Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites
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.
Authors
- Alberto C. Naveira Garabato (ORCID: https://orcid.org/0000-0001-6071-605X)
- Aditya Narayanan (ORCID: https://orcid.org/0000-0002-8967-2211)
- Matthew R. Mazloff (ORCID: https://orcid.org/0000-0002-1650-5850)
- Rafael Catany
- Verónica González‐Gambau (ORCID: https://orcid.org/0000-0002-6380-3754)
- Alessandro Silvano (ORCID: https://orcid.org/0000-0002-6441-1496)
- F. Alexander Haumann (ORCID: https://orcid.org/0000-0002-8218-977X)
- Theo Spira (ORCID: https://orcid.org/0009-0008-8183-8775)
- Estrella Olmedo (ORCID: https://orcid.org/0000-0002-3178-1554)
- Antonio Turiel (ORCID: https://orcid.org/0000-0001-6103-224X)
- Roberto Sabia
Institutions
- Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (DE)
- Consejo Superior de Investigaciones Científicas (ES)
- Scripps Institution of Oceanography (US)
- National Oceanography Centre (GB)
- European Space Agency (FR)
- Institut Català de Ciències del Clima (ES)
- Argans (United Kingdom) (GB)
- Institut de Ciències del Mar (ES)
- European Space Research Institute (IT)
- University of Southampton (GB)
- Ludwig-Maximilians-Universität München (DE)
- University of Gothenburg (SE)
Publication Details
- Journal
- Proceedings of the National Academy of Sciences
- Published
- 2025-06-30
- DOI
- https://doi.org/10.1073/pnas.2500440122
- Citations
- 14
- Primary Topic
- Arctic and Antarctic ice dynamics
- Type
- article
- Field-Weighted Citation Impact
- 18.21
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- European Space Agency
- Ministerio de Ciencia e Innovación
- Natural Environment Research Council
- European Research Council