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Ice Sheet Dynamics (ice + sheet_dynamics)

Distribution by Scientific Domains

Earth and Environmental Science	75%

Selected Abstracts

The Antarctic palaeo record and its role in improving predictions of future Antarctic Ice Sheet change,

JOURNAL OF QUATERNARY SCIENCE, Issue 1 2010
Michael J. Bentley
Abstract This paper reviews the ways in which the palaeo record of Antarctic Ice Sheet change can be used to improve understanding of contemporary ice sheet behaviour, and thus enhance predictions of future sea-level change. The main areas where the palaeo ice sheet record can contribute are understanding long-term ice sheet trajectory; providing data against which ice sheet models can be tested; to identify and understand the range and types of natural ice sheet behaviour; to balance the global water budget; to correct contemporary glaciological measurements of mass change; and to understand the relationship between polar ecosystems and the ice sheet. I review each in turn and argue that research priorities include understanding past West Antarctic Ice Sheet collapse and its timing; a focus on the palaeo record of rapid retreat events and how these unfolded in the geological past; improving the number and range of ice sheet reconstructions, particularly through the Holocene; continuing to investigate the potential for using sediments and landforms to parameterise basal conditions in ice sheet models; and understanding past East Antarctic Ice Sheet dynamics, particularly the evidence for partial deglaciation. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Macro-scale bed roughness of the siple coast ice streams in West Antarctica

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2004
Martin J. Siegert
Abstract Subglacial bed conditions are key to understanding ice stream behaviour and evolution, with bed roughness re,ecting substrate composition and ,ow resistance. Here we present an analysis of bed roughness in the Siple Coast region of West Antarctica from airborne radio-echo sounding data. The ice streams are associated generally with low bed roughness values, which decrease downstream. The bed of the slow-,owing Ice Stream C (,10 000 km2) is also characterized by being smooth at all scales (wavelengths ranging from 5 km to in excess of 40 km). Furthermore, the bed is smooth either side of Ice Stream C. This suggests the location of the ice stream is controlled by internal ice sheet dynamics rather than by bed morphology. If the ice stream were encouraged to migrate laterally, when active, there would be little resistance offered by the subglacial morphology. Other inter-ice stream regions are rough, however, indicating a subglacial topographic in,uence on ice stream position. Bed roughness increases up-,ow of ice streams, which, unless the bed is modi,ed, may limit the inland migration of these systems. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Streamlined bedrock terrain and fast ice flow, Jakobshavns Isbrae, West Greenland: implications for ice stream and ice sheet dynamics

BOREAS, Issue 1 2005
DAVID H. ROBERTS
This study investigates the marginal subglacial bedrock bedforms of Jakobshavns Isbrae, West Greenland, in order to examine the processes governing bedform evolution in ice stream and ice sheet areas, and to reconstruct the interplay between ice stream and ice sheet dynamics. Differences in bedform morphology (roche moutonnee or whaleback) are used to explore contrasts in basal conditions between fast and slow ice flow. Bedform density is higher in ice stream areas and whalebacks are common. We interpret that this is related to higher ice velocities and thicker ice which suppress bed separation. However, modification of whalebacks by plucking occurs during deglaciation due to ice thinning, flow deceleration, crevassing and fluctuations in basal water pressure. The bedform evidence points to widespread basal sliding during past advances of Jakobshavns Isbrae. This was encouraged by increased basal temperatures and melting at depth, as well as the steep marginal gradients of Jakobshavns Isfjord which allowed rapid downslope evacuation of meltwater leading to strong ice/bedrock coupling and scouring. In contrast to soft-bedded ice stream bedforms, the occurrence of fixed basal perturbations and higher bed roughness in rigid bed settings prevents the basal ice subsole from maintaining a stable form which, coupled with secondary plucking, counteracts the development of bedforms with high elongation ratios. Cross-cutting striae and double-plucked, rectilinear bedforms suggest that Jakobshavns Isbrae became partially unconfined during growth phases, causing localised diffluent flow and changes in ice sheet dynamics around Disko Bugt. It is likely that Disko Bugt harboured a convergent ice flow system during repeated glacial cycles, resulting in the formation of a large coalesced ice stream which reached the continental shelf edge. [source]