Geophysikalisches Kolloquium: Transient Simulation of Deglacial Climate Evolution in CCSM3: from the Last Glacial Maximum to Bølling-Allerød Warming

This is a preliminary report on our on-going effort towards a transient simulation of the climate evolution of the last 21,000 years.
We present the first synchronously coupled atmosphere-ocean general circulation model (CCSM3) simulation of the transient evolution of global climate from the Last Glacial Maximum 21,000 years ago to the abrupt Bølling-Allerød (BA) warming 14,500 years ago. Our model reproduces the major features of the deglaciation evolution, including the magnitude of the climate response, suggesting good agreement between observed and model climate sensitivity. The model simulates the abrupt BA warming in the Northern Hemisphere as a transient response of the Atlantic meridional overturning circulation (AMOC) to the termination of freshwater discharge associated with Heinrich event 1, but only if this discharge is terminated several hundreds of years prior to the BA. Three effects contribute to this large magnitude of BA warming: the warming from ongoing CO2 rise, the AMOC recovery, and an AMOC overshoot. This response is in contrast to the mechanism involving nonlinear bifurcation of multiple equilibria in the AMOC as simulated  previously in climate models of intermediate complexity.

Date

08.01.2009

Time

15:15 h

Place

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

Speaker

Zhengyu Liu, Center for Climatic Research, Univ. Wisconsin-Madison, U.S.A.


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