Science Daily: The Climate Changes, Get Used To It

1 05 2007

Climate has cycles, we know that much.  Why should this warming period be any different than previous ones?

Our records reflect details of the climatic evolution in the Atlantic region since the end of the last Ice Age to the present day. We would have liked to compare our results to similar data sets from other parts of the South Atlantic, but no other records provide the same degree of resolution, says Professor Björck. After the end of the last Glacial both Hemispheres became warmer as a result of melting ice sheets, but during the last 9000 years we can identify a persistent “seesaw” pattern. When the South Atlantic was warm it was cold in the North Atlantic and vice versa.

This is most certainly related to large-scale ocean circulation in the Atlantic Ocean. The main current system – “the Great Ocean Conveyor” – is driven by sinking of dense, relatively cold and salty water in the northern North Atlantic. This results in southward-flowing deep-water that is replaced by warm surface water brought to high northern latitudes from the tropics and ultimately from the South Atlantic, says Svante Björck, and continues:

The deep-water formation in the north is dependent on cooling of surface water with a high salt content. If sufficiently large amounts of fresh water are supplied to the North Atlantic, such as from melting ice-sheets or major increases in precipitation, the deep-water formation, and hence the transport of warm surface water from the south, may cease or at least decrease substantially.

This is known to have happened repeatedly during the present Interglacial (the warm period since the last Ice Age). Minor disturbances have taken place in recent time, such as the Great Salt Anomaly in the 1970s, which seriously affected the cod population around the Faroe Islands. Our results from Nightingale Island in the Tristan da Cunha island group, between South Africa and Argentina, for the first time give evidence of warming of the South Atlantic associated with cooling in the north. This is a major breakthrough in palaeoclimate research.

h/t- HotAir 

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