end of winter snow water equivalent (SWE) at the Big Bear and Little Bear lake basins in 2017. The UAS uses structure from motion photogrammetry to create a 10cm resolution raster of the snow surface which is then subtracted from a bare ground LiDAR obtained raster to calculate snow depth at each pixel. These methods will be applied through the entire snowmelt period to determine SWE until the basin is completely snow-free. Discharge will be measured by a compound v-notch weir instrumented with water level recorders installed at the outlet of both lakes, which will be validated using an acoustic doppler velocimeter in the outlet channel downstream. An eddy

144 covariance system was installed at the edge of Big Bear Lake and positioned downwind of the mean wind direction to collect evaporative, latent and sensible heat fluxes. Lake level data of surrounding lakes will be combined with the lake level and water balance data collected from Big Bear and Little Bear in order to evaluate the timing and amount of excess inputs, and how they vary across the range of lakes. This research will provide knowledge about key components of water resources at local and regional scales. Northerners need better information on how these resources will change, so they can make informed decisions about protecting them. Creating a better understanding of how specific processes will change in a warming climate can allow for better prediction of how these lakes will change in the future. This intensive field program will accompany concurrent research documenting lakes changes in air photos from 1950’s, and inform future GEOtop modeling which will test future climate scenarios.

Bouchard, F., Turner, K.W., MacDonald, L.A., Deakin, C., White, H., Farquharson, N., Medeiros, A.S., Wolfe, B.B., Hall, R.I., Pienitz, R., Edwards, T.W.D., 2013. Vulnerability of shallow subarctic lakes to evaporate and desiccate when snowmelt runoff is low. Geophys. Res. Lett., v. 40, p. 6112–6117. Lantz, T.C., Kokelj, S. V., 2008. Increasing rates of retrogressive thaw slump activity in the Mackenzie Delta region, N.W.T., Canada. Geophys. Res. Lett., v. 35, p. 1–5. Marsh, P., Neumann, N.N., 2001. Processes controlling the rapid drainage of two ice-rich permafrost-dammed lakes in NW Canada. Hydrol. Process., v. 15, p. 3433–3446. Smith, L.C., Sheng, Y., MacDonald, G.M., Hinzman, L.D., 2005. Disappearing Arctic lakes. Science, v. 308, p. 1429. Turner, K.W., Wolfe, B.B., Edwards, T.W.D., Lantz, T.C., Hall, R.I., Larocque, G., 2014. Controls on water balance of shallow thermokarst lakes and their relations with catchment characteristics: a multi-year, landscape-scale assessment based on water isotope tracers and remote sensing in Old Crow Flats, Yukon (Canada). Glob. Chang. Biol., v. 20, p. 1585–1603. Vaughan, D.G., Comiso, J.C., Allison, I., Carrasco, J., Kaser, G., Kwok, R., Mote, P., Murray, T., Paul, F., Ren, J., Rignot, E., Solomina, O., Steffen, K., Zhang, T., 2013. Observations: Cryosphere. Clim. Chang. 2013 Phys. Sci. Basis. Contrib. Work. Gr. I to Fifth Assess. Rep. Intergov.

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Figure 1. Average Annual Temperature 1955-2015, Trail Valley Creek, NWT, Canada.

Figure 2. Measurements of Lake Level, Average Daily Temperature, Daily Precipitation, and Basin Snowcover at Big Bear Lake from May - August, 2016.

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PALEOENVIRONMENTAL RECONSTRUCTION FROM THE SEDIMENT RECORD OF THE VARVED PROGLACIAL LINNÉVATNET, SVALBARD, NORWEGIAN HIGH ARCTIC

