The ocean is a key component in the global transports of heat and fresh water. Climate variations at interannual, decadal (and larger) time scales are strongly coupled to changes in the ocean circulation. This is particularly obvious over north-western Europe where the relatively warm climate is very sensitive to small changes of the North Atlantic Current branch of the Gulf Stream. The ultimate goal of this research is to understand and correctly simulate the ocean component of the climate system. This takes place in a world wide effort. At IMAU we focus our attention on a few critical areas and issues, aiming at a better understanding of the wind-driven and thermohaline circulation in the oceans and their role in the maintenance of the global thermohaline circulation.