The global warming is not uniformly distributed over the Earth. The polar regions are especially sensitive for climate change and the warming in the Arctic is more than twice as fast as for the Earth on average. The effects of this warming are large, with a dramatic loss of sea ice as an example.

The Baltic Sea is one of the best-surveyed and studied seas on Earth. Yet the Baltic Sea circulation and its role in the complex climate system is neither fully quantified nor understood, in spite of important implications for coastal societies of the Baltic Sea region.

Over long timescales, the circulation systems co-evolve with ice sheets, mountain ranges, and redistributions of carbon between the atmosphere, ocean and land. The circulation and associated feedbacks influence exchanges of energy and materials between compartments of the climate system, and create teleconnections and natural climate variability.

In the North Atlantic, a mighty current system conveys, via the Gulf Stream and North Atlantic Current, warm surface waters to northerly subpolar areas where deep water is formed. This current system, which is an important link in the global ocean circulation connecting the Atlantic and Pacific Oceans, also carries warm Atlantic water into the Arctic Ocean.