AMOC collapse may already be locked in, new study suggests
A new study argues that collapse of the Atlantic Meridional Overturning Circulation, the current system that keeps Northern Europe mild, may already be unavoidable even if warming stopped today.
Researchers led by Philip Holden of the UK-based Open University ran large ensembles of Earth system model simulations to estimate the odds that AMOC collapse is already “committed.” Depending on how much meltwater is assumed to be flowing off the Greenland ice sheet, they put the probability at 10 to 23 percent. Under a worst-case emissions scenario, that rises to 80 percent by 2100.
“There is a significant probability that we’re already committed to collapse, and we can’t change that even now,” Holden told New Scientist, which first reported the findings.
The AMOC carries warm, salty water north from the tropics, where it cools, sinks and flows back south. A collapse would cool Northern Europe sharply even as the rest of the planet keeps warming and would shift rainfall patterns and sea levels elsewhere. Greenland meltwater is central to the mechanism: enough fresh water dilutes the salty water that needs to sink for the circulation to keep running.
The paper is not yet peer-reviewed. It was posted to EarthArXiv on June 27 and was still under review when Trex, a climate-risk analytics firm Holden also works with, briefed financial clients on it.
The finding lands on ground Iceland has already staked out. In November 2025, the government designated a possible AMOC shutdown a national security threat, and in April its Climate Council pressed the environment minister to scale up emissions cuts, citing projections of roughly 50 percent weakening by the end of the century. A study putting a number on the odds that collapse is already unavoidable adds weight to that argument, even if it does not settle it.
The IPCC’s own assessment calls an abrupt collapse before 2100 “very unlikely,” though with only medium confidence. Where the truth lands, Greenland sits at the center of it, both as the main driver of a potential collapse and as one of the places likely to feel it first.