Williams, Gwenyth1 and Retelle, Michael1

1Department of Geology, Bates College

Arctic environments are highly sensitive to local climate variability, which can be reconstructed using a number of proxies. Varved sediments from glacier-fed lakes provide high resolution paleoclimate proxies in the high arctic environment. Linnévatnet is a proglacial deep lake on Western Spitsbergen, Svalbard in the Norwegian High Arctic. The distinctly seasonal arctic climate and deep-lake setting allow for the deposition of annually laminated sediments. Sediments are sourced from glacier-fed Linnéelva at the southern end of the lake, a currently- stagnant cirque glacier to the West, and overland flow from alluvial fans that occurs mainly during melt and rain events (Snyder et al., 2000). Two sediment cores, each measuring approximately 26 centimeters in length, were collected from the East Basin of Linnévatnet at coring sites C (more proximal) and D (more distal) in July, 2016 (Figure 1). The cores were subsampled for grain size, bulk density, and for the production of thin sections. Magnetic susceptibility and ITRAX X-ray fluorescence were measured on the archive halves of the cores. Lead 210 and cesium 137 geochronology and varve measurements from previous studies were used to corroborate the varve chronology. Varve thicknesses were measured and the annual layers were counted. Varves in Core C extend back to approximately 150 years before present while the record in Core D extends to approximately 250 years before present. Overall, varve thickness decreases downcore. The increase in sedimentation rate during the past several decades follows a similar trend as the warming following the Little Ice Age, a cool period during which glaciers reached their maximum Holocene extent (D’Andrea et al., 2012). The cores showed very little variation in bulk density downcore, indicating that the effect of compaction was low. Grain size analysis indicated that density was instead driven by mean grain size. Similarly, loss on ignition measurements indicated that organic content remained consistent. Coal from the Carboniferous Billefjorden group that underlies the center of the valley is the main organic component of the sediments (Svendsen and Mangerud, 1997). ITRAX XRF profiles show two calcium peaks in both cores. These same peaks have been seen in other cores taken from Linnévatnet at proximal and distal locations (Dowey, 2013, Merkert, 2015). They correspond to areas with varves with large summer layers. An artificial core collected by Merkert (2015) shows the source of calcium as the eastern side of the valley, consistent with the limestones and dolomites present in the bedrock geology of the region. Svendsen and Mangerud (1997) recorded an increase in calcium carbonate content during periods of little glacial activity. Other relevant element

147 geochemistry was used to identify sediment provenance and the events leading to their deposition.

Dowey, C. W., 2013, 600 Years of Late Holocene Climate Variability Inferred from a Varved Proglacial Sediment Record Linnévatnet, Svalbard, Norway, Standard Theses. 7. Merkert, B. G., 2015, Paleoclimatic implication of lake sediment geochemistry in Linnévatnet, Spitsbergen, Svalbard, Standard Theses. 21. Snyder, J. A. W., A.; Miller, G. H., 2000, Holocene cirque glacier activity in western Spitsbergen, Svalbard: sediment records from proglacial Linnévatnet: The Holocene, v. 10, no. 5, p. 555-563. Svendsen, J. I., and Mangerud, J., 1997, Holocene glacial and climatic variations on Spitsbergen, Svalbard: The Holocene, v. 7, no. 1, p. 45-57.

Figure 1. Study location with an inset of Linnédalen. Cores were collected at sites C and D.

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RAPID THINNING AND ACCELERATION AT THE COLD-BASED VAVILOV ICE CAP, SEVERNAYA ZEMLYA, RUSSIA

Willis, Michael J.1, Pritchard, Matthew E.1, Zheng, Whyjay1, Durkin IV, William J.1, Ramage, Joan M.2, Dowdeswell, Julian A.3, Benham, Toby J.3, Bassford, Robin P.4

1Department of Earth and Atmospheric Sciences, Cornell University 2Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado-Boulder 3Department of Earth and Environmental Sciences, Lehigh University 4Scott Polar Research Institute, University of Cambridge, UK 5Hardenhuish School, Chippenham, Wiltshire, UK

