Quantifying Forces Controlling the 2004-2005 Retreat, Mass Loss, and Speed-up of Kangerlussuaq Glacier, Greenland from Remotely Sensed Data PDF Download
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Author: David Patrick McCormick (II.) Publisher: ISBN: Category : Languages : en Pages : 57
Book Description
Kangerlussuaq Glacier, in SE Greenland, is the largest outlet glacier on the east coast of Greenland, draining approximately 3% of the Greenland Ice Sheet (GrIS). In 2004/05 this glacier underwent a dramatic retreat, as well as acceleration and mass loss, indicating a significant change in ice dynamics. During this time, the ice velocity increased from 6-8 km/yr to 14 km/yr, resulting in a peak mass loss of 40 Gt/yr by 2005, approximately 20% of the mass loss of the whole SE GrIS. Other SE Greenland outlet glaciers exhibited synchronous acceleration, retreat and thinning, and thus in 2004/05 the mass loss from SE Greenland dominated the overall mass balance of the GrIS. My study investigated the possible causes of increased outlet glacier mass loss in this sector by reconstructing the surface history and using the force budget technique to quantify the forces that control the flow of Kangerlussuaq Glacier before and after its major acceleration event. I used multiple sets of remotely sensed data, including repeat stereo imagery from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on the Terra satellite and from the Satellite Pour l`Observation de la Terre (SPOT) satellite, as well as a bedrock DEM from radar observations provided by Center for Remote Sensing of Ice Sheets (CReSIS) to reconstruct the ice sheet surface topography and velocity in 2003 and 2006. These input data were then used to generate 2D force balance models. Previous studies have suggested that speed-up and thinning of Kangerlussuaq Glacier was caused by a collapse of the calving front in 2004/05 resulting in a loss of back-stress. However, my surface reconstruction revealed that thinning began in the summer of 2002; at least two years before the start of the rapid thinning and retreat of the calving front. This discovery was made possible by using the Surface Elevation Reconstruction And Change Detection (SERAC) method to combine the laser altimetry data and the stereo-image DEMs to improve the accuracy of the DEMs and to generate a high-resolution, accurate elevation change record. The force balance analysis showed only small changes in driving and resisting stresses between 2003 and 2006 despite the significant retreat. Therefore, I reject the hypothesis that the speed-up was the result of a collapsed calving front. My results suggest the speed-up was in part due to a change in the subglacial hydrology that caused a change in effective basal pressure. The 2003-2004 period showed below-average meltwater runoff that may have reduced water entering the subglacial drainage system. If subglacial drainage is through a network of tunnels, a reduction in the subglacial water flux would lower the effective basal pressure. Because the sliding velocity is inversely proportional to the effective pressure, this would increase the sliding speed. The increase in surface melt and runoff starting in 2005 would have increased the subglacial water flux again, and the resulting increase in effective pressure would have caused the glacier to slow down.
Author: David Patrick McCormick (II.) Publisher: ISBN: Category : Languages : en Pages : 57
Book Description
Kangerlussuaq Glacier, in SE Greenland, is the largest outlet glacier on the east coast of Greenland, draining approximately 3% of the Greenland Ice Sheet (GrIS). In 2004/05 this glacier underwent a dramatic retreat, as well as acceleration and mass loss, indicating a significant change in ice dynamics. During this time, the ice velocity increased from 6-8 km/yr to 14 km/yr, resulting in a peak mass loss of 40 Gt/yr by 2005, approximately 20% of the mass loss of the whole SE GrIS. Other SE Greenland outlet glaciers exhibited synchronous acceleration, retreat and thinning, and thus in 2004/05 the mass loss from SE Greenland dominated the overall mass balance of the GrIS. My study investigated the possible causes of increased outlet glacier mass loss in this sector by reconstructing the surface history and using the force budget technique to quantify the forces that control the flow of Kangerlussuaq Glacier before and after its major acceleration event. I used multiple sets of remotely sensed data, including repeat stereo imagery from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on the Terra satellite and from the Satellite Pour l`Observation de la Terre (SPOT) satellite, as well as a bedrock DEM from radar observations provided by Center for Remote Sensing of Ice Sheets (CReSIS) to reconstruct the ice sheet surface topography and velocity in 2003 and 2006. These input data were then used to generate 2D force balance models. Previous studies have suggested that speed-up and thinning of Kangerlussuaq Glacier was caused by a collapse of the calving front in 2004/05 resulting in a loss of back-stress. However, my surface reconstruction revealed that thinning began in the summer of 2002; at least two years before the start of the rapid thinning and retreat of the calving front. This discovery was made possible by using the Surface Elevation Reconstruction And Change Detection (SERAC) method to combine the laser altimetry data and the stereo-image DEMs to improve the accuracy of the DEMs and to generate a high-resolution, accurate elevation change record. The force balance analysis showed only small changes in driving and resisting stresses between 2003 and 2006 despite the significant retreat. Therefore, I reject the hypothesis that the speed-up was the result of a collapsed calving front. My results suggest the speed-up was in part due to a change in the subglacial hydrology that caused a change in effective basal pressure. The 2003-2004 period showed below-average meltwater runoff that may have reduced water entering the subglacial drainage system. If subglacial drainage is through a network of tunnels, a reduction in the subglacial water flux would lower the effective basal pressure. Because the sliding velocity is inversely proportional to the effective pressure, this would increase the sliding speed. The increase in surface melt and runoff starting in 2005 would have increased the subglacial water flux again, and the resulting increase in effective pressure would have caused the glacier to slow down.
