Variation of Southern Ocean sea level and its possible relation with Antarctic sea ice

The variation of the Southern Ocean (SO) sea level and its possible relation with Antarctic sea ice are investigated. The dataset used results from a space-time objective analysis which merges one-year simultaneous ERS-1 and TOPEX/POSEIDON altimeter data. The main results are as follows, (1) The study confirms and complements previous ones in that the sea level variability in the SO is complex and bathymetrically controlled. The Antarctic Circumpolar Current is dominated by the annual component. For the western boundary currents, however, the semi-annual component is equally or more important. (2) A new result is obtained showing that, in the Brazil/Malvinas Confluence region, the locations of the annual and semi-annual energies are geographically separated, the maxima of which are comparable instead of being semiannual dominant. (3) A striking feature revealed by this study is that the annual cycles of sea level variations in the western boundary current zone (35 degrees-45 degrees S) and seasonal sea ice zone (60 degrees-70 degrees S) are nearly 180 degrees out of phase. This suggests that two contrary governing processes, speculated to be the solar cycle and sea ice cycle, co-exist in the SO. (4) It is argued that the variations of the SO sea level and Antarctic sea ice are strongly coupled through steric effect as well as insulating effect of the sea ice cover.