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The Austral Ocean is making temperature rise

The results of a study carried out in the Austral ocean by several French and Australian laboratories for the past 25 years were released on January 21st,2021. The assessments are even worse than the scientific’ forecasts, calling for an overall warming of deep waters temperature, raising concerns about ice melting, water rising and global warming.

Austral Ocean: an important area but not much studied

Published in Nature communication journal, the study details the results gathered through the SUVOSTRAL observation program. Led by several geophysics, oceanography, and climate laboratories, among which the CNRS and Australian CSIRO, the study is unprecedented as this is the longest temperature transcript done in this region of the world. While playing a major role in storing the world ocean heat, the Austral Ocean is the marine area the least monitored across the planet.

More specifically, during 25years, scientists sailed several times the 2 700km connecting Tasmania to the Arctic in the Austral Ocean. During each journey, 6 times a year, temperature sensors were launched every 20km, sometimes reaching 800m deep. This fastidious work allowed the establishment of an average temperature structure of the Austral Ocean’s few first meters. And results are alarming.

The alarming warming of deep waters

Scientifics have indeed been observing in the past decades, the rise of the Austral Ocean’s temperature. Some variations were however highlighted; in the north, all waters are strongly warming up, whereas in the south extremity of the area, close to the Artic, surface waters have been marked by a slight cooling… Which is nothing to be happy about!

This cooling is in fact due to the direct contact between the ocean surface and the icy air of the south ocean. However, it is just a matter of going down a few meters, to highlight an important warming of deep waters. Deep waters cannot cool down, as they can’t mix with less salty surface waters blended with continental melting ice.

Even if the rising of 0.05°C per decade seems quite low, it nonetheless remains alarming as warm waters go up more and more quickly to the surface every day. During this last decade, they rose by 39m, gradually leading to the cold surface reduction and foreshadowing really serious consequences.  

Tremendous consequences caused by this warming

Indeed, while directly impacting the world climate, rising of these warmed deep waters threatens to invade continental plateau, accelerating the Antarctic ice melting and rising of sea levels.

Strongly underestimated until now, these changes observed in the Austral Ocean must now be considered. The recent results underlining the reach of deep water warming, we are causing, must allow us to reconsider the ocean actual changes, the lost of ice cap mass, and push us to act even more in favor of marine protection.