Direct observations of ocean currents over the past two decades and numerical model simulations have revealed a remarkable stability of the North Atlantic overturning strength.
However, most climate models predict a 20 per cent weakening of the current by the end of this century.
Scientists note that rising atmospheric temperature related to the build-up of greenhouse gases might at least temporarily counteract the cooling effect on Europe if North Atlantic underwater currents slow. However, the western edge of Europe, particularly the United Kingdom and Scandinavia, could cool substantially nonetheless.
Some 20 institutes from nine European countries, coordinated by the Institution of Oceanography at the University of Hamburg, are now cooperating in extensive studies of the THC through project THOR, for "ThermoHaline Overturning at Risk?"
Another pair of projects, RAPID and RAPID-WATCH, involves researchers from the UK, Norway, the Netherlands and the United States in the collection of annual readings from 19 monitoring devices across the Atlantic at 26.5 degrees North. Statistically relevant data will be available after a decade of readings in 2014.
Large-scale salinity changes might also be in store for the Baltic Sea, one of the largest brackish-water ecosystems in the world, says Thomas Neumann, at Germany's Leibnitz-Institute for Baltic Sea Research. Its salinity is controlled by the amount of freshwater flowing off the surrounding land, as well as how much water is exchanged with the North Sea.
The circulation pattern where the two seas meet prevents mixing of the Baltic's surface and deep water, creating conditions of low or even no oxygen in the lower layer. Life in this zone has become highly adapted to the resulting extremes in salinity and oxygen conditions.
Within the next century, warming and other
|Contact: Terry Collins|
Flanders Marine Institute (VLIZ)