DOCSLIB.ORG

Stratigraphic Analysis of Firn Cores from an Antarctic Ice Shelf Firn Aquifer

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Stratigraphic Analysis of Firn Cores from an Antarctic Ice Shelf Firn Aquifer water Article Stratigraphic Analysis of Firn Cores from an Antarctic Ice Shelf Firn Aquifer Shelley MacDonell 1,* , Francisco Fernandoy 2 , Paula Villar 2 and Arno Hammann 1,† 1 Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Raúl Bitrán 1305, La Serena 1700000, Chile; [email protected] 2 Laboratorio de Análisis Isotópico, Universidad Andrés Bello, Viña del Mar 2531015, Chile; [email protected] (F.F.); [email protected] (P.V.) * Correspondence: [email protected] † Now at: Asiaq—Greenland Survey, Qatserisut, Nuuk 3900, Greenland. Abstract: In recent decades, several large ice shelves in the Antarctic Peninsula region have experi- enced significant ice loss, likely driven by a combination of oceanic, atmospheric and hydrological processes. All three areas need further research, however, in the case of the role of liquid water the first concern is to address the paucity of field measurements. Despite this shortage of field observations, several authors have proposed the existence of firn aquifers on Antarctic ice shelves, however little is known about their distribution, formation, extension and role in ice shelf mechanics. In this study we present the discovery of saturated firn at three drill sites on the Müller Ice Shelf (67◦140 S; 66◦520 W), which leads us to conclude that either a large contiguous or several disconnected smaller firn aquifers exist on this ice shelf. From the stratigraphic analysis of three short firn cores extracted during February 2019 we describe a new classification system to identify the structures and morphological signatures of refrozen meltwater, identify evidence of superficial meltwater percolation, and use this information to propose a conceptual model of firn aquifer development Citation: MacDonell, S.; Fernandoy, on the Müller Ice Shelf. The detailed stratigraphic analysis of the sampled cores will provide an F.; Villar, P.; Hammann, A. invaluable baseline for modelling studies. Stratigraphic Analysis of Firn Cores from an Antarctic Ice Shelf Firn Keywords: ice shelf; firn aquifer; ice core; stratigraphy; glacier hydrology; Antarctica Aquifer. Water 2021, 13, 731. https://doi.org/10.3390/w13050731 Academic Editor: Michael Kuhn 1. Introduction Liquid water plays key roles in the cryosphere, for example: the flow of land ice is Received: 5 February 2021 predominately controlled by the quantity of liquid water present (e.g., [1]); energy fluxes in Accepted: 3 March 2021 Published: 8 March 2021 snowpacks are influenced by the presence and behaviour of liquid water (e.g., [2]); and many theories of ice shelf disintegration involve the presence and action of water (e.g., [3]). Publisher’s Note: MDPI stays neutral While the hydrological system on land-based glaciers is well defined, very few direct field with regard to jurisdictional claims in observations have been carried out on ice shelves (e.g., [4]). published maps and institutional affil- Understanding the distribution of liquid and refrozen water on ice shelves is im- iations. portant for understanding ice mechanics and ice shelf dynamics [5,6]. Liquid water can cause hydrofracturing (when increased pressure is exerted by water on the tips of vertical fractures) [3,7] and when accumulated into ponds, can cause bending stresses and fracture formation from rapid drainage events [3,8–12]. On ice sheets, the refreezing of liquid water in superficial firn [13] can cause the impedance of water percolation, therein enhancing Copyright: © 2021 by the authors. either runoff or internal ponding. Comparatively, on Antarctic ice shelves, [14] identified Licensee MDPI, Basel, Switzerland. This article is an open access article such a refrozen surface on the Larsen C ice shelf using geophysical surveys, [6] reported distributed under the terms and from remotely sensed images meltwater being exported via a supraglacial stream network conditions of the Creative Commons and [4] described the hydrological properties of a firn aquifer on the Wilkins Ice Shelf. The Attribution (CC BY) license (https:// diversity of hydrological system structures, and possible impacts makes realistic modelling creativecommons.org/licenses/by/ of ice sheet and ice shelf processes difficult [15,16]. This is further exacerbated by the dearth 4.0/). of field measurements of the mechanical and hydrological properties of ice shelves. Water 2021, 13, 731. https://doi.org/10.3390/w13050731 https://www.mdpi.com/journal/water Water 2021, 13, x FOR PEER REVIEW 2 of 18 Water 2021, 13, 731 by the dearth of field measurements of the mechanical and hydrological properties2 of of ice 17 shelves. Several authors have proposed the existence of firn aquifers on Antarctic ice shelves (e.g., [4,17]), however little is known about their distribution, formation, extension and Several authors have proposed the existence of firn aquifers on