Diagram showing the flow of the North Atlantic and Norwegian Atlantic Currents

The North Atlantic and Norwegian Atlantic Currents carry warm, salty, tropical surface waters northward, where they surrender heat to the atmosphere, tempering winters in Europe. The waters become colder and denser and sink to the depths of the seas north of the Greenland- Scotland Ridge. The ridge, stretching from East Greenland to Iceland and across to Scotland, is an undersea barrier between the northern seas and the North Atlantic. The Denmark Strait is a critical passageway through the ridge. (Ruth Curry, WHOI, and Cecilie Mauritzen, Norwegian Meteorological Institute, © Woods Hole Oceanographic Institution)