North Atlantic Marine Heatwaves Growing Increasingly Frequent, Intense

Nature, 4 June 2025

The North Atlantic Ocean experienced an unprecedented marine heatwave in summer 2023, driven by unusually weak winds which slowed heat redistribution and rapidly warmed the ocean’s surface. In a single summer, this heatwave warmed North Atlantic waters at a speed equivalent to two decades of typical regional warming. Record-breaking low wind speeds resulted in a shallow upper ocean layer rapidly absorbing solar heat, but unable to properly mix with cooler waters below. The heatwave intensified extreme weather, coral bleaching, and hurricanes such as Idalia, with significant damage across parts of the southeastern United States. Long-term warming reduces the density of surface waters, further inhibiting vertical mixing and increasing the susceptibility of thin surface waters to rapid temperature spikes, with costly consequences for fisheries and weather stability.

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