NADW forms when waters from the oceanic thermocline upwell to the surface, cool, and sink in the seas around Greenland.
Heat is transferred from ocean to atmosphere in the process.
Partly because these seas were ice covered, NADW formation was generally slow during glacial times. Intensification of NADW formation would cause rapid warmings in Greenland and other land masses adjacent to the North Atlantic, which can explain the impressive magnitude of the climate changes as well as their rapidity. Most of the 23 Greenland interstadial events observed at GISP2 are not yet associated with major changes in Antarctic climate. Diminution of NADW formation would eventually reverse the climate amelioration and return Greenland and Antarctica to cold, glacial conditions.