Comer Fellowships in Abrupt Climate Change:
Accomplishments (2004-2006) and Proposed Work

 


Our Team

David Battisti, University of Washington

Cecilia Bitz, University of Washington

Joe Barsugli, University of Colorado

Susan Bates, University of Washington

Camille Li, University of Washington


 

Overview of the Project

 

Overview: The Dansgaard-Oeschger ( D/O ) events in the Greenland Ice Core records demonstrate that abrupt climate change can occur even though there is no evidence for any equally abrupt astronomical or geological forcing mechanism. This leads us and many others to conclude that D/O events represent an instability of the climate system itself that occurs during glacial times. Existing theories focus on the instability of the ocean circulation as a "driver" of the abrupt changes. However, the stability of the climate system is determined by the interaction of all the components of the climate - the ocean, the atmosphere, and the cryosphere-and we believe that a satisfactory explanation of the D/O events and their global expression will only be reached by considering the stability properties of the entire climate system.

The Comer Fellowships that were awarded to Battisti have been used to begin a systematic investigation of how the various components of the climate system interact to produce abrupt climate change. The work that has been completed so far has focused on the central role of wintertime North Atlantic sea-ice as the proximate cause for both the Greenland record and many of the far-flung paleo-proxies that show D/O -like behavior. While the importance of ocean heat flux (partly determined by the thermohaline circulation) has been postulated for some time, in the past year (using the Comer Fellowships) we have uncovered evidence that the atmosphere itself may possesses fundamental instabilities that are manifest during certain phases of the glacial cycle.

How the ocean circulation modes and the sea-ice dynamics couple to the atmospheric circulation in the northern Atlantic is presently being investigated and will be completed with a two-year extension of the Comer Fellowships. In addition, this framework leads us to the hypothesis - also to be investigated in the next two years -- that the Tropical climate system, along with the size of the Laurentide Ice Sheet, may be an important regulator of the North Atlantic climate system. When conditions are correct, slow Tropical changes may push the North Atlantic climate system over a stability threshold, and the response of the Tropics to the North Atlantic changes may help lock these changes in place.