scholarly journals Ice sheet response to sub-shelf melt rates in coupled and uncoupled peri-Antarctic ice-sheet model simulations

2021 ◽  
Author(s):  
Lars Zipf ◽  
Charles Pelletier ◽  
Konstanze Haubner ◽  
Sainan Sun ◽  
Frank Pattyn
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Ocean Model ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Main Driver ◽  
First Results ◽  
The Impact ◽  
Ice Model

<p>Sub-shelf melting is the main driver of Antarctica's ice sheet mass loss. However, sub-shelf melt rate parameterizations for standalone ice models lack the capability to capture complex ocean circulation within ice shelf cavities. To overcome drawbacks of standalone models and to improve melt parameterizations, high resolution coupling of ice sheet and ocean models are capable of hindcasting past decennia and be compared to observations.</p><p>Here, we present first results of a hindcast (1985-2018) of the new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration, developed within the framework of the PARAMOUR project. The configuration is based on the ocean and sea ice model NEMO3.6-LIM3 and the ice sheet model f.ETISh v1.7. The coupling routine facilitates exchange of monthly sub-shelf melt rates (from ocean to ice model) and evolving ice shelf cavity geometry (from ice to ocean model).</p><p>We investigate the impact of the coupling frequency (more precisely, the frequency of updating the ice shelf cavity geometry within the ocean model) on the sub-shelf melt rates and its feedback on the ice dynamics. We further compare the sub-shelf melt rates of the coupled setup to those of the standalone ice sheet model with different sub-shelf melt rate parametrizations (ISMIP6, plume, PICO, PICOP) and investigate the sensitivity of the response of the ice sheet for the different basal melt rate patterns on decadal time scales.</p>

First results from coupling the Parallel Ice Sheet Model with the Modular Ocean Model via an Antarctic ice-shelf cavity module

2021 ◽  
Author(s):  
Moritz Kreuzer ◽  
Ronja Reese ◽  
Willem Huiskamp ◽  
Stefan Petri ◽  
Torsten Albrecht ◽  
...  
Keyword(s):  
Time Scales ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
First Results ◽  
The Antarctic

<p>The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. To study global and long term interactions, we developed a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degrees, respectively. We present first results from our coupled setup and discuss stability, feedbacks, and interactions of the Antarctic Ice Sheet and the global ocean system on millennial time scales.</p>

scholarly journals Experimental design for three interrelated Marine Ice-Sheet and Ocean Model Intercomparison Projects

2015 ◽  
Vol 8 (11) ◽  
pp. 9859-9924 ◽  
Author(s):  
X. S. Asay-Davis ◽  
S. L. Cornford ◽  
G. Durand ◽  
B. K. Galton-Fenzi ◽  
R. M. Gladstone ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Ocean Model ◽  
Model Verification ◽  
Second Phase ◽  
Model Intercomparison ◽  
Ice Shelf ◽  
Amundsen Sea ◽  
Ice Dynamics ◽  
Future Projections

Abstract. Coupled ice sheet-ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions in the West Antarctic Ice Sheet (WAIS). Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the ice shelf-ocean MIP second phase (ISOMIP+) and coupled ice sheet-ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for evaluation of the participating models.

Comparison of peri-Antarctic sub-shelf melt rates in coupled and uncoupled ice-sheet model simulations

2020 ◽  
Author(s):  
Lars Zipf ◽  
Charles Pelletier ◽  
Konstanze Haubner ◽  
Sainan Sun ◽  
Hugues Goosse ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Optimal Solution ◽  
Ocean Model ◽  
Model Framework ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
First Results ◽  
Framework Conditions ◽  
The Antarctic

