Stirring of sea-ice meltwater enhances submescale fronts in the Southern Ocean

State-of-the-art autonomous underwater gliders were used to observe key physical properties of the surface ocean following the melt of sea-ice. Fine-scale fronts (sharp changes in density) of less than 10 km at horizontal scales revealed that sea-ice melt not only stabilizes the upper ocean, but also provides additional energy for small eddies and filaments to form. In turn, eddies enhance the ocean response to winds.

The Seaglider aboard the S.A. Agulhas II ready for deployment. Photo credit: Johan Edholm.

Sea-ice melt around Antarctica is an annual event in which the state of the surface ocean is transformed, during which over 15 trillion liters of freshwater enter the upper ocean. This fresh layer separates the upper ocean from the deep ocean and suppresses the exchange of heat and gases—like carbon dioxide—between the deep ocean and the atmosphere, with important implications for the climate system.

The paper Stirring of Sea-Ice Meltwater Enhances Submesoscale Fronts in the Southern Ocean used state-of-the-art autonomous underwater gliders to observe key physical properties of the surface ocean following the melt of sea-ice. The presence of fine-scale fronts (sharp changes in density), of less than 10 km at horizontal scales, revealed that sea-ice melt not only stabilizes the upper ocean, but also provides additional energy for small eddies and filaments to form. While the eddies are unable to extend deeper than the fresher surface layer, they enhance ocean mixing in response to winds.

These findings may contribute to the improvement of global climate models and our understanding of how the ocean will react to changes in sea-ice under a warmer climate.

The work was financially supported by grants from Wallenberg Academy Fellowship (WAF 2015.0186), Swedish Research Council (VR 2019-04400), STINT-NRF Mobility Grant (STNT180910357293), NRF-SANAP (SNA170522231782, SANAP200324510487), the Young Researchers Establishment Fund (YREF 2019 0000007361), the European Union’s Horizon 2020 research and innovation program under Grant agreement no. 821001 (SO-CHIC), ONR (N00014-19-1-2421), NSF (1756956, 1829969), and a Linde Center Discovery Fund grant

FOR MORE INFORMATION

Giddy, I., Swart, S., du Plessis, M., Thompson, A. F., & Nicholson, S.-A. (2021). Stirring of sea-ice meltwater enhances submesoscale fronts in the Southern Ocean. Journal of Geophysical Research: Oceans, 126, e2020JC016814. https://doi.org/10.1029/2020JC016814