The cold-based outlet glacier of the Vavilov icecap in the Russian Arctic has no previous history of surges, but has been advancing for decades, possibly because of increased precipitation over the last ~500 years. In 2012, as the glacier advanced over low-friction marine sediments, it accelerated and thinned at an unprecedented rate. We show that cold-based glacier systems may evolve with unprecedented speed when their basal boundary conditions change, resulting in very large dynamic ice mass losses over very short time-scales. The ~300 to 600 m thick, 1,820 km2 Vavilov Ice Cap, on October Revolution Island in the Russian Arctic [Figure 1] is frozen to its bed(1, 2). Palynological study of the ice core suggests precipitation at the ice cap became increasingly focused from the southwest about 500 years ago(3, 4). From 1952 to 1985 the western part of the ice cap advanced around 400 m (~12 m/yr)(3). The rate of advance accelerated significantly to ~75 m/yr between 1998 and 2011 [Figure 2]. By 2012, the ice front had pushed into the Kara Sea, overridden the terminal moraine and formed an unconfined marine-terminating piedmont glacier. The bed beneath the offshore portion of the glacier is likely low-friction, saturated marine sediments similar to those commonly found offshore around other Arctic ice caps, such as those in Svalbard(6). The ice front achieved full flotation (as revealed by a flattening of the profile of surface elevation, Figure 1) and advanced into the Kara Sea more than 5,000 m in the one-year period between April 2015 and April 2016 [Figures 1, 2]. The removal of lateral shear stresses, the reduction of resistive basal stresses and the rapid divergence of flow at the ice front were compensated for by a simultaneous speed up and steepening [Figure 1] of the inland ice – surface velocity measured by satellites has accelerated from a peak rate of around 20 m/yr in 1996 (3), to 9125±354 m/yr (25.10±0.97 m/day – uncertainties are 2 standard deviations) in 2016. There are no apparent air temperature anomalies that would drive the glacier dynamic changes from 2005 to present at the Golomyanny weather station, near sea level approximately 80 km to the west, but climate data are not available on the ice cap, where conditions may be different. Passive microwave observations of ice-surface wetness suggest 2011 and 2012 had extended melt seasons compared to previous years. High-resolution optical satellite images

149 from that time indicate that supraglacial streams and moulins are relatively rare but, even so, supraglacial meltwater from small rivers and ponds may have been able to penetrate the ice in warmer periods, and helped precondition the ice cap for rapid flow. Fluctuations in ice motion in 2015 and 2016 measured by pixel- tracking of Landsat-8 images, may be tied to an actively evolving drainage system beneath the ice, like that observed in Greenland(11) and/or to the presence or absence of sea ice at the terminus. Digital Elevation Models (DEMs) derived from sub-meter resolution satellite imagery are co-registered to ICESat returns over bedrock for the region and detail the remarkable evolution in ice-surface elevations between 2012 and 2016 [Figure 1]. Ice height differences between a DEM produced by digitizing Russian military maps, sourced from aerial photos in 1984, and ICESat controlled DEMs produced in April 2013 show 10-20 meters of thinning at altitudes of between 200 m and 600 m and an ice front advance of about 2.5 km over the 29-year interval. From April 2014 to April 2015 thinning of up to 50 meters propagates about 8 km inland from the former coastline. The ice front thickens considerably and the ice advances rapidly. Changes between April 2015 to April 2016 indicate full activation of the outlet glacier with thinning propagating to within 5 km of the summit region of the ice cap. The most pervasive thinning of more than 100 m/year (> 0.30 m/day) occurs along the center flowline ~11 km inland from the former coastline [Figure 1]. The geodetic mass balance of the grounded portion of the ice cap between 1984 and April 2013 is slightly negative at -0.04±0.02 km3/yr w.e. and is in agreement with modeled rates(1). Between April 2014 and April 2015 the mass balance is 21 times more negative, at - 0.84±0.004 km3/yr w.e.. Between 2015 and 2016 the mass loss is 5 times greater still at -4.48±0.004 km3/yr w.e. (~100 fold increase on long-term rates). This is the single largest mass imbalance occurring in the Russian High Arctic, for comparison, the mass budget for the entire of the Russian Arctic region was - 9.1±2.0 Gt/yr between 2004 and 2009(12). The Vavilov rate equates to a loss of about 0.9% of the total volume of the 570 km3 ice cap per year. The collapse of the Vavilov ice cap initiated as changes in the precipitation pattern drove an ice front advance over marine sediments. Continuity and possible preconditioning by internal warming caused by the percolation and refreezing of surface water (9,10) forced the inland ice to steepen rapidly, accelerate and thin. The initiation of rapid flow likely caused both strain softening and heating, producing water at the bed-sediment interface, which in turn promoted further sliding, possibly involving the clay rich substrate. That a seemingly stable ice cap like Vavilov can rapidly lose mass in such a catastrophic manner suggests a possible new mechanism for marine terminating ice caps and ice sheets with sub-glacial bed elevations that are largely above sea level to experience rapid dynamic changes. While it has long been recognized that marine-terminating glaciers that have reverse-bed slopes with bed elevations that are well below sea level can experience instabilities that may propagate inland, possibly triggering collapse(14), the general acceptance that cold, polar ice caps will only respond slowly to a warming climate and changes in

