Ocean circulation in a warming climate

Nature 451, 286-288 (17 January 2008)

Climate models predict that the ocean's circulation will weaken in response to global warming, but the warming at the end of the last ice age suggests a different outcome.

There is an old truism in climate circles that the cold climate at the Last Glacial Maximum (LGM), which occurred 21,000 years ago, had stronger winds. This idea fits with the common observation that it is windier in the winter than in the summer because there is greater thermal contrast within the atmosphere in the winter hemisphere. Temperature reconstructions from the LGM show that Equator-to-pole gradients in sea surface temperature were indeed larger — that is, the polar oceans were colder than the tropical ocean at the LGM in comparison with the temperature differences today.

It is now becoming clear that the winds in the atmosphere drive most of the circulation in the ocean.