Satellite data confirm Southern Ocean has entered a new physical state
A study published in the journal Proceedings of the National Academy of Sciences (PNAS) has revealed a significant shift in the Southern Ocean’s surface conditions. This shift is marked by a rapid increase in surface salinity and a corresponding decline in Antarctic sea ice extent. Based on satellite and ocean float data, the findings indicate that the Southern Ocean may have entered a new physical state not previously observed in the modern observational era.
Icebergs blocking the LMG from departing the Palmer Station pier. Credit: Bob Farrell/U.S. Antarctic Program
- Remote sensing confirms a shift from long-term freshening to increasing surface salinity south of 50° S, beginning around 2015.
- Denser surface waters are enhancing vertical mixing, allowing warmer subsurface water to reach the surface, accelerating Antarctic ice loss.
- The shift in surface salinity and stratification could impact deep ocean water formation and disrupt components of the global thermohaline circulation, including the Atlantic Meridional Overturning Circulation (AMOC).
Researchers from the University of Southampton, the European Space Agency, and several international institutions analyzed over a decade of satellite-based sea surface salinity (SSS) data, sea ice extent measurements, and in situ ocean profiles from Argo floats. Their objective was to assess recent changes in the upper layers of the polar Southern Ocean, specifically south of 50°S, and examine how these changes relate to sea ice coverage.
For decades, the surface of the Southern Ocean had been gradually freshening. This trend, widely observed, was thought to support the persistence of sea ice by maintaining strong ocean stratification that keeps warmer deep waters separated from the colder surface.
The study found that beginning in 2015, surface salinity levels began rising sharply across the circumpolar Southern Ocean. In some regions, anomalies exceeded 0.2 practical salinity scale (pss) units. This increase in salinity led to a weakening of upper-ocean stratification, reducing the stability of the vertical density gradient that typically separates deep and surface waters.
The change in water composition suggests a change in the balance of the components the ocean circulation in the Southern Hemisphere. Fresher surface water close to the sea ice edge is being replaced by more saline waters.
According to the research team, the consequences of this reversal (freshening to salinification) are already becoming visible.
The weakened stratification allowed warmer subsurface waters to rise more easily to the surface, contributing to reduced sea ice formation. This coincided with a record-low sea ice extent observed in late 2016, followed by several years of continued sea ice minima.
“We are witnessing a real change in ocean properties in the Southern Hemisphere, something not seen before,” said Antonio Turiel, ICM-CSIC researcher and co-author of the study.
“Climate models predict freshening of surface waters in the Southern Ocean, yet we are observing the opposite, an increase in salinity.
“While discussions focus on the potential collapse of the AMOC [Atlantic Meridional Overturning Circulation] in the North Atlantic, we are seeing drastic changes in the Southern Ocean, with declining sea ice coverage and a saltier upper ocean. This could have global climate impacts.”
The study also reports the reappearance of the Maud Rise polynya, a large, open area of water in the sea ice, over the eastern Weddell Sea in 2016 and 2017. This phenomenon had not occurred since the 1970s.
This discovery was made possible by a technical breakthrough developed by the Barcelona Expert Center (BEC), a laboratory of ICM-CSIC specializing in satellite ocean observation.
Until recently, the Southern Ocean region was virtually inaccessible to satellites due to low temperatures and the complex, changing dynamics of sea ice. As a result, the BEC team developed a new data processor for the European SMOS satellite, tailored to the geographic and climatic variability of the polar environment.
In response to the urgent need to better understand these processes, BEC launched two new ESA-funded projects in 2025: ARCTIC-FLOW, which focuses on freshwater and density fluxes in the Arctic Ocean, and CCI OSHF (Ocean Surface Heat Flux), which is dedicated to analyzing heat flux at the ocean surface. Both projects aim to develop satellite methodologies essential for monitoring, understanding, and anticipating such phenomena.
References:
1 Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites – Alessandro Silvano et al. – PNAS – June 30, 2025 – https://doi.org/10.1073/pnas.2500440122 – OPEN ACCESS
2 A change in the Southern Ocean structure can have climate implications – ICM-CSIC – July 1, 2025
I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.
You, any person with scientific knowledge of the claims of climate science doctrine and scare mongering, MUST realize this information massively takes down all the fearful climate claims and doctrine — in spite of the articles obvious self imposed blinders, Antarctic ice increased after 2016, feebly attempting to reinforce climate scare doctrine. Increased salinity is decreased acidity, so global warming will not make the oceans more acid. They say in this article the mixing of ocean waters is increasing and making the oceans warmer at depth, even while recent articles from NASA detailed how Antarctic waters behaved with far more complexity than expected and so were colder than they thought they were and anybody knows deep oceans waters are cold because the heavy weight of water bearing down on waters in the deep compresses water making it colder, permanently — that is why France and England pumped nuclear wastes into deep Atlantic waters many years ago! Of course, if global warming were real, which it isn’t, that would cover up what they did.
this paper is pure cuackademic pseudo science