Flexi Says: Downwelling of cold, dense water drives the deep ocean "conveyor belt," or thermohaline circulation. Downwelling occurs in the North Atlantic, where the surface water is usually more dense than the water below. This causes the surface water to sink. However, melting sea ice is now adding a lot of fresh water to the ocean in the North Atlantic. Fresh water is less dense than salt water, so the added fresh water lowers the overall density of the ocean water. If the density of the water lowers enough, downwelling may stop. This could disrupt deep ocean circulation.
