Warming Could Slow Ocean Currents

Larry O’Hanlon, Discovery News
March 1, 2007 — There is both good and bad news about the conveyor belt of heat-moving currents in the North Atlantic Ocean.A new study of 17 different climate models concludes that the thermohaline circulation, which drives the Gulf Stream and helps warm Europe, won’t stop dead and abruptly change regional climates anytime this century. That’s the good news.

“Abrupt climate change in this century is unlikely,” said climate researcher Andrew Weaver of Canada’s University of Victoria.

  The thermohaline circulation is seen as one of the few climate switches that could be flipped quickly and morph climates worldwide — at least in theory.
In the 2004 movie The Day After Tomorrow, the large-scale circulation came to a speedy halt, hurling Europe into another ice age in a matter of days — a wildly exagerated scenario. But despite Hollywood’s over-the-top version, abrupt climate change over years or decades is a genuine concern.

And now for the bad news.

Many experts have thought it would take something dramatic, like the complete meltdown of Greenland’s ice sheet (and subsequent dumping of buoyant freshwater into the ocean) to throw a wrench into the thermohaline circulation. The models show that may not be the case.

The warming of ocean surface temperatures alone may be enough to slow the circulation.

All of the models showed a reduction in the conveyor belt-like thermohaline circulation over time, said Weaver. “But it turns out it’s not the freshwater that’s driving it,” he added.