Impact of shallow sills on circulation regimes and submarine melting in glacial fjords

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Author(s)Bao, Weiyang
Author(s)Moffat, Carlos
Date Accessioned2024-03-15T19:11:58Z
Date Available2024-03-15T19:11:58Z
Publication Date2024-01-09
DescriptionThis article was originally published in The Cryosphere. The version of record is available at: https://doi.org/10.5194/tc-18-187-2024. © Author(s) 2024. This work is distributed under the Creative Commons Attribution 4.0 License.
AbstractThe 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.
SponsorWeiyang Bao was supported by a fellowship from the School of Marine Science and Policy, University of Delaware. Carlos Moffat received support from the COPAS Coastal program (ANID FB210021). Both authors were supported by the University of Delaware Research Foundation (grant no. 18A00956).
CitationBao, W. and Moffat, C.: Impact of shallow sills on circulation regimes and submarine melting in glacial fjords, The Cryosphere, 18, 187–203, https://doi.org/10.5194/tc-18-187-2024, 2024.
ISSN1994-0424
URLhttps://udspace.udel.edu/handle/19716/34199
Languageen_US
PublisherThe Cryosphere
dc.rightsAttribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
TitleImpact of shallow sills on circulation regimes and submarine melting in glacial fjords
TypeArticle
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