Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites
Abstract
For decades, the surface of the polar Southern Ocean (south of 50°S) has been freshening—an expected response to a warming climate. This freshening enhanced upper-ocean stratification, reducing the upward transport of subsurface heat and possibly contributing to sea ice expansion. It also limited the formation of open-ocean polynyas. Using satellite observations, we reveal a marked increase in surface salinity across the circumpolar Southern Ocean since 2015. This shift has weakened upper-ocean stratification, coinciding with a dramatic decline in Antarctic sea ice coverage. Additionally, rising salinity facilitated the reemergence of the Maud Rise polynya in the Weddell Sea, a phenomenon last observed in the mid-1970s. Crucially, we demonstrate that satellites can now monitor these changes in real time, providing essential evidence of the Southern Ocean’s potential transition toward persistently reduced sea ice coverage.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (11)
Alessandro Silvano
Ocean and Earth Science, National Oceanography Centre, University of Southampton
Aditya Narayanan
Ocean and Earth Science, National Oceanography Centre, University of Southampton
Rafael Catany
ARGANS Ltd.
Estrella Olmedo
Barcelona Expert Center on Remote Sensing, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas
Verónica González‐Gambau
Barcelona Expert Center on Remote Sensing, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas
Antonio Turiel
Barcelona Expert Center on Remote Sensing, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas
Roberto Sabia
European Space Agency, European Space Research Institute
Matthew R. Mazloff
Scripps Institution of Oceanography, University of California
Theo Spira
Department of Marine Sciences, University of Gothenburg
F. Alexander Haumann
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
Alberto C. Naveira Garabato
Ocean and Earth Science, National Oceanography Centre, University of Southampton