Britain faces big chill as ocean current slows
By Jonathan Leake, Science Editor
The Times Online (UK)
May 08, 2005
CLIMATE change researchers have detected the first signs of a slowdown in the Gulf Stream - the mighty ocean current that keeps Britain and Europe from freezing.
They have found that one of the "engines" driving the Gulf Stream - the sinking of supercooled water in the Greenland Sea - has weakened to less than a quarter of its former strength.
The weakening, apparently caused by global warming, could herald big changes in the current over the next few years or decades. Paradoxically, it could lead to Britain and northwestern and Europe undergoing a sharp drop in temperatures.
Such a change has long been predicted by scientists but the new research is among the first to show clear experimental evidence of the phenomenon.
Peter Wadhams, professor of ocean physics at Cambridge University, hitched rides under the Arctic ice cap in Royal Navy submarines and used ships to take measurements across the Greenland Sea.
"Until recently we would find giant 'chimneys' in the sea where columns of cold, dense water were sinking from the surface to the seabed 3,000 metres below, but now they have almost disappeared," he said.
"As the water sank it was replaced by warm water flowing in from the south, which kept the circulation going. If that two and they were so weak that the sinking water could not reach the seabed," said Wadhams, who disclosed the findings at a meeting of the European Geosciences Union in Vienna.
The exact effect of such changes is hard to predict because currents and weather systems take years to respond and because there are two other areas around the north Atlantic where water sinks, helping to maintain circulation. Less is known about how climate change is affecting these.
However, Wadhams suggests the effect could be dramatic. "One of the frightening things in the film The Day After Tomorrow showed how the circulation in the Atlantic Ocean is upset because the sinking of cold water in the north Atlantic suddenly stops," he said.
"The sinking is stopping, albeit much more slowly than in the film - over years rather than a few days. If it continues, the effect will be to cool the climate of northern Europe."
One possibility is that Europe will freeze; another is that the slowing of the Gulf Stream may keep Europe cool as global warming heats the rest of the world - but with more extremes of weather.
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