AMOC Slowdown Accelerating
Studies point to a growing probability of shutdown
The Atlantic Meridional Overturning Circulation (AMOC), a major ocean current system that regulates climate across the Atlantic, is weakening — and faster than previously thought. A new study published in Nature Geoscience finds that current climate models underestimate the rate of decline because they overlook the impact of melting ice from Greenland and other sources. By accounting for this, researchers estimate the AMOC has slowed by nearly 5% per decade since 1950 (1).
This updated analysis contrasts with earlier studies, which warned of AMOC weakening but underestimated the speed of change. Most climate models used by the IPCC had projected a gradual decline, with little risk of collapse this century. The new findings suggest a different story:
“It is very likely (90–100% probability) that the AMOC will weaken faster than current models predict if ice melt is included.” (2)
This accelerated weakening dramatically raises the risk of an AMOC shutdown, which would have severe consequences: altering weather patterns, worsening droughts and floods, and cooling parts of Europe even as the rest of the planet warms. Previous studies suggested a shutdown by 2100 was possible but unlikely. This study suggests a far higher probability, in line with previous statements—it might be a coin toss.
Get Matthias Honegger’s stories in your inbox
Join Medium for free to get updates from this writer.
The message is clear: the risk of AMOC tipping into collapse is increasing, and the timeline may be shorter than previously anticipated.
While the consequences would be dramatic—plunging Northern Europe into a polar climate, drying out the Sahel, and probably causing other disruptions elsewhere—they would play out over the course of several decades. Nonetheless, it is urgent that we consider such possibilities and ask: What are the implications, including knock-on effects for which we may need to prepare?
(1) This is a translation of the study’s finding that the AMOC has slowed by 0.46 sverdrups per decade. While the term “sverdrups” is highly technical, the study essentially indicates a decline of approximately 5% of AMOC strength per decade since 1950. This number was derived from the improved data–model agreement in the study, which includes the effects of meltwater forcing.
(2) This comes directly from the Nature Geoscience paper, which states that it is “very likely” (a term defined as 90–100% probability in IPCC language) that the AMOC will weaken faster than the projections in CMIP6 models if meltwater forcing is taken into account.
