The Southern Influence

Abstract

CLIMATOLOGY Changes in oceanic thermohaline circulation, triggered by variations in the flux of glacial melt water to the North Atlantic Ocean that affect the formation rate of North Atlantic Deep Water, can produce rapid dramatic changes in climate. Deep water does not originate exclusively in the North Atlantic, however; it also is made around the edges of Antarctica, where it is referred to as Antarctic Bottom Water. Although most of the attention given to the question of how the modification of sea surface salinity by the addition of glacial melt waters affects thermohaline circulation is still directed at Northern Hemisphere deepwater formation sites, the role of the Southern Ocean is now being investigated more vigorously. Seidov et al. use an ocean circulation model to examine the character of deepwater formation as a function of systematic changes in freshwater fluxes in both the Northern and Southern Hemispheres. They find that thermohaline circulation is driven by both deepwater sources and that the Southern Ocean can overpower the North Atlantic and become a major factor in long-term climate change, illustrating the importance of high-latitude freshwater fluxes in governing climate.— HJS Global Planet. Change 30 , 257 (2001).