<p>Sub-shelf melting is the main driver of the mass loss of the Antarctic ice sheet. Various parametrizations exist to estimate basal melt rates within standalone ice sheet models, but they are not able to capture complex ocean circulation. Therefore, high resolution coupled ice sheet-ocean models are the ultimate approach to simulate observed sub-shelf melt rates on short time scales and thereby improve projections of future Antarctic sea level contribution.</p><p>Here, we present first results of a hindcast (last 30 years) of the new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration, developed within the framework of the PARAMOUR project. The configuration, which captures whole Antarctica, is based on the ocean and sea ice model NEMO3.6-LIM3, providing the ice sheet model with monthly sub-shelf melt rates, and the Antarctic ice sheet model f.ETISh v1.5, providing the updated ice shelf cavity geometry to the ocean model. Different difficulties are tackled for the coupling: The initialisation of the ice sheet model is optimised for the chosen resolution of 8km, which is a tradeoff between capturing the main features for the peri-Antarctic setup and respecting the model purpose as fast ice sheet model. Framework conditions for the coupling, e.g. a constant ice-ocean mask, are tested and implemented. The optimal solution to estimate sub-shelf melt for small ice shelves that are not resolved in the ocean model due to the different resolution of the ice sheet and the ocean model, is investigated.<br>Sub-shelf melt rates of the coupled setup are compared to those modeled by the standalone ocean model and those of the standalone ice sheet model with different sub-shelf melt rate parametrizations (ISMIP6, plume, PICO, PICOP) and the sensitivity of the response of the ice sheet for the different basal melt rate patterns are investigated.</p>

scholarly journals Experimental design for three interrelated marine ice sheet and ocean model intercomparison projects: MISMIP v. 3 (MISMIP +), ISOMIP v. 2 (ISOMIP +) and MISOMIP v. 1 (MISOMIP1)

2016 ◽  
Vol 9 (7) ◽  
pp. 2471-2497 ◽  
Author(s):  
Xylar S. Asay-Davis ◽  
Stephen L. Cornford ◽  
Gaël Durand ◽  
Benjamin K. Galton-Fenzi ◽  
Rupert M. Gladstone ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Ocean Model ◽  
Model Verification ◽  
Second Phase ◽  
Model Intercomparison ◽  
Ice Shelf ◽  
Amundsen Sea ◽  
Ice Dynamics ◽  
Future Projections

Abstract. Coupled ice sheet–ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions of the West Antarctic Ice Sheet (WAIS). Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the Ice Shelf-Ocean MIP second phase (ISOMIP+) and coupled ice sheet–ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for the evaluation of the participating models.

scholarly journals Antarctic ice sheet fertilises the Southern Ocean

2014 ◽  
Vol 11 (10) ◽  
pp. 2635-2643 ◽  
Author(s):  
R. Death ◽  
J. L. Wadham ◽  
F. Monteiro ◽  
A. M. Le Brocq ◽  
M. Tranter ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Ice Sheet ◽  
Ocean Model ◽  
Coastal Sediments ◽  
Global Ocean ◽  
Iron Cycling ◽  
Antarctic Ice Sheet ◽  
Significant Control ◽  
Subglacial Meltwater ◽  
The Impact

Abstract. Southern Ocean (SO) marine primary productivity (PP) is strongly influenced by the availability of iron in surface waters, which is thought to exert a significant control upon atmospheric CO2 concentrations on glacial/interglacial timescales. The zone bordering the Antarctic Ice Sheet exhibits high PP and seasonal plankton blooms in response to light and variations in iron availability. The sources of iron stimulating elevated SO PP are in debate. Established contributors include dust, coastal sediments/upwelling, icebergs and sea ice. Subglacial meltwater exported at the ice margin is a more recent suggestion, arising from intense iron cycling beneath the ice sheet. Icebergs and subglacial meltwater may supply a large amount of bioavailable iron to the SO, estimated in this study at 0.07–0.2 Tg yr−1. Here we apply the MIT global ocean model (Follows et al., 2007) to determine the potential impact of this level of iron export from the ice sheet upon SO PP. The export of iron from the ice sheet raises modelled SO PP by up to 40%, and provides one plausible explanation for seasonally very high in situ measurements of PP in the near-coastal zone. The impact on SO PP is greatest in coastal regions, which are also areas of high measured marine PP. These results suggest that the export of Antarctic runoff and icebergs may have an important impact on SO PP and should be included in future biogeochemical modelling.

scholarly journals Antarctic Ice Sheet fertilises the Southern Ocean

2013 ◽  
Vol 10 (7) ◽  
pp. 12551-12570 ◽  
Author(s):  
R. Death ◽  
J. L. Wadham ◽  
F. Monteiro ◽  
A. M. Le Brocq ◽  
M. Tranter ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Ice Sheet ◽  
Ocean Model ◽  
Coastal Sediments ◽  
Global Ocean ◽  
Iron Cycling ◽  
Antarctic Ice Sheet ◽  
Significant Control ◽  
Subglacial Meltwater ◽  
The Impact

