The oceans and the atmosphere are intimately linked in determining global climate. The greenhouse gas carbon dioxide is a key player in this, its concentration in the atmosphere being dynamically controlled via generation from the biosphere, geosphere and hydrosphere, and through ‘draw down’ into carbon reservoirs of short-term historical and long-term geological timescales. Physical and biological processes in the oceans play a central role in atmospheric carbon dioxide regulation. Hence, public concern over climate change immediately confronts our knowledge of the oceanic carbon cycle, both now and in the past. The North Atlantic is of special interest, being an extremely dynamic ocean with an enormous effect on the heat and humidity balance of the Northern Hemisphere and, in consequence, on the agriculture and lifestyles of the populations of North America, Europe and Asia. There is considerable controversy over the role of the North Atlantic in drawing down man-made CO 2 from the atmosphere and hence in determining climate. Predicting the impact of the increased levels of atmospheric CO 2 which are being generated anthropogenically depends upon quantification of sources, sinks and the processes inter-relating them.