Antarctic ice shelves role in ice shelf mechanics. In this study we present the discovery of fully saturated firn (e.g., [4,17]), however little is known about their distribution, formation, extension and on the Müller Ice Shelf, which leads us towards the conclusion of at least one large firn role in ice shelf mechanics. In this study we present the discovery of fully saturated firn onaquifer the Müller or disconnected Ice Shelf, which smaller leads firn us aquifers towards on the this conclusion ice shelf. ofWe at will least present one large results firn aquiferbased on or disconnectedthe stratigraphic smaller analysis firn aquifers of three on short this icefirn shelf. cores We extracted will present during results February based on2019. the In stratigraphic particular, this analysis study of aims three to shortdevelop firn a coresclassification extracted system during to February identify the 2019. struc- In particular,tures and morphological this study aims signatures to develop of a refrozen classification meltwater, system identify to identify evidence the structures of superficial and morphologicalmeltwater percolation, signatures and of refrozenuse this informat meltwater,ion identify to construct evidence a conceptual of superficial understanding meltwater percolation,firn aquifers and on usethe Müller this information Ice Shelf. to construct a conceptual understanding firn aquifers on the Müller Ice Shelf. 2. Materials and Methods 2.2.1. Materials Study Area and Methods 2.1. StudyThe Müller Area Ice Shelf is the northern-most ice shelf on the Antarctic Peninsula (AP) (67°14The′ S; Müller 66°52′ IceW) Shelf(Figure is the1). It northern-most is located on the ice shelfwestern on theside Antarctic of the AP Peninsula and drains (AP) the ◦ 0 ◦ 0 (67Arrowsmith14 S; 66 52Peninsula.W) (Figure It is1 fed). It by is the located Brückner on the and western Antevs side glaciers of the and AP terminates and drains in the the ArrowsmithLallemand Fjord. Peninsula. The Itice is shelf fed by is therelatively Brückner small and Antevs(40 km2 glaciers) and has and been terminates experiencing in the 2 Lallemandphases of advance Fjord. The and ice retreat shelf issince relatively at least small the Little (40 km Ice) andAge has[18], been and experiencing now covers approx- phases ofimately advance 50% and of retreatthe area since recorded at least in the 1957 Little [19] Ice. An Age important [18], and question now covers is why approximately the Müller 50%Ice Shelf of the remains area recorded extant, whereas in 1957 its [19 neighbours]. An important (e.g., Jones question Ice shelf) is why have the collapsed Müller [19]. Ice ShelfHypotheses remains related extant, to whereas ice shelf its geometry, neighbours the (e.g.,amount Jones of ice Ice discharge shelf) have relative collapsed to catch- [19]. Hypothesesment size as related well as to protection ice shelf geometry, from the theocean amount have of been ice dischargeproposed, relative but the to relationship catchment sizebetween as well the as ice protection shelf, climate from theand ocean ocean have processes been proposed,remain unclear. but the relationship between the ice shelf, climate and ocean processes remain unclear. (a) (b) Figure 1. Map of the study area. (a) shows the position on the Antarctic Peninsula, (b) shows the wider Müller Ice Shelf region, and the red points correspond to the ice core extraction sites. Water 2021, 13, x FOR PEER REVIEW 3 of 18 Water 2021, 13, 731 3 of 17 Figure 1. Map of the study area. (a) shows the position on the Antarctic Peninsula, (b) shows the wider Müller Ice Shelf region, and the red points correspond to the ice core extraction sites. 2.2. Sample Collection and Handling A series of of three three short short firn firn cores cores were were colle collectedcted from from the the Müller Müller Ice Ice Shelf Shelf between between 20 and20 and 22 February 22 February 2019 2019(Figures (Figures 1 and1 2).and The2). drill The used drill had used a maximum had a maximum reach of reach 20 m, ofbut ultimately20 m, but ultimately core lengths core were lengths determined were determined by the presence by the of presence saturated of material saturated impeding material theimpeding deeper the penetration deeper penetration of the device. of the The device. core TheM1 corewas M1located was locatedat the confluence at the confluence of the ◦ 0 ◦ 0 Brücknerof the Brückner and Antevs and Antevs glaciers glaciers (67°15′15.5 (67 ″15 S; 15.5”66°53′ S;44.5 66″ 53W)44.5” and reached W) and a reached depth of a depth16.72 m. of 16.72M2 was m. M2located was locatednear the near centre the centreof the of ice the shelf ice shelf in the in thearea area fed fed by by the the Antevs Antevs Glacier ◦ 0 ◦ 0 (67(67°1515′16.816.8”″ S; S; 66°50 66 50′59.859.8”″ W), W), and and was was 18.54 18.54 m m long. long. Comparatively, Comparatively, M3 was 3.72 m long and was extracted near the eastern limit of the ice shelf also fed by the AntevsAntevs GlacierGlacier ◦ 0 ◦ 0 (67(67°1515′37.637.6”″ S; S; 66°48 66 48′22.322.3”″ W).
