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Author: Kaitlin M. Walsh Publisher: ISBN: Category : Languages : en Pages :
Book Description
Abstract: Outlet glaciers and ice caps on the periphery of the Greenland Ice Sheet have been observed to be extremely sensitive to climate. The limited studies conducted on the marine-terminating glaciers of eastern Greenland's Geikie Plateau and Blosseville Coast suggest exceptionally rapid rates of mass loss and short-term variability in ice dynamics. This study is targeted at a region of central east Greenland for which GRACE mass-anomaly observations show substantial recent mass-loss since its launch in March 2002. Additionally, glaciers in this region terminate into Denmark Straight, which is a thermodynamic transition zone between the Arctic and North Atlantic oceans. Extensive glacial change has been more pronounced through the Denmark Straight and south of the straight, which supports the hypothesis that ocean dynamics, specifically the Irminger Current and East Greenland Current, are supporting increased melt at the ice-ocean interface. It is possible that an appreciable amount of melt and ice loss south of Kangerdlugssuaq is occurring as a result of warmer subpolar water flowing into glacial fjords. We present changes to 38 marine-terminating glaciers as observed using Landsat-7 ETM+ imagery to develop a time series of changing front positions and flow speeds of these glaciers from 2000 to 2010. ASTER DEMs were used to quantify elevation change and thinning. Additionally, we examine sea surface temperatures at five sites along the east Greenland coast to identify possible correlations between warming of the sea surface and increased melt at the glacier termini.
Author: Kaitlin M. Walsh Publisher: ISBN: Category : Languages : en Pages :
Book Description
Abstract: Outlet glaciers and ice caps on the periphery of the Greenland Ice Sheet have been observed to be extremely sensitive to climate. The limited studies conducted on the marine-terminating glaciers of eastern Greenland's Geikie Plateau and Blosseville Coast suggest exceptionally rapid rates of mass loss and short-term variability in ice dynamics. This study is targeted at a region of central east Greenland for which GRACE mass-anomaly observations show substantial recent mass-loss since its launch in March 2002. Additionally, glaciers in this region terminate into Denmark Straight, which is a thermodynamic transition zone between the Arctic and North Atlantic oceans. Extensive glacial change has been more pronounced through the Denmark Straight and south of the straight, which supports the hypothesis that ocean dynamics, specifically the Irminger Current and East Greenland Current, are supporting increased melt at the ice-ocean interface. It is possible that an appreciable amount of melt and ice loss south of Kangerdlugssuaq is occurring as a result of warmer subpolar water flowing into glacial fjords. We present changes to 38 marine-terminating glaciers as observed using Landsat-7 ETM+ imagery to develop a time series of changing front positions and flow speeds of these glaciers from 2000 to 2010. ASTER DEMs were used to quantify elevation change and thinning. Additionally, we examine sea surface temperatures at five sites along the east Greenland coast to identify possible correlations between warming of the sea surface and increased melt at the glacier termini.
Author: Laura C. Gillard Publisher: ISBN: Category : Glaciers Languages : en Pages : 87
Book Description
Higher latitudes have experienced a significant change in climate and physical processes within recent years. This study focuses on the Greenland Ice Sheet and surrounding ocean waters. It has been shown that relatively warm ocean waters may accelerate melt production of marine terminating glaciers. We explore and classify the pathways for the warmer Atlantic waters that reach the fjords along the coasts of Greenland. Additionally, given that the melt of these glaciers is accelerating, we look at the pathways of the low salinity melt waters from these coastal glaciers and where it is taken up in the surrounding basins. This analysis was carried out using an Arctic and North Hemisphere Atlantic (ANHA) configuration of the Nucleus for European Modelling of the Ocean (NEMO) ocean/sea-ice general circulation model run at both 1/4° and 1/12° resolution. Pathways were determined using the ARIANE Lagrangian float package using both forward and backward trajectories. Warm waters that reached the north and west coast of Greenland tended to be fed by the relatively warm and saline Irminger Current. The south east and the east Greenland coast tended to have warm waters advected to them through Nordic Seas.
Author: Intergovernmental Panel on Climate Change (IPCC) Publisher: Cambridge University Press ISBN: 9781009157971 Category : Science Languages : en Pages : 755
Book Description
The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.
