The summer of 2023 was extraordinary for the world’s oceans. Across the North Atlantic and Mediterranean, marine heatwaves (MHWs) reached record-breaking intensity, persistence, and spatial extent, contributing to the highest global surface air and sea surface temperatures on record. A recent study unpacks the large-scale atmospheric processes that fueled these extremes, highlighting the interplay between long-term anthropogenic warming and short-term climate variability.
By combining NOAA OISST v2.1 and ERA5 reanalysis datasets with a multivariate technique—regularized generalized canonical correlation analysis (RGCCA)—the authors provide a novel lens on atmosphere–ocean coupling. They identify clear regional contrasts: the Subtropical Atlantic sustained the longest MHW, the Northwest Atlantic experienced the most intense warming, and the Western Mediterranean faced the highest frequency of events.
Two well-known climate modes, the North Atlantic Oscillation (NAO) and the Scandinavian Pattern (SCAN), emerged as key modulators. Their compound phases created persistent atmospheric ridges, weakened the Azores High, suppressed winds, and altered air–sea heat fluxes—all conditions favoring surface warming and stratification. Remarkably, the leading RGCCA mode explained over 40% of SST anomaly variability, with strong correlations (r = 0.81–0.94) between atmospheric configurations and MHW evolution.
This integrative approach underscores the novelty of viewing marine heatwaves as products of interacting teleconnections, rather than isolated drivers. Beyond advancing scientific understanding, the study demonstrates the value of including atmospheric indicators in early warning systems and adaptation planning, essential tools in an era of escalating marine heat stress.
Behr, L., Xoplaki, E., Luther, N., Josey, S., and Luterbacher, J., 2025: Atmospheric patterns drive marine heatwaves in the North Atlantic and Mediterranean Sea during summer 2023. Env. Res. Lett., 20 104020, DOI 10.1088/1748-9326/ae0055
