scholarly journals Dynamic response of Antarctic ice shelves to bedrock uncertainty

2014 ◽  
Vol 8 (4) ◽  
pp. 1561-1576 ◽  
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.

scholarly journals Dynamic response of Antarctic ice shelves to bedrock uncertainty

2014 ◽  
Vol 8 (1) ◽  
pp. 479-508 ◽  
Author(s):  
S. Sun ◽  
S. L. Cornford ◽  
Y. Liu ◽  
J. C. Moore
Keyword(s):  
Sea Level ◽  
Small Amplitude ◽  
Spatial Scales ◽  
Random Noise ◽  
Ice Sheet ◽  
Data Uncertainty ◽  
Frequency Noise ◽  
Noise Power ◽  
Ice Shelf ◽  
Coherent Noise

Abstract. Bedrock geometry is an essential boundary condition in ice sheet modelling. The shape of the bedrock on fine scales can influences 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 bed rock topography provided by bedmap2 in the catchments of Pine Island Glacier, the Amery Ice Shelf, and a region of East Antarctica including the Denman and Totten Glaciers. 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. Lower frequency coherent noise, which generates broad spatial scale (over 10s of km) errors in topography with relatively gently slopes, while higher frequency noise has steeper slopes over smaller spatial scales. We find that the small amplitude fluctuations result in only minor changes in the way these glaciers evolve. However, lower frequency noise is more important than higher frequency noise even when the features have the same height amplitudes and the total noise power is maintained. This provides optimism for credible sea level rise estimates with presently achievable densities of thickness measurements. Pine Island Glacier appears to be the most sensitive to errors in bed topography, while Lambert–Amery is stable under the present day observational data uncertainty. Totten–Denman region may undergo a retreat around Totten ice shelf, where the bedrock is lower than the sea level, especially if basal melt rates increase.

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

2014 ◽  
Vol 8 (3) ◽  
pp. 1057-1068 ◽  
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.

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

2013 ◽  
Vol 7 (6) ◽  
pp. 5683-5709
Author(s):  
Y. Gong ◽  
S. L. Cornford ◽  
A. J. Payne
Keyword(s):  
Global Environmental Change ◽  
Ice Sheet ◽  
Adaptive Mesh ◽  
Ice Shelf ◽  
Dynamic Simulations ◽  
Amery Ice Shelf ◽  
Grounding Line ◽  
Polar Ice Sheets ◽  
Basal Melting ◽  
Lambert Glacier

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.

scholarly journals Modelling of a marine glacier and ice-sheet-ice-shelf transition zone based on asymptotic analysis

1996 ◽  
Vol 23 ◽  
pp. 59-67 ◽  
Author(s):  
Vladimir A. Chugunov ◽  
Alexander V. Wilchinsky
Keyword(s):  
Boundary Conditions ◽  
Transition Zone ◽  
Spatial Scales ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Stream Length ◽  
Glacier Surface ◽  
Ice Surface ◽  
Grounding Line ◽  
The Difference

All parts of a two-dimensional, isothermal, stationary marine glacier (grounded ice sheet, ice shelf and transition zone) with constant viscosity are analysed by perturbation methods. In so doing, all zones of different flow patterns can be considered separately. Correlations between spatial scales for all parts can be expressed in terms of the typical ice-surface slope distant from the ocean, which reflects exterior conditions of the glacier’s existence. In considering the ice-sheet–ice-shelf transition zone, a small parameter characterizing the difference between ice and water densities is used. Such an analysis allows us to find boundary conditions at the grounding line for the grounded ice mass. Glacier-surface profiles are determined by numerical methods. The grounding-line position found by using the boundary conditions derived in this paper differs from that obtained by using Thomas and Bentley’s (1978) boundary conditions by about 10% of the grounded ice-stream length.

scholarly journals Impact of ocean forcing on the Aurora Basin in the 21st and 22nd centuries

2016 ◽  
Vol 57 (73) ◽  
pp. 79-86 ◽  
Author(s):  
S. Sun ◽  
S. L. Cornford ◽  
D. E. Gwyther ◽  
R. M. Gladstone ◽  
B. K. Galton-Fenzi ◽  
...  
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Ice Sheet ◽  
Adaptive Mesh ◽  
Global Climate Models ◽  
Ice Shelf ◽  
Amundsen Sea ◽  
Ice Shelves ◽  
Future Warming ◽  
East West

