Melting Arctic Sea Ice and Ocean Circulation Seawater moves through the Atlantic as part of the thermohaline circulation (also called the Global Ocean Conveyor), the regular pattern by which seawater travels the world’s oceans. The water in the Global Ocean Conveyor circulates because of differences in water density, which are caused by differences in temperature and salinity. Colder water is denser than warmer water, while saltier water is denser than less salty water or fresh water. Water heated near the Equator travels at the surface of the ocean north into cold high latitudes where it becomes cooler. As it cools, it becomes denser and sinks to the deep ocean.