Author: Andrew K. Melkonian Publisher: ISBN: Category : Languages : en Pages : 624
Book Description
Glaciers outside the icesheets currently supply roughly the same amount of water to sea level rise (SLR) as Antarctica and Greenland and will likely constitute a significant fraction of SLR through 2100. SLR is one of the biggest challenges facing humanity, and much uncertainty remains regarding the contribution of glacier mass loss to SLR. Here we examine glaciers in the Patagonia region of southern Chile/Argentina, the Russian High Arctic (RHA) and Alaska, which have all contributed disproportionately to SLR, a trend that is expected to continue through 2100. The RHA is projected to be among the largest contributors, with total mass loss exceeding Alaska for 2006-2100 despite its smaller ice volume. We focus on several icefields, including two that have received relatively little attention, the Cordillera Darwin Icefield (CDI, 69.6? W, 54.6? S, 2,600 km2 of glaciated area) in the Patagonia region of southern Chile, and the Novaya Zemlya Icefield (NovZ, 65? W, 76? N, 22,100 km2 of glaciated area) in the Russian High Arctic. We also examine the Juneau Icefield (JIF, 58.3? N to 59.7? N, 3,830 km2) and Stikine Icefield (56.75? N to 58.5? N, 5,800 km2) in southeast Alaska. We produce high-resolution maps of surface elevation change rates (dh) and dt velocities for these icefields. dh dt are calculated by applying a weighted lin- ear regression to horizontally- and vertically-aligned digital elevation models (DEMs), revealing thinning patterns for individual glacier basins and allowing us to estimate total mass loss for each icefield. To our knowledge, the work presented here includes the first published study to use the technique of DEM time series to study mass loss of entire icefields. Velocities are measured by pixel-tracking applied to satellite image pairs, helping constrain the dynamic component of mass loss and detect acceleration. We provide a brief overview of the impact of changing various pixel-tracking parameters on velocity measurements, demonstrating, for example, how the ability to adjust parameters helps maximize coverage compared to working with fixed parameter values. We find an average mass loss rate at the CDI of -3.9"1.5 Gt yr-1 between 2000 and 2011, the first produced for this icefield. Three marine-terminating glaciers that cover 12% of the icefield area account for 31% of mass loss. Velocity measurements at the largest of these, the rapidly retreating Marinelli Glacier, constrain the lower bound on the annual calving flux as approximately 82"41% of the average mass loss rate for the glacier. The disproportionate mass loss contribution of the three tidewater glaciers, coupled with the high calving flux and retreat at Marinelli Glacier, provide evidence that dynamic mass loss is an important component of thinning at the CDI. At NovZ, we extend estimates of mass loss back to 1952 and up to the present. We find that the recent average thinning rate of -0.41"0.10 m water equivalent yr-1 (m w.e. yr-1, or elevation change at density of 1000 kg m-3) from 2012-2013/2014 is higher than the long-term average of -0.24"0.04 m w.e. yr-1 from 1952-2013/2014. Some of the increase is likely due to warming in the region, as recent thinning is higher than the long-term average at both land- and marine-terminating glaciers. There is also evidence of a dynamic component, because recent thinning, retreat and front velocities are all substantially greater at tidewater-terminating glaciers than land-terminating glaciers. The impact of ice dynamics is particularly apparent at Inostrantseva Glacier (INO), which ac- celerated at some point after 2006, leading to rapid retreat and thinning there. We compare our results at the CDI and NovZ with our dh dt and velocities for the JIF and Stikine in southeast Alaska. We explore how variations in climate, hypsometry and dynamics all contribute to the different magnitudes and patterns of mass loss at each icefield. The methods presented here for the assessment of icefield mass loss will help better constrain their contributions to SLR over the coming century.
