Eueng-nan Yeh

Examining several Southern Ocean data sets

The Southern Hemisphere ocean covers approximately 45% of the Earths surface and poses a major scientific challenge to initiatives such as the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS) programs, whose goals include elucidation of its deep circulation and its contributions to global bio-geochemical budgets. The Southern Ocean is generally regarded as the region south of about 30°S and, in many respects, is quite different from its northern counterpart. Unlike the oceanic and atmospheric flows in the Northern Hemisphere, the Circumpolar Current “Nowlin and Klinck, 1986” and surface winds have relatively unobstructed circulations around Antarctica that allow the exchange of water between basins and result in the most intense wind forcing in the global ocean. An analysis of the annual cycle of sea level using Geosat altimetry has shown that seasonal changes in the surface ocean circulation are much weaker in the Southern Hemisphere than in the Northern Hemisphere. Also, comparison of the pigment fields obtained from the Nimbus-7/Coastal Zone Color Scanner (CZCS) indicates that the biology of the northern and southern oceans is quite different in that the northern oceans exhibit a pronounced spring bloom, while the Southern Ocean is relatively constant the year round “Esaias et al., 1986; Feldman et al. 1989”. The cause of this dissimilarity is a topic of some debate, with various arguments focusing on differences in trace nutrient supply, physical forcing, and illumination.