Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica
Understanding the interannual variability of surface mass balance (SMB) and surface melting in Antarctica is key to quantify the signal-to-noise ratio in climate trends, identify opportunities for multi-year climate predictions and assess the ability of climate models to respond to climate variabili...
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Online Access: | https://doi.org/10.5194/tc-14-229-2020 https://tc.copernicus.org/articles/14/229/2020/ |
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ftcopernicus:oai:publications.copernicus.org:tc76533 2023-05-15T13:23:54+02:00 Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica Donat-Magnin, Marion Jourdain, Nicolas C. Gallée, Hubert Amory, Charles Kittel, Christoph Fettweis, Xavier Wille, Jonathan D. Favier, Vincent Drira, Amine Agosta, Cécile 2020-01-27 application/pdf https://doi.org/10.5194/tc-14-229-2020 https://tc.copernicus.org/articles/14/229/2020/ eng eng doi:10.5194/tc-14-229-2020 https://tc.copernicus.org/articles/14/229/2020/ eISSN: 1994-0424 Text 2020 ftcopernicus https://doi.org/10.5194/tc-14-229-2020 2020-07-20T16:22:28Z Understanding the interannual variability of surface mass balance (SMB) and surface melting in Antarctica is key to quantify the signal-to-noise ratio in climate trends, identify opportunities for multi-year climate predictions and assess the ability of climate models to respond to climate variability. Here we simulate summer SMB and surface melting from 1979 to 2017 using the Regional Atmosphere Model (MAR) at 10 km resolution over the drainage basins of the Amundsen Sea glaciers in West Antarctica. Our simulations reproduce the mean present-day climate in terms of near-surface temperature (mean overestimation of 0.10 ∘ C), near-surface wind speed (mean underestimation of 0.42 m s −1 ), and SMB (relative bias <20 % over Thwaites glacier). The simulated interannual variability of SMB and melting is also close to observation-based estimates. For all the Amundsen glacial drainage basins, the interannual variability of summer SMB and surface melting is driven by two distinct mechanisms: high summer SMB tends to occur when the Amundsen Sea Low (ASL) is shifted southward and westward, while high summer melt rates tend to occur when ASL is shallower (i.e. anticyclonic anomaly). Both mechanisms create a northerly flow anomaly that increases moisture convergence and cloud cover over the Amundsen Sea and therefore favors snowfall and downward longwave radiation over the ice sheet. The part of interannual summer SMB variance explained by the ASL longitudinal migrations increases westward and reaches 40 % for Getz. Interannual variation in the ASL relative central pressure is the largest driver of melt rate variability, with 11 % to 21 % of explained variance (increasing westward). While high summer SMB and melt rates are both favored by positive phases of El Niño–Southern Oscillation (ENSO), the Southern Oscillation Index (SOI) only explains 5 % to 16 % of SMB or melt rate interannual variance in our simulations, with moderate statistical significance. However, the part explained by SOI in the previous austral winter is greater, suggesting that at least a part of the ENSO–SMB and ENSO–melt relationships in summer is inherited from the previous austral winter. Possible mechanisms involve sea ice advection from the Ross Sea and intrusions of circumpolar deep water combined with melt-induced ocean overturning circulation in ice shelf cavities. Finally, we do not find any correlation with the Southern Annular Mode (SAM) in summer. Text Amundsen Sea Antarc* Antarctica Ice Sheet Ice Shelf Ross Sea Sea ice Thwaites Glacier West Antarctica Copernicus Publications: E-Journals Austral Ross Sea West Antarctica Amundsen Sea Soi ENVELOPE(30.704,30.704,66.481,66.481) Thwaites Glacier ENVELOPE(-106.750,-106.750,-75.500,-75.500) Getz ENVELOPE(-145.217,-145.217,-76.550,-76.550) The Cryosphere 14 1 229 249 |
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Open Polar |
