Calving Processes and the Dynamics of Calving Glaciers ⁎ Douglas I
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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. -
Basal Control of Supraglacial Meltwater Catchments on the Greenland Ice Sheet
The Cryosphere, 12, 3383–3407, 2018 https://doi.org/10.5194/tc-12-3383-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Basal control of supraglacial meltwater catchments on the Greenland Ice Sheet Josh Crozier1, Leif Karlstrom1, and Kang Yang2,3 1University of Oregon Department of Earth Sciences, Eugene, Oregon, USA 2School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China 3Joint Center for Global Change Studies, Beijing 100875, China Correspondence: Josh Crozier ([email protected]) Received: 5 April 2018 – Discussion started: 17 May 2018 Revised: 13 October 2018 – Accepted: 15 October 2018 – Published: 29 October 2018 Abstract. Ice surface topography controls the routing of sur- sliding regimes. Predicted changes to subglacial hydraulic face meltwater generated in the ablation zones of glaciers and flow pathways directly caused by changing ice surface to- ice sheets. Meltwater routing is a direct source of ice mass pography are subtle, but temporal changes in basal sliding or loss as well as a primary influence on subglacial hydrology ice thickness have potentially significant influences on IDC and basal sliding of the ice sheet. Although the processes spatial distribution. We suggest that changes to IDC size and that determine ice sheet topography at the largest scales are number density could affect subglacial hydrology primarily known, controls on the topographic features that influence by dispersing the englacial–subglacial input of surface melt- meltwater routing at supraglacial internally drained catch- water. ment (IDC) scales ( < 10s of km) are less well constrained. Here we examine the effects of two processes on ice sheet surface topography: transfer of bed topography to the surface of flowing ice and thermal–fluvial erosion by supraglacial 1 Introduction meltwater streams. -
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. -
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. -
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. -
Anatomy of the Marine Ice Cliff Instability
Anatomy of the Marine Ice Cliff Instability Jeremy N. Bassis1, Brandon Berg2, Doug Benn3 1Department of Climate and Space, University of Michigan, Ann Arbor, MI, USA 2Department of Physics, University of Michigan, Ann Arbor, MI, USA 3School of Geography and Sustainable Development, St. Andrews University, Scotland Ice sheets grounded on retrograde beds are susceptible to disintegration through a process called the marine ice sheet instability. This instability results from the dynamic thinning of ice near the grounding zone separating floating from grounded portions of the ice sheet. Recently, a new instability called the marine ice cliff instability has been proposed. Unlike the marine ice sheet instability, the marine ice cliff instability is controlled by the brittle failure of ice and thus has the potential to result in much more rapid ice sheet collapse. Here we explore the interplay between ductile and brittle processes using a model where ice obeys the usual power-law creep rheology of intact ice up to a yield strength. Above the yield strength, we introduce a separate, much weaker rheology, that incorporates quasi-brittle failure along faults and fractures. We first tested the model by applying it to study the formation of localized rifts in shear zones of idealized ice shelves. These experiments show that wide rifts localize along the shear margins and portions of the ice shelf where the stress in the ice exceeds the yield strength. These rifts decrease the buttressing capacity of the ice shelves, but can also extend to become the detachment boundary of icebergs. Next, application of the model to idealized glaciers shows that for grounded glaciers, failure localizes near the terminus in “serac” type slumping events followed by buoyant calving of the submerged portion of the glacier. -
Seismic Model Report.Pdf
