ABSTRACT
The Atlantic waters that descend at the brink of the Arctic Ocean form a segment of the great ribbon of moving water dubbed the oceanic conveyor belt. Waters of the conveyor belt rise up in the middle of the Pacific Ocean and flow westward around the tip of Africa. The Atlantic Ocean became saltier, and the modern conveyor belt formed, leaving the upper Arctic Ocean only weakly connected to the warm Atlantic and allowing it to cool down in its polar isolation. The entire polar region is much colder than it was shortly before the ice age began; the transition to the colder, modern state is what permitted continental glaciers, including the persistent Greenland ice cap, to grow. Three great ice caps occupied the land during each glacial maximum of the modern ice age—one centered in eastern Canada, one in Greenland, and one in Scandinavia.
