Variability of the thermohaline circulation (THC)

Europe's relative warmth is maintained by the poleward surface branch of the Atlantic Ocean thermohaline circulation. There is paleoceanographic evidence for significant variability and even shifts between different modes of thermohaline circulation. Coupled ocean-atmosphere climate modelling allows first insight into the relative role of the various drivers of the Atlantic thermohaline circulation variability, i.e. the North Atlantic Oscillation, the tropical Atlantic variability, the ocean basin exchanges, small scale processes like high-latitude convection, overflows and mixing as well as effects of changes in the hydrological circle, the atmospheric CO2-content and solar radiation. The strong need for continous model improvement requires concerted efforts in ocean time series observations and relevant process studies. New instrumentation and methods, both for in situ measurements and remote satellite sensing are becoming available to help on the way forward towards as improved understanding of North Atlantic climate varibility.