Load more

Recommended publications
  • Lecture 21: Glaciers and Paleoclimate Read: Chapter 15 Homework Due Thursday Nov
    Learning Objectives (LO) Lecture 21: Glaciers and Paleoclimate Read: Chapter 15 Homework due Thursday Nov. 12 What we’ll learn today:! 1. 1. Glaciers and where they occur! 2. 2. Compare depositional and erosional features of glaciers! 3. 3. Earth-Sun orbital parameters, relevance to interglacial periods ! A glacier is a river of ice. Glaciers can range in size from: 100s of m (mountain glaciers) to 100s of km (continental ice sheets) Most glaciers are 1000s to 100,000s of years old! The Snowline is the lowest elevation of a perennial (2 yrs) snow field. Glaciers can only form above the snowline, where snow does not completely melt in the summer. Requirements: Cold temperatures Polar latitudes or high elevations Sufficient snow Flat area for snow to accumulate Permafrost is permanently frozen soil beneath a seasonal active layer that supports plant life Glaciers are made of compressed, recrystallized snow. Snow buildup in the zone of accumulation flows downhill into the zone of wastage. Glacier-Covered Areas Glacier Coverage (km2) No glaciers in Australia! 160,000 glaciers total 47 countries have glaciers 94% of Earth’s ice is in Greenland and Antarctica Mountain Glaciers are Retreating Worldwide The Antarctic Ice Sheet The Greenland Ice Sheet Glaciers flow downhill through ductile (plastic) deformation & by basal sliding. Brittle deformation near the surface makes cracks, or crevasses. Antarctic ice sheet: ductile flow extends into the ocean to form an ice shelf. Wilkins Ice shelf Breakup http://www.youtube.com/watch?v=XUltAHerfpk The Greenland Ice Sheet has fewer and smaller ice shelves. Erosional Features Unique erosional landforms remain after glaciers melt.
    [Show full text]
  • Minimal Geological Methane Emissions During the Younger Dryas-Preboreal Abrupt Warming Event
    UC San Diego UC San Diego Previously Published Works Title Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt warming event. Permalink https://escholarship.org/uc/item/1j0249ms Journal Nature, 548(7668) ISSN 0028-0836 Authors Petrenko, Vasilii V Smith, Andrew M Schaefer, Hinrich et al. Publication Date 2017-08-01 DOI 10.1038/nature23316 Peer reviewed eScholarship.org Powered by the California Digital Library University of California LETTER doi:10.1038/nature23316 Minimal geological methane emissions during the Younger Dryas–Preboreal abrupt warming event Vasilii V. Petrenko1, Andrew M. Smith2, Hinrich Schaefer3, Katja Riedel3, Edward Brook4, Daniel Baggenstos5,6, Christina Harth5, Quan Hua2, Christo Buizert4, Adrian Schilt4, Xavier Fain7, Logan Mitchell4,8, Thomas Bauska4,9, Anais Orsi5,10, Ray F. Weiss5 & Jeffrey P. Severinghaus5 Methane (CH4) is a powerful greenhouse gas and plays a key part atmosphere can only produce combined estimates of natural geological in global atmospheric chemistry. Natural geological emissions and anthropogenic fossil CH4 emissions (refs 2, 12). (fossil methane vented naturally from marine and terrestrial Polar ice contains samples of the preindustrial atmosphere and seeps and mud volcanoes) are thought to contribute around offers the opportunity to quantify geological CH4 in the absence of 52 teragrams of methane per year to the global methane source, anthropogenic fossil CH4. A recent study used a combination of revised 13 13 about 10 per cent of the total, but both bottom-up methods source δ C isotopic signatures and published ice core δ CH4 data to 1 −1 2 (measuring emissions) and top-down approaches (measuring estimate natural geological CH4 at 51 ±​ 20 Tg CH4 yr (1σ range) , atmospheric mole fractions and isotopes)2 for constraining these in agreement with the bottom-up assessment of ref.