ABSTRACTThe grounded ice in the Totten and Dalton glaciers is an essential component of the buttressing for the marine-based Aurora basin, and hence their stability is important to the future rate of mass loss from East Antarctica. Totten and Vanderford glaciers are joined by a deep east-west running subglacial trench between the continental ice sheet and Law Dome, while a shallower trench links the Totten and Dalton glaciers. All three glaciers flow into the ocean close to the Antarctic circle and experience ocean-driven ice shelf melt rates comparable with the Amundsen Sea Embayment. We investigate this combination of trenches and ice shelves with the BISICLES adaptive mesh ice-sheet model and ocean-forcing melt rates derived from two global climate models. We find that ice shelf ablation at a rate comparable with the present day is sufficient to cause widespread grounding line retreat in an east-west direction across Totten and Dalton glaciers, with projected future warming causing faster retreat. Meanwhile, southward retreat is limited by the shallower ocean facing slopes between the coast and the bulk of the Aurora sub-glacial trench. However the two climate models produce completely different future ice shelf basal melt rates in this region: HadCM3 drives increasing sub-ice shelf melting to ~2150, while ECHAM5 shows little or no increase in sub-ice shelf melting under the two greenhouse gas forcing scenarios.

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

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.

scholarly journals Modelling of a marine glacier and ice-sheet-ice-shelf transition zone based on asymptotic analysis

1996 ◽  
Vol 23 ◽  
pp. 59-67 ◽  
Author(s):  
Vladimir A. Chugunov ◽  
Alexander V. Wilchinsky
Keyword(s):  
Boundary Conditions ◽  
Transition Zone ◽  
Spatial Scales ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Stream Length ◽  
Glacier Surface ◽  
Ice Surface ◽  
Grounding Line ◽  
The Difference

All parts of a two-dimensional, isothermal, stationary marine glacier (grounded ice sheet, ice shelf and transition zone) with constant viscosity are analysed by perturbation methods. In so doing, all zones of different flow patterns can be considered separately. Correlations between spatial scales for all parts can be expressed in terms of the typical ice-surface slope distant from the ocean, which reflects exterior conditions of the glacier’s existence. In considering the ice-sheet–ice-shelf transition zone, a small parameter characterizing the difference between ice and water densities is used. Such an analysis allows us to find boundary conditions at the grounding line for the grounded ice mass. Glacier-surface profiles are determined by numerical methods. The grounding-line position found by using the boundary conditions derived in this paper differs from that obtained by using Thomas and Bentley’s (1978) boundary conditions by about 10% of the grounded ice-stream length.

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

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.

scholarly journals Atmospheric extremes triggered the biggest calving event in more than 50 years at the Amery Ice shelf in September 2019

2020 ◽  
Author(s):  
Diana Francis ◽  
Kyle S. Mattingly ◽  
Stef Lhermitte ◽  
Marouane Temimi ◽  
Petra Heil
Keyword(s):  
High Pressure ◽  
Sea Level ◽  
Ice Sheet ◽  
Atmospheric Conditions ◽  
Ice Shelf ◽  
Air Masses ◽  
Sources Of Uncertainty ◽  
Amery Ice Shelf ◽  
Heat And Moisture

Abstract. Ice shelf instability is one of the main sources of uncertainty in Antarctica's contribution to future sea level rise. Calving events play crucial role in ice shelf weakening but remain unpredictable and their governing processes are still poorly understood. In this study, we analyze the unexpected September 2019 calving event from the Amery Ice Shelf, the largest since 1963 and which occurred almost a decade earlier than expected, to better understand the role of the atmosphere in calving. We find that atmospheric extremes provided a deterministic role in this event. The calving was triggered by the occurrence of a series of anomalously-deep and stationary explosive twin polar cyclones over the Cooperation and Davis Seas which generated strong offshore winds leading to increased sea ice removal, fracture amplification along the pre-existing rift, and ultimately calving of the massive iceberg. The observed record-anomalous atmospheric conditions were promoted by blocking ridges and Antarctic-wide anomalous poleward transport of heat and moisture. Blocking highs helped in (i) directing moist and warm air masses towards the ice shelf and in (ii) maintaining stationary the observed extreme cyclones at the front of the ice shelf for several days. Accumulation of cold air over the ice sheet, due to the blocking highs, led to the formation of an intense cold-high pressure over the ice sheet, which helped fuel sustained anomalously-deep cyclones via increased baroclinicity. Our results stress the importance of atmospheric extremes in ice shelf instability and the need to be accounted for when considering Antarctic ice shelf variability and contribution to sea level, especially given that more of these extremes are predicted under a warmer climate.

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