scholarly journals The sensitivity of the Greenland ice sheet to glacial-interglacial oceanic forcing

2017 ◽  
Author(s):  
Ilaria Tabone ◽  
Javier Blasco ◽  
Alexander Robinson ◽  
Jorge Alvarez-Solas ◽  
Marisa Montoya
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Sensitivity ◽  
Glacial Cycles ◽  
The Past ◽  
Oceanic Forcing ◽  
Atmospheric Variations ◽  
Glacial Periods

Abstract. Observations suggest that during the last decades the Greenland Ice Sheet (GrIS) has experienced a gradually accelerating mass loss, in part due to the observed acceleration of several of Greenland’s marine-terminating glaciers. Recent studies directly attribute this to increasing North Atlantic temperatures, which have triggered melting of the GrIS outlet glaciers, grounding-line retreat and enhanced ice discharge into the ocean, contributing to an acceleration of sea level rise. Reconstructions suggest that the influence of the ocean has been of primary importance in the past as well. This was the case not only in interglacial periods, when warmer climates led to a rapid retreat of the GrIS to land above sea level, but also in glacial periods, when the GrIS expanded as far as the continental shelf break, and was thus more directly exposed to ocean changes. However, the GrIS response to paleo oceanic variations has not been investigated from a modelling perspective so far. In this work the evolution of the GrIS over the past two glacial cycles has been studied using a three-dimensional hybrid ice-sheet/ice-shelf model. We assess the effect of the variation of oceanic temperatures on the GrIS evolution on glacial-interglacial timescales through changes in submarine melting. The results show a very high sensitivity of the GrIS to the changing oceanic conditions. Oceanic forcing is found to be the dominant driver of the GrIS expansion in glacial times and retreat in interglacial periods. If switched off, paleo atmospheric variations alone are not able to yield a reliable glacial configuration of the GrIS. This work therefore suggests that considering the ocean as an active forcing should become standard in paleo ice sheet modelling.

scholarly journals The sensitivity of the Greenland Ice Sheet to glacial–interglacial oceanic forcing

2018 ◽  
Vol 14 (4) ◽  
pp. 455-472 ◽  
Author(s):  
Ilaria Tabone ◽  
Javier Blasco ◽  
Alexander Robinson ◽  
Jorge Alvarez-Solas ◽  
Marisa Montoya
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Sensitivity ◽  
Glacial Cycles ◽  
The Past ◽  
Primary Driver ◽  
Oceanic Forcing ◽  
Atmospheric Variations

Abstract. Observations suggest that during the last decades the Greenland Ice Sheet (GrIS) has experienced a gradually accelerating mass loss, in part due to the observed speed-up of several of Greenland's marine-terminating glaciers. Recent studies directly attribute this to warming North Atlantic temperatures, which have triggered melting of the outlet glaciers of the GrIS, grounding-line retreat and enhanced ice discharge into the ocean, contributing to an acceleration of sea-level rise. Reconstructions suggest that the influence of the ocean has been of primary importance in the past as well. This was the case not only in interglacial periods, when warmer climates led to a rapid retreat of the GrIS to land above sea level, but also in glacial periods, when the GrIS expanded as far as the continental shelf break and was thus more directly exposed to oceanic changes. However, the GrIS response to palaeo-oceanic variations has yet to be investigated in detail from a mechanistic modelling perspective. In this work, the evolution of the GrIS over the past two glacial cycles is studied using a three-dimensional hybrid ice-sheet–shelf model. We assess the effect of the variation of oceanic temperatures on the GrIS evolution on glacial–interglacial timescales through changes in submarine melting. The results show a very high sensitivity of the GrIS to changing oceanic conditions. Oceanic forcing is found to be a primary driver of GrIS expansion in glacial times and of retreat in interglacial periods. If switched off, palaeo-atmospheric variations alone are not able to yield a reliable glacial configuration of the GrIS. This work therefore suggests that considering the ocean as an active forcing should become standard practice in palaeo-ice-sheet modelling.

scholarly journals Basal temperature conditions of the Greenland ice sheet during the glacial cycles

1996 ◽  
Vol 23 ◽  
pp. 226-236 ◽  
Author(s):  
Philippe Huybrechts
Keyword(s):  
Steady State ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Ice Thickness ◽  
Glacial Cycle ◽  
Glacial Cycles ◽  
Temperature Conditions ◽  
Strongly Damped

A high-resolution, three-dimensional thermomechanical ice-sheet model, which includes isostasy, the possibility of ice-sheet expansion on the continental shelf and refined climatic parameterizations, was used to investigate the basal thermal regime of the Greenland ice sheet. The thermodynamic calculations take into account the usual terms of heat flow within the ice, a thermally active bedrock layer and all of the effects associated with changes in ice thickness and flow pattern. Basal temperature conditions are documented with respect to glacial–interracial shifts in climatic boundary conditions, both in steady state as during simulations over the last two glacial cycles using the GRIP δ180 record. It is found that the basal temperature field shows a large sensitivity in steady-state experiments but that, during a glacial cycle, basal temperature variations are strongly damped, in particular in central areas. A comparison has been made with measured data from deep ice cores and the implications are discussed.

