May 15, 2007: Recent changes in the Arctic Hydrosphere: Implications for the Global Ocean Circulation

Peter Schlosser, Columbia University, New York; Lamont-Doherty Earth Observatory


Recent studies have revealed large and rapid changes in the Arctic system including its hydrosphere. Changes in the Arctic Ocean circulation became apparent in the mid to late 1980’s and early 1990’s, just at a time when the community tried to obtain the first detailed picture of the water mass structure and circulation in this remote region of the world ocean. Once basin-scale observations were available it turned out that the initially isolated observations of shifting water mass properties or circulation branches were part of a pan-Arctic pattern of change that includes not only the ocean, but the entire Arctic hydrosphere, as well as virtually all other components of the Arctic system.

The changes in the Arctic Ocean are not isolated features of a remote ocean basin. Significant changes in water mass properties have been observed in the Nordic seas and the North Atlantic. They raise the question of a possible slowdown of the Meridional Overturning Circulation in the Atlantic Ocean (the headwaters of the ‘Great Ocean Conveyor Belt’). Such changes are not unexpected and have been predicted by numerical models. In fact, simulations of the future MOC using coupled models with greenhouse gas forcing project even stronger changes in the decades and centuries ahead.

This presentation will review the observed changes in the Arctic hydrosphere with emphasis on their link to lower latitudes. A key question for the future will be if a slowdown of the MOC in a warmer world would lead to a cooling of the surface ocean and the atmosphere in the northern hemisphere.