Modeling the response of Lambert Glacier–Amery Ice Shelf system, East Antarctic, to uncertain climate forcing over the 21st and 22nd centuries

Abstract. The interaction between the climate system and the large polar ice sheets regions is a key process in global environmental change. We carried out ice dynamic simulations of one of the largest drainage systems in East Antarctica: the Lambert Glacier–Amery Ice Shelf system, with an adaptive mesh ice sheet model. The ice sheet model is driven by surface accumulation and basal melt rates computed by two ocean and two atmosphere models. The change of the ice thickness and velocity in the ice shelf is mainly influenced by the basal melting distribution, but, although the ice shelf thins in the most of the simulations, there is little grounding line retreat. We find that the Lambert Glacier grounding line can retreat as much as 30 km if there is sufficient thinning of the ice shelf south of Clemence Massif, but none of the ocean models provide sufficiently high melt rates in that region. Overall, the increased accumulation computed by the atmosphere models outweighs ice stream acceleration so that the net contribution to sea level rise is negative.

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Modelling the response of the Lambert Glacier–Amery Ice Shelf system, East Antarctica, to uncertain climate forcing over the 21st and 22nd centuries

The Cryosphere ◽

10.5194/tc-8-1057-2014 ◽

2014 ◽

Vol 8 (3) ◽

pp. 1057-1068 ◽

Cited By ~ 20

Author(s):

Y. Gong ◽

S. L. Cornford ◽

A. J. Payne

Keyword(s):

Climate Model ◽

Global Environmental Change ◽

Ice Sheet ◽

Adaptive Mesh ◽

Ocean Model ◽

East Antarctica ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Grounding Line ◽

Lambert Glacier

Abstract. The interaction between the climate system and the large polar ice sheet regions is a key process in global environmental change. We carried out dynamic ice simulations of one of the largest drainage systems in East Antarctica: the Lambert Glacier–Amery Ice Shelf system, with an adaptive mesh ice sheet model. The ice sheet model is driven by surface accumulation and basal melt rates computed by the FESOM (Finite-Element Sea-Ice Ocean Model) ocean model and the RACMO2 (Regional Atmospheric Climate Model) and LMDZ4 (Laboratoire de Météorologie Dynamique Zoom) atmosphere models. The change of ice thickness and velocity in the ice shelf is mainly influenced by the basal melt distribution, but, although the ice shelf thins in most of the simulations, there is little grounding line retreat. We find that the Lambert Glacier grounding line can retreat as much as 40 km if there is sufficient thinning of the ice shelf south of Clemence Massif, but the ocean model does not provide sufficiently high melt rates in that region. Overall, the increased accumulation computed by the atmosphere models outweighs ice stream acceleration so that the net contribution to sea level rise is negative.

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Revisiting Ice Flux and Mass Balance of the Lambert Glacier–Amery Ice Shelf System Using Multi-Remote-Sensing Datasets, East Antarctica

Remote Sensing ◽

10.3390/rs14020391 ◽

2022 ◽

Vol 14 (2) ◽

pp. 391

Author(s):

Derui Xu ◽

Xueyuan Tang ◽

Shuhu Yang ◽

Yun Zhang ◽

Lijuan Wang ◽

...

Keyword(s):

Remote Sensing ◽

Mass Balance ◽

Ice Sheet ◽

East Antarctica ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Amery Ice Shelf ◽

Grounding Line ◽

Lambert Glacier ◽

The Antarctic

Due to rapid global warming, the relationship between the mass loss of the Antarctic ice sheet and rising sea levels are attracting widespread attention. The Lambert–Amery glacial system is the largest drainage system in East Antarctica, and its mass balance has an important influence on the stability of the Antarctic ice sheet. In this paper, the recent ice flux in the Lambert Glacier of the Lambert–Amery system was systematically analyzed based on recently updated remote sensing data. According to Landsat-8 ice velocity data from 2018 to April 2019 and the updated Bedmachine v2 ice thickness dataset in 2021, the contribution of ice flux approximately 140 km downstream from Dome A in the Lambert Glacier area to downstream from the glacier is 8.5 ± 1.9, and the ice flux in the middle of the convergence region is 18.9 ± 2.9. The ice mass input into the Amery ice shelf through the grounding line of the whole glacier is 19.9 ± 1.3. The ice flux output from the mainstream area of the grounding line is 19.3 ± 1.0. Using the annual SMB data of the regional atmospheric climate model (RACMO v2.3) as the quality input, the mass balance of the upper, middle, and lower reaches of the Lambert Glacier was analyzed. The results show that recent positive accumulation appears in the middle region of the glacier (about 74–78°S, 67–85°E) and the net accumulation of the whole glacier is 2.4 ± 3.5. Although the mass balance of the Lambert Glacier continues to show a positive accumulation, and the positive value in the region is decreasing compared with values obtained in early 2000.

