Unlike forecasts, surface waters around Antarctica become more salty, a phenomenon that worsens the melting of ice. This unexpected discovery questions established climatic models and raises concerns for balance planetary.
Since 2015, record reduction in Antarctic Sea Ice, equivalent to the area of Greenlandcoincides with a sudden increase in oceanic salinity. An international team, led by theUniversity of Southamptonrevealed this worrying mechanism thanks to data satellites and in situ measures.
A vicious circle: salt and heat
Normally, the ocean consists of superimposed layers: cold and little salty water remains on the surface, while warmer and salty water remains in depth. This natural separation prevents the heat of the depths from going up.
But when the surface becomes more salty, this organization is disturbed. Surface water begins to flow and mix the layers. The heat of the depths then rises to the surface, melt the ice below faster.
The return of the polynia of Maud Rise, a giant hole in the ice floe, illustrates this disturbance. Absent since the 1970s, its reappearance reports a sustainable upheaval in oceanic conditions.
Crédit: In Earth Observatory
Climate models anticipated a decline in ice, but not as fast. The increased salinity creates a feedback loop: less ice exposes the ocean more to the sun, amplifying warming.
Global consequences
The Antarctic Banquise plays a key role by reflecting solar light. Its gradual disappearance could modify the sea currents and global climatic regimes, with repercussions on polar ecosystems and beyond.
The absorption of CO₂ by the southern ocean could also decrease, reducing its role of climate buffer. The species dependent on ice, such as emperors, are directly threatened by these changes.
Continuous monitoring of this region, although difficult, is essential to understand the evolution of the climate system. Satellites and underwater robots provide essential data to anticipate future upheavals.