    [Show full text]
  • Sea Level and Climate Introduction
    Sea Level and Climate Introduction Global sea level and the Earth’s climate are closely linked. The Earth’s climate has warmed about 1°C (1.8°F) during the last 100 years. As the climate has warmed following the end of a recent cold period known as the “Little Ice Age” in the 19th century, sea level has been rising about 1 to 2 millimeters per year due to the reduction in volume of ice caps, ice fields, and mountain glaciers in addition to the thermal expansion of ocean water. If present trends continue, including an increase in global temperatures caused by increased greenhouse-gas emissions, many of the world’s mountain glaciers will disap- pear. For example, at the current rate of melting, most glaciers will be gone from Glacier National Park, Montana, by the middle of the next century (fig. 1). In Iceland, about 11 percent of the island is covered by glaciers (mostly ice caps). If warm- ing continues, Iceland’s glaciers will decrease by 40 percent by 2100 and virtually disappear by 2200. Most of the current global land ice mass is located in the Antarctic and Greenland ice sheets (table 1). Complete melt- ing of these ice sheets could lead to a sea-level rise of about 80 meters, whereas melting of all other glaciers could lead to a Figure 1. Grinnell Glacier in Glacier National Park, Montana; sea-level rise of only one-half meter. photograph by Carl H. Key, USGS, in 1981. The glacier has been retreating rapidly since the early 1900’s.
    [Show full text]
  • Calving Processes and the Dynamics of Calving Glaciers ⁎ Douglas I
    Earth-Science Reviews 82 (2007) 143–179 www.elsevier.com/locate/earscirev Calving processes and the dynamics of calving glaciers ⁎ Douglas I. Benn a,b, , Charles R. Warren a, Ruth H. Mottram a a School of Geography and Geosciences, University of St Andrews, KY16 9AL, UK b The University Centre in Svalbard, PO Box 156, N-9171 Longyearbyen, Norway Received 26 October 2006; accepted 13 February 2007 Available online 27 February 2007 Abstract Calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world. Calving rates can increase dramatically in response to increases in velocity and/or retreat of the glacier margin, with important implications for sea level change. Despite their importance, calving and related dynamic processes are poorly represented in the current generation of ice sheet models. This is largely because understanding the ‘calving problem’ involves several other long-standing problems in glaciology, combined with the difficulties and dangers of field data collection. In this paper, we systematically review different aspects of the calving problem, and outline a new framework for representing calving processes in ice sheet models. We define a hierarchy of calving processes, to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events. The first-order control on calving is the strain rate arising from spatial variations in velocity (particularly sliding speed), which determines the location and depth of surface crevasses. Superimposed on this first-order process are second-order processes that can further erode the ice margin.
    [Show full text]
  • Ice Flow Impacts the Firn Structure of Greenland's Percolation Zone
    University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 2019 Ice Flow Impacts the Firn Structure of Greenland's Percolation Zone Rosemary C. Leone University of Montana, Missoula Follow this and additional works at: https://scholarworks.umt.edu/etd Part of the Glaciology Commons Let us know how access to this document benefits ou.y Recommended Citation Leone, Rosemary C., "Ice Flow Impacts the Firn Structure of Greenland's Percolation Zone" (2019). Graduate Student Theses, Dissertations, & Professional Papers. 11474. https://scholarworks.umt.edu/etd/11474 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. ICE FLOW IMPACTS THE FIRN STRUCTURE OF GREENLAND’S PERCOLATION ZONE By ROSEMARY CLAIRE LEONE Bachelor of Science, Colorado School of Mines, Golden, CO, 2015 Thesis presented in partial fulfillMent of the requireMents for the degree of Master of Science in Geosciences The University of Montana Missoula, MT DeceMber 2019 Approved by: Scott Whittenburg, Dean of The Graduate School Graduate School Dr. Joel T. Harper, Chair DepartMent of Geosciences Dr. Toby W. Meierbachtol DepartMent of Geosciences Dr. Jesse V. Johnson DepartMent of Computer Science i Leone, RoseMary, M.S, Fall 2019 Geosciences Ice Flow Impacts the Firn Structure of Greenland’s Percolation Zone Chairperson: Dr. Joel T. Harper One diMensional siMulations of firn evolution neglect horizontal transport as the firn column Moves down slope during burial.
