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

In the vast, warming ocean, there is one notable exception: a patch of water south of Greenland that has been getting colder. Known as the cold blob or the North Atlantic warming hole, this anomaly has puzzled scientists for decades. New research has strengthened the link between this cooling patch and a major ocean current system that is showing signs of slowing — a development with potentially far-reaching consequences for Europe and beyond.

What is the 'Cold Blob'?

The cold blob is a region in the subpolar North Atlantic that has cooled by nearly 1°C since 1900, even as the rest of the global ocean has warmed . It is widely described as the only place on Earth that has consistently gotten colder over recent decades .

The Connection to the AMOC

The Atlantic Meridional Overturning Circulation (AMOC) is a system of ocean currents that acts like a giant conveyor belt, transporting warm tropical water northward. A growing body of evidence points to the cold blob as a direct surface signature of a slowing AMOC . As the AMOC weakens, less heat reaches the subpolar North Atlantic, creating a local cooling deficit.

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 .