In the wintertime in the Labrador Sea, eastward travelling cold dry air from the Canadian Arctic archipelago and storms from northeast American encounter their first bit of ocean over the subpolar North Atlantic. Ocean sea surface temperatures in this region are warmer than the surface temperatures over land since they can’t remain below -1 degrees for long. This means that the ocean is warm relative to the atmosphere, and so gives off heat to the atmosphere which cools the surface waters. When waters become cooler, they become denser; if they get denser than the waters beneath them, they sink, mixing with deeper water. This process is called “deep convection”, and the end result is a well-mixed deep water mass. There are only a few places in the world where deep convection can occur in the open ocean (as opposed to continental shelves or marginal seas), including the Labrador Sea (between Canada and Greenland), Irminger Sea (between Greenland and Iceland).