Author: Whyjay Zheng Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Glacier thinning and retreat have accelerated globally in the last century and are the largest contributor to rising sea levels. For the Arctic region, observations and modeling results have shown that extensive warming is taking place. However, the recent glacier dynamics (mass balance and ice discharge) in many Arctic regions have not been well studied due to the remote nature of these glaciers.This thesis uses multiple types of satellite data to quantify the mass balance and ice discharge for three Arctic regions showing dramatic glacier change in recent decades possibly due to Arctic warming. The objective is to resolve the mass budget and velocity pattern on a per glacier basis and understand the mechanisms driving recent changes. To facilitate the entire workflow, our research team has developed the Cryosphere and Remote Sensing Toolkit (CARST) software, and I am the lead author. CARST provides useful python and bash scripts that use satellite imagery, particularly SAR and optical images, to monitor changes of glaciers and ice caps through time. The first study area is Franz Josef Land (FJL), Russia, which is currently subjected to a rapidly-warming climate in the Arctic. I combine surface elevation data derived from different sources and times, including the WorldView satellite series and the ArcticDEM data set (2011-2015), SPOT-5 (2007), CryoSat-2 (2011-2015), and a digitized cartographic map (1953). I calculate elevation change rate (dh/dt) in two different periods, and the results show a two-fold rate of ice loss over the past 60 years, from _2.18 ± 0.72 Gt/yr (1953-2011/2015 average) to _4.43 ± 0.78 Gt/yr (2011-2015). Despite being spatially variable, a trend of increased thinning from NE towards SW is discovered, suggesting a link to the local gradient in temperature and precipitation. Ice loss is mostly focused on marine-terminating glaciers probably due to the interaction between glaciers and warming ocean water. These retreating glaciers generated a new island in 2016 and more islands are likely to emerge in the foreseeable future as FJL's ice loss has reached an unprecedented rate. The research focus in the following chapter shifts to the neighboring archipelago called Severnaya Zemlya, Russia. A surge-like collapse initiated in 2013 in Vavilov Ice Cap, one of many ice caps in this region. By spring 2019, this ice cap had lost 9.5 Gt of ice. Using time series of surface elevation and glacier velocity derived from multiple satellite data sets such as WorldView (elevation), ArcticDEM (elevation), ASTER (elevation), Landsat 8 (velocity), Sentinel-1, (velocity), Sentinel-2 (velocity), Radarsat-2 (velocity), and ALOS-2 (velocity), I identify a shift of flow pattern starting in 2017 when shear margins formed within the grounded marine piedmont fan. Multiple summer speedups occurred after the new flow pattern formed, possibly with the aid of basal lubrication due to surface melt. With the analysis using multiple physical models, it is suggested that the collapsed ice cap has entered a new ice stream-like regime in which diffusion of surface thinning controls the glacier dynamics. This is the first documented case of an ice stream-like feature ever being formed, and this glacier now flows at a higher speed and drains the ice cap more efficiently. To publicize the findings and their scientific implications, I made two videos showing the temporal changes of the terminus position and speed pattern, which are available on Youtube. In the last chapter, I further develop a physical framework for the glacier perturbation model to understand how different glaciers respond to basal lubrication. The modified 1-D flowline model suggests two physical quantities, Péclet number (Pe) and a value dubbed J0, governing glacier vulnerability to basal lubrication. To test the model, I use the Ice Thickness Models Intercomparison eXperiment (ITMIX) data set and the NASA MEaSUREs ITS_LIVE data set. ITMIX contains velocity, elevation, and ice thickness data from Austfonna Ice Cap, Svalbard, where multiple glacier collapse events occurred within the past 10 years. I calculate Pe and |J0| using data from the ITMIX and compare them with the speed change revealed by the ITS_LIVE data set. The results show that a low Pe and a high |J0| correspond to the high magnitude of glacier speedup during 1995-2018, as suggested by the model prediction. My analysis implies that basal lubrication can lead to a prolonged or even permanent change of glacier dynamics for some glaciers. These "weak" glaciers might be able to waste ice more rapidly than we thought, posing a warning of an underestimated sea level rise projection.
Author: Carlos R. Mechoso Publisher: Cambridge University Press ISBN: 1108492703 Category : Science Languages : en Pages : 359
Book Description
A comprehensive review of interactions between the climates of different ocean basins and their key contributions to global climate variability and change. Providing essential theory and discussing outstanding examples as well as impacts on monsoons, it a useful resource for graduate students and researchers in the atmospheric and ocean sciences.