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Representation of basal melting in idealised coupled ice sheet ocean models

10.5194/egusphere-egu21-10448 ◽

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&#8211;ocean experiments under the first phase of the Marine Ice Sheet&#8211;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, &#160;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>

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Dynamic response of Antarctic ice shelves to bedrock uncertainty

The Cryosphere ◽

10.5194/tc-8-1561-2014 ◽

2014 ◽

Vol 8 (4) ◽

pp. 1561-1576 ◽

Cited By ~ 17

Author(s):

S. Sun ◽

S. L. Cornford ◽

Y. Liu ◽

J. C. Moore

Keyword(s):

Small Amplitude ◽

Spatial Scales ◽

Random Noise ◽

Ice Sheet ◽

Adaptive Mesh ◽

Data Uncertainty ◽

Frequency Noise ◽

Noise Power ◽

Ice Shelf ◽

Amery Ice Shelf

Abstract. Accurate and extensive bedrock geometry data is essential in ice sheet modelling. The shape of the bedrock on fine scales can influence ice sheet evolution, for example through the formation of pinning points that alter grounding line dynamics. Here we test the sensitivity of the BISICLES adaptive mesh ice sheet model to small-amplitude height fluctuations on different spatial scales in the bedrock topography provided by Bedmap2 in the catchments of Pine Island Glacier, the Amery Ice shelf and a region of East Antarctica including the Aurora Basin, Law Dome and Totten Glacier. We generate an ensemble of bedrock topographies by adding random noise to the Bedmap2 data with amplitude determined by the accompanying estimates of bedrock uncertainty. We find that the small-amplitude fluctuations result in only minor changes in the way these glaciers evolve. However, lower-frequency noise, with a broad spatial scale (over tens of kilometres) is more important than higher-frequency noise even when the features have the same height amplitudes and the total noise power is maintained. This is cause for optimism regarding credible sea level rise estimates with presently achievable density of thickness measurements. Pine Island Glacier and the region around Totten Glacier and Law Dome undergo substantial retreat and appear to be more sensitive to errors in bed topography than the Amery Ice shelf region which remains stable under the present-day observational data uncertainty.

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Marine ice sheet model performance depends on basal sliding physics and sub-shelf melting

The Cryosphere ◽

10.5194/tc-11-319-2017 ◽

2017 ◽

Vol 11 (1) ◽

pp. 319-329 ◽

Cited By ~ 23

Author(s):

Rupert Michael Gladstone ◽

Roland Charles Warner ◽

Benjamin Keith Galton-Fenzi ◽

Olivier Gagliardini ◽

Thomas Zwinger ◽

...

Keyword(s):

Flow Line ◽

Ice Sheet ◽

Model Performance ◽

Effective Pressure ◽

Physical Processes ◽

Ice Shelf ◽

Grounding Line ◽

Basal Sliding ◽

Power Law Function ◽

Basal Melting

Abstract. Computer models are necessary for understanding and predicting marine ice sheet behaviour. However, there is uncertainty over implementation of physical processes at the ice base, both for grounded and floating glacial ice. Here we implement several sliding relations in a marine ice sheet flow-line model accounting for all stress components and demonstrate that model resolution requirements are strongly dependent on both the choice of basal sliding relation and the spatial distribution of ice shelf basal melting.Sliding relations that reduce the magnitude of the step change in basal drag from grounded ice to floating ice (where basal drag is set to zero) show reduced dependence on resolution compared to a commonly used relation, in which basal drag is purely a power law function of basal ice velocity. Sliding relations in which basal drag goes smoothly to zero as the grounding line is approached from inland (due to a physically motivated incorporation of effective pressure at the bed) provide further reduction in resolution dependence.A similar issue is found with the imposition of basal melt under the floating part of the ice shelf: melt parameterisations that reduce the abruptness of change in basal melting from grounded ice (where basal melt is set to zero) to floating ice provide improved convergence with resolution compared to parameterisations in which high melt occurs adjacent to the grounding line.Thus physical processes, such as sub-glacial outflow (which could cause high melt near the grounding line), impact on capability to simulate marine ice sheets. If there exists an abrupt change across the grounding line in either basal drag or basal melting, then high resolution will be required to solve the problem. However, the plausible combination of a physical dependency of basal drag on effective pressure, and the possibility of low ice shelf basal melt rates next to the grounding line, may mean that some marine ice sheet systems can be reliably simulated at a coarser resolution than currently thought necessary.