150 boundary conditions should be questioned, especially when glaciers can advance over soft clay-rich sediments.

1. R. P. Bassford et al., Arctic, Antarctic, and Alpine Research 38, 1-12 (2006). 2. M. Stievenard et al., Journal of Glaciology 42, (1996). 3. R. P. Bassford, M. J. Siegert, J. A. Dowdeswell, Arctic, Antarctic, and Alpine Research 38, 13- 20 (2006). 4. A. Andreev, A., V. Nikolaev, I., D. Y. Boi'sheiyanov, V. Petrov, N., Géographie physique et Quaternaire 51, 379-389 (1997). 5. A. Solheim, "The depositional environment of surging sub-polar tidewater glaciers : a case study of the morphology, sedimentation and sediment properties in a surge affected marine basin outside Nordaustlandet, Northern Barents Sea," Norsk Polarinstitutt Skrifter No. 194 (Norsk Polarinstitutt, Oslo, Noway, 1991). 6. T. Moon et al., Geophysical Research Letters, 2014GL061836 (2014). 7. M. J. Willis, B. G. Herried, M. G. Bevis, R. E. Bell, Nature, (2015). 8. T. Dunse et al., The Cryosphere 9, 197-215 (2015). 9. R. M. DeConto, D. Pollard, Nature 531, 591-597 (2016).

Figure 1. Elevation changes at Vavilov Ice Cap, Russian High Arctic. A-C) Shaded Digital Elevation Models from Worldview stereo imagery for Spring 2014 through 2016. The westward advance of the outlet glacier and propagation of thinning inland can be seen through time; (d.) shows elevations along the centerline of the outlet glacier compared with an earlier DEM (from 1984) and bed topography.

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Figure 2. Evolution of front position with time superimposed over Landsat-8 Panchromatic image from spring 2016. Black line is centerline flow-profile. Extents traced by hand. Zero km is the position of the coastline before the glacier advanced, pre-1985.

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SALTMARSH RECORD OF POST LITTLE ICE AGE MASS BALANCE CHANGES IN SOUTHEAST GREENLAND

Woodroffe, Sarah1, Barlow, Natasha1, Wake, Leanne2, Kjeldsen, Kristian3, Bjork, Anders3, Kjaer, Kurt3, Long, Antony1

1Department of Geography, Durham University, UK 2Faculty of Engineering and Environment, Northumbria University, UK 3Centre for Geogenetics, Natural History Museum, University of Copenhagen, Denmark

Saltmarshes provide excellent archives of relative sea-level (RSL) changes over a range of different timescales. In Greenland they yield precise RSL data over the past few decades to hundreds of years that can help constrain Greenland Ice Sheet mass changes during and after the Little Ice Age (LIA). They are particularly valuable as they provide a longer term context upon which to evaluate recent tide gauge and GPS records which span only the past decade or so. In Southeast Greenland the current rate of crustal uplift recorded by GPS is approximately +7 mm/yr at the open coast and up to +18 mm/yr close to the ice sheet margin, which reflects high rates of recent mass loss. This study investigates a fossil saltmarsh located within 5 km of the ice sheet margin at the head of Skjoldungen fjord in southeast Greenland. The aim is to use RSL data to establish the timing and magnitude of mass loss since the end of the LIA. This is the first time that saltmarshes so close to the ice sheet margin have been utilised to create high precision proxy-GPS data for the last few hundred years. Microfossil (diatom) evidence from saltmarsh sediments at the Skjoldungen study site record a recent change from RSL rise to stable RSL, then RSL fall during the past 200 years. We interpret the change from RSL rise to stable RSL as evidence for the initial onset of mass loss locally from the Greenland Ice Sheet at the end of the Little Ice Age. Later RSL fall occurs as mass loss accelerates during the 20th Century. We use a combination of dating methods to establish the timing of the initial RSL slowdown and rates of RSL rise during the LIA and fall during the 20th Century. We then compare our RSL record to geophysical model predictions of local RSL change due to post-LIA Greenland mass loss and consider the contribution of other factors (e.g. thermosteric effects, fingerprint of glacial melt elsewhere) to RSL during the 20th Century in this location. This study provides the first direct evidence that saltmarsh sediments from near-field sites can be used to reconstruct the timing of recent mass loss change from the Greenland Ice Sheet, extending direct GPS observations back to the end of the Little Ice Age and beyond using geological data.

