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
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.