The thermohaline circulation, involving high latitude sinking and distributed upwelling and mixing at lower latitudes, is heavily involved in the longer time scales of climate variability. Tropical SST changes have displayed decadal trends and strong correlations with long term rain and drought cycles as well as tropical storm frequency. However, we remain largely ignorant of the processes controlling such variability. Thus, much remains to be done to achieve some measure of predictability. Monitoring strategies and systems need to be refined and expanded.
Models are essential tools for developing adequate understanding and predictive capabilities.
Paleoclimatic data are essential for describing the past states of the ocean-atmosphere system the decadal to centennial time scales. The thermohaline circulation, with its strong conveyor belt circulation, is a major factor in climate, as it carries much of the poleward heat flux, and has been characterised as having dramatic variability in the paleoclimatic record. A major focus will be on the thermohaline circulation in the Atlantic, but the thermohaline circulation in the Southern Hemisphere is of interest as well. Also, the role of the Southern Ocean in the communication of heat and freshwater anomalies and water masses between basins, and their influence on climate is of interest. It is especially important to develop a monitoring strategy for this vast, infrequently sampled stretch of ocean.