Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites
- Alessandro Silvano
- Aditya Narayanan
- Rafael Catany
- Estrella Olmedo
- Verónica González‐Gambau
- Antonio Turiel
- Roberto Sabia
- Matthew R. Mazloff
- Theo Spira
- F. Alexander Haumann
- Alberto C. Naveira Garabato
2025-06-30
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.