North Atlantic Oscillation

The pathways associated with the transformation of warm subtropical waters into colder subpolar and polar waters in the northern North Atlantic. Along the subpolar gyre pathway the red to yellow transition indicates the cooling to Labrador Sea Water, which flows back to the subtropical gyre in the west as an intermediate depth current (yellow). In the Norwegian and Greenland Seas the red to blue/purple transitions indicate the transformation to a variety of colder waters that spill southwards across the shallow ridge system connecting northern Europe, Iceland, Green-land, and northern North America. These overflows form up into a deep current also flowing back to the subtropics (purple), but beneath the Labrador Sea Water. The green pathway also indicates cold waters—but so influenced by continental runnoff as to remain light and near the sea surface on the continental shelf. (Illustration by Jack Cook, Woods Hole Oceanographic Institution)