Glider observed surface buoyancy forcing from an atmospheric river in the Weddell Sea during austral summer 2019

Atmospheric rivers (ARs) dominate moisture transport globally, accounting for 90% of poleward atmospheric freshwater transport in the mid-to-high latitudes while only covering 10% of the surface. Yet, it is unknown what impact ARs have on the surface ocean buoyancy in the high latitudes. This is explored using high-resolution surface observations from a Wave glider deployed at a site in the Southern Ocean (54°S, 0°E) during austral summer. During this time (19 December 2018 - 12 February 2019, 55 days) we show that when ARs combine with storms over this area, the associated precipitation is enhanced significantly (162%). AR-induced precipitation events provided a major source of surface ocean buoyancy equivalent to the input of surface heat fluxes on a daily timescale. Cumulatively, ARs account for 44% of the summer precipitation equating to 9% of surface buoyancy gain. These results show that AR variability is a previously unaccounted driver of Southern Ocean surface buoyancy that may ultimately impact upper ocean water mass transformation and the dynamics of the ocean surface boundary layer.