Shoaled glacial Atlantic Ocean Circulation despite vigorous tidal Dissipation: Vertical Stratification matters

During the Last Glacial Maximum (LGM), tidal dissipation was about three times higher than today, which could have led to a considerable increase in vertical mixing. This would enhance the glacial Atlantic Meridional Overturning Circulation (AMOC), contradicting the shoaled AMOC as indicated by paleo proxies. Here, we conduct ocean model simulations to investigate the impact of background climate conditions and tidal mixing on the AMOC during LGM. Our results show that the shoaled glacial AMOC is mainly due to strong glacial ocean stratification and enhanced glacial Antarctic Bottom Water (AABW), irrespective of enhanced tidal dissipation. Enhanced tides only play an important role if they are applied to a present background climate with relatively weak ocean stratification. Given the critical role of AMOC in (de-)glacial climate evolution, our results highlight the complex interactions of ocean stratification and tidal dissipation that have been neglected so far.