Seasonal and interannual variations of the upper ocean energetics between Tasmania and Antarctica

Nine years of Topex/Poseidon and ERS satellite altimetry and XBT data from the SURVOSTRAL program were used to analyze the seasonal and interannual variations of the eddy energetics in terms of its spatial distribution and relation with the upper ocean heat content. Eddy kinetic energy is calculated in two frequency bands one associated with transient and the other with low-frequency variability. The two eddy components have distinct geographical distribution. At the SURVOSTRAL line, the transient eddy energy is twice the low-frequency energy, with maximum transient energy occurring during the austral summer period and maximum low-frequency energy in winter. The site is one of growing eddy energy. Eddy momentum flux is northward over the SURVOSTRAL line, and the summertime eddy heat flux is poleward across the Subantarctic and Subtropical Fronts, and equatorward either side of the fronts. Eddy fluxes are strongly influenced by their position relative to the bathymetry and the mean current.