Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers
Frontal ablation has caused 32 %–66 % of Greenland Ice Sheet mass loss since 1972, and despite its importance in driving terminus change, ocean thermal forcing remains crudely incorporated into large-scale ice sheet models. In Greenland, local fjord-scale processes modify the magnitude of thermal fo...
Published in: | The Cryosphere |
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Copernicus Publications
2024
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00072007 2024-04-14T08:11:58+00:00 Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers Hager, Alexander O. Sutherland, David A. Slater, Donald A. 2024-02 electronic https://doi.org/10.5194/tc-18-911-2024 https://noa.gwlb.de/receive/cop_mods_00072007 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00070241/tc-18-911-2024.pdf https://tc.copernicus.org/articles/18/911/2024/tc-18-911-2024.pdf eng eng Copernicus Publications The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424 https://doi.org/10.5194/tc-18-911-2024 https://noa.gwlb.de/receive/cop_mods_00072007 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00070241/tc-18-911-2024.pdf https://tc.copernicus.org/articles/18/911/2024/tc-18-911-2024.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2024 ftnonlinearchiv https://doi.org/10.5194/tc-18-911-2024 2024-03-19T12:18:16Z Frontal ablation has caused 32 %–66 % of Greenland Ice Sheet mass loss since 1972, and despite its importance in driving terminus change, ocean thermal forcing remains crudely incorporated into large-scale ice sheet models. In Greenland, local fjord-scale processes modify the magnitude of thermal forcing at the ice–ocean boundary but are too small scale to be resolved in current global climate models. For example, simulations used in the Ice Sheet Intercomparison Project for CMIP6 (ISMIP6) to predict future ice sheet change rely on the extrapolation of regional ocean water properties into fjords to drive terminus ablation. However, the accuracy of this approach has not previously been tested due to the scarcity of observations in Greenland fjords, as well as the inability of fjord-scale models to realistically incorporate icebergs. By employing the recently developed IceBerg package within the Massachusetts Institute of Technology general circulation model (MITgcm), we here evaluate the ability of ocean thermal forcing parameterizations to predict thermal forcing at tidewater glacier termini. This is accomplished through sensitivity experiments using a set of idealized Greenland fjords, each forced with equivalent ocean boundary conditions but with varying tidal amplitudes, subglacial discharge, iceberg coverage, and bathymetry. Our results indicate that the bathymetric obstruction of external water is the primary control on near-glacier thermal forcing, followed by iceberg submarine melting. Despite identical ocean boundary conditions, we find that the simulated fjord processes can modify grounding line thermal forcing by as much as 3 °C, the magnitude of which is largely controlled by the relative depth of bathymetric sills to the Polar Water–Atlantic Water thermocline. However, using a common adjustment for fjord bathymetry we can still predict grounding line thermal forcing within 0.2 °C in our simulations. Finally, we introduce new parameterizations that additionally account for iceberg-driven cooling that ... Article in Journal/Newspaper glacier Greenland Ice Sheet The Cryosphere Tidewater Niedersächsisches Online-Archiv NOA Greenland The Cryosphere 18 2 911 932 |
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Open Polar |
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Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
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article Verlagsveröffentlichung Hager, Alexander O. Sutherland, David A. Slater, Donald A. Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers |
topic_facet |
article Verlagsveröffentlichung |
description |
Frontal ablation has caused 32 %–66 % of Greenland Ice Sheet mass loss since 1972, and despite its importance in driving terminus change, ocean thermal forcing remains crudely incorporated into large-scale ice sheet models. In Greenland, local fjord-scale processes modify the magnitude of thermal forcing at the ice–ocean boundary but are too small scale to be resolved in current global climate models. For example, simulations used in the Ice Sheet Intercomparison Project for CMIP6 (ISMIP6) to predict future ice sheet change rely on the extrapolation of regional ocean water properties into fjords to drive terminus ablation. However, the accuracy of this approach has not previously been tested due to the scarcity of observations in Greenland fjords, as well as the inability of fjord-scale models to realistically incorporate icebergs. By employing the recently developed IceBerg package within the Massachusetts Institute of Technology general circulation model (MITgcm), we here evaluate the ability of ocean thermal forcing parameterizations to predict thermal forcing at tidewater glacier termini. This is accomplished through sensitivity experiments using a set of idealized Greenland fjords, each forced with equivalent ocean boundary conditions but with varying tidal amplitudes, subglacial discharge, iceberg coverage, and bathymetry. Our results indicate that the bathymetric obstruction of external water is the primary control on near-glacier thermal forcing, followed by iceberg submarine melting. Despite identical ocean boundary conditions, we find that the simulated fjord processes can modify grounding line thermal forcing by as much as 3 °C, the magnitude of which is largely controlled by the relative depth of bathymetric sills to the Polar Water–Atlantic Water thermocline. However, using a common adjustment for fjord bathymetry we can still predict grounding line thermal forcing within 0.2 °C in our simulations. Finally, we introduce new parameterizations that additionally account for iceberg-driven cooling that ... |
format |
Article in Journal/Newspaper |
author |
Hager, Alexander O. Sutherland, David A. Slater, Donald A. |
author_facet |
Hager, Alexander O. Sutherland, David A. Slater, Donald A. |
author_sort |
Hager, Alexander O. |
title |
Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers |
title_short |
Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers |
title_full |
Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers |
title_fullStr |
Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers |
title_full_unstemmed |
Local forcing mechanisms challenge parameterizations of ocean thermal forcing for Greenland tidewater glaciers |
title_sort |
local forcing mechanisms challenge parameterizations of ocean thermal forcing for greenland tidewater glaciers |
publisher |
Copernicus Publications |
publishDate |
2024 |
url |
https://doi.org/10.5194/tc-18-911-2024 https://noa.gwlb.de/receive/cop_mods_00072007 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00070241/tc-18-911-2024.pdf https://tc.copernicus.org/articles/18/911/2024/tc-18-911-2024.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
glacier Greenland Ice Sheet The Cryosphere Tidewater |
genre_facet |
glacier Greenland Ice Sheet The Cryosphere Tidewater |
op_relation |
The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424 https://doi.org/10.5194/tc-18-911-2024 https://noa.gwlb.de/receive/cop_mods_00072007 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00070241/tc-18-911-2024.pdf https://tc.copernicus.org/articles/18/911/2024/tc-18-911-2024.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/tc-18-911-2024 |
container_title |
The Cryosphere |
container_volume |
18 |
container_issue |
2 |
container_start_page |
911 |
op_container_end_page |
932 |
_version_ |
1796309706728275968 |