ORCID Profile
0000-0002-6576-5384
Current Organisation
University of Wisconsin Madison
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Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-7822
Abstract: & & Uncertainty tied to the mechanics of the fast motion of the Greenland Ice Sheet plagues sea-level rise predictions. Much of this uncertainty arises from imperfect representations of physical processes in constitutive relationships for basal slip and internal ice deformation, with continued misalignment between model output and borehole field data. To investigate further, we model two isolated cuboid domains from the fast-moving Sermeq Kujalleq (a.k.a Store Glacier), incorporating temperate ice rheology (softer ice at the melting point) and statistically realistic variogram-generated bed topography. Our results indicate a hitherto unappreciated complexity in ice-sheet basal motion over rough beds. Realistic topographic variability leads to highly variable basal slip rates (from & to & % of surface velocity over ~1km), complex and variable deformation patterns, and a basal temperate ice layer that varies greatly in thickness in agreement with borehole observations (from & to & m). Velocity variations at the relatively smooth upper boundary of the temperate ice layer are significantly less variable, indicating that the slim basal temperate ice layer is an important control on ice motion. These results suggest that inversion procedures for basal traction over rough beds (including parts of Antarctica) may also be accounting for deformation within a temperate ice layer, which is problematic if the inclusion of a temperate ice layer and rough topography means commonly used basal slip relationships are no longer applicable.& & &
Publisher: American Association for the Advancement of Science (AAAS)
Date: 10-02-2023
Abstract: Uncertainty associated with ice sheet motion plagues sea level rise predictions. Much of this uncertainty arises from imperfect representations of physical processes including basal slip and internal ice deformation, with ice sheet models largely incapable of reproducing borehole-based observations. Here, we model isolated three-dimensional domains from fast-moving (Sermeq Kujalleq/Store Glacier) and slow-moving (Isunnguata Sermia) ice sheet settings in Greenland. By incorporating realistic geostatistically simulated topography, we show that a spatially highly variable layer of temperate ice (much softer ice at the pressure-melting point) forms naturally in both settings, alongside ice motion patterns which erge substantially from those obtained using smoothly varying BedMachine topography. Temperate ice is vertically extensive ( meters) in deep troughs but thins notably ( meters) over bedrock highs, with basal slip rates reaching or % of surface velocity dependent on topography and temperate layer thickness. Developing parameterizations of the net effect of this complex motion can improve the realism of predictive ice sheet models.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-8460
Abstract: & & The majority of Greenland& #8217 s outlet glaciers are Isbr& #230 -type, with high driving stresses, steep surface slopes, flow through deep channels, and with a basal layer of temperate ice theorised to thicken towards the coastal margin. Understanding the formation processes and thermodynamic influence of this temperate ice is important as limited laboratory testing indicates temperate ice has a viscosity 5-10 times lower than cold ice with no liquid phase. Furthermore, limited field data suggests lower rates of deformation within basal temperate ice than in the cold ice directly overlying it, which is presently unexplained. Here, we present preliminary results from a 3D finite-element model of an idealised Isbrae-type glacier built with Elmer/Ice, incorporating water-content-dependent ice viscosity, basal melting, and a parameterization of basal crevassing, and use it to investigate the formation and thermodynamic behaviour of temperate ice in response to varying bedforms and model parameters. We find that the observed decrease in strain in temperate ice close to the glacier base can be explained by a high strain area close to the cold-temperate transition zone. We further compare our model results to temperate ice variability observed at Sermeq Kujalleq (Store Glacier) to determine key temperate ice parameters requiring further investigation. These results provide a more complete understanding of the heterogeneous ice deformation behind the fast movement of Greenland& #8217 s Isbr& #230 -type glaciers and can therefore help to improve predictions of future glacier flow.& &
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Marianne Haseloff.