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THE EARLY HOLOCENE GLACIATION IN BAFFIN BAY PROJECT: INITIAL RESULTS

Young, Nicolás1, Miller, Gifford2, Briner, Jason3, Schaefer, Joerg1, Crump, Sarah2, Lesnek, Alia3, Pendleton, Simon2

1Lamont-Doherty Earth Observatory, Columbia University 2INSTAAR and Department of Geological Sciences, University of Colorado- Boulder 3Department of Geology, University at Buffalo

Gauging the sensitivity of ice sheets to short-term climate variability is at the forefront of the scientific community’s and public’s interest because short- term ice-sheet change will drive 21st century sea-level rise. Do ice sheets react abruptly to centennial-scale climate forcing, or are millennial-scale climate trends required to elicit a large-scale ice-sheet response? Within this framework, the early Holocene is of particular interest because both the Laurentide and Greenland ice sheets (LIS & GrIS) were rapidly retreating at this time within a climate regime that was as warm or warmer than today, yet at least two abrupt (centennial scale) cooling events interrupted this warmth. Reconstructions of ice- sheet behavior through the early Holocene provide a natural test for assessing the sensitivity of ice sheet to temperature change, both warming and cooling, on human-relevant timescales. In 2015, our team began a series of field campaigns in Baffin Island and southwestern Greenland aimed at reconstructing, in detail, the early Holocene behavior of the LIS, GrIS and independent mountain glaciers. Our efforts build off previous results from the broader Baffin Bay region indicating that fast-flowing Greenland and Laurentide marine termini advanced and deposited moraines in response to the short-lived 9.3 and 8.2 ka cooling events (Briner et al., 2009; Young et al., 2012; 2013). Here, our primary goals are to 1) establish how land- terminating regions of ice sheets, which are more representative of broader ice- sheet margins, respond to abrupt climate change, and 2) reconstruct the early Holocene behavior of mountain glacier systems (a proxy for summertime temperature) to evaluate what climatic conditions influenced the GrIS and LIS during the early Holocene. To tackle these objectives, we undertook an aggressive 10Be dating approach, coupled with select lake coring efforts, to directly constrain the age of prominent moraines located on Baffin Island and southwestern Greenland. Here, I will present initial 10Be ages from 2 of our 3 planned field seasons that constrain the timing of early Holocene advances of a Baffin Island mountain glacier and once sector of the southwestern GrIS.

Briner, J. P., A. C. Bini, and R. S. Anderson (2009), Rapid early Holocene retreat of a Laurentide outlet glacier through an Arctic fjord, Nat. Geosci., 2, 496–499, doi:10.1038/ngeo556. Young, N. E., J. P. Briner, D. H. Rood, and R. C. Finkel (2012), Glacier Extent During the Younger Dryas and 8.2-ka Event on Baffin Island, Arctic Canada, Science, 337(6100), 1330–1333, doi:10.1126/science.1222759. Young, N. E., J. P. Briner, D. H. Rood, R. C. Finkel, L. B. Corbett, and P. R. Bierman (2013), Age

154 of the Fjord Stade moraines in the Disko Bugt region, western Greenland, and the 9.3 and 8.2 ka cooling events, Quat. Sci. Rev., 60, 76–90, doi:10.1016/j.quascirev. 2012.09.028.