Abstract. Southern Ocean (SO) marine primary productivity (PP) is strongly influenced by the availability of iron in surface waters, which is thought to exert a significant control upon atmospheric CO2 concentrations on glacial/interglacial timescales. The zone bordering the Antarctic Ice Sheet exhibits high PP and seasonal plankton blooms in response to light and variations in iron availability. The sources of iron stimulating elevated SO PP are in debate. Established contributors include dust, coastal sediments/upwelling, icebergs and sea ice. Subglacial meltwater exported at the ice margin is a more recent suggestion, arising from intense iron cycling beneath the ice sheet. Icebergs and subglacial meltwater may supply a large amount of bioavailable iron to the SO, estimated in this study at 0.07–1.0 Tg yr−1. Here we apply the MIT global ocean model (Follows et al., 2007) to determine the potential impact of this level of iron export from the ice sheet upon SO PP. The export of iron from the ice sheet raises modelled SO PP by up to 40%, and provides one plausible explanation for very high seasonally observed PP in the near-coastal zone. The impact on SO PP is greatest in coastal regions, which are also areas of high observed marine PP. These results suggest that the export of Antarctic runoff and icebergs may have an important impact on SO PP and should be included in future biogeochemical modelling.

Representation of basal melting in idealised coupled ice sheet ocean models

2021 ◽  
Author(s):  
Chen Zhao ◽  
Rupert Gladstone ◽  
Ben Galton-Fenzi ◽  
David Gwyther
Keyword(s):  
Ocean Circulation ◽  
Critical Role ◽  
Ice Sheet ◽  
Ocean Model ◽  
Periodic Pattern ◽  
Regional Ocean Modeling System ◽  
Ice Shelf ◽  
Grounding Line ◽  
Ocean Models ◽  
Basal Melting

<p>The ocean-driven basal melting has important implications for the stability of ice shelves in Antarctic, which largely affects the ice sheet mass balance, ocean circulation, and subsequently global sea level rise. Due to the limited observations in the ice shelf cavities, the couple ice sheet ocean models have been playing a critical role in examining the processes governing basal melting. In this study we use the Framework for Ice Sheet-Ocean Coupling (FISOC) to couple the Elmer/Ice full-stokes ice sheet model and the Regional Ocean Modeling System (ROMS) ocean model to model ice shelf/ocean interactions for an idealised three-dimensional domain. Experiments followed the coupled ice sheet–ocean experiments under the first phase of the Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP1). A periodic pattern in the simulated mean basal melting rates is found to be highly consistent with the maximum barotropic stream function and also the grounding line retreat row by row,  which is likely to be related with the gyre break down near the grounding line caused by some non-physical instability events from the ocean bottom. Sensitivity tests are carried out, showing that this periodic pattern is not sensitive to the choice of couple time intervals and horizontal eddy viscosities but sensitive to vertical resolution in the ocean model, the chosen critical water column thickness in the wet-dry scheme, and the tracer properties for the nudging dry cells at the ice-ocean interface boundary. Further simulations are necessary to better explain the mechanism involved in the couple ice-ocean system, which is very significant for its application on the realistic ice-ocean systems in polar regions.</p>

scholarly journals Antarctic glacier-tongue velocities from Landsat images: first results

1993 ◽  
Vol 17 ◽  
pp. 356-366 ◽  
Author(s):  
B.K. Lucchitta ◽  
Κ.F. Mullins ◽  
A.L. Allison ◽  
J.G. Ferrigno
Keyword(s):  
Ice Sheet ◽  
Ice Shelf ◽  
Landsat Images ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Ice Shelves ◽  
Glacier Tongue ◽  
West Antarctic ◽  
First Results

We measured the velocities of six glacier tongues and a few tongues within ice shelves distributed around the Antarctic coastline by determining the displacement of crevasse patterns seen on sequential Landsat images. The velocities range from less than 0.2 km a−1 for East Antarctic ice-shelf tongues to more than 2.5 km a−1 for the Thwaites Glacier Tongue. All glacier tongues show increases in velocity toward their distal margins. In general, the tongues of glaciers draining the West Antarctic ice sheet have moved significantly faster than those in East Antarctica. This observation may be significant in light of the hypothesized possible disintegration of the West Antarctic ice sheet.