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Ocean-forced evolution of the Amundsen Sea catchment, West Antarctica, by 2100

The Cryosphere ◽

10.5194/tc-14-1245-2020 ◽

2020 ◽

Vol 14 (4) ◽

pp. 1245-1258

Author(s):

Alanna V. Alevropoulos-Borrill ◽

Isabel J. Nias ◽

Antony J. Payne ◽

Nicholas R. Golledge ◽

Rory J. Bingham

Keyword(s):

Sea Level ◽

21St Century ◽

Adaptive Mesh Refinement ◽

Ice Sheet ◽

Adaptive Mesh ◽

Ocean Temperature ◽

Ice Shelf ◽

Ice Streams ◽

Amundsen Sea ◽

Grounding Line

Abstract. The response of ice streams in the Amundsen Sea Embayment (ASE) to future climate forcing is highly uncertain. Here we present projections of 21st century response of ASE ice streams to modelled local ocean temperature change using a subset of Coupled Model Intercomparison Project (CMIP5) simulations. We use the BISICLES adaptive mesh refinement (AMR) ice sheet model, with high-resolution grounding line resolving capabilities, to explore grounding line migration in response to projected sub-ice-shelf basal melting. We find a contribution to sea level rise of between 2.0 and 4.5 cm by 2100 under RCP8.5 conditions from the CMIP5 subset, where the mass loss response is linearly related to the mean ocean temperature anomaly. To account for uncertainty associated with model initialization, we perform three further sets of CMIP5-forced experiments using different parameterizations that explore perturbations to the prescription of initial basal melt, the basal traction coefficient and the ice stiffening factor. We find that the response of the ASE to ocean temperature forcing is highly dependent on the parameter fields obtained in the initialization procedure, where the sensitivity of the ASE ice streams to the sub-ice-shelf melt forcing is dependent on the choice of parameter set. Accounting for ice sheet model parameter uncertainty results in a projected range in sea level equivalent contribution from the ASE of between −0.02 and 12.1 cm by the end of the 21st century.

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Brief communication: PICOP, a new ocean melt parameterization under ice shelves combining PICO and a plume model

The Cryosphere ◽

10.5194/tc-13-1043-2019 ◽

2019 ◽

Vol 13 (3) ◽

pp. 1043-1049 ◽

Cited By ~ 7

Author(s):

Tyler Pelle ◽

Mathieu Morlighem ◽

Johannes H. Bondzio

Keyword(s):

Ocean Circulation ◽

Numerical Models ◽

Three Dimensional ◽

Ice Sheet ◽

Ice Shelf ◽

Ice Streams ◽

Amundsen Sea ◽

Ice Shelves ◽

Grounding Line ◽

Basal Melting

Abstract. Basal melting at the bottom of Antarctic ice shelves is a major control on glacier dynamics, as it modulates the amount of buttressing that floating ice shelves exert onto the ice streams feeding them. Three-dimensional ocean circulation numerical models provide reliable estimates of basal melt rates but remain too computationally expensive for century-scale projections. Ice sheet modelers therefore routinely rely on simplified parameterizations based on either ice shelf depth or more sophisticated box models. However, existing parameterizations do not accurately resolve the complex spatial patterns of sub-shelf melt rates that have been observed over Antarctica's ice shelves, especially in the vicinity of the grounding line, where basal melting is one of the primary drivers of grounding line migration. In this study, we couple the Potsdam Ice-shelf Cavity mOdel (PICO, Reese et al., 2018) to a buoyant plume melt rate parameterization (Lazeroms et al., 2018) to create PICOP, a novel basal melt rate parameterization that is easy to implement in transient ice sheet numerical models and produces a melt rate field that is in excellent agreement with the spatial distribution and magnitude of observations for several ocean basins. We test PICOP on the Amundsen Sea sector of West Antarctica, Totten, and Moscow University ice shelves in East Antarctica and the Filchner-Ronne Ice Shelf and compare the results to PICO. We find that PICOP is able to reproduce inferred high melt rates beneath Pine Island, Thwaites, and Totten glaciers (on the order of 100 m yr−1) and removes the “banding” pattern observed in melt rates produced by PICO over the Filchner-Ronne Ice Shelf. PICOP resolves many of the issues contemporary basal melt rate parameterizations face and is therefore a valuable tool for those looking to make future projections of Antarctic glaciers.