    [Show full text]
  • Comparison of Remote Sensing Extraction Methods for Glacier Firn Line- Considering Urumqi Glacier No.1 As the Experimental Area
    E3S Web of Conferences 218, 04024 (2020) https://doi.org/10.1051/e3sconf/202021804024 ISEESE 2020 Comparison of remote sensing extraction methods for glacier firn line- considering Urumqi Glacier No.1 as the experimental area YANJUN ZHAO1, JUN ZHAO1, XIAOYING YUE2and YANQIANG WANG1 1College of Geography and Environmental Science, Northwest Normal University, Lanzhou, China 2State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources/Tien Shan Glaciological Station, Chinese Academy of Sciences, Lanzhou, China Abstract. In mid-latitude glaciers, the altitude of the snowline at the end of the ablating season can be used to indicate the equilibrium line, which can be used as an approximation for it. In this paper, Urumqi Glacier No.1 was selected as the experimental area while Landsat TM/ETM+/OLI images were used to analyze and compare the accuracy as well as applicability of the visual interpretation, Normalized Difference Snow Index, single-band threshold and albedo remote sensing inversion methods for the extraction of the firn lines. The results show that the visual interpretation and the albedo remote sensing inversion methods have strong adaptability, alonger with the high accuracy of the extracted firn line while it is followed by the Normalized Difference Snow Index and the single-band threshold methods. In the year with extremely negative mass balance, the altitude deviation of the firn line extracted by different methods is increased. Except for the years with extremely negative mass balance, the altitude of the firn line at the end of the ablating season has a good indication for the altitude of the balance line.
    [Show full text]
  • Glacier (And Ice Sheet) Mass Balance
    Glacier (and ice sheet) Mass Balance The long-term average position of the highest (late summer) firn line ! is termed the Equilibrium Line Altitude (ELA) Firn is old snow How an ice sheet works (roughly): Accumulation zone ablation zone ice land ocean • Net accumulation creates surface slope Why is the NH insolation important for global ice• sheetSurface advance slope causes (Milankovitch ice to flow towards theory)? edges • Accumulation (and mass flow) is balanced by ablation and/or calving Why focus on summertime? Ice sheets are very sensitive to Normal summertime temperatures! • Ice sheet has parabolic shape. • line represents melt zone • small warming increases melt zone (horizontal area) a lot because of shape! Slightly warmer Influence of shape Warmer climate freezing line Normal freezing line ground Furthermore temperature has a powerful influence on melting rate Temperature and Ice Mass Balance Summer Temperature main factor determining ice growth e.g., a warming will Expand ablation area, lengthen melt season, increase the melt rate, and increase proportion of precip falling as rain It may also bring more precip to the region Since ablation rate increases rapidly with increasing temperature – Summer melting controls ice sheet fate* – Orbital timescales - Summer insolation must control ice sheet growth *Not true for Antarctica in near term though, where it ʼs too cold to melt much at surface Temperature and Ice Mass Balance Rule of thumb is that 1C warming causes an additional 1m of melt (see slope of ablation curve at right)
    [Show full text]
  • A Globally Complete Inventory of Glaciers
    Journal of Glaciology, Vol. 60, No. 221, 2014 doi: 10.3189/2014JoG13J176 537 The Randolph Glacier Inventory: a globally complete inventory of glaciers W. Tad PFEFFER,1 Anthony A. ARENDT,2 Andrew BLISS,2 Tobias BOLCH,3,4 J. Graham COGLEY,5 Alex S. GARDNER,6 Jon-Ove HAGEN,7 Regine HOCK,2,8 Georg KASER,9 Christian KIENHOLZ,2 Evan S. MILES,10 Geir MOHOLDT,11 Nico MOÈ LG,3 Frank PAUL,3 Valentina RADICÂ ,12 Philipp RASTNER,3 Bruce H. RAUP,13 Justin RICH,2 Martin J. SHARP,14 THE RANDOLPH CONSORTIUM15 1Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA 2Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA 3Department of Geography, University of ZuÈrich, ZuÈrich, Switzerland 4Institute for Cartography, Technische UniversitaÈt Dresden, Dresden, Germany 5Department of Geography, Trent University, Peterborough, Ontario, Canada E-mail: [email protected] 6Graduate School of Geography, Clark University, Worcester, MA, USA 7Department of Geosciences, University of Oslo, Oslo, Norway 8Department of Earth Sciences, Uppsala University, Uppsala, Sweden 9Institute of Meteorology and Geophysics, University of Innsbruck, Innsbruck, Austria 10Scott Polar Research Institute, University of Cambridge, Cambridge, UK 11Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA 12Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada 13National Snow and Ice Data Center, University of Colorado, Boulder, CO, USA 14Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada 15A complete list of Consortium authors is in the Appendix ABSTRACT. The Randolph Glacier Inventory (RGI) is a globally complete collection of digital outlines of glaciers, excluding the ice sheets, developed to meet the needs of the Fifth Assessment of the Intergovernmental Panel on Climate Change for estimates of past and future mass balance.
