Transient Simulation of Last Deglaciation Climate Evolution with a New Mechanism for Bølling-Allerød Warming

We conducted the first synchronously coupled atmosphere-ocean general circulation model simulation from the Last Glacial Maximum to Bølling-Allerød (BA) warming. Our model reproduces several major features of the deglaciation climate evolution, suggesting a good agreement in climate sensitivity between the model and observation. In particular, our model simulates the abrupt BA warming as a transient response of the Atlantic meridional overturning circulation (AMOC) to a sudden termination of freshwater discharge in the North Atlantic prior to BA. In contrast to previous mechanisms that invoke the AMOC multiple equilibrium and Southern Hemisphere climate forcing, we propose that the BA transition is caused by the superposition of the climatic response to the transient CO2 forcing, the AMOC recovery from the Heinrich event 1, and an AMOC overshoot. A brief discussion will also be presented on the deglaciation evolution after BA.