Thinning surface layer of ocean leaves waters more susceptible to extreme warming events
When thick, the surface layer of the ocean acts as a buffer to extreme marine heating—but a new study from CU Boulder shows this “mixed layer” is becoming shallower each year. The thinner it becomes, the easier it is to warm. The new work could explain recent extreme marine heatwaves, and point at a future of more frequent and destructive ocean warming events as global temperatures continue to climb.
“Marine heatwaves will be more intense and happen more often in the future,” said Dillon Amaya, a CIRES Visiting Fellow and lead author on the study out this week in the Bulletin of the American Meteorological Society’s Explaining Extreme Events. “And we are now understanding the mechanics of why. When the mixed layer is thin, it takes less heat to warm the ocean more.”
The mixed layer—the water in which temperature remains consistent—blankets the top 20-200 meters of the ocean. Its thickness is responsible for heat events: the thicker it is, the more the layer can act as a buffer to shield the waters below from incoming hot air. But as this armour thins, the mixed layer becomes more susceptible to rapid swings in temperature.
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