The Last Glacial Maximum (LGM), that period of time 21,000 years ago when the earth was glaciated and significantly colder than today, provides a unique set of boundary conditions to test climate general circulation models. This proposal aims to use simulations of the LGM to determine if the Walker Circulation, a coupled atmosphere-ocean system in the tropical Pacific, was stronger or weaker at that time. The project will attempt to address several important questions including:
1) How important are changes in the hydrological cycle, sea surface temperature gradients, and exposure of the Sunda shelf in affecting past intensity of the Walker Circulation? 2) What is the impact of model bias in the interaction among these mechanisms? 3) Can the different reconstructions of past climate in the tropical Pacific be reconciled and used to constrain each of these mechanisms? 4) How well do state-of-the-art climate models simulate the response of the Walker circulation to the exposure of the Sunda shelf due to lower sea level during the LGM.
The models to be used in the study were also used to produce key paleoclimate simulations that will be discussed in the IPCC AR5 reports. Thus the evaluation of the performance of the different models will be very valuable to the climate research community.