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MONITORING LAND-ICE ELEVATION CHANGES IN FRANZ JOSEF LAND USING REMOTE SENSING

Zheng, Whyjay1, Pritchard, Matthew E.1, Willis, Michael J.1,2

1Department of Earth and Atmospheric Sciences, Cornell University 2INSTAAR and Department of Geological Sciences, University of Colorado- Boulder

Remote sensing has been a great tool to look at the recent changes in remote areas of the cryosphere, and here we focus on a specific region called Franz Josef Land (FJL), in the Russian Arctic, where we describe land ice changes using elevation data derived from satellite stereo imagery. Franz Josef Land is an archipelago that consists of 191 islands with a total surface area roughly the same as the state of Hawaii (16,134 km^2) and where land ice covers ~85% of the surface. It is generally classified as a polar desert with a mean annual temperature of -12.4 degree C, an average annual precipitation of 259 mm w.e.[1,2], and the summer temperature is typically at 0 degree C[3]. Over the past few decades, the Arctic has warmed at a speed almost double the global average, corresponding to a significant loss of Arctic sea ice [4]. However, some areas of Arctic land ice, including FJL, are thought to be close to neutral mass balance over the past decades, although data is limited because of their remote location. Measurements from various satellites has been used in the recent years, but the uneven spatial distribution of both measurements and elevation changes has made it hard to determine if FJL has gained or lost ice mass. For example, both the mean mass change derived from GRACE gravity anomalies in 2004 to 2009 (0.7 +- 3.5$ Gt/yr) and the mean elevation change calculated from the ICESat laser altimeter data during the same time span (0.9 +- 0.7 Gt/yr)[1], have a large uncertainty due to a coarse resolution. In terms of spatial variation of elevation changes, the spatial distribution has ranged within +- 100 m in 1953- 2008[6], and it can vary significantly in a single ice cap of several tens of kilometers wide. To better resolve the details of FJL mass loss on a glacier-by-glacier basis across the entire region, we compare digital elevation models (DEM) from optical stereo imagery collected at different times. We use the ArcticDEM dataset, which is derived from the high-resolution (2-m) imagery of WorldView satellite series in 2011-2015. It has 564 DEM scenes in FJL open to the public, and all the DEM strips are automatically produced by Surface Extraction from TIN-based Searchspace Minimization (SETSM) software with high-performance computing. In this study, we only focus on 385 scenes with an "ICESat transformation vector" which means a DEM can be adjusted to match measurements of ICESat satellite laser altimeter over bedrock, where surface elevation is assumed to be fixed. This correction is applied to each DEM as the first step. In addition to ArcticDEM, we also use other DEMs derived from WorldView imagery but not included in ArcticDEM. These extra DEMs are processed by the NASA Ames Stereo Pipeline (ASP) tool suite and are also adjusted by ICESat data over