scholarly journals Submarine melt as a potential trigger of the North East Greenland Ice Stream margin retreat during Marine Isotope Stage 3

2019 ◽  
Vol 13 (7) ◽  
pp. 1911-1923 ◽  
Author(s):  
Ilaria Tabone ◽  
Alexander Robinson ◽  
Jorge Alvarez-Solas ◽  
Marisa Montoya
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
High Sensitivity ◽  
Marine Isotope Stage ◽  
Atmospheric Conditions ◽  
North East ◽  
Ice Stream ◽  
Grounding Line ◽  
Oceanic Forcing ◽  
Marine Isotope Stage 3

Abstract. The Northeast Greenland Ice Stream (NEGIS) has been suffering a significant ice mass loss during the last decades. This is partly due to increasing oceanic temperatures in the subpolar North Atlantic, which enhance submarine basal melting and mass discharge. This demonstrates the high sensitivity of this region to oceanic changes. In addition, a recent study suggested that the NEGIS grounding line was 20–40 km behind its present-day location for 15 ka during Marine Isotope Stage (MIS) 3. This is in contrast with Greenland temperature records indicating cold atmospheric conditions at that time, expected to favour ice-sheet expansion. To explain this anomalous retreat a combination of atmospheric and external forcings has been invoked. Yet, as the ocean is found to be a primary driver of the ongoing retreat of the NEGIS glaciers, the effect of past oceanic changes in their paleo evolution cannot be ruled out and should be explored in detail. Here we investigate the sensitivity of the NEGIS to the oceanic forcing during the last glacial period using a three-dimensional hybrid ice-sheet–shelf model. We find that a sufficiently high oceanic forcing could account for a NEGIS ice-margin retreat of several tens of kilometres, potentially explaining the recently proposed NEGIS grounding-line retreat during Marine Isotope Stage 3.

scholarly journals Glacier dynamics over the last quarter of a century at Jakobshavn Isbræ

2015 ◽  
Vol 9 (5) ◽  
pp. 4865-4892
Author(s):  
I. S. Muresan ◽  
S. A. Khan ◽  
A. Aschwanden ◽  
C. Khroulev ◽  
T. Van Dam ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
21St Century ◽  
Greenland Ice Sheet ◽  
Outlet Glacier ◽  
The Past ◽  
Glacier Dynamics ◽  
The Future ◽  
Oceanic Forcing

Abstract. Observations over the past two decades show substantial ice loss associated with the speedup of marine terminating glaciers in Greenland. Here we use a regional 3-D outlet glacier model to simulate the behaviour of Jakobshavn Isbræ (JI) located in west Greenland. Using atmospheric and oceanic forcing we tune our model to reproduce the observed frontal changes of JI during 1990–2014. We identify two major accelerations. The first occurs in 1998, and is triggered by moderate thinning prior to 1998. The second acceleration, which starts in 2003 and peaks in summer 2004, is triggered by the final breakup of the floating tongue, which generates a reduction in buttressing at the JI terminus. This results in further thinning, and as the slope steepens inland, sustained high velocities have been observed at JI over the last decade. As opposed to other regions on the Greenland Ice Sheet (GrIS), where dynamically induced mass loss has slowed down over recent years, both modelled and observed results for JI suggest a continuation of the acceleration in mass loss. Further, we find that our model is not able to capture the 2012 peak in the observed velocities. Our analysis suggests that the 2012 acceleration of JI is likely the result of an exceptionally long melt season dominated by extreme melt events. Considering that such extreme surface melt events are expected to intensify in the future, our findings suggest that the 21st century projections of the GrIS mass loss and the future sea level rise may be larger than predicted by existing modelling results.

scholarly journals Basal temperature conditions of the Greenland ice sheet during the glacial cycles

1996 ◽  
Vol 23 ◽  
pp. 226-236 ◽  
Author(s):  
Philippe Huybrechts
Keyword(s):  
Steady State ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Ice Thickness ◽  
Glacial Cycle ◽  
Glacial Cycles ◽  
Temperature Conditions ◽  
Strongly Damped

A high-resolution, three-dimensional thermomechanical ice-sheet model, which includes isostasy, the possibility of ice-sheet expansion on the continental shelf and refined climatic parameterizations, was used to investigate the basal thermal regime of the Greenland ice sheet. The thermodynamic calculations take into account the usual terms of heat flow within the ice, a thermally active bedrock layer and all of the effects associated with changes in ice thickness and flow pattern. Basal temperature conditions are documented with respect to glacial–interracial shifts in climatic boundary conditions, both in steady state as during simulations over the last two glacial cycles using the GRIP δ 180 record. It is found that the basal temperature field shows a large sensitivity in steady-state experiments but that, during a glacial cycle, basal temperature variations are strongly damped, in particular in central areas. A comparison has been made with measured data from deep ice cores and the implications are discussed.

