Limited impact of Greenland meltwater on abruptness and reversibility of future Atlantic overturning changes

All climate models project that the Atlantic Meridional Overturning Circulation (AMOC) will weaken in the 21st century, but most models neglect increasing runoff from the Greenland ice sheet. Greenland meltwater is expected to exacerbate AMOC weakening, and omitting it increases the uncertainty in assessing the possibility of an abrupt AMOC collapse or tipping. Here, we test the abruptness and reversibility of AMOC changes under strong future global warming in a state-of-the-art climate model with and without high-end but physically plausible Greenland meltwater forcing. In this model, Greenland meltwater significantly exacerbates future AMOC weakening especially after 2100, but the AMOC changes until 2300 are neither abrupt nor irreversible on centennial timescales, even with added meltwater. While accounting for Greenland meltwater will increase the accuracy of climate projections, our results do not suggest a major role of Greenland meltwater for assessing the risk of future AMOC tipping.