Shutdown of thermohaline circulation
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A summary of the path of the thermohaline circulation. Blue paths represent deep-water currents, while red paths represent surface currents
Shutdown or slowdown of the thermohaline circulation is a postulated effect of global warming.
There is some speculation that global warming could, via a shutdown or slowdown of the thermohaline circulation, trigger localized cooling in the North Atlantic and lead to cooling, or lesser warming, in that region. This would affect in particular areas like Iceland, Ireland, the Nordic countries, and Britain that are warmed by the North Atlantic drift. The chances of this occurring are unclear; there is some evidence for the stability of the Gulf Stream but a possible weakening of the North Atlantic drift; and there is evidence of warming in northern Europe and nearby seas, rather than the reverse. The future is undecided as studies of the Florida Current suggest that the Gulf Stream weakens with cooling and strengthens with warming, being weakest (by ~10%) during the Little Ice Age and strongest during 1,000-1,100 yr BP, the Medieval Warm Period (Lund, Lynch-Stieglitz,and Curry, Nature (2006) 444: 601-604).