Auger M., Morrow R., Kestenare E., Sallée J.-B., Cowley R., 2021 – Southern Ocean in-situ temperature trends over 25 years emerge from interannual variability, Nat Commun 12, 514 (2021).
The paper has been cited in an Washington Post article, dedicated to the Southern Ocean and its warming waters. In this article, Matthis highlights the fact that “we cannot predict if the situation will be the same as in West Antarctica all around the continent in the future, but we are now observing changes going into that direction”.
“This study shows the threat of subsurface water warming, that can affect Antarctic ice cap all around Antarctica. Our hope for future studies is a better understanding of the Southern Ocean models. Ocean models are affected by the lack of observation[s] in the region, and a better representation of the Southern Ocean by the models would be an important step forward,” Auger wrote.
Despite playing a major role in global ocean heat storage, the Southern Ocean remains the most sparsely measured region of the global ocean. Here, a unique 25-year temperature time-series of the upper 800 m, repeated several times a year across the Southern Ocean, allows us to document the long-term change within water-masses and how it compares to the interannual variability. Three regions stand out as having strong trends that dominate over interannual variability: warming of the subantarctic waters (0.29 ± 0.09 °C per decade); cooling of the near-surface subpolar waters (−0.07 ± 0.04 °C per decade); and warming of the subsurface subpolar deep waters (0.04 ± 0.01 °C per decade). Although this subsurface warming of subpolar deep waters is small, it is the most robust long-term trend of our section, being in a region with weak interannual variability. This robust warming is associated with a large shoaling of the maximum temperature core in the subpolar deep water (39 ± 09 m per decade), which has been significantly underestimated by a factor of 3 to 10 in past studies. We find temperature changes of comparable magnitude to those reported in Amundsen–Bellingshausen Seas, which calls for a reconsideration of current ocean changes with important consequences for our understanding of future Antarctic ice-sheet mass loss.