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

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’.


Publication status:
Authors: Meredith, Michael P. ORCIDORCID record for Michael P. Meredith, Abrahamsen, E. Povl ORCIDORCID record for E. Povl Abrahamsen, Haumann, F. Alexander ORCIDORCID record for F. Alexander Haumann, Leng, Melanie J. ORCIDORCID record for Melanie J. Leng, Arrowsmith, Carol, Barham, Mark ORCIDORCID record for Mark Barham, Firing, Yvonne L. ORCIDORCID record for Yvonne L. Firing, King, Brian A. ORCIDORCID record for Brian A. King, Brown, Peter ORCIDORCID record for Peter Brown, Brearley, J. Alexander ORCIDORCID record for J. Alexander Brearley, Meijers, Andrew J.S. ORCIDORCID record for Andrew J.S. Meijers, Sallée, Jean-Baptiste, Akhoudas, Camille, Tarling, Geraint A. ORCIDORCID record for Geraint A. Tarling

On this site: Andrew Meijers, Povl Abrahamsen, Fabian Haumann, Geraint Tarling, Alexander Brearley, Mark Barham, Michael Meredith
26 June, 2023
Philosophical Transactions of the Royal Society of London, A / 381
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