The modern and glacial overturning circulation in the Atlantic ocean in PMIP coupled model simulations

Model results differ widely. The AMOC slows down considerably (by 20-40%) during the LGM as compared to the modern climate in four models, there is a slight reduction in one model and four models show a substantial increase in AMOC strength (by 10-40%).

It is found that a major controlling factor for the AMOC response is the density contrast between Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW) at their source regions. Changes in the density contrast are determined by the opposing effects of changes in temperature and salinity, with more saline AABW as compared to NADW consistently found in all models and less cooling of AABW in all models but one.