What a weakening AMOC means for northern communities

Public anxiety over the Atlantic Meridional Overturning Circulation (AMOC) spiked again this year as headlines warned that the system could soon collapse and plunge northern Europe into an ice age. Scientists say those claims are exaggerated. The AMOC is showing signs of weakening, but research does not support the idea of an abrupt shutdown in the near future.

To help clarify what the science actually shows, Dr. Zhuomin (Jasmine) Chen, Senior Research Scientist and physical oceanographer at the Gulf of Maine Research Institute (GMRI), and Dr. Janet Duffy-Anderson, GMRI’s Chief Scientific Officer, provided the following expert explanations on the AMOC, what is known about its current state, and what changes could mean for communities that depend on the North Atlantic.

Below, the authors respond to common questions about the AMOC and its role in a changing climate.

What is the AMOC?

The Atlantic Meridional Overturning Circulation (AMOC) is a vast, three-dimensional system of ocean currents in the Atlantic Ocean that transports warm, salty water northward near the surface from the tip of southern Africa to the northern North Atlantic and returns colder, denser water southward at depth. This conveyor belt circulation plays a key role in regulating Earth’s climate by moving heat between the tropics and the poles. One of its best-known components, the Gulf Stream, helps keep northern Europe much milder than other regions at similar latitudes.

When the AMOC slows, it can alter weather patterns, influence sea level rise along the U.S. East Coast, change heat and carbon uptake in the ocean, and potentially contribute to deoxygenation and disruptions in marine ecosystems, impacting North Atlantic fish stocks. Scientists have observed signs of a gradual weakening in the AMOC, but there’s currently no evidence of an imminent collapse.

Why have some news outlets been reporting it will soon collapse and usher in a new ice age for London, Stockholm, and northern Europe?

Headlines warning of an AMOC collapse often arise from misinterpreting model results or from studies designed to test extreme, hypothetical scenarios. Some studies explore what could happen if greenhouse-gas emissions continue unchecked and Greenland’s ice melt sharply increases freshwater input into the North Atlantic. In theory, these extreme conditions could weaken the AMOC significantly or even shut it down completely. However, in many of these experiments, scientists are testing the limits of the system, and important factors such as heat or freshwater inputs are unrealistically large compared to current projections for Greenland ice melt, precipitation, and river runoff.

In reality, there is no evidence of an abrupt tipping point occurring today. The latest Intergovernmentental Panel on Climate Change (IPCC) reports conclude that the AMOC will likely weaken gradually over the 21st century, but that a complete collapse before 2100 is very unlikely.

What does the research actually say?

Observational records and model simulations indicate the AMOC has weakened by roughly 15 percent since the mid-20th century, likely linked to melting Greenland ice and increased freshwater input into the North Atlantic. This reduces the connection between the surface and deep ocean that drives the AMOC conveyor belt.

Most modern climate models project a continued, gradual weakening under high greenhouse-gas emission scenarios, but not a total shutdown. However, even a modest slowdown can still profoundly affect regional climate and marine ecosystems, altering weather patterns, fisheries productivity, and carbon uptake.

At GMRI, our modeling work helps downscale these cross-global changes to understand their implications for the Northeast U.S. Shelf and Gulf of Maine, which is already one of the fastest-warming ocean regions on Earth.

Can we stop or reverse this pending change?

We can’t flip a switch to restore the AMOC, but we can influence its long-term trajectory by reducing greenhouse-gas emissions. Reducing emissions slows ocean warming and polar ice melt, both major contributors to weakened circulation.
Every ton of carbon we avoid adds resilience to this system. Sustained global climate mitigation can reduce warming and freshwater input, helping stabilize ocean circulation and reduce the risk of crossing critical thresholds.

How can we prepare?

Preparation means building climate resilience at both global and local scales. For coastal communities, that includes anticipating sea-level rise, adapting fisheries management to shifting species, and improving climate-forecasting tools.

Research institutions like GMRI work closely with NOAA, universities, and local partners to turn complex climate-ocean science into information that helps decision-makers plan for the future. By understanding how regional oceans respond to global change, we can design solutions that protect both ecosystems and coastal livelihoods.

What are some of the real implications of the AMOC collapsing or changing? Why should we care?

Even without a full collapse, a weakened AMOC can reshape our world. Along the U.S. East Coast, it could raise regional sea levels by several inches. In Europe, it might modestly cool winters even as global temperatures rise. Changes in circulation can also shift nutrient and oxygen distributions, affecting plankton, fish, and entire marine food webs.

For scientists and coastal communities, the message is clear: ocean circulation changes slowly, but its impacts can cascade through climate, ecosystems, and economies dependent on predictable ocean conditions.

Will the Arctic region be hit harder or be more insulated from changes?

The Arctic will likely experience both amplified warming and complex circulation feedbacks. The Arctic is both a driver and a responder in this system. A weaker AMOC can mean less heat transported northward, but the Arctic is still warming nearly four times faster than the global average due to greenhouse-gas buildup and ice-albedo feedbacks.

Freshwater from melting sea ice and Greenland’s glaciers also feeds back into the AMOC, making the connection between Arctic change and Atlantic circulation a two-way street. Scientists are closely monitoring how these processes interact because they shape the future of both polar and mid-latitude climates.

How is GMRI researching and monitoring this situation? What is GMRI?

At GMRI, our physical oceanography modeling team, led by Dr. Zhuomin Chen, uses advanced regional ocean models (including regional MOM6 and ROMS coupled with biogeochemistry) dynamically downscaled from global Earth System Models under multiple climate scenarios. These simulations help us understand how shifts in the Gulf Stream Warm-Core Rings and the AMOC influence temperature, circulation, and marine habitat shifts in the Gulf of Maine and the broader Northwest Atlantic.

We work hand-in-hand with NOAA, academic partners, and local stakeholders to track warming trends, assess ecosystem impacts, and translate this science into practical guidance for climate-ready fisheries and resilient coastal economies.