The ocean current that gives western Europe its relatively balmy climate is stuttering, raising fears that it might fail entirely and plunge the continent into a mini ice age.
The dramatic finding comes from a study of ocean circulation in the North Atlantic, which found a 30% reduction in the warm currents that carry water north from the Gulf Stream.
The slow-down, which has long been predicted as a possible consequence of global warming, will give renewed urgency to intergovernmental talks in Montreal, Canada, this week on a successor to the Kyoto Protocol.
[. . .] But Bryden’s study has revealed that while one area of sinking water, on the Canadian side of Greenland, still seems to be functioning as normal, a second area on the European side has partially shut down and is sending only half as much deep water south as before. The two southward flows can be distinguished because they travel at different depths.
Nobody is clear on what has gone wrong. Suggestions for blame include the melting of sea ice or increased flow from Siberian rivers into the Arctic. Both would load fresh water into the surface ocean, making it less dense and so preventing it from sinking, which in turn would slow the flow of tropical water from the south. And either could be triggered by man-made climate change. Some climate models predict that global warming could lead to such a shutdown later this century.