Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica
Ocean-driven melting of Antarctic ice shelves is causing accelerating loss of grounded ice from the Antarctic continent. However, the ocean processes governing ice shelf melting are not well understood, contributing to uncertainty in projections of Antarctica's contribution to sea level. Here,...
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2022
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ftdoajarticles:oai:doaj.org/article:0a3d83d180c446dd988319d033a81a7a 2023-05-15T13:22:02+02:00 Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica M. Rosevear B. Galton-Fenzi C. Stevens 2022-07-01T00:00:00Z https://doi.org/10.5194/os-18-1109-2022 https://doaj.org/article/0a3d83d180c446dd988319d033a81a7a EN eng Copernicus Publications https://os.copernicus.org/articles/18/1109/2022/os-18-1109-2022.pdf https://doaj.org/toc/1812-0784 https://doaj.org/toc/1812-0792 doi:10.5194/os-18-1109-2022 1812-0784 1812-0792 https://doaj.org/article/0a3d83d180c446dd988319d033a81a7a Ocean Science, Vol 18, Pp 1109-1130 (2022) Geography. Anthropology. Recreation G Environmental sciences GE1-350 article 2022 ftdoajarticles https://doi.org/10.5194/os-18-1109-2022 2022-12-30T23:46:23Z Ocean-driven melting of Antarctic ice shelves is causing accelerating loss of grounded ice from the Antarctic continent. However, the ocean processes governing ice shelf melting are not well understood, contributing to uncertainty in projections of Antarctica's contribution to sea level. Here, we analyse oceanographic data and in situ measurements of ice shelf melt collected from an instrumented mooring beneath the centre of the Amery Ice Shelf, East Antarctica. This is the first direct measurement of basal melting from the Amery Ice Shelf and was made through the novel application of an upward-facing acoustic Doppler current profiler (ADCP). ADCP data were also used to map a region of the ice base, revealing a steep topographic feature or “scarp” in the ice with vertical and horizontal scales of ∼ 20 and ∼ 40 m , respectively. The annually averaged ADCP-derived melt rate of 0.51 ± 0.18 m yr −1 is consistent with previous modelling results and glaciological estimates. There is significant seasonal variation around the mean melt rate, with a 40 % increase in melting in May and a 60 % decrease in September. Melting is driven by temperatures ∼ 0.2 ∘ C above the local freezing point and background and tidal currents, which have typical speeds of 3.0 and 10.0 cm s −1 , respectively. We use the coincident measurements of ice shelf melt and oceanographic forcing to evaluate parameterisations of ice–ocean interactions and find that parameterisations in which there is an explicit dependence of the melt rate on current speed beneath the ice tend to overestimate the local melt rate at AM06 by between 200 % and 400 %, depending on the choice of drag coefficient. A convective parameterisation in which melting is a function of the slope of the ice base is also evaluated and is shown to underpredict melting by 20 % at this site. By combining these new estimates with available observations from other ice shelves, we show that the commonly used current speed-dependent parameterisation overestimates melting at all but the coldest ... Article in Journal/Newspaper Amery Ice Shelf Antarc* Antarctic Antarctica East Antarctica Ice Shelf Ice Shelves Directory of Open Access Journals: DOAJ Articles Antarctic The Antarctic East Antarctica Amery ENVELOPE(-94.063,-94.063,56.565,56.565) Amery Ice Shelf ENVELOPE(71.000,71.000,-69.750,-69.750) Ocean Science 18 4 1109 1130 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Geography. Anthropology. Recreation G Environmental sciences GE1-350 |
spellingShingle |
Geography. Anthropology. Recreation G Environmental sciences GE1-350 M. Rosevear B. Galton-Fenzi C. Stevens Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica |
topic_facet |
Geography. Anthropology. Recreation G Environmental sciences GE1-350 |
description |
Ocean-driven melting of Antarctic ice shelves is causing accelerating loss of grounded ice from the Antarctic continent. However, the ocean processes governing ice shelf melting are not well understood, contributing to uncertainty in projections of Antarctica's contribution to sea level. Here, we analyse oceanographic data and in situ measurements of ice shelf melt collected from an instrumented mooring beneath the centre of the Amery Ice Shelf, East Antarctica. This is the first direct measurement of basal melting from the Amery Ice Shelf and was made through the novel application of an upward-facing acoustic Doppler current profiler (ADCP). ADCP data were also used to map a region of the ice base, revealing a steep topographic feature or “scarp” in the ice with vertical and horizontal scales of ∼ 20 and ∼ 40 m , respectively. The annually averaged ADCP-derived melt rate of 0.51 ± 0.18 m yr −1 is consistent with previous modelling results and glaciological estimates. There is significant seasonal variation around the mean melt rate, with a 40 % increase in melting in May and a 60 % decrease in September. Melting is driven by temperatures ∼ 0.2 ∘ C above the local freezing point and background and tidal currents, which have typical speeds of 3.0 and 10.0 cm s −1 , respectively. We use the coincident measurements of ice shelf melt and oceanographic forcing to evaluate parameterisations of ice–ocean interactions and find that parameterisations in which there is an explicit dependence of the melt rate on current speed beneath the ice tend to overestimate the local melt rate at AM06 by between 200 % and 400 %, depending on the choice of drag coefficient. A convective parameterisation in which melting is a function of the slope of the ice base is also evaluated and is shown to underpredict melting by 20 % at this site. By combining these new estimates with available observations from other ice shelves, we show that the commonly used current speed-dependent parameterisation overestimates melting at all but the coldest ... |
format |
Article in Journal/Newspaper |
author |
M. Rosevear B. Galton-Fenzi C. Stevens |
author_facet |
M. Rosevear B. Galton-Fenzi C. Stevens |
author_sort |
M. Rosevear |
title |
Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica |
title_short |
Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica |
title_full |
Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica |
title_fullStr |
Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica |
title_full_unstemmed |
Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica |
title_sort |
evaluation of basal melting parameterisations using in situ ocean and melting observations from the amery ice shelf, east antarctica |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/os-18-1109-2022 https://doaj.org/article/0a3d83d180c446dd988319d033a81a7a |
long_lat |
ENVELOPE(-94.063,-94.063,56.565,56.565) ENVELOPE(71.000,71.000,-69.750,-69.750) |
geographic |
Antarctic The Antarctic East Antarctica Amery Amery Ice Shelf |
geographic_facet |
Antarctic The Antarctic East Antarctica Amery Amery Ice Shelf |
genre |
Amery Ice Shelf Antarc* Antarctic Antarctica East Antarctica Ice Shelf Ice Shelves |
genre_facet |
Amery Ice Shelf Antarc* Antarctic Antarctica East Antarctica Ice Shelf Ice Shelves |
op_source |
Ocean Science, Vol 18, Pp 1109-1130 (2022) |
op_relation |
https://os.copernicus.org/articles/18/1109/2022/os-18-1109-2022.pdf https://doaj.org/toc/1812-0784 https://doaj.org/toc/1812-0792 doi:10.5194/os-18-1109-2022 1812-0784 1812-0792 https://doaj.org/article/0a3d83d180c446dd988319d033a81a7a |
op_doi |
https://doi.org/10.5194/os-18-1109-2022 |
container_title |
Ocean Science |
container_volume |
18 |
container_issue |
4 |
container_start_page |
1109 |
op_container_end_page |
1130 |
_version_ |
1766362979478011904 |