Join us to hear Uriel Zajaczkovski, a Postdoctoral Investigator from WHOI, to give the last Physical Oceanography Seminar of the semester.

Title: A study of the Southern Ocean: Mean state, eddy genesis & demise, and energy pathways

Abstract:

Satellite altimetry and output from an assimilating numerical model suggests that the Southern Ocean has two distinct eddy motion regimes. North and south of the Antarctic Circumpolar Current (ACC), eddies propagate westward with a mean meridional drift directed poleward for cyclonic eddies (CEs) and equatorward for anticyclonic eddies (AEs). Eddies formed within the boundaries of the ACC have an effective eastward propagation with respect to the mean deep ACC flow, and the mean meridional drift is reversed, with warm-core AEs propagating poleward and cold-core CEs propagating equatorward. This circulation pattern drives downgradient eddy heat transport, which could potentially transport a significant fraction of the net poleward ACC eddy heat flux. 

The generation of relatively large amplitude eddies is not a ubiquitous feature of the SO but rather a phenomenon that is constrained to five isolated, well-defined “hotspots”. These hotspots are located downstream of major topographic features, with their boundaries closely following f/H contours. Eddies generated in these locations show no evidence of a bias in polarity and decay within the boundaries of the generation area. Eddies tend to disperse along f/H contours rather than following lines of latitude. These hotspots have enhanced values of both buoyancy (BP) and shear production (SP). The mean potential density field estimated from Argo floats shows that inside the hotspots, isopycnal slopes are steep, indicating availability of potential energy. Hotspot locations can be explained by the combined effect of topography, standing meanders that enhance baroclinic instability, and availability of potential energy to generate eddies via baroclinic instabilities.