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Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Understanding the interannual variability of surface mass balance (SMB) and surface melting in Antarctica is key to quantify the signal-to-noise ratio in climate trends, identify opportunities for multi-year climate predictions and assess the ability of climate models to respond to climate variability. Here we simulate summer SMB and surface melting from 1979 to 2017 using the Regional Atmosphere Model (MAR) at 10 km resolution over the drainage basins of the Amundsen Sea glaciers in West Antarctica. Our simulations reproduce the mean present-day climate in terms of near-surface temperature (mean overestimation of 0.10 ∘ C), near-surface wind speed (mean underestimation of 0.42 m s −1 ), and SMB (relative bias <20 % over Thwaites glacier). The simulated interannual variability of SMB and melting is also close to observation-based estimates. For all the Amundsen glacial drainage basins, the interannual variability of summer SMB and surface melting is driven by two distinct mechanisms: high summer SMB tends to occur when the Amundsen Sea Low (ASL) is shifted southward and westward, while high summer melt rates tend to occur when ASL is shallower (i.e. anticyclonic anomaly). Both mechanisms create a northerly flow anomaly that increases moisture convergence and cloud cover over the Amundsen Sea and therefore favors snowfall and downward longwave radiation over the ice sheet. The part of interannual summer SMB variance explained by the ASL longitudinal migrations increases westward and reaches 40 % for Getz. Interannual variation in the ASL relative central pressure is the largest driver of melt rate variability, with 11 % to 21 % of explained variance (increasing westward). While high summer SMB and melt rates are both favored by positive phases of El Niño–Southern Oscillation (ENSO), the Southern Oscillation Index (SOI) only explains 5 % to 16 % of SMB or melt rate interannual variance in our simulations, with moderate statistical significance. However, the part explained by SOI in the previous austral winter is greater, suggesting that at least a part of the ENSO–SMB and ENSO–melt relationships in summer is inherited from the previous austral winter. Possible mechanisms involve sea ice advection from the Ross Sea and intrusions of circumpolar deep water combined with melt-induced ocean overturning circulation in ice shelf cavities. Finally, we do not find any correlation with the Southern Annular Mode (SAM) in summer. |
format |
Text |
author |
Donat-Magnin, Marion Jourdain, Nicolas C. Gallée, Hubert Amory, Charles Kittel, Christoph Fettweis, Xavier Wille, Jonathan D. Favier, Vincent Drira, Amine Agosta, Cécile |
spellingShingle |
Donat-Magnin, Marion Jourdain, Nicolas C. Gallée, Hubert Amory, Charles Kittel, Christoph Fettweis, Xavier Wille, Jonathan D. Favier, Vincent Drira, Amine Agosta, Cécile Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica |
author_facet |
Donat-Magnin, Marion Jourdain, Nicolas C. Gallée, Hubert Amory, Charles Kittel, Christoph Fettweis, Xavier Wille, Jonathan D. Favier, Vincent Drira, Amine Agosta, Cécile |
author_sort |
Donat-Magnin, Marion |
title |
Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica |
title_short |
Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica |
title_full |
Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica |
title_fullStr |
Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica |
title_full_unstemmed |
Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica |
title_sort |
interannual variability of summer surface mass balance and surface melting in the amundsen sector, west antarctica |
publishDate |
2020 |
url |
https://doi.org/10.5194/tc-14-229-2020 https://tc.copernicus.org/articles/14/229/2020/ |
long_lat |
ENVELOPE(30.704,30.704,66.481,66.481) ENVELOPE(-106.750,-106.750,-75.500,-75.500) ENVELOPE(-145.217,-145.217,-76.550,-76.550) |
geographic |
Austral Ross Sea West Antarctica Amundsen Sea Soi Thwaites Glacier Getz |
geographic_facet |
Austral Ross Sea West Antarctica Amundsen Sea Soi Thwaites Glacier Getz |
genre |
Amundsen Sea Antarc* Antarctica Ice Sheet Ice Shelf Ross Sea Sea ice Thwaites Glacier West Antarctica |
genre_facet |
Amundsen Sea Antarc* Antarctica Ice Sheet Ice Shelf Ross Sea Sea ice Thwaites Glacier West Antarctica |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-14-229-2020 https://tc.copernicus.org/articles/14/229/2020/ |
op_doi |
https://doi.org/10.5194/tc-14-229-2020 |
container_title |
The Cryosphere |
container_volume |
14 |
container_issue |
1 |
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229 |
op_container_end_page |
249 |
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1766376215346675712 |