Thermohaline circulation, also called the Global Ocean Conveyor, moves water between the deep and surface ocean worldwide.
Image courtesy Argonne National Laboratory
Melting Arctic Sea Ice and the Global Ocean Conveyor
Seawater moves through the Atlantic as part of the Global Ocean Conveyor. That’s the way that seawater travels the world’s oceans. The water in the Global Ocean Conveyor moves around because of differences in water density. In the North Atlantic, the differences in water density are mainly caused by differences in temperature. Colder water is denser than warmer water. Water heated in the warm tropics. The warm water travels at the surface of the ocean north into the cold north polar region. The chilly temperatures cool the water. As it cools, it becomes denser and sinks to the deep ocean. More warm surface water flows in to take its place. Then that water cools, sinks, and the pattern continues.
Melting Arctic sea ice could change this pattern, or stop it altogether.
Arctic sea ice is melting fast as the climate warms. When the sea ice melts, it adds freshwater to the ocean making the seawater less dense. The less dense water will not be able to sink and circulate through the deep ocean as it does currently. This will disrupt or stop the Global Ocean Conveyor and could cause climate to cool in Europe and North America.
This would not be the first time that the Global Ocean Conveyor was stopped. There is evidence from sedimentary rocks and ice cores that it has shut down several times in the past. Those shut downs have caused changes in climate that are preserved in the rocks and fossils from the time.
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