New climate modeling indicates that the Atlantic Meridional Overturning Circulation may weaken steadily due to Greenland meltwater but could recover if atmospheric carbon dioxide levels decline.
The Atlantic Meridional Overturning Circulation brings warm tropical water into the North Atlantic, where it cools, sinks and flows south. Fresh meltwater from Greenland is mixing with this water and slowing the process.
Modeling by Oliver Mehling at Utrecht University and colleagues shows atmospheric warming alone could reduce AMOC strength by 60 percent by 2300. Adding increasing Greenland meltwater would cut it by a further 20 percent.
If carbon dioxide levels fall by 1 percent annually from 2250, the circulation would recover fully by around 2400. Mehling stated that Greenland meltwater alone is not sufficient to push the AMOC across a tipping point.
Louise Sime of the British Antarctic Survey noted that the AMOC appears strongly dependent on cumulative CO2 emissions rather than crossing an irreversible threshold. Other models have produced different results, leaving the risk of a tipping point unresolved.