Author: Twila Moon Publisher: ISBN: Category : Ice sheets Languages : en Pages : 116
Book Description
Outlet glacier ice dynamics, including ice-flow speed, play a key role in determining Greenland Ice Sheet mass loss, which is a significant contributor to global sea-level rise. Mass loss from the Greenland Ice Sheet increased significantly over the last several decades and current mass losses of 260-380 Gt ice/yr contribute 0.7-1.1 mm/yr to global sea-level rise (~10%). Understanding the potentially complex interactions among glacier, ocean, and climate, however, remains a challenge and limits certainty in modeling and predicting future ice sheet behavior and associated risks to society. This thesis focuses on understanding the seasonal to interannual scale changes in outlet glacier velocity across the Greenland Ice Sheet and how velocity fluctuations are connected to other elements of the ice sheet-ocean-atmosphere system. 1) Interannual velocity patterns Earlier observations on several of Greenland's outlet glaciers, starting near the turn of the 21st century, indicated rapid (annual-scale) and large (>100%) increases in glacier velocity. Combining data from several satellites, we produce a decade-long (2000 to 2010) record documenting the ongoing velocity evolution of nearly all (200+) of Greenland's major outlet glaciers, revealing complex spatial and temporal patterns. Changes on fast-flow marine-terminating glaciers contrast with steady velocities on ice-shelf-terminating glaciers and slow speeds on land-terminating glaciers. Regionally, glaciers in the northwest accelerated steadily, with more variability in the southeast and relatively steady flow elsewhere. Intraregional variability shows a complex response to regional and local forcing. Observed acceleration indicates that sea level rise from Greenland may fall well below earlier proposed upper bounds. 2) Seasonal velocity patterns. Greenland mass loss includes runoff of surface melt and ice discharge via marine-terminating outlet glaciers, the latter now making up a third to a half of total ice loss. The magnitude of ice discharge depends in part on ice-flow speed, which has broadly increased since 2000 but varies locally, regionally, and from year-to-year. Research on a few Greenland glaciers also shows that speed varies seasonally. However, for many regions of the ice sheet, including wide swaths of the west, northwest, and southeast coasts where ice loss is increasing most rapidly, there are few or no records of seasonal velocity variation. We present 5-year records of seasonal velocity measurements for 55 glaciers distributed around the ice sheet margin. We find 3 distinct seasonal velocity patterns. The different patterns indicate varying glacier sensitivity to ice-front (terminus) position and likely regional differences in basal hydrology in which some subglacial systems do transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. Our findings highlight the need for modeling and observation of diverse glacier systems in order to understand the full spectrum of ice-sheet dynamics. 3) Seasonal to interannual glacier and sea ice behavior and interaction Focusing on 16 northwestern Greenland glaciers during 2009-2012, we examine terminus position, sea ice and ice m??lange conditions, seasonal velocity changes, topography, and climate, with extended 1999-2012 records for 4 glaciers. There is a strong correlation between near-terminus sea ice/mélange conditions and terminus position. In several cases, late-forming and inconsistent sea ice/mélange may induce sustained retreat. For all of the 13-year records and most of the 4-year records, sustained, multi-year retreat is accompanied by velocity increase. Seasonal speedup, which is observed across the region, may, however, be more heavily influenced by melt interacting with the subglacial hydrologic system than seasonal terminus variation. Projections of continued warming and longer ice-free periods around Greenland suggest that notable retreat over wide areas may continue. Sustained retreat is likely to be associated with multi-year speedup, though both processes are modulated by local topography. The timing of seasonal ice dynamics patterns may also shift.
Author: Marit Reigstad Publisher: Frontiers Media SA ISBN: 2889637514 Category : Languages : en Pages : 325
Book Description
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Author: Robert M. Sanchez Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Mass loss of the Greenland Ice Sheet is expected to accelerate in the 21st century in response to both a warming atmosphere and ocean, with consequences for sea level rise, polar ecosystems and potentially the global overturning circulation. Glacial fjords connect Greenland's marine-terminating glaciers with the continental shelf, and fjord circulation plays a critical role in modulating the import of heat from the ocean and the export of freshwater from the ice sheet. Understanding fjord dynamics is crucial to predicting the cryosphere and ocean response to a changing climate. However, representing glacial fjord dynamics in climate models is an ongoing challenge because fjord circulation is complex and sensitive to glacial forcing that is poorly understood. Additionally, there are limited observations available for constraining models and theory. This dissertation aims to improve our understanding of fjord dynamics, focusing on key aspects (heat variability, freshwater residence time, and fjord exchange) which need to be included in glacial fjord parameterizations. We use three approaches combining novel observations, idealized, modeling and numerical simulations to investigate the dynamics of fjord circulation at different spatial scales. First, we investigate the heat content variability in the fjord using acoustic travel time (Chapter 2). We demonstrate that acoustic travel time can be used to model fjord stratification during winter months and monitor heat content variability at synoptic and seasonal timescales. Secondly, we use a combination of in situ observations and an idealized box model to evaluate freshwater residence time in a west Greenland Fjord (Chapter 3). We find that meltwater from the ice sheet is mixed downward across multiple layers near the glacier terminus resulting in freshwater storage and a delay in freshwater export from the fjord. Finally we analyze a multi-year realistically forced numerical simulation of Sermilik Fjord in southeast Greenland and identify the impact of shelf and glacial forcing on fjord exchange (Chapter 4). We show that the glacial-driven circulation is more efficient at renewing the fjord and that the sign of the exchange flow is related to the along-shelf wind stress. This dissertation strengthens our understanding of the fundamental connections between oceans and glaciers, and will lead to improved representation of ice-ocean interactions in climate models.
