In warming seas, marine heatwaves are getting worse

IN a warming world, it’s not unusual for a place to break temperature records at the hottest time of the year. But this year, the world's oceans have done it twice — four full months apart.

In places like the Gulf of Mexico off the coast of Florida, waters are running as hot as 33C. Experts are worried: corals have been bleaching for weeks, and the North Atlantic usually heats up until the end of August.

It’s a series of marine heatwaves that are devastating ecosystems and unsettling fishing communities.

Oceans around the world are hotter than ever, and coral reefs are bleaching more and more often.

Like the heatwaves that hit our cities, marine heatwaves see temperatures stay high for weeks or months on end.

These events have the potential to completely upend marine ecosystems. Every species has a preferred temperature, and when the heat is too much to bear, mobile species leave in search of cooler waters, while neighbours from hotter areas move in.

This game of musical chairs disrupts food chains, often leaving fishers empty-handed.

Some species, like corals, can’t move at all. Instead they bleach, turning white as they evacuate algae that they depend on to survive. Reefs have recovered from bleaching in the past, given enough time — but with many reefs still early in the recovery process from bleaching events just a few years ago, experts are concerned.

When the current heatwaves will end is anyone's guess. But with global warming fuelling warming trends in every major ocean things are likely to worsen until well after greenhouse gas emissions end.

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James Goldie is the Data and Digital Storytelling Lead and Suzannah Lyons is the Senior Commissioning Editor at 360info