Salinity and Climate (00:01:17)[24-Feb-10] When these waters at very high latitudes - (your) Greenland, Iceland - when they sink in the wintertime (it's) because they are very dense. Those waters sink, they spread to the global ocean and (eventually) they need to return. When they return, they are returning in the surface waters. That's why it's referred to as an "overturning".
So these warm waters are returning at the surface, going back to those high latitudes in the Norwegian and Greenland seas. And when they're doing that, when they're returning, they're bringing very warm water with them. Because that return means they're coming through the equatorial regions of the tropics where the atmosphere is very warm and the oceans are warmed.
So when those warm waters are returning, as they're moving up to the higher and higher latitudes, then they're releasing that heat to the atmosphere. Then the winds blow over the ocean, they pick up that heat, and those winds over the Atlantic Ocean are moving from the North American continent to the European continent. So these westerly winds are picking up that heat and moisture and dumping it all over the British Isles and northern Europe. So if there's any change to that overturning circulation, that means that northern Europe and the British Isles would be robbed of that heat, due to those waters that are returning to the high latitudes. Credit: Susan Lozier.