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Modelling present-day basal melt rates for Antarctic ice shelves using a parametrization of buoyant meltwater plumes

10.5194/tc-2017-58 ◽

2017 ◽

Cited By ~ 5

Author(s):

Werner M. J. Lazeroms ◽

Adrian Jenkins ◽

G. Hilmar Gudmundsson ◽

Roderik S. W. van de Wal

Keyword(s):

Temperature Field ◽

Ice Sheet ◽

Detailed Knowledge ◽

Ocean Temperature ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Grounding Line ◽

Basal Melting ◽

The Antarctic

Abstract. Basal melting below ice shelves is a major factor in the decline of the Antarctic ice sheet, which can contribute significantly to possible future sea-level rise. Therefore, it is important to have an adequate description of the basal melt rates for use in ice-dynamical models. Most current ice models use rather simple parametrizations based on the local balance of heat between ice and ocean. In this work, however, we use a recently derived parametrization of the melt rates based on a buoyant meltwater plume travelling upward beneath an ice shelf. This plume parametrization combines a nonlinear ocean temperature sensitivity with an inherent geometry dependence, which is mainly described by the grounding-line depth zgl and the local slope α of the ice-shelf base. For the first time, this type of parametrization is evaluated on a two-dimensional grid covering the entire Antarctic continent. In order to apply the essentially one-dimensional parametrization to realistic ice-shelf geometries, we present an algorithm that determines effective values for zgl and α for any point beneath an ice shelf. Furthermore, since detailed knowledge of temperatures and flow patterns in the ice-shelf cavities is sparse or absent, we construct an effective ocean temperature field from observational data with the purpose of matching (area-averaged) melt rates from the model with observed present-day melt rates. The result is a realistic map of basal melt rates around Antarctica, not only in terms of average values, but also in terms of the spatial pattern, with high melt rates typically occurring near the grounding line. The plume parametrization and the effective temperature field are therefore promising tools for future simulations of the Antarctic ice sheet.

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Recent advance of the grounding line of Lambert Glacier, Antarctica, deduced from satellite-radar altimetry

Annals of Glaciology ◽

10.1017/s0260305500016219 ◽

1994 ◽

Vol 20 ◽

pp. 43-47 ◽

Cited By ~ 1

Author(s):

Ute C. Herzfeld ◽

Craig S. Lingle ◽

Li-Her Lee

Keyword(s):

Ordinary Kriging ◽

Altimeter Data ◽

Fine Scale ◽

Radar Altimeter ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Grounding Line ◽

Satellite Radar ◽

Lambert Glacier ◽

Satellite Radar Altimetry

Satellite radar-altimeter data from Seasat (1978) and the Geosat Exact Repeat Mission (1987–89) are evaluated to investigate the question of advance or retreat of Lambert Glacier, Amery Ice Shelf, East Antarctica. New maps based on a fine-scale 3 km grid arc calculated using ordinary kriging. The break in slope at the 100 m elevation contour, relative to the WGS 1984 ellipsoid, is taken as a proxy for the grounding line. Measurements indicate that the irregular grounding line, which includes shoals, advanced approximately 10km between 1978 and 1987‐89, corresponding to a mean advance rate of about 1000 m year-1.

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Marine ice sheet model performance depends on basal sliding physics and sub-shelf melting

10.5194/tc-2016-149 ◽

2016 ◽

Cited By ~ 2

Author(s):

Rupert Michael Gladstone ◽

Roland Charles Warner ◽

Benjamin Keith Galton-Fenzi ◽

Olivier Gagliardini ◽

Thomas Zwinger ◽

...

Keyword(s):

Ice Sheet ◽

Model Performance ◽

Effective Pressure ◽

Physical Processes ◽

Ice Shelf ◽

Grounding Line ◽

Basal Sliding ◽

Power Law Function ◽

Ice Velocity ◽

Basal Melting

Abstract. Computer models are necessary for understanding and predicting marine ice sheet behaviour. However, there is uncertainty over implementation of physical processes at the ice base, both for grounded and floating glacial ice. Here we implement several sliding relations in a marine ice sheet flowline model accounting for all stress components, and demonstrate that model resolution requirements are strongly dependent on both the choice of basal sliding relation and the spatial distribution of ice shelf basal melting. Sliding relations that reduce the magnitude of the step change in basal drag from grounded ice to floating ice (where basal drag is set to zero) show reduced dependence on resolution compared to a commonly used relation, in which basal drag is purely a power law function of basal ice velocity. Sliding relations in which basal drag goes smoothly to zero as the grounding line is approached from inland (due to a physically motivated incorporation of effective pressure at the bed) provide further reduction to resolution dependence. A similar issue is found with the imposition of basal melt under the floating part of the ice shelf: melt parameterisations that reduce the abruptness of change in basal melting from grounded ice (where basal melt is set to zero) to floating ice provide improved convergence with resolution compared to parameterisations in which high melt occurs adjacent to the grounding line. Thus physical processes, such as sub-glacial outflow (which could cause high melt near the grounding line), would impact on capability to simulate marine ice sheets. For any given marine ice sheet the basal physics, both grounded and floating, governs the feasibility of simulating the system. The combination of a physical dependency of basal drag on effective pressure and low ice shelf basal melt rates near the grounding line mean that some marine ice sheet systems can be reliably simulated at a coarser resolution than currently thought necessary.

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