The melting of the Greenland ice sheet is causing more extreme heat in Europe, contributing to the major heatwaves experienced there so far this year.
The surge of cold meltwater into the North Atlantic is altering ocean temperatures and shifting the jet stream to favour heatwaves in western Europe and the Mediterranean, a study undergoing peer review has found. As Greenland ice loss accelerates, Europe may suffer more frequent and intense heatwaves than climate models currently predict.
This newly discovered “atmospheric bridge” played a major role in the unprecedented heatwaves this summer, according to Marilena Oltmanns at the UK’s National Oceanography Centre, who is one of the study’s authors.
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“Europe heats up faster. This is because of the jet stream shift,” she says. “In future years… it will be even more extreme. In the future we will think this [year’s heatwave] was not a heatwave; this was nice.”
The steady rise in global temperature has increased heatwaves. But it’s still debated whether changes in prevailing weather patterns are also contributing.
In the past 30 years, high-pressure ridges – large areas of elevated air pressure that look like a ridge or upside-down U on weather maps – have been forming more frequently over Europe, the study finds, leading to sunny skies and extreme heat. These ridges are caused by waviness in the jet stream, the band of strong winds that circles the northern hemisphere. When the more or less straight-flowing jet stream meanders northward around western Europe, it allows warm air from the central Atlantic and Sahara desert to pour into the ridge that’s been created.
Years with extensive high-pressure ridges over Europe have resulted in heatwaves like the one that killed 70,000 people in 2003.
The researchers say the formation of the ridges can be traced back to Greenland through a cascade of climate events. In the summer before years of extensive ridging, an average of 81 billion tonnes more meltwater rushes off the ice sheet, they found. The cold meltwater lowers sea surface temperatures as it spreads through the North Atlantic in the autumn and winter. Its freshness inhibits mixing with saltier, warmer deep layers, further cooling the surface.
These pulses of meltwater cooling come on top of the “cold blob,” a long-term decline in ocean temperatures in the North Atlantic that some scientists blame on the weakening of the Atlantic Meridional Overturning Circulation (AMOC) system of currents. Together, they create a sharp temperature front between the cold waters and the warmer surface waters further south in the Atlantic.
As warm air masses rise to the south of the front and cold masses descend to the north of it, they begin to swirl and generate cyclones. This makes the jet stream wavier. It tends to meander southward of these cyclones, then back northward over western Europe, creating the persistent, high-pressure ridges and heatwaves there.
Most worryingly, climate models don’t fully capture this process, according to Oltmanns.
“This is a big problem,” she says. “It’s going to be even more intense in terms of heatwaves and droughts, in particular in the Mediterranean region, so the weather extremes are likely underestimated.”
A study in July found that the jet stream has shifted southward in the Atlantic in recent decades, similar to the pattern shown in the study. But it concluded that this was due to natural fluctuations in the climate and would eventually reverse.
Meltwater from Greenland could be forcing the jet stream to meander, according to John Methven at the University of Reading, UK, who was one of the authors of the July study. But the weakening of the AMOC or changes in atmospheric circulation over the North Atlantic could also be causing this shift.
“That’s the weak link as far as I’m concerned, the link between the cold blob and whatever’s melting in Greenland is not established, and there might be other things going on,” he says.
If North Atlantic cooling continues to affect the jet stream, it could cause not just heatwaves but also other extreme weather, according to Oltmanns. The research linked it to an unprecedented derecho, a stream of thunderstorms and strong winds, in the Mediterranean in 2022. Winds reached more than 60 metres per second, and fist-sized hail killed 12 people.
“We [will] have more droughts at some locations, flooding events at others, and the variability on top of this increases,” she says.
Research Square DOI: fre10.21203/rs.3.rs-10342381/v1
Facts Only
* Marilena Oltmanns is an author of a study undergoing peer review at the UK’s National Oceanography Centre.
* John Methven is an author of a July study from the University of Reading, UK.
* Greenland ice sheet meltwater enters the North Atlantic Ocean.
* Average meltwater increase of 81 billion tonnes occurs in the summer preceding years of extensive high-pressure ridges over Europe.
* High-pressure ridges over Europe are associated with sunny skies and extreme heat.
* The jet stream is a band of strong winds circling the northern hemisphere.
* A "cold blob" refers to a long-term decline in North Atlantic ocean temperatures.
* The Atlantic Meridional Overturning Circulation (AMOC) is a system of ocean currents.
* A heatwave in 2003 resulted in 70,000 deaths.
* A derecho in the Mediterranean in 2022 involved winds over 60 metres per second and killed 12 people.
* Western Europe and the Mediterranean are the primary geographic areas affected by these heatwaves.
Executive Summary
Accelerated melting of the Greenland ice sheet is linked to an increase in extreme heatwaves across western Europe and the Mediterranean. The mechanism involves a surge of cold meltwater into the North Atlantic, which lowers sea surface temperatures and interacts with the existing "cold blob" caused by a weakening Atlantic Meridional Overturning Circulation (AMOC). This temperature gradient disrupts the jet stream, causing it to meander and create high-pressure ridges that draw warm air from the Sahara and central Atlantic into Europe.
There is scientific debate regarding the primary drivers of these shifts. While some researchers argue that Greenland's meltwater is a forcing agent, others suggest these patterns may result from natural climate fluctuations or broader atmospheric circulation changes. Current climate models may not fully capture these specific "atmospheric bridge" processes, potentially leading to an underestimation of future droughts and heatwaves. This suggests a risk of increased weather variability, including both extreme heat and severe storm events like derechos.
Full Take
The strongest version of this narrative posits that a specific, newly identified feedback loop—the "atmospheric bridge"—explains why Europe is warming faster than global models predict. By linking cryogenic collapse in Greenland to meteorological extremes in the Mediterranean, the research provides a tangible mechanism for "non-linear" climate acceleration.
This is a news report on a preprint study, necessitating SKEPTICAL MODE. The narrative relies heavily on the tension between current climate models and new findings. While it presents a counter-perspective from the University of Reading, the framing emphasizes the "problem" of underestimated extremes. However, the piece avoids load-bearing manipulation; it acknowledges the peer-review status and explicitly presents the disagreement between authors regarding the "weak link" in the causal chain.
Patterns detected: none
The driving paradigm is one of systemic instability. It assumes that the climate is moving from a state of predictable fluctuation into a state of chaotic volatility where historical data no longer serves as a reliable guide. The implication for human agency is a transition from "mitigation" to "crisis management," as infrastructure designed for 20th-century norms becomes obsolete. The cost is borne by populations in the Mediterranean and Western Europe, while the benefit of this research is a more precise (albeit more alarming) risk assessment for urban planning and agriculture.
Bridge Questions:
1. How would the data change if the "cold blob" were found to be independent of Greenland's meltwater?
2. What specific variables are missing from current climate models that would allow them to capture this "atmospheric bridge"?
Counterstrike Scan:
A coordinated influence campaign would use this narrative to trigger immediate panic or policy shifts by presenting the "underestimated" nature of the models as a reason to abandon current strategies for emergency measures. The actual content does not match this; it maintains a measured tone and includes necessary scientific caveats.