2002 October 02 Wednesday
Abrupt Climate Change

Dr. Robert B. Gagosian, President and Director of Woods Hole Oceanographic Institution, has written an article about the prospects of abrupt climate change. The most probable way for this to happen would be for the large flows in the oceans to suddenly shift to a different pattern. This is believed to have happened as recently as 500 years ago in the North Atlantic. There are worrisome signs that it could happen again:

At some point, the North Atlantic will no longer absorb any more fresh water. It will begin to pile up on the surface. When that happens, the Great Ocean Conveyor will be clogged. It will back up and cease functioning.

The very recent freshening signal in the North Atlantic is arguably the biggest and most dramatic change in ocean property that has ever been measured in the global ocean. Already, surface waters in the Greenland Sea are sinking at a rate 20 percent slower than in the 1970s.

At what percent will the Ocean Conveyor stop? 25 percent? 40 percent? 60 percent? This is not like a dimmer switch, but more like a light switch. It probably goes from “on” to “off.”

We can’t yet determine the precise source or sources of this additional fresh water. Global warming may be melting glaciers, or Arctic sea ice. In recent decades, the volume of Arctic sea ice has decreased by 40 percent. And if North Atlantic sinking slows down, less salty Gulf Stream waters flow northward—which exacerbates the situation.

Share |      By Randall Parker at 2002 October 02 01:26 PM 


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