Impact of shallow sills on circulation regimes and submarine melting in glacial fjords
The increased melting and rapid retreat of marine-terminating glaciers is a key contributor to sea-level rise. In glacial fjords with shallow sills common in Patagonia, Alaska, and other systems, these bathymetric features can act as a first-order control on the dynamics. However, our understanding...
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Copernicus Publications
2024
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ftdoajarticles:oai:doaj.org/article:d652c5a2f8d2499c8b8f5292ab5b26f7 2024-02-11T10:03:59+01:00 Impact of shallow sills on circulation regimes and submarine melting in glacial fjords W. Bao C. Moffat 2024-01-01T00:00:00Z https://doi.org/10.5194/tc-18-187-2024 https://doaj.org/article/d652c5a2f8d2499c8b8f5292ab5b26f7 EN eng Copernicus Publications https://tc.copernicus.org/articles/18/187/2024/tc-18-187-2024.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-18-187-2024 1994-0416 1994-0424 https://doaj.org/article/d652c5a2f8d2499c8b8f5292ab5b26f7 The Cryosphere, Vol 18, Pp 187-203 (2024) Environmental sciences GE1-350 Geology QE1-996.5 article 2024 ftdoajarticles https://doi.org/10.5194/tc-18-187-2024 2024-01-14T01:50:39Z The increased melting and rapid retreat of marine-terminating glaciers is a key contributor to sea-level rise. In glacial fjords with shallow sills common in Patagonia, Alaska, and other systems, these bathymetric features can act as a first-order control on the dynamics. However, our understanding of how this shallow bathymetry interacts with the subglacial discharge from the glacier and impacts the fjord circulation, water properties, and rates of submarine melting is limited. To address this gap, we conduct idealized numerical simulations using a coupled plume–ocean fjord model spanning a wide range of initial ocean conditions, sill depths, and subglacial discharge. A previously documented circulation regime leads to strong mixing and vertical transport over the sill, where up to ∼ 70 % of the colder water from the upper-layer outflow is refluxed into the deeper layer, cooling the incoming warm oceanic water by as much as 1 ∘ C and reducing the stratification near the glacier front. When the initial stratification is relatively strong or the subglacial discharge is relatively weak, an additional unsteady circulation regime arises where the freshwater flow can become trapped below the sill depth for weeks to months, creating an effective cooling mechanism for the deep water. We also find that submarine melting often increases when a shallow sill is added to a glacial fjord due to the reduction of stratification – which increases submarine melting – dominating over the cooling effect as the oceanic inflow is modified by the presence of the sill. These results underscore that shallow-silled fjords can have distinct dynamics that strongly modulate oceanic properties and the melting rates of marine-terminating glaciers. Article in Journal/Newspaper glacier glaciers The Cryosphere Alaska Directory of Open Access Journals: DOAJ Articles Patagonia The Cryosphere 18 1 187 203 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
spellingShingle |
Environmental sciences GE1-350 Geology QE1-996.5 W. Bao C. Moffat Impact of shallow sills on circulation regimes and submarine melting in glacial fjords |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
The increased melting and rapid retreat of marine-terminating glaciers is a key contributor to sea-level rise. In glacial fjords with shallow sills common in Patagonia, Alaska, and other systems, these bathymetric features can act as a first-order control on the dynamics. However, our understanding of how this shallow bathymetry interacts with the subglacial discharge from the glacier and impacts the fjord circulation, water properties, and rates of submarine melting is limited. To address this gap, we conduct idealized numerical simulations using a coupled plume–ocean fjord model spanning a wide range of initial ocean conditions, sill depths, and subglacial discharge. A previously documented circulation regime leads to strong mixing and vertical transport over the sill, where up to ∼ 70 % of the colder water from the upper-layer outflow is refluxed into the deeper layer, cooling the incoming warm oceanic water by as much as 1 ∘ C and reducing the stratification near the glacier front. When the initial stratification is relatively strong or the subglacial discharge is relatively weak, an additional unsteady circulation regime arises where the freshwater flow can become trapped below the sill depth for weeks to months, creating an effective cooling mechanism for the deep water. We also find that submarine melting often increases when a shallow sill is added to a glacial fjord due to the reduction of stratification – which increases submarine melting – dominating over the cooling effect as the oceanic inflow is modified by the presence of the sill. These results underscore that shallow-silled fjords can have distinct dynamics that strongly modulate oceanic properties and the melting rates of marine-terminating glaciers. |
format |
Article in Journal/Newspaper |
author |
W. Bao C. Moffat |
author_facet |
W. Bao C. Moffat |
author_sort |
W. Bao |
title |
Impact of shallow sills on circulation regimes and submarine melting in glacial fjords |
title_short |
Impact of shallow sills on circulation regimes and submarine melting in glacial fjords |
title_full |
Impact of shallow sills on circulation regimes and submarine melting in glacial fjords |
title_fullStr |
Impact of shallow sills on circulation regimes and submarine melting in glacial fjords |
title_full_unstemmed |
Impact of shallow sills on circulation regimes and submarine melting in glacial fjords |
title_sort |
impact of shallow sills on circulation regimes and submarine melting in glacial fjords |
publisher |
Copernicus Publications |
publishDate |
2024 |
url |
https://doi.org/10.5194/tc-18-187-2024 https://doaj.org/article/d652c5a2f8d2499c8b8f5292ab5b26f7 |
geographic |
Patagonia |
geographic_facet |
Patagonia |
genre |
glacier glaciers The Cryosphere Alaska |
genre_facet |
glacier glaciers The Cryosphere Alaska |
op_source |
The Cryosphere, Vol 18, Pp 187-203 (2024) |
op_relation |
https://tc.copernicus.org/articles/18/187/2024/tc-18-187-2024.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-18-187-2024 1994-0416 1994-0424 https://doaj.org/article/d652c5a2f8d2499c8b8f5292ab5b26f7 |
op_doi |
https://doi.org/10.5194/tc-18-187-2024 |
container_title |
The Cryosphere |
container_volume |
18 |
container_issue |
1 |
container_start_page |
187 |
op_container_end_page |
203 |
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1790600397801390080 |