Auger M. auteur aut IRD Morrow R. auteur aut IRD Kestenare Elodie auteur aut IRD Sallee J. B. auteur aut IRD Cowley R. auteur aut IRD text journalArticle eng text/pdf reformatted digital access 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 800m, 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 (0.290.09 degrees C per decade); cooling of the near-surface subpolar waters (-0.07 +/- 0.04 degrees C per decade); and warming of the subsurface subpolar deep waters (0.04 +/- 0.01 degrees 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 +/- 09m 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. The Southern Ocean takes up the most heat and carbon, yet because of its remote and harsh location, it remains relatively sparsely measured. Here the authors use a 25 year temperature series which shows a clear, long term trend in subsurface warming that emerges from interannual variability. specialized OCEAN AUSTRAL 032 12 1 514 [9 p.] 2021 2041-1723 https://www.documentation.ird.fr/hor/fdi:010080903 10.1038/s41467-020-20781-1 2041-1723 [F B010080903] https://www.documentation.ird.fr/hor/fdi:010080903 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers21-02/010080903.pdf IRD - Base Horizon / Pleins textes 2021-03-10 2025-02-24 fdi:010080903 fre