Contrary to previous expectations, the surface waters around Antarctica are becoming saltier—not fresher—even though sea ice is melting rapidly.
Traditionally, melting sea ice adds freshwater, which reduces salinity. However, satellite data from the European Space Agency’s SMOS mission shows an unexpected rise in salinity, challenging established scientific assumptions.
The exact cause is still being investigated. One theory suggests that meltwater from glaciers and ice shelves may be sinking quickly because of its density, leaving saltier water at the surface. Additionally, shifting wind patterns and ocean mixing could also be contributing factors.
Saltier water is denser and allows heat from deeper ocean layers to rise, melting sea ice from below. This prevents new ice from forming and reduces the ocean’s ability to trap heat in its depths.
As sea ice melts, the ocean absorbs more heat. The saltier surface water then makes it easier for that heat to rise, which causes even more melting—creating a self-reinforcing feedback loop that accelerates ice loss.
The Maud Rise polynya is a large, ice-free area in the Weddell Sea. Its reappearance after several decades indicates major disruptions in ocean-ice dynamics caused by changes in salinity and heat distribution.
• Disruption of deep ocean currents that regulate global climate
• Acceleration of global warming
• Shrinking habitats for Antarctic wildlife such as penguins and seals
• Gradual rise in global sea levels
This discovery is based on data collected from the ESA’s SMOS satellite and over 15 years of ocean measurements. Algorithms developed by research institutions in the UK and Spain under ESA’s Science for Society programme were used to monitor changes in ocean salinity.
The findings indicate that Antarctica may be approaching a climate tipping point—a stage where environmental changes become irreversible. Persistent loss of sea ice could permanently alter the Southern Ocean’s structure and circulation.
Continuous high-resolution monitoring of Antarctic waters and ice conditions, along with global climate mitigation efforts, is essential to understand and reduce the long-term environmental damage.
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