Slowdown of AMOC ocean current may be gradual and reversible
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- Oliver Mehling at Utrecht University led the modeling study, published in Science Advances, concluding that "Greenland meltwater alone is not sufficient to push the AMOC across a tipping point" and that the conventional picture of irreversible collapse is "too simplistic."
- The model projects atmospheric warming alone would weaken the AMOC by 60% by 2300, and adding increasing Greenland meltwater would reduce its strength by another 20% — an 80% drop that could freeze western European crops, ice over the North Sea and disrupt tropical monsoon rains.
- If atmospheric CO2 decreases by 1% per year starting in 2250, the AMOC would fully recover by approximately 2400, because the circulation is "strongly linearly dependent on cumulative CO2 emissions," according to outside commentator Louise Sime of the British Antarctic Survey.
- René van Westen, also at Utrecht University, previously found in a different model that massive Greenland melt would irreversibly collapse the AMOC — but his experiment added meltwater at a constant rate rather than simulating the real-world acceleration over time.
- Jonathan Baker of the UK Met Office cautioned that the new study is "another contribution to the evidence base, rather than one that settles the question of AMOC tipping point risk," noting that other models do cross the tipping point under 21st-century climate change.
- Greenland is currently losing 30 million tonnes of ice every hour, and Antarctic meltwater remains an uncertain additional factor that could either weaken or, depending on timing, help preserve the global salinity-driven circulation.
Why it matters: The finding reframes AMOC risk from a binary tipping-point threat into a linear, emissions-dependent decline — but the source explicitly states an 80% weakening still produces crop-killing cold in Europe and North Sea ice, and competing models still show irreversible collapse. For policymakers, this means AMOC disruption is a matter of cumulative emissions, not a single threshold — yet the debate over whether a true tipping point exists remains unresolved across models.
