2/9/09

And what would happen if the Gulf Stream stopped?


International Polar Foundation. Scienciepoles
http://www.scienciepoles.org/




For most people, slowing or even stopping the Gulf Stream could only be a sci-fi story. This vast oceanic current on the surface of the Atlantic, which runs from the intertropical zone towards the shores of Europe (thus ensuring our warm winters and temperate summers) cannot simply "break down". However, a reduction in its intensity, or even its coming to a complete halt, is not impossible. The climatic history of our planet shows this. The Gulf Stream has already seen some major disturbances to its "flow".
Canadian, American and British researchers, whose work was partly funded by the European Union's 5th Framework research programme, reckon that over the past ten years, the global warming of our planet has modified the salinity of its oceans, which in turn may disturb the circulation of marine currents (known as thermohaline circulation).
A question of salinity
It is the increased evaporation of surface water in temperate regions, generating a significant surplus of water vapour in the atmosphere and more precipitation of fresh water at higher latitudes, that could be bringing about such a change in the salinity of the North Atlantic.
Water with a lower salt concentration does not drop easily to the ocean depths, which is what usually happens to the Gulf Stream to the north of Iceland. It is here that this famous current now plunges to the ocean floor before returning to the tropics and then, further south, towards the Antarctic Ocean. In other words, this deep ocean current is the (conveyor-belt like) "return" of the surface Gulf Stream.
After more intense rainfall, however, the additional fresh water in the mix inhibits the Gulf Stream's drop towards the ocean floor, and jams up this vast, worldwide climatic mechanism. This in turn interferes with, or even blocks off, the Gulf Stream on the surface.
Consequences: if the Gulf Stream malfunctions, then Europe, deprived of its effects, will in turn lurch towards a new era of lower temperatures. In other words, winters in Lisbon may become as rigorous as those in New York.
Fact or fiction? The climatic history of our planet shows that such a development in the past - a considerable influx of fresh water in the North Atlantic resulting from a massive offloading of ice from the American ice sheet - has already seen the Gulf Stream mechanism put "out of order".

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