156 bedrock. To compare these DEMs with older height data, we use a digitalized Russian cartographic map from 1953, which is adjusted by the same ICESat data and then georeferenced by ground control points (GCPs). These GCPs are set by matching surface features (e.g. nunataks) between the digitalized DEM and WorldView-derived DEMs. The remaining difference between ICESat data and each DEM over bedrock is assumed to be the DEM uncertainty. The typical DEM uncertainty is 9.2 m for the 1953 cartographic DEM; For the WorldView-derived DEMs, it is around 0.5-0.6 m, but can be up to 3 m for some strips. For comparison, the intrinsic precision of the ICESat elevations can be better than 0.05 m under optimal conditions[7], and is estimated to be 0.78 m over Russian Arctic glaciers[1]. We use two approaches to calculate the ice-elevation change rate (abbreviated as dh/dt). The first one is differencing just two DEMs collected at different times. Since there are many DEM strips in FJL in 2011-2015, we select a subset to reflect the earliest measurement with the least uncertainty, and then mosaic them into a completed DEM across the whole region, which is then compared with the 1953 cartographic DEM. Using the same idea, a WorldView- derived DEM representing the latest measurement with the least uncertainty is made from other selected DEMs. Thus, the long-term dh/dt (1953-2010s) is given by subtracting the earliest measurement in 2010s from the cartographic data in 1953, and the recent dh/dt in 2010s is calculated by DEM differencing between the latest and the oldest WorldView measurements. The second approach is to apply a linear regression model to time series of DEM heights. This is because we have hundreds of DEM strips which sometimes overlap the same area, where we can sample through all DEMs to form time series. Note that this approach gives more robust dh/dt estimates than DEM differencing, but it requires more data overlapping in the same area. The DEM count varies place to place in FJL, from only 1 to more than 10 points in 2011-2015. This will be improved in the future as more data from 2016 and 2017 become available. The long-term dh/dt (1953-2010s) results (Fig. 1) show that about 39.8% of the surface area has thinned and another 60.2% has thickened. The average dh/dt corresponds to a negative mass change rate of -1.88 +- 0.57 Gt/yr, or a mean thickness reduction of -149 +- 45$ mm w.e. Despite the low average thinning rate at around 0.16 m/yr, there are 9 glaciers where the thinning rate is up to 3-4 m/yr. Most other glaciers have thinned for this 60-year time span, while ice caps have acted differently. Major thickening events are primarily located at some ice caps without any outlet marine-terminating glaciers, or also terminating in bedrock. A prominent example is the Windy Ice Cap, the biggest and easternmost ice cap in FJL, with a thickening rate around 1 m/yr. In addition, many boundaries between ice and sea have retreated 1-3 km, not only at glacier termini but also at the edge of ice caps. In contrast to the long-term dh/dt, recent dh/dt (in 2011-2015) calculated from both DEM differencing and the linear regression model suggests that more ice caps and glaciers have started to thin at a higher rate (Fig. 2). 77.3% of the surface area has thinned since 2011, and only the remaining 22.7% has thickened. The average recent dh/dt corresponds to a mass change rate of -4.89 +- 0.60 Gt/yr, or a mean thickness reduction of -389 +-

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48$ mm w.e., which is 2.6 times faster than the long-term rate. Although spatially variable, the dh/dt is as low as -10 m/yr at a few outlet glaciers. Note that the locations of these quick-thinning glaciers has also changed, but some similarities still exist, e.g. the most thinning is in the southwest of FJL and most thickening is in the northeast of FJL (consistent with results from [1) and [5]). In southwestern FJL, nearly all glaciers have thinned at 1-5 m/yr, while there is an ice cap with a thickening rate less than 1 m/yr in the other side of FJL. More ice fronts have started or continued to retreat, resulting in a shrinkage of ice area, regardless of whether ice is thinning or thickening. The Windy Ice Cap, highlighted by its widespread thickening during the long-term time span, has not thickened during the recent time period; instead, fluctuations of elevation changes have been observed, which suggest that the thickening trend has been disrupted, or that the seasonal signals have started to dominate the elevation due to weakened thickening trend. This will be addressed by an analysis of fitness over a linear regression model. To conclude, this study gives us strong evidence that FJL had a negative ice balance in 1953-2010s, and it has been 2.6 times lower since 2010s. 37.3% of the surface area has changed from slight thickening to thinning. Meanwhile, ice fronts have also retreated for over 60 years, which also makes land ice smaller in terms of area. The SW-NE thinning-thickening pattern is the major similarity shared with long-term and recent years, but there are several areas where mass loss has accelerated in recent years.

[1] Moholdt, G., Wouters, B., & Gardner, A. S. (2012). Recent mass changes of glaciers in the Russian High Arctic. Geophysical Research Letters, 39(10), 1–5. [2] Climate data frrom http://www.pogodaiklimat.ru/climate/20046.htm, retrieved 17 November 2012. [3] Barr, Susan (1995). Franz Josef Land. Oslo: Norwegian Polar Institute. ISBN 82-7666-095-9. [4] Screen, J. A., & Simmonds, I. (2010). The central role of diminishing sea ice in recent Arctic temperature amplification. Nature, 464(7293), 1334–1337. [5] Dowdeswell, J. A. et al. (1997). The Mass Balance of Circum-Arctic Glaciers and Recent Climate Change. Quaternary Research, 48(1), 1–14. [6] Sharov, A. I. (2008). Franz Josef Land Region: Glacier changes in 1950-2000s[map]. Graz: Joanneum Research. [7] Fricker, H. A. et al. (2005). Assessment of ICESat performance at the Salar de Uyuni, Bolivia. Geophysical Research Letters, 32(L21S06).

