onsdag 29 juli 2009

Would Europeans Freeze Without the Gulf Stream?

People in Britain and Northern Europe commonly believe that a relatively comfortable life is possible because of the Gulf Stream. which brings warm water from Sargasso causing the temperature to be 15-20 degrees warmer than in in eastern North America/Alaska.

Some fear the fresh water from melting ice in the Arctic can slow down the Gulf Stream or even reverse its direction, thus causing a form ice age in Northern Europe.

What does science tell? Richard Seager at Columbia University reports:
  • The notion that the Gulf Stream is responsible for keeping Europe  anomalously warm turns out to be a myth.
  • Fifty percent of the winter temperature difference across the North Atlantic is caused by the eastward atmospheric transport of heat released by the ocean that was absorbed and stored in the summer.
  • Fifty percent is caused by the stationary waves of the atmospheric flow.
  • The ocean heat transport contributes a small warming across the basin.
  • The seasonal ocean heat storage and pattern of atmospheric heat transport add up to make winters in western Europe 15 to 20 degrees C warmer than those in eastern North America. A very similar process occurs across the Pacific Ocean. The ocean heat transport warms the North Atlantic Ocean and the land on both sides by a modest few degrees C. The only place where the ocean heat transport fundamentally alters climate is along the coast of northern Norway which would be sea ice-covered were it not for the warm northward flowing Norwegian Current. 
  • Any cooling tendency would probably be overwhelmed by the direct radiatively-driven warming by rising greenhouse gases
So, except for northern Norway, we don't have to freeze if the Gulf Stream slows down and even changes direction by freshening of the waters caused by anthropogenic climate change via melting glaciers and increased water vapor transport into high latitudes.

But what is the truth? Can Computational Fluid Dynamics CFD help to give an answer? Now or in 50 years? What is state-of-the-art of CFD? According to Journal of Fluid Mechanics, the leading scientific journal? Compare with Gulf Stream Shut Down and Abrupt Climate Change.

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