The Oil Drum

About the possible shutdown of the Gulf Stream.

There's been lots of talk about that happening, but recall that the Gulf Stream is a wind driven current, the result of wind patterns which force water toward the west in mid-ocean of the Northern Hemisphere. The water piles up against the continents and then flows northwards. As it does so, the Coriolis Effect causes the flow to turn toward the east. The same sort of wind driven current is evident in the Western Pacific, the Kuroshio Current.

That said, the other part of the problem often mentioned is that of the Thermohaline Circulation (THC). The Gulf Stream branches as it crosses the mid-Atlantic, most of it flowing back toward the South. The North Atlantic Drift Current brings some of the Gulf Stream waters toward the north of Europe, thence continues as the Norwegian Current flowing westward toward the Greenland and Labrador Seas, cooling enough along the way to sink to the bottom of the Atlantic.

http://www.meer.org/M10.htm

Were the THC to stop, Europe would be much colder. This is thought to have happened during the Younger Dryas and also during an event about 8200 years ago. Some models used to study climate change have suggested that the THC might slow or shutdown due to increased greenhouse gases. Others model experiments have suggested that warming from increasing greenhouse gases will counteract the cooling which might otherwise result from a shutdown of the THC.

The THC has been seen to vary over time, perhaps as part of a natural internal oscillation of the Earth's oceans. There was a partial shutdown noted in the Greenland Sea during the early 1980's, which MAY have been associated with the colder winters seen in North America and Europe of that period. It's reasonable to expect a return of such conditions, but, whether the result will be a permanent cooling, ie., another Ice Age is subject of considerable question.

E. Swanson, MsME Ret?, AAAS, AGU