Melting Icesheets May Be Weakenening Meridional Overturning Circulation
06.11.2006 - Other
Measurements from a network of monitors stretching across the Atlantic Ocean could offer an early warning of "sudden climate change", scientists have said. The first set of results were presented at a climate conference on "Rapid Climate Change" in Birmingham (UK). These results are confirming a weakening of the Meridional Overturning Circulation, although not as important as previously thought.
In the framework of the RAPID Programme, Scientists have positionned an array of 19 "moorings" at 26.5 degrees north in the Atlantic Ocean, giving them an insight to the Meridional Overturning Circulation (MOC) that acts as the Earth's "heat pump", distributing heat via the ocean from the equator to northern regions. Each mooring consists of a wire up to 5,000m long that stretches from the sea floor to about 15m below the surface and measure temperature, conductivity, pressure, and current speed and direction. By the time it reaches the northern latitudes around Greenland and Iceland, the water has cooled so much that it sinks towards the ocean's floor and heads south again, a process known as "overturning".
Professor Harry Bryden, from the UK's National Oceanography Centre, was the lead author on a paper published in the journal Nature last year suggesting that the overturning circulation had declined by 30% over the past 50 years (possibly as a result of melting ice sheets making Arctic region water less salty and therefore less dense and so less likely to sink to the ocean floor). That figure was based on a series of data snapshots. Using the first year's continuous data from the array, the researchers have adjusted their calculations.
According to the BBC's report Professor Bryden observed "we concluded that there was some evidence of a small decrease but not as big as we reported in the Nature paper last year. But we have had a decrease ... in the order of 10% of the overturning circulation in the past 25 years."
