Model Shows Greenland Melt Weakens AMOC Gradually Without Tipping Point

Modeling research published in Science Advances finds that rapid melting of the Greenland ice sheet will weaken the Atlantic Meridional Overturning Circulation steadily but will not push the system past an irreversible tipping point. The study, led by Oliver Mehling at Utrecht University, used a state-of-the-art climate model to separate the effects of atmospheric warming from the influx of fresh meltwater.

Atmospheric warming alone reduces AMOC strength by 60 percent by 2300 in the simulation.

Adding increasing volumes of Greenland meltwater produces an additional 20 percent decline. The combined reduction reaches 80 percent, a level that could freeze crops in western Europe, cover the North Sea in ice, and disrupt tropical monsoon rains.

The model shows full recovery of the AMOC by about 2400 if atmospheric carbon dioxide concentrations begin declining by 1 percent per year starting in 2250.

Mehling stated that Greenland meltwater alone is not sufficient to push the AMOC across a tipping point and described the conventional view of an irreversible collapse as too simplistic. Louise Sime at the British Antarctic Survey noted that the AMOC appears strongly linearly dependent on cumulative CO2 emissions rather than exhibiting a sudden drop.

A prior study by René van Westen at the same university found irreversible collapse when meltwater was added at a constant rate, but the new work incorporates an increasing rate that matches observed conditions.

Jonathan Baker at the UK Met Office described the paper as an additional contribution to the evidence base rather than a resolution of the tipping-point question. The results remain model-dependent, as other simulations cross a tipping point under 21st-century emissions pathways.