Greenland Meltwater Driving European Heatwaves: Study
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- Researchers at the UK's National Oceanography Centre, led by Marilena Oltmanns, identified an "atmospheric bridge" in which Greenland meltwater cools North Atlantic surface temperatures and forces the jet stream to meander, creating persistent high-pressure ridges over Europe
- In summers preceding years of extensive European ridging, an average of 81 billion tonnes more meltwater than usual rushed off the Greenland ice sheet, according to the study still undergoing peer review
- High-pressure ridges have formed more frequently over Europe over the past 30 years, with the pattern linked to deadly heatwaves including the 2003 event that killed 70,000 people
- Oltmanns warned that climate models do not fully capture the meltwater-jet stream mechanism, meaning "weather extremes are likely underestimated," particularly for droughts in the Mediterranean
- The same mechanism was linked to the unprecedented 2022 Mediterranean derecho, where winds exceeded 60 metres per second and fist-sized hail killed 12 people
- John Methven at the University of Reading called the cold blob-to-Greenland connection the "weak link," noting that AMOC weakening or natural atmospheric fluctuations could equally explain the jet stream shift
Why it matters: If Greenland meltwater is indeed driving the jet-stream pattern, European heat and drought projections may be too optimistic — Oltmanns says this year's heatwaves will eventually be seen as mild. Mediterranean agriculture, water systems, and public health planning face greater risk than models currently forecast, while a competing July study still attributes the shift to natural variability that may reverse.
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