Tracing the impacts of recent rapid sea ice changes and the A68 megaberg on the surface freshwater balance of the Weddell and Scotia Seas

Meredith, Michael P. ORCID:; Abrahamsen, E. Povl ORCID:; Haumann, F. Alexander ORCID:; Leng, Melanie J. ORCID:; Arrowsmith, Carol; Barham, Mark ORCID:; Firing, Yvonne L. ORCID:; King, Brian A. ORCID:; Brown, Peter ORCID:; Brearley, J. Alexander ORCID:; Meijers, Andrew J.S. ORCID:; Sallée, Jean-Baptiste; Akhoudas, Camille; Tarling, Geraint A. ORCID: 2023 Tracing the impacts of recent rapid sea ice changes and the A68 megaberg on the surface freshwater balance of the Weddell and Scotia Seas. Philosophical Transactions of the Royal Society of London, A, 381 (2249), 20220162. 21, pp.

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The Southern Ocean upper-layer freshwater balance exerts a global climatic influence by modulating density stratification and biological productivity, and hence the exchange of heat and carbon between the atmosphere and the ocean interior. It is thus important to understand and quantify the time-varying freshwater inputs, which is challenging from measurements of salinity alone. Here we use seawater oxygen isotopes from samples collected between 2016 and 2021 along a transect spanning the Scotia and northern Weddell Seas to separate the freshwater contributions from sea ice and meteoric sources. The unprecedented retreat of sea ice in 2016 is evidenced as a strong increase in sea ice melt across the northern Weddell Sea, with surface values increasing approximately two percentage points between 2016 and 2018 and column inventories increasing approximately 1 to 2 m. Surface meteoric water concentrations exceeded 4% in early 2021 close to South Georgia due to meltwater from the A68 megaberg; smaller icebergs may influence meteoric water at other times also. Both these inputs highlight the importance of a changing cryosphere for upper-ocean freshening; potential future sea ice retreats and increases in iceberg calving would enhance the impacts of these freshwater sources on the ocean and climate. This article is part of a discussion meeting issue ‘Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities’.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 1364-503X
Additional Keywords: Sea ice melt; Iceberg meltwater; Freshwater; Isotopic tracers; Southern Ocean; Antarctica
Date made live: 09 May 2023 08:54 +0 (UTC)

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