Wind‐controlled export of Antarctic Bottom Water from the Weddell Sea Hot

Antarctic Bottom Water (AABW) is a key water mass in the Meridional Overturning Circulation, filling much of the abyssal layers of the world ocean. The Weddell Sea is the predominant site for AABW formation, and the source for the AABW that occupies the densest layers of the Atlantic Ocean.

Several studies have shown a decadal warming of the AABW layer in the Atlantic, superimposed on significant interannual variability. Recent studies suggest that interannual variability of the AABW in the Scotia Sea may be linked to changes in the baroclinicity of the Weddell Gyre, with the vertical changes in the density structure at the northern edge of the Weddell Sea acting to control the export of AABW across the rough topography of the South Scotia Ridge and toward the Atlantic. Under the assumption that the cyclonicity of atmospheric forcing drives the baroclinicity of the gyre, we test this hypothesis by analysing the properties of AABW during 15 occupations of the SR1b hydrographic section (1993-2009) in the eastern Drake Passage, just downstream of the Weddell Sea in the AABW circulation, and reanalysis atmospheric forcing data.

The time series of thermohaline properties constructed from the data show significant interannual variability (0.05ºC/0.005 in potential temperature/salinity). Positive correlations between the property time series and the zonal wind stress over the northern rim of the Weddell Sea are found at approximately five months lag. Our results suggest that the wind stress influences the variability of AABW properties downstream of the Weddell Sea by contracting/relaxing isopycnals through baroclinic adjustment, thus leading to warmer/cooler AABW being exported in the Scotia Sea/Drake Passage region, from where it can penetrate into the Atlantic