Cascading of Seasonal and Interannual Variability Between Upper Ocean
Processes and the Slope Current in the Cosmonaut Sea off East Antarctica
Abstract
The current system in the Cosmonaut Sea off East Antarctica is subjected
to large-scale climate change, which in turn affects the nutrient
availability and productivity of the region. The Copernicus merged
absolute dynamic topography (ADT) data were employed to analyze the
variability of major currents and potential driving mechanisms behind.
The main currents in the Cosmonaut Sea are revealed to be the Antarctic
Circumpolar Current (ACC), the Weddell Gyre Eastern Branch (WGeb) and
the Antarctic Slope Current (ASC); and strong seasonal and interannual
variations are also found associated with these currents. ACC and ASC
both are stronger in autumn and weaker in spring and summer, while the
WGeb expends eastward in winter and retreats in summer. At the
interannual timescale, the Southern Annular Mode (SAM) could reinforce
westerlies during its positive phase, pushing ACC southward and
suppressing westward ASC, and vice versa. Studies on related mechanisms
suggest the crucial role of winds in the barotropic modulation of ocean
dynamics. The westerlies affect the meridional gradient of the sea level
through Ekman transport, inducing the change of barotropic geostrophic
currents. The changing atmospheric and oceanic circulations have
possible influence on the southward Sverdrup transport maintaining the
Antarctic Slope Front (ASF) crucial to the ASC thereafter. The WGeb
might also perform an intermediate role in the southward cascading of
variability from ACC to ASC. This indicates that the response of
regional ocean dynamics to circumpolar atmospheric variations could be
understood from the view of cascading processes.