Shutdown of Atlantic Meridional Overturning Circulation Induced by Precession

The weakening or shutdown of Atlantic Meridional Overturning Circulation (AMOC) likely played a significant role in the glacial inception during the past million years. Previous modeling studies have shown that orbital forcing could have been triggered multiple AMOC weakening or shutdown, but it is still unclear which orbital parameter is the most essential trigger. In this study, we performed multiple long simulations with a fully coupled atmosphere-ocean general circulation model, CESM1.2.2, to investigate the influence precession on AMOC. It is found that precession is able to trigger a shutdown of AMOC. However, this happens only when the eccentricity is high and the atmospheric CO₂ concentration is relatively low. The growth and expansion of Arctic sea ice is responsible for the shutdown. Therefore, the results may advance our understanding of the mechanisms driving the glacial-interglacial cycles of the Quaternary Period, and may be related to the mid-Pleistocene transition.