Portela E. auteur aut IRD Kolodziejczyk N. auteur aut IRD Maes Christophe auteur aut IRD Thierry V. auteur aut IRD text journalArticle eng text/pdf born digital access Using an Argo dataset and the ECCOv4 reanalysis, a volume budget was performed to address the main mechanisms driving the volume change of the interior water masses in the Southern Hemisphere oceans between 2006 and 2015. The subduction rates and the isopycnal and diapycnal water-mass transformation were estimated in a density-spiciness (sigma-tau) framework. Spiciness, defined as thermohaline variations along isopycnals, was added to the potential density coordinates to discriminate between water masses spreading on isopycnal layers. The main positive volume trends were found to be associated with the Subantarctic Mode Waters (SAMW) in the South Pacific and South Indian Ocean basins, revealing a lightening of the upper waters in the Southern Hemisphere. The SAMW exhibits a two-layer density structure in which subduction and diapycnal transformation from the lower to the upper layers accounted for most of the upper-layer volume gain and lower-layer volume loss, respectively. The Antarctic Intermediate Waters, defined here between the 27.2 and 27.5 kg m(-3) isopycnals, showed the strongest negative volume trends. This volume loss can be explained by their negative isopyncal transformation southward of the Antarctic Circumpolar Current into the fresher and colder Antarctic Winter Waters (AAWW) and northward into spicier tropical/subtropical Intermediate Waters. The AAWW is destroyed by obduction back into the mixed layer so that its net volume change remains nearly zero. The proposed mechanisms to explain the transformation within the Intermediate Waters are discussed in the context of Southern Ocean dynamics. The sigma-tau decomposition provided new insight on the spatial and temporal water-mass variability and driving mechanisms over the last decade. specialized Southern Hemisphere Water masses storage Isopycnal mixing Water budget balance In situ oceanic observations Decadal variability OCEAN INDIEN 032 50 2 361-381 2020 0022-3670 https://www.documentation.ird.fr/hor/fdi:010077860 10.1175/jpo-d-19-0128.1 0022-3670 [F B010077860] https://www.documentation.ird.fr/hor/fdi:010077860 https://www.documentation.ird.fr/intranet/publi/2020/02/010077860.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2020-03-11 2025-02-24 fdi:010077860 fre