The Southern Ocean is Changing: Saltier Waters and Vanishing Sea Ice

Redacción HC
07/08/2025

The Southern Ocean, one of the planet's most remote and least understood regions, is undergoing a radical transformation that could have global consequences. A recent study published in Proceedings of the National Academy of Sciences reveals that since 2015, the surface of this vast ocean has become saltier and less prone to forming sea ice. This phenomenon marks an abrupt shift toward a new oceanic state with implications for the global climate.

A Reversal in Climate History

For decades, scientists observed that the Southern Ocean's surface was becoming fresher, strengthening stratification—the separation of ocean layers that limits vertical mixing and favors the persistence of sea ice. However, the team led by Alessandro Silvano from the University of Southampton discovered that this trend has surprisingly reversed over the past decade.

Using satellite data from the European Space Agency and Argo floats, researchers detected a systematic increase in surface salinity since 2015. Simultaneously, sea ice extent has plummeted, reaching historic lows equivalent to the loss of an area the size of Greenland.

More Salt, Less Ice: A Vicious Cycle

Rising surface salinity weakens ocean stratification, allowing heat stored in deeper layers to reach the surface. This process accelerates sea ice melting from below and feeds a feedback loop that worsens ice loss.

One sign of this new oceanic state was the re-emergence of the Maud Rise polynya, an open water area in the heart of the Southern Ocean not seen since the 1970s. This phenomenon underscores the fragility of the polar climate balance.

Global and Latin American Implications

The Southern Ocean plays a key role in regulating the global climate by influencing the thermohaline circulation, which distributes heat and nutrients worldwide. Its disruption could impact climate patterns in the southern hemisphere, including changes in rainfall and droughts in South America.

For scientists and policymakers, these findings highlight the need to strengthen monitoring systems and update climate models. The authors recommend expanding the Argo float network and satellite missions to anticipate abrupt changes that could destabilize the global climate system.

The Future of Polar Monitoring

This study also demonstrates the power of real-time satellite observation to understand and monitor inaccessible regions. Combining satellite technologies with in-situ observations enables the detection of transformations that previously went unnoticed.

As Alessandro Silvano warns: "We are witnessing a state change in the Southern Ocean that could accelerate global warming." This call to action emphasizes the urgency of closely monitoring the icy heart of the planet.