Scientific Report GEFSC Loan 925 The Character and Extent of subglacial Deformation and its Links to Glacier Dynamics in the Tarfala Basin, northern Sweden Jeffrey Evans, David Graham, and Joseph Pomeroy Polar and Alpine Research Group, Loughborough University ABSTRACT A pilot passive seismology experiment was conducted across the main overdeepening of Storglaciaren in the Tarfala Basin, northern Sweden, in July 2010, to see whether basal microseismic waveforms could be detected beneath a small polythermal arctic glacier and to investigate the spatial and temporal distribution of such waveforms in relation to known glacier flow dynamics. The high ablation rate made it difficult to keep geophones buried and well- coupled to the glacier during the experiment and reduced the number of days of good quality data collection. Event counts and the subsequent characterisation of typical and atypical waveforms showed that the dominant waveforms detected were from near-surface events such as crevassing. Although basal sliding is known to occur in the overdeepening, no convincing examples of basal waveforms were detected, which suggests basal microseismic signals are rare or difficult to detect beneath polythermal glaciers like Storglaciaren, a finding that is consistent with results from alpine glaciers in Switzerland. The data- set could prove useful to glaciologists interested in the dynamics of near-surface events such as crevassing, the opening and closing of englacial water conduits, or temporal and spatial changes in the glacier’s stress field. Background Smith (2006) found that pervasive soft-bed deformation characterised parts of the Rutland Ice Stream in West Antarctica and produced 6 times fewer basal microseismic signals than regions where basal sliding or stick slip movement dominated. -
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. -
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) -
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. -
Glaciers and Their Significance for the Earth Nature - Vladimir M
HYDROLOGICAL CYCLE – Vol. IV - Glaciers and Their Significance for the Earth Nature - Vladimir M. Kotlyakov GLACIERS AND THEIR SIGNIFICANCE FOR THE EARTH NATURE Vladimir M. Kotlyakov Institute of Geography, Russian Academy of Sciences, Moscow, Russia Keywords: Chionosphere, cryosphere, glacial epochs, glacier, glacier-derived runoff, glacier oscillations, glacio-climatic indices, glaciology, glaciosphere, ice, ice formation zones, snow line, theory of glaciation Contents 1. Introduction 2. Development of glaciology 3. Ice as a natural substance 4. Snow and ice in the Nature system of the Earth 5. Snow line and glaciers 6. Regime of surface processes 7. Regime of internal processes 8. Runoff from glaciers 9. Potentialities for the glacier resource use 10. Interaction between glaciation and climate 11. Glacier oscillations 12. Past glaciation of the Earth Glossary Bibliography Biographical Sketch Summary Past, present and future of glaciation are a major focus of interest for glaciology, i.e. the science of the natural systems, whose properties and dynamics are determined by glacial ice. Glaciology is the science at the interfaces between geography, hydrology, geology, and geophysics. Not only glaciers and ice sheets are its subjects, but also are atmospheric ice, snow cover, ice of water basins and streams, underground ice and aufeises (naleds). Ice is a mono-mineral rock. Ten crystal ice variants and one amorphous variety of the ice are known.UNESCO Only the ice-1 variant has been – reve EOLSSaled in the Nature. A cryosphere is formed in the region of interaction between the atmosphere, hydrosphere and lithosphere, and it is characterized bySAMPLE negative or zero temperature. CHAPTERS Glaciology itself studies the glaciosphere that is a totality of snow-ice formations on the Earth's surface. -
S41467-018-05625-3.Pdf
ARTICLE DOI: 10.1038/s41467-018-05625-3 OPEN Holocene reconfiguration and readvance of the East Antarctic Ice Sheet Sarah L. Greenwood 1, Lauren M. Simkins2,3, Anna Ruth W. Halberstadt 2,4, Lindsay O. Prothro2 & John B. Anderson2 How ice sheets respond to changes in their grounding line is important in understanding ice sheet vulnerability to climate and ocean changes. The interplay between regional grounding 1234567890():,; line change and potentially diverse ice flow behaviour of contributing catchments is relevant to an ice sheet’s stability and resilience to change. At the last glacial maximum, marine-based ice streams in the western Ross Sea were fed by numerous catchments draining the East Antarctic Ice Sheet. Here we present geomorphological and acoustic stratigraphic evidence of ice sheet reorganisation in the South Victoria Land (SVL) sector of the western Ross Sea. The opening of a grounding line embayment unzipped ice sheet sub-sectors, enabled an ice flow direction change and triggered enhanced flow from SVL outlet glaciers. These relatively small catchments behaved independently of regional grounding line retreat, instead driving an ice sheet readvance that delivered a significant volume of ice to the ocean and was sustained for centuries. 1 Department of Geological Sciences, Stockholm University, Stockholm 10691, Sweden. 2 Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX 77005, USA. 3 Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, USA. 4 Department