Author: W. S. B. Paterson Publisher: Elsevier ISBN: 1483287254 Category : Science Languages : en Pages : 491
Book Description
This updated and expanded version of the second edition explains the physical principles underlying the behaviour of glaciers and ice sheets. The text has been revised in order to keep pace with the extensive developments which have occurred since 1981. A new chapter, of major interest, concentrates on the deformation of subglacial till. The book concludes with a chapter on information regarding past climate and atmospheric composition obtainable from ice cores.
Author: C.J. van der Veen Publisher: Springer Science & Business Media ISBN: 9400937458 Category : Science Languages : en Pages : 376
Book Description
Few scientists doubt the prediction that the antropogenic release of carbon dioxide in the atmosphere will lead to some warming of the earth's climate. So there is good reason to investigate the possible effects of such a warming, in dependence of geographical and social economic setting. Many bodies, governmental or not, have organized meetings and issued reports in which the carbon dioxide problem is defined, reviewed, and possible threats assessed. The rate at which such reports are produced still increases. However, while more and more people are getting involved in the 'carbon dioxide business', the number of investigators working on the basic problems grows, in our view, too slowly. Many fundamental questions are still not answered in a satisfactory way, and the carbon dioxide building rests on a few thin pillars. One such fundamental question concerns the change in sea level associated with a climatic warming of a few degrees. A number of processes can be listed that could all lead to changes of the order of tens of centimeters (e. g. thermal expansion, change in mass balance of glaciers and ice sheets). But the picture of the carbon dioxide problem has frequently be made more dramatic by suggesting that the West Antarctic Ice Sheet is unstable, implying a certain probability of a 5 m higher sea-level stand within a few centuries.
Author: Bruno Latour Publisher: MIT Press ISBN: 0262044455 Category : Art Languages : en Pages : 473
Book Description
Artists and writers portray the disorientation of a world facing climate change. This monumental volume, drawn from a 2020 exhibition at the ZKM Center for Art and Media, portrays the disorientation of life in world facing climate change. It traces this disorientation to the disconnection between two different definitions of the land on which modernizing humans live: the sovereign nation from which they derive their rights, and another one, hidden, from which they gain their wealth—the land they live on, and the land they live from. Charting the land they will inhabit, they find not a globe, not the iconic “blue marble,” but a series of critical zones—patchy, heterogenous, discontinuous. With short pieces, longer essays, and more than 500 illustrations, the contributors explore the new landscape on which it may be possible for humans to land—what it means to be “on Earth,” whether the critical zone, the Gaia, or the terrestrial. They consider geopolitical conflicts and tools redesigned for the new “geopolitics of life forms.” The “thought exhibition” described in this book can opens a fictional space to explore the new climate regime; the rest of the story is unknown. Contributors include Dipesh Chakrabarty, Pierre Charbonnier, Emanuele Coccia, Vinciane Despret, Jerôme Gaillarde, Donna Haraway, Joseph Leo Koerner, Timothy Lenton, Richard Powers, Simon Schaffer, Isabelle Stengers, Bronislaw Szerszynski, Jan A. Zalasiewicz, Siegfried Zielinski Copublished with ZKM | Center for Art and Media Karlsruhe
Author: Luke Copland Publisher: Springer ISBN: 9402411011 Category : Science Languages : en Pages : 426
Book Description
This book provides an overview of the current state of knowledge of Arctic ice shelves, ice islands and related features. Ice shelves are permanent areas of ice which float on the ocean surface while attached to the coast, and typically occur in very cold environments where perennial sea ice builds up to great thickness, and/or where glaciers flow off the land and are preserved on the ocean surface. These landscape features are relatively poorly studied in the Arctic, yet they are potentially highly sensitive indicators of climate change because they respond to changes in atmospheric, oceanic and glaciological conditions. Recent fracturing and breakup events of ice shelves in the Canadian High Arctic have attracted significant scientific and public attention, and produced large ice islands which may pose a risk to Arctic shipping and offshore infrastructure. Much has been published about Antarctic ice shelves, but to date there has not been a dedicated book about Arctic ice shelves or ice islands. This book fills that gap.
Author: Reinhard Pienitz Publisher: Springer Science & Business Media ISBN: 1402021267 Category : Science Languages : en Pages : 579
Book Description
Concerns about the effects of global climate change have focused attention on the vulnerability of circumpolar regions. This book offers a synthesis of the spectrum of techniques available for generating long-term environmental records from circumpolar lakes.
Author: David Patrick McCormick (II.)
Author: David Patrick McCormick (II.)
Author: Andrew K. Melkonian
Author: Whyjay Zheng
Author: Carlos R. Mechoso
Author: W. S. B. Paterson
Author: C.J. van der Veen
Author: Bruno Latour
Author: Anker Weidick
Author: Luke Copland
Author: Reinhard Pienitz