Will the North Atlantic Ocean thermohaline circulation weaken during the 21st century?

The North Atlantic Ocean thermohaline circulation is examined in three expe riments using the Climate System Model. They are a control integration for 1870 conditions, and particular emission scenarios for the 20th and 21st ce nturies. It is found that the strength of the thermohaline circulation does not change significantly over the 21st century. This is in contrast to sev eral other recent studies, which have projected a significant reduction ove r the 21st century. The reason for the difference is that the Northwest Atl antic becomes warmer and more saline in the Climate System Model. These cha nges combine to make little change to the surface ocean density in this reg ion, and hence to the rate of deep water formation. Caveats about the Clima te System Model and other coupled-climate models are then discussed.