    [Show full text]
  • Saving the Arctic the Urgent Need to Cut Black Carbon Emissions and Slow Climate Change
    AP PHOTO/IAN JOUGHIN PHOTO/IAN AP Saving the Arctic The Urgent Need to Cut Black Carbon Emissions and Slow Climate Change By Rebecca Lefton and Cathleen Kelly August 2014 WWW.AMERICANPROGRESS.ORG Saving the Arctic The Urgent Need to Cut Black Carbon Emissions and Slow Climate Change By Rebecca Lefton and Cathleen Kelly August 2014 Contents 1 Introduction and summary 3 Where does black carbon come from? 6 Future black carbon emissions in the Arctic 9 Why cutting black carbon outside the Arctic matters 13 Recommendations 19 Conclusion 20 Appendix 24 Endnotes Introduction and summary The Arctic is warming at a rate twice as fast as the rest of the world, in part because of the harsh effects of black carbon pollution on the region, which is made up mostly of snow and ice.1 Black carbon—one of the main components of soot—is a deadly and widespread air pollutant and a potent driver of climate change, espe- cially in the near term and on a regional basis. In colder, icier regions such as the Arctic, it peppers the Arctic snow with heat-absorbing black particles, increasing the amount of heat absorbed and rapidly accelerating local warming. This accel- eration exposes darker ground or water, causing snow and ice melt and lowering the amount of heat reflected away from the Earth.2 Combating climate change requires immediate and long-term cuts in heat-trap- ping carbon pollution, or CO2, around the globe. But reducing carbon pollution alone will not be enough to avoid the worst effects of a rapidly warming Arctic— slashing black carbon emissions near the Arctic and globally must also be part of the solution.
    [Show full text]
  • Impact of Increasing Antarctic Ice-Shelf Melting on Southern Ocean Hydrography
    Journal of Glaciology, Vol. 58, No. 212, 2012 doi: 10.3189/2012JoG12J009 1191 Impact of increasing Antarctic ice-shelf melting on Southern Ocean hydrography Caixin WANG,1,2 Keguang WANG3 1Department of Physics, University of Helsinki, Helsinki, Finland E-mail: [email protected] 2Norwegian Polar Institute, Tromsø, Norway 3Norwegian Meteorological Institute, Tromsø, Norway ABSTRACT. Southern Ocean hydrography has undergone substantial changes in recent decades, concurrent with an increase in the rate of Antarctic ice-shelf melting (AISM). We investigate the impact of increasing AISM on hydrography through a twin numerical experiment, with and without AISM, using a global coupled sea-ice/ocean climate model. The difference between these simulations gives a qualitative understanding of the impact of increasing AISM on hydrography. It is found that increasing AISM tends to freshen the surface water, warm the intermediate and deep waters, and freshen and warm the bottom water in the Southern Ocean. Such effects are consistent with the recent observed trends, suggesting that increasing AISM is likely a significant contributor to the changes in the Southern Ocean. Our analyses indicate potential positive feedback between hydrography and AISM that would amplify the effect on both Southern Ocean hydrography and Antarctic ice-shelf loss caused by external factors such as changing Southern Hemisphere winds. 1. INTRODUCTION ice thermodynamic model following Semtner (1976). The 8 The Southern Ocean has undergone significant changes in model has a mean resolution of 2 in the horizontal, and recent decades (see review by Jacobs, 2006): for example, 31 vertical layers in the ocean model with grid spacing from rising temperature in the upper 3000 m (Levitus and others, 10 m in the top 100 m to 500 m at the bottom, and 1 (for 2000, 2005; Gille, 2002, 2003), and decreasing salinity in dynamics) or 3 (for thermodynamics) vertical layers in the 8 high-latitude waters (Jacobs and others, 2002; Whitworth, sea-ice model.
