Zonal distribution of circumpolar deep water transformation rates and its relation to heat content on Antarctic shelves

We analyze 15-year of observational data and a 5-year Southern Ocean model simulation to quantify the transformation rates of Circumpolar Deep Water (CDW) and the associated heat loss to the surface. This study finds that over the continental shelves of East Antarctica and the Weddell and Ross Seas,...

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Bibliographic Details
Published in:Journal of Geophysical Research: Oceans
Main Authors: Narayanan, Aditya, Gille, Sarah T., Mazloff, Matthew R., Plessis, Marcel D. du, Murali, K., Roquet, Fabien
Format: Article in Journal/Newspaper
Language:English
Published: 2023
Subjects:
Antarctic
East Antarctica
Southern Ocean
Weddell
Weddell Sea
Antarc*
Antarctica
Ice Shelf
Ice Shelves
Online Access:https://eprints.soton.ac.uk/477561/
https://eprints.soton.ac.uk/477561/1/JGR_Oceans_2023_Narayanan_Zonal_Distribution_of_Circumpolar_Deep_Water_Transformation_Rates_and_Its_Relation_to_Heat.pdf
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Summary:We analyze 15-year of observational data and a 5-year Southern Ocean model simulation to quantify the transformation rates of Circumpolar Deep Water (CDW) and the associated heat loss to the surface. This study finds that over the continental shelves of East Antarctica and the Weddell and Ross Seas, surface buoyancy fluxes transform ∼4.4 Sv of surface waters into CDW, providing a path for CDW to lose heat to the surface. In addition, ∼6.6 Sv of CDW are mixed with surface waters in the Weddell and Ross subpolar gyres. In contrast, enhanced stratification inhibits the outcropping of CDW isopycnals, reducing their transformation rates by a factor of ∼8 over the continental shelf and by a factor of ∼3 over the deeper ocean in the Amundsen and Bellingshausen Seas. The CDW retains its offshore warm properties as it intrudes over the continental shelves, resulting in elevated bottom temperatures there. This analysis demonstrates the importance of processes in subpolar gyres to erode CDW and to facilitate further transformation on the continental shelves, significantly reducing the heat able to access ice shelf fronts. This sheltering effect is strongest in the western Weddell Sea and tends to diminish toward the east, which helps explain the large zonal differences in continental-shelf bottom temperatures and the melt rates of Antarctic ice shelves.

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