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Low-salinity water in the Southern Ocean kept CO₂ locked away for decades
4 Nov 2025
Low-salinity water in the Southern Ocean kept CO₂ locked away for decades - New study reveals an overlooked oceanic carbon storage mechanism
Scientists from the Ludwig-Maximilians Universität (LMU) Munich and the Alfred Wegener Institute (AWI) have discovered that since the 1990s, more CO2-rich deep waters have been rising towards the surface of the Southern Ocean — but that the freshening of the Southern Ocean has, so far, kept this CO2 trapped below the surface, delaying its release to the atmosphere. This mechanism influences when and how much CO2 returns to the atmosphere, and it helps explain why the Southern Ocean has remained such an efficient climate buffer (for now).
The study, published in Nature Climate Change, provides an important insight into the global carbon cycle. The Southern Ocean absorbs roughly 10 % of the anthropogenic CO₂ emissions. Even subtle shifts in salinity caused e.g. by melting ice or changes in ocean circulation could therefore significantly alter the ocean’s role as a carbon sink.
The lead-author Dr. Lea Olivier is a postdoctoral researcher in the AWI-LMU joint research group for Southern Ocean-Climate Interactions (SO-CLIM), which is led by Prof. Dr. Alexander Haumann. The SO-CLIM team focuses on understanding how Southern Ocean physical and biogeochemical processes such as changes in salinity and density influence global climate dynamics.