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Figure 1. The long-term dh/dt (1953-2010s) map of Franz Josef Land made by DEM differencing.

Figure 2. The recent dh/dt (2011-2015) map of Franz Josef Land made by DEM differencing.

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Workshop Participants Kim Diana Connolly University at Buffalo Estelle Allan

GEOTOP-UQAM Megan Corcoran

University at Buffalo Patrick Alexander

NASA Goddard Institute Pierre-Olivier Couette for Space Studies Université Laval

Benjamin Amann Owen Cowling Queen’s University, ON University at Buffalo

John Andrews Sarah Crump INSTAAR, University of Colorado INSTAAR, University of Colorado

Nína Aradóttir Beata Csatho University Centre in Svalbard (UNIS) University at Buffalo

James Baichtal Lorelei Curtin Tongass National Forest Lamont-Doherty Earth Observatory

Columbia University Thomas Ballinger

Texas State University Josh Cuzzone

University of California-Irvine David Barclay

SUNY Cortland Sarah Das

Woods Hole Oceanographic Institution Casey Beel

Queens University Anne de Vernal

GEOTOP-UQAM Helena Bergstedt

University of Salzburg Geoffrey Dipre

Byrd Polar & Climate Research Center Jason Briner Ohio State University University at Buffalo

Jacob Downs Laura-Ann Broom University of Montana Dalhousie University

William Durkin IV Etienne Brouard Cornell University Université Laval

Michael Dyonisius Calvin Campbell University of Rochester Geological Survey of Canada

Lea Maria Frederiksen Isla Castañeda University of Copenhagen University of Massachusetts-Amherst University Centre in Svalbard (UNIS)

Allison Cluett Helen Habicht University at Buffalo University of Massachusetts-Amherst

161

Lena Håkansson Gifford Miller University Centre in Svalbard (UNIS) INSTAAR, University of Colorado

David Harning Rohi Muthyala INSTAAR, CU-Boulder Rutgers University University of Iceland Peter Neff Benjamin Hmiel University of Rochester University of Rochester Obinna Nzekwe Erik Holmlund Institut National de la Recherche Stockholm University Scientifique Erik Orantes Heather Ipsen University at Buffalo Syracuse University NOAA-CREST

Anne Jennings Matthew Osman INSTAAR, CU-Boulder Massachusetts Institute of Technology Woods Hole Oceanographic Institution Jesse Johnson University of Montana Marie-Michèle Ouellet-Bernier Université du Québec à Montréal Rabia Kalfaoglu Moskow State University Christof Pearce Bolin Centre for Climate Research Samuel Kelley (Stockholm University) University of Waterloo Simon Pendleton Paul Knutz INSTAAR, University of Colorado Geological Survey of Denmark and Greenland (GEUS) Vasilii Petrenko University of Rochester Darren Larsen Occidental College Philip Place University of Rochester Sasha Leidman Rutgers University Noel Potter Bates College Charlotte Lindqvist University at Buffalo Sarah Principato Gettysburg College Alia Lesnek University at Buffalo Matt Pritchard Cornell University Joseph Licciardi University at New Hampshire Michael Retelle Bate College Claire Markonic Bates College Jessey Rice University of Waterloo

162

Carolyn Roberts University of Buffalo

Heidi Roop University of Washington

Joerg Schaefer Lamont-Doherty Earth Observatory Columbia University

Avriel Schweinsberg University at Buffalo

Kenta Suzuki Hokkaido University

Eric Steig University of Washington

Elizabeth Thomas University at Buffalo

Joseph Tulenko University at Buffalo

Lindsay Wendler University at Buffalo

Evan Wilcox Cold Regions Research Centre (Wilfrid Laurier University)

Gwenyth Williams Bates College

Sarah Woodroffe Durham University

Nicolás Young Lamont-Doherty Earth Observatory Columbia University

Whyjay Zheng Cornell University

163

Notes

164

Notes

165

Notes

166