Interannual variability of the outflow of Weddell Sea bottom water

The Weddell Sea Bottom Water (WSBW) export from 1999 to 2019 displays distinct seasonal and interannual variability. From 2014 into 2017 a marked salinity decrease was recorded, with the lowest salinity, 34.615, attained in early 2016. The reduced salinity is derived from the V‐shaped trough formed by a double front along the shelf break of the Weddell Gyre's western boundary, which is filled with a blend of surface water and modified Weddell Deep Water. We estimate that when the V‐shaped apex attains a depth of greater than ~700m, the thermobaric effect promotes its descent into the WSBW. We propose that this occurred during anomalously strong cyclonic wind stress curl over the Weddell Gyre from 2014 into 2017, which increased the intensity of the gyre and its western boundary current, deepening the V‐shape trough. The WSBW salinity increased to its prior to 2014 values as the wind stress relaxed in 2018.