The North Atlantic 'Cold Blob': A Signal of AMOC Weakening and What It Means for Europe

A 2025 study led by Penn State University found that the cold blob is driven by a combination of reduced ocean heat transport and colder, drier atmospheric conditions, with each factor contributing about equally . A 2026 study in Geophysical Research Letters reinforced this link using direct observational data . The AMOC is now thought to be at its weakest in at least a millennium, and multiple studies warn it may be approaching a tipping point toward collapse .

Did the Cold Blob Drive Europe's 2019 Heat Dome?

No — there is no direct causal link between the cold blob or AMOC weakening and the record-shattering European heatwaves of June and July 2019.

The 2019 heat domes were driven by distinct meteorological mechanisms. The June heatwave was triggered by a persistent planetary-scale Rossby wave (a giant meander in the jet stream) and a subtropical ridge that pulled a Saharan air mass northward into Europe . The July heatwave was caused by a massive area of high pressure called an "omega block" that trapped hot air over the continent . Land-surface feedbacks amplified its intensity .

France's all-time record of 45.9°C was recorded on June 28, 2019 . The July heatwave set new national records in Belgium (41.8°C), the Netherlands (40.7°C), Luxembourg (40.8°C), and the UK . The World Weather Attribution group found that climate change made the June 2019 heatwave about 4°C hotter than it would have been in a pre-industrial climate .

The bottom line: the 2019 heatwaves were driven by atmospheric blocking patterns and anthropogenic warming — not by the cold blob or AMOC weakening.

The Escalating Risk of an AMOC Shutdown

Scientific assessments of the risk of an AMOC shutdown have shifted dramatically. A 2025 high-resolution modeling study found that the AMOC is no longer a "low-likelihood" event and that models showing the most extreme slowdowns are the most accurate . A 2026 Yale E360 report quotes oceanographers saying the risk has escalated to roughly a 50/50 chance of collapse within our lifetimes . A 2023 Nature Communications study estimated a collapse window of 2037–2109 (with 95% confidence) .

However, it's important to note that the IPCC's AR6 assessment still says a 21st-century collapse is "very unlikely" (medium confidence), though this assessment predates many of the newer studies . The scientific consensus is now widely described as "significantly more likely than previously thought" .

What an AMOC Shutdown Would Mean

If the AMOC were to shut down, the consequences would be severe and well-documented in climate models:

• Harsher European winters: A shutdown would cut the ocean's northward heat supply, causing severe winter cooling (up to 4°C or more) across northern Europe, even as the rest of the planet continues to warm .
• Droughts in South Asia and parts of Africa: The tropical rainfall belt (the Intertropical Convergence Zone, or ITCZ) would shift southward, disrupting the African and Asian monsoons on which millions of people depend for agriculture .
• Sea level rise around the North Atlantic: Reduced ocean circulation would cause water to pile up along the North American and European coasts, significantly amplifying local sea level rise .

The UK Met Office states these impacts are "robust and seen in many models" , and a 2024 NIH review confirms that AMOC shutdown consistently produces these effects across every major climate model .