Dive into the secrets of the Southern Ocean

A view of Antarctica in November 2019 (JOHAN ORDONEZ / AFP)

The team of CNRS geochemist and ecologist Laurent Chauvaud has reported incredible images and sounds of their diving under the Antarctic sea ice. The sounds of the ice floe breaking and cracking against the waves are reminiscent of a mountain glacier and the creaking of its seracs.

Under the surface, we observe a universe that is initially very mineral or we meet penguins and marine mammals, such as seals, around the columns of ice. But this universe is also very contrasted when we then descend lower. At 70 meters deep and where we discover algae and crustaceans in flamboyant colors. Surprising reds and yellows as the light is absent at this depth.

Extreme conditions for scientific expeditions

To recover these images and sounds, it was necessary to work in very difficult conditions. Imagine 18-meter hollows and razor-sharp icebergs for ship hulls. This year, the Swings expedition took on the French TAAF boat, the Marion Dufresne, around fifty scientists for three months, from January to March during the summer season in the Southern Ocean where we can count on milder weather.

They came back with a lot of samples to analyze and some scares. But the explorer Jean-Louis Etienne wants to launch his Polar Pod for 2023, a sort of rocket of the seas, to be able to stay in this ocean during the southern winter and its storms. The southern winter will also begin soon.

It is important to know more about this ocean, first of all because it is immense: more than 20 million km2, or a quarter of the world’s ocean surface. It goes around the globe, absorbs a third of atmospheric carbon, half of the heat and above all it distributes nutrients in other oceans. A bit like a conveyor belt that circulates freshness and organic materials among its Pacific, Atlantic and Indian neighbors.

If its surface waters remain cold, they become softer and softer with the melting of the sea ice, this can change this thermohaline circulation of which it is a key factor. On the other hand, a Franco-Australian study showed that some more in-depth had warmed up over the past 25 years. Understanding what is happening to one of our gigantic carbon sinks is essential, as our climate future and his are so closely linked.

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