Coupled solid Earth – Antarctic ice sheet simulations with VILMA and PISM

2021 ◽  
Author(s):  
Torsten Albrecht ◽  
Meike Bagge ◽  
Ricarda Winkelmann ◽  
Volker Klemann
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Climate Modeling ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Glacial Cycles ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Isostatic Adjustment

<p><span>The Antarctic Ice Sheet rests on a bed that is characterized by tectonical activity and hence by a heterogeneous rheology. Spots of extremely weak lithosphere structure could have strong impacts on the Glacial Isostatic Adjustment and hence on the stability of the ice sheet, possibly also for confined glacier regions and on timescales of decades down to even years (Barletta et al., 2018).</span><span><br><br></span><span>We coupled the VIscoelastic Lithosphere and MAntle model (VILMA) to the Parallel Ice Sheet Model (PISM) </span><span>and ran simulations over the last two glacial cycles. In this framework, VILMA considers both viscoelastic deformations of the solid Earth and gravitationally consistent mass redistribution in the ocean by solving for the sea-level equation (Martinec et al., 2018)</span><span>. In turn, PISM interprets this as a vertical shift in bed topography that directly affects the stress balance within the ice sheet and hence the grounding line dynamics at the interface of ice, ocean and bedrock.</span><span><br><br></span><span>Here we present first results of the coupled Antarctic glacial-cycle simulations and investigate technical aspects, such as optimal coupling time steps, iteration schemes and convergence, for both one-dimensional and three-dimensional Earth structures. This project is part of the </span><span>German Climate Modeling Initiative, PalMod2.</span></p><p> </p><p><span>References:</span></p><p><sup><span>Barletta et al., 2018. <em>Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability. </em><strong>Science</strong>, <em>360</em>, pp.1335-1339. DOI: 10.1126/science.aao1447</span></sup></p><p><sup><span>Martinec et al., 2018. <em>A benchmark study of numerical implementations of the sea level equation in GIA modelling</em>. </span><span><strong>Geophysical Journal International</strong></span><span>, <em>215</em>(1), pp.389-414. DOI: 10.1093/gji/ggy280</span></sup></p><p> </p>

scholarly journals A computationally efficient model for the Greenland ice sheet

2012 ◽  
Vol 6 (4) ◽  
pp. 2751-2788 ◽  
Author(s):  
J. Haqq-Misra ◽  
P. Applegate ◽  
B. Tuttle ◽  
R. Nicholas ◽  
K. Keller
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Flow Line ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Computationally Efficient ◽  
Dimensional Parameter ◽  
One Dimensional ◽  
Wide Range

Abstract. We present a one-dimensional model of the Greenland Ice Sheet (GIS) for use in analysis of future sea level rise. Simulations using complex three-dimensional models suggest that the GIS may respond in a nonlinear manner to anthropogenic climate forcing and cause potentially nontrivial sea level rise. These GIS projections are, however, deeply uncertain. Analyzing these uncertainties is complicated by the substantial computational demand of the current generation of complex three-dimensional GIS models. As a result, it is typically computationally infeasible to perform the large number of model evaluations required to carefully explore a multi-dimensional parameter space, to fuse models with observational constraints, or to assess risk-management strategies in Integrated Assessment Models (IAMs) of climate change. Here we introduce GLISTEN (GreenLand Ice Sheet ENhanced), a computationally efficient, mechanistically based, one-dimensional flow-line model of GIS mass balance capable of reproducing key instrumental and paleo-observations as well as emulating more complex models. GLISTEN is based on a simple model developed by Pattyn (2006). We have updated and extended this original model by improving its computational functionality and representation of physical processes such as precipitation, ablation, and basal sliding. The computational efficiency of GLISTEN enables a systematic and extensive analysis of the GIS behavior across a wide range of relevant parameters and can be used to represent a potential GIS threshold response in IAMs. We demonstrate the utility of GLISTEN by performing a pre-calibration and analysis. We find that the added representation of processes in GLISTEN, along with pre-calibration of the model, considerably improves the hindcast skill of paleo-observations.

Could climate engineering save the Greenland Ice Sheet?

2016 ◽  
Author(s):  
Patrick J. Applegate ◽  
K. Keller
Keyword(s):  
Sea Level Rise ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Sea Level ◽  
Computer Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Upper Atmosphere ◽  
Climate Engineering ◽  
Air Temperatures

Engineering the climate through albedo modification (AM) could slow, but probably would not stop, melting of the Greenland Ice Sheet. Albedo modification is a technology that could reduce surface air temperatures through putting reflective particles into the upper atmosphere. AM has never been tested, but it might reduce surface air temperatures faster and more cheaply than reducing greenhouse gas emissions. Some scientists claim that AM would also prevent or reverse sea-level rise. But, are these claims true? The Greenland Ice Sheet will melt faster at higher temperatures, adding to sea-level rise. However, it's not clear that reducing temperatures through AM will stop or reverse sea-level rise due to Greenland Ice Sheet melting. We used a computer model of the Greenland Ice Sheet to examine its contributions to future sea level rise, with and without AM. Our results show that AM would probably reduce the rate of sea-level rise from the Greenland Ice Sheet. However, sea-level rise would likely continue even with AM, and the ice sheet would not regrow quickly. Albedo modification might buy time to prepare for sea-level rise, but problems could arise if policymakers assume that AM will stop sea-level rise completely.

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