Automated mapping of Antarctic supraglacial lakes and streams using machine learning

2020 ◽  
Author(s):  
Mariel Dirscherl ◽  
Andreas Dietz ◽  
Celia Baumhoer ◽  
Christof Kneisel ◽  
Claudia Kuenzer
Keyword(s):  
Machine Learning ◽  
Mass Balance ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Supraglacial Lakes ◽  
The Antarctic ◽  
Sentinel 2

<p>Antarctica stores ~91 % of the global ice mass making it the biggest potential contributor to global sea-level-rise. With increased surface air temperatures during austral summer as well as in consequence of global climate change, the ice sheet is subject to surface melting resulting in the formation of supraglacial lakes in local surface depressions. Supraglacial meltwater features may impact Antarctic ice dynamics and mass balance through three main processes. First of all, it may cause enhanced ice thinning thus a potentially negative Antarctic Surface Mass Balance (SMB). Second, the temporary injection of meltwater to the glacier bed may cause transient ice speed accelerations and increased ice discharge. The last mechanism involves a process called hydrofracturing i.e. meltwater-induced ice shelf collapse caused by the downward propagation of surface meltwater into crevasses or fractures, as observed along large coastal sections of the northern Antarctic Peninsula. Despite the known impact of supraglacial meltwater features on ice dynamics and mass balance, the Antarctic surface hydrological network remains largely understudied with an automated method for supraglacial lake and stream detection still missing. Spaceborne remote sensing and data of the Sentinel missions in particular provide an excellent basis for the monitoring of the Antarctic surface hydrological network at unprecedented spatial and temporal coverage.</p><p>In this study, we employ state-of-the-art machine learning for automated supraglacial lake and stream mapping on basis of optical Sentinel-2 satellite data. With more detail, we use a total of 72 Sentinel-2 acquisitions distributed across the Antarctic Ice Sheet together with topographic information to train and test the selected machine learning algorithm. In general, our machine learning workflow is designed to discriminate between surface water, ice/snow, rock and shadow being further supported by several automated post-processing steps. In order to ensure the algorithm’s transferability in space and time, the acquisitions used for training the machine learning model are chosen to cover the full circle of the 2019 melt season and the data selected for testing the algorithm span the 2017 and 2018 melt seasons. Supraglacial lake predictions are presented for several regions of interest on the East and West Antarctic Ice Sheet as well as along the Antarctic Peninsula and are validated against randomly sampled points in the underlying Sentinel-2 RGB images. To highlight the performance of our model, we specifically focus on the example of the Amery Ice Shelf in East Antarctica, where we applied our algorithm on Sentinel-2 data in order to present the temporal evolution of maximum lake extent during three consecutive melt seasons (2017, 2018 and 2019).</p>

A circumpolar coupled ocean – Antarctic ice sheet configuration for investigating recent changes in Southern Ocean heat content

2020 ◽  
Author(s):  
Charles Pelletier ◽  
Lars Zipf ◽  
Konstanze Haubner ◽  
Hugues Goosse ◽  
Frank Pattyn ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ice Sheet ◽  
Heat Content ◽  
Ice Shelf ◽  
Sea Ice Extent ◽  
Antarctic Ice Sheet ◽  
Antarctic Sea Ice ◽  
Physical Phenomena ◽  
The Impact

<p>From 2016 on, observed tendencies of Southern Ocean sea surface temperatures and Antarctic sea ice extent (SIE) have shifted from cooling down (with SIE increase) to warming up (SIE decrease). This change of Southern Ocean surface thermal properties has been sustained since, which indicates that it is not solely due to the interannual variability of the atmosphere, but also to modifications in the ocean itself. Among other physical phenomena, the acceleration of continental ice shelf melt, through its subsequent impact on the Southern Ocean stratification, has been proposed as one of the potential meaningful drivers of the sea ice changes. Reciprocally, recent studies suggest that besides atmosphere forcings, the upper ocean thermal content bears significant impact on ice shelf melt rates and dynamics. Here we present a new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration aiming at investigating the impact of this ocean – continental ice feedback, developed within the framework of the PARAMOUR project. Our setting relies on the ocean and sea ice model NEMO3.6-LIM3 sending ice shelf melt rates to the Antarctic ice sheet model f.ETISh v1.5, who in turn responds to it and provides updated ice shelf cavity geometry. Both technical aspects and first coupled results are presented.</p>

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