Emerging links between Greenland ice melt, Euro-Mediterranean heat extremes, and destructive convective storms

Juan Jesús González-Alemán , Marilena Oltmanns, Sergi Gonzalez-Herrero, Markus G. Donat, Frederic Vitart, Franscisco Doblas Reyes, David Barriopedro, Jacopo Riboldi, Carlos Calvo-Sancho, Bernat Jiménez-Esteve, Pep Cos, Michael Wehner

Greenland ice loss is accelerating, but its consequences beyond sea-level rise remain poorly understood. At the same time, the Euro-Mediterranean region is facing unprecedented summer climate extremes where the underlying mechanisms have been long debated. Here we present the first evidence of a far-reaching cascading mechanism by which Greenland ice sheet melting acts as a major forcing of hemispheric-scale, spring-summer atmospheric circulation shifts with potential high-impact effects. This has already exacerbated record-breaking and catastrophic western Euro-Mediterranean climate events, and has taken part in its accelerated warming trend relative to the global mean. Using reanalysis data, a high-resolution climate model ensemble, and process-based diagnostics, we demonstrate that these processes have contributed to recent European atmospheric heatwaves with severe socioeconomic and human impacts, marine heatwaves causing mass mortality events, and extreme convective storms such as the historic Mediterranean derecho that led to serious destruction and loss of human lives. These links situate the mechanism within the broader Earth system and points out anthropogenic climate change as a likely forcing, suggesting that cascading impacts will intensify as ice loss accelerates. We also find that CMIP6 models cannot simulate the cascading mechanism, most likely because of their inability to simulate localised freshwater influx correctly, thus indicating that current projections of future climate may be underestimating these impacts. Our findings thus point out Greenland melting as a previously unreported major driver of spring-summer large-scale circulation changes, with potential for a systemic amplification of long-range regional climate hazards. These hazards include confirmed profound socioeconomic, human and ecological consequences with unforeseeable future effects. Thus, incorporating these processes is essential for forecasts systems, Earth system models, and long-term projections, posing a significant gap in our ability to project future risk and representing a major step towards effective early-warning and mitigation strategies.