Drivers of the extreme North Atlantic marine heatwave during 2023

This study analyzes the unprecedented marine heatwave in the North Atlantic during summer 2023, which recorded the highest sea surface temperature anomalies in the satellite era. Researchers investigate the underlying causes and drivers of this event, focusing on how a combination of weakened surface winds, anomalously shallow ocean mixed layers, and pre-existing ocean warming—exacerbated by climate change—contributed to the rapid development and persistence of the heatwave. The study places this event within a broader context of increasing ocean stratification and changing atmospheric-oceanic dynamics.

The researchers found that the 2023 marine heatwave was primarily driven by positive air-sea heat fluxes and a significantly shallower mixed layer depth, which allowed the ocean surface to warm more rapidly. Climate change has intensified these drivers by increasing ocean stratification and reducing mixed layer depth trends. The event had broad implications, including reinforcing extreme weather in Europe and disrupting marine ecosystems. The study underscores how climate change is not only increasing average ocean temperatures but also making extreme marine heat events more frequent and intense.