    [Show full text]
  • Dear Editor and Reviewers
    Dear Editor and Reviewers, We are grateful for your constructive review of our manuscript. We made our best to address all the suggestions and provide an improved and fully revised manuscript. A response to each of the reviewers’ comments is given below but we would like to highlight the most important updates of manuscript: - We now present a research article with improved visuals and more in-depth discussion. - We compare our FAC dataset and maps to three regional climate models. - The construction of empirical functions is slightly updated, simplified and presented in the main text. We thank the reviewers for improving significantly the study. Sincerely, Baptiste Vandecrux on behalf of the co-authors Review #1 by Sergey Marchenko Reviewer’s comment Authors’ response General comments Physical geography. Authors use the mean annual air temperature and net surface accumulation as arguments in functions describing the spatial distribution of FAC10. The functions are fitted to minimize the misfit with empirical estimates of FAC10 from cores. One important thing that is missing in the text is a detailed description of the physical (or may be practical) motivation for the choice of the above mentioned arguments. Both characteristics (net annual surface accumulation and mean annual air temperature) integrate the effects of processes occurring during the cold and warm parts of a year. Net annual surface accumulation is the result of mass accumulation in winter and surface melt in In our study 풃̅̇ is defined as “net snow summer. While the first one can be expected to be positively linked with FAC (more accumulation in accumulation” (snowfall + deposition – sublimation) and is not “Net annual surface winter -> more pores), the second one can be expected to be negatively linked with FAC (more melt accumulation”.
    [Show full text]
  • ISS Massbalance2018 2Hr for Website.Key
    Glacier summer school 2018, McCarthy, Alaska What is mass balance ? Regine Hock Claridenfirn, Switzerland, 1916 1914 • Terminology, Definitions, Units • Conventional and reference surface mass balance • Firn line, snow line, ELA • Glacier runoff • Global mass changes PART I Terminology Claridenfirn, Switzerland, 1916 1914 Background General reference for mass-balance terminology has been Anonymous,1969, J. Glaciology 8(52). in practice diverging and inconsistent and confusing use of terminology new methods, e.g. remote sensing, require update Working group (2008-2012) by GLOSSARY International Association of OF GLACIER Cryospheric Sciences (IACS) MASS BALANCE aims to update and revise Anonymous (1969) AND and to provide a consistent terminology for all RELATED glaciers (i.e. mountain glaciers, ice caps and ice sheets) TERMS Cogley, J.G., R. Hock, L.A. Rasmussen, A.A. Arendt, A. Bauder, R.J. Braithwaite, P. Jansson, G. Kaser, M. Möller, L. Nicholson and M. Zemp, 2011, Glossary of Glacier Mass Balance and Related Terms, IHP-VII Technical Documents in Hydrology No. 86, IACS Contribution No. 2, UNESCO-IHP, Paris. Can be downloaded from: http://www.cryosphericsciences.org/mass_balance_glossary/ massbalanceglossary Glacier mass balance Mass balance is the change in the mass of a glacier, or part of the glacier, over a stated span of time: =mass budget t . • SPACE: study volume needs to be ‘mass imbalance’ ΔM = ∫ Mdt defined t1 • mass balance is often quoted for volumes other than that of the whole glacier, for example a column of unit cross section • important to report the domain ! •TIME: the time period (esp important € for comparison with model results) • mass change can be studied over any period Net gain of mass • often done over a year or winter/summer seasons --> Annual mass balance (formerly ‘Net’) Firn line Long-term ELA Accumulation area: acc > abl Net loss of mass Ablation area: acc < abl Equilibrium line: acc = abl t .
    [Show full text]