A new open-access publication Slowdown of Antarctic Bottom Water export driven by climatic wind and sea-ice changes by Shenjie Zhou, Andrew J. S. Meijers, Michael P. Meredith, E. Povl Abrahamsen, Paul R. Holland, Alessandro Silvano, Jean-Baptiste Sallée & Svein Østerhus is out!
Antarctic Bottom Water (AABW) is a key water mass in the global overturning circulation, occupying most of the world ocean abyss and pivotal for deep ocean ventilation and oceanic heat and carbon exchanges on multidecadal to millennial timescales. The Weddell Sea contributes nearly a half of global AABW through Weddell Sea Deep Water (WSDW), which, along with denser underlying Weddell Sea Bottom Water (WSBW), is formed on the continental shelves via complex processes that include sea ice production. Here we report a multidecadal decline of WSBW volume observed in repeat hydrographic sections. A 30% reduction of WSBW volume since 1992 is found, with the most significant volume decrease seen in the densest WSBW classes. This is likely driven by a multidecadal reduction in dense water production on the Weddell Sea continental shelf associated with a >40% decline in the sea ice formation rate there. The ice production decrease is driven by northerly wind trends, partly in response to a phase transition of the Interdecadal Pacific Oscillation since the early 1990s, with intrinsic variability from the Amundsen Sea Low superposed. These results reveal key influences on the export of waters to the Atlantic abyss and their sensitivity to large-scale, multidecadal climate variability.