Abstract

Radar altimetry is used to document year-round variability in the Ross Gyre (RG), Antarctica, during 2011-2015. The RG is characterized by a bounded recirculating component, and a westward ‘throughflow’ to the south. Maximum Covariance Analysis of the sea-surface height (SSH) and ocean surface stress curl reveals two modes of variability. The first represents a large-scale SSH change forced by the Antarctic Oscillation. The second represents semiannual variability in gyre area and strength, driven by fluctuations in sea level pressure associated with the Amundsen Sea Low (ASL). Variability in the throughflow is also linked to the ASL . An adequate description of the oceanic circulation is achieved only when sea ice drag is accounted for in the ocean surface stress. The drivers of RG variability unveiled here bear strongly on our understanding of the oceanic forcing of Antarctic Ice Sheet melting, and of the downstream propagation of its ocean freshening footprint.