Ocean heat waves remake Pacific and Caribbean habitats

Enlarge / Although these corals are colored, they've been bleached, in that they have lost their photosynthetic symbiotes. (credit: ARC Centre of Excellence for Coral Reef Studies / Gergely Torda)

Climate change tends to deal in averages. We measure its progress using the global mean temperature, and we use climate models to project what that value will be in the future. But those average changes don't always capture what future climate change will be like. While you can raise an average by increasing every day's temperature by a tiny amount, it's also possible to raise an average by throwing in an occasional extreme event. Heat waves and extreme storms have indicated that nature seems to be going for the latter option.

A new paper shows that this kind of climate change isn't just affecting the sorts of weather we typically experience; it's happening in the oceans as well. The study shows that, over the course of less than a century, the frequency of oceanic heat waves went up by more than 50 percent. The study looked into the effects these events are having on ecosystems, and it showed that we're pushing species toward the poles without affecting all of them equally.

Heating the ocean's waves

When the subject is the atmosphere, the common practice is to track the frequency and extent of heat waves and even to determine if they have been influenced by climate change. By contrast, there was no widely accepted definition of when warming waters constituted a heat wave until 2016. That's in part because of the differences in the driving process and scale. Localized ocean heat waves can be driven by a corresponding heat wave in the atmosphere, while El Nino events are driven by large-scale current patterns that influence most of the Pacific.

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