Author: Laura B. Levy Publisher: ISBN: Category : Languages : en Pages : 408
Book Description
"The Greenland Ice Sheet (GrIS) is responding sensitively to climate change and its meltwater has the potential to influence global sea level. Recently, large changes in the GrIS have occurred including increased velocities of outlet glaciers and melt over ~97% of the ice sheet. One means to understand modern and help predict future changes in the GrIS is to examine how it responded to past climate conditions. In this dissertation I provide a longer-term perspective of changes in the GrIS as well as in smaller, independent glaciers near the ice sheet margins (i.e., "local" glaciers). My research documents the past extents of the GrIS in central East and southern West Greenland during the Holocene Epoch (11,600 yrs ago-present) and provides evidence for climate conditions along the ice sheet margin during late glacial time (~17,500-11,600 yrs ago) and the Holocene Epoch. I use geomorphic mapping, surface exposure dating and lake sediment analyses to demonstrate that the GrIS and local glaciers in central East Greenland were receding during the Younger Dryas cold event (~12,900-11,600 yrs ago) and deposited the Milne Land stade moraines at the end of the Younger Dryas. I hypothesize that these ice marginal fluctuations were primarily influenced by air or ocean surface temperatures. I document the Holocene fluctuations of a local glacier that completely disappeared indicating peak warm conditions between ~9.3 and 6.0 cal kyr BP. The formation of this glacier at 2.6 cal kyr BP and its persistence from ~1.9 cal kyr BP-present suggests cold conditions during late Holocene time. I also use geomorphic mapping and surface exposure dating to document the extents of the GrIS in southern West Greenland, near Kangerlussuaq. I show that the Keglen, Ørkendalen and Historical moraines were deposited at 7.3 ka, 6.3 ka, and by ~AD 1950, respectively. These data indicate that the GrIS was as small as or smaller than at present during much of middle to late Holocene time. Finally, I synthesize my results and discuss possible causes of GrIS marginal changes in central East and southern West Greenland including changes in air and ocean temperatures and changes in sea level."
Author: Sophie Ann Goliber Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Since the 1980s, the Greenland ice sheet has been losing ice mass at an increased rate. Our current understanding of the complex physical processes that control dynamic mass loss is incomplete and, therefore, leads to a wide range of possible future contributions to sea level. Ice dynamics, or changes due to changes in ice flux, is dominated by the behavior of fast-moving outlet glaciers in Greenland. These glaciers are changing through melting of the terminus face and/or calving of icebergs; the combination of these processes and ice motion determines the position of a glacier terminus. In understanding how and why outlet glacier termini change over time compared to external forcing and internal glacier dynamics, we are able to move toward a better understanding of marine-terminating glaciers. In this dissertation, I use terminus traces to observe how and why marine-terminating glaciers change in order to better understand the mechanisms behind these complex heterogeneous changes in Greenland. I develop the largest database of manually-traced marine-terminating glacier terminus data for use in scientific and machine learning applications. These data have been collected, cleaned, assigned with appropriate metadata, including image scenes, and compiled so that they can be easily accessed by scientists. Then I use the location of the termini to identify features in the bed topography that inhibit the retreat of glaciers following the onset of ocean warming and widespread glacier retreat in the late 1990s. I find that the slope and lateral dimensions of bed features exhibit the strongest correlation to retreat and that the shape of the bed features allows different styles of terminus retreat, which may be indicative of how different ablation mechanisms are distributed across termini. Finally, I produce a time series of terminus morphological properties for four glaciers in western Greenland to identify the characteristics that are indicative of calving processes with the goal of categorizing glaciers by calving style. I find that a concave shape and low sinuosity are present at glaciers that calve via buoyant flexure, while the opposite is true at glaciers that are dominated by melt-induced calving via serac failure. I also find that glaciers do not persistently fit into single calving styles and may change over time. By studying how the terminus changes over time compared to external forcing and internal glacier dynamics, we are able to move toward a better understanding of marine-terminating glaciers
Author: Kaitlin M. Walsh
Author: Kaitlin M. Walsh
Author: Laura C. Gillard
Author: Intergovernmental Panel on Climate Change (IPCC)
Author: Twila Moon
Author: Marit Reigstad
Author: Robert M. Sanchez
Author: Laura B. Levy
Author: Sophie Ann Goliber
Author: Klaus Strübing
Author: Roger G. Barry