Marine heatwaves are becoming far more common and intense

Researchers at the University of New South Wales are reporting that warming ocean temperatures have caused marine heatwaves to increase in number, duration, and intensity over the past century.

The study has revealed that, between 1925 and 2016, the frequency of marine heatwaves rose by an average of 34 percent while the length of the events jumped by 17 percent. Overall, the researchers found a 54 percent increase in the number of marine heatwave days every year.

“Our research also found that from 1982 there was a noticeable acceleration of the trend in marine heatwaves,” said lead author Dr. Eric Oliver.

“While some of us may enjoy the warmer waters when we go swimming, these heatwaves have significant impacts on ecosystems, biodiversity, fisheries, tourism and aquaculture. There are often profound economic consequences that go hand in hand with these events.”

As a result of a marine heatwave in 2001, ecosystems in Western Australia permanently transformed from being dominated by kelp to being dominated by seaweed. A marine heatwave in the Gulf of Mexico in 2012 led to an abundance of lobsters that drove prices down and stifled profits.

When warm ocean temperatures persisted in the North Pacific from 2014 to 2016, large amounts of marine mammals were stranded from harmful algal blooms along coastlines. This particular heatwave was also responsible for changing large-scale weather patterns in the Pacific Northwest.

The research team examined the long-term trend of marine heatwaves by combining satellite measurements with data that had been obtained from ships and land stations over the course of a century. By removing the influences of natural variability, they were able to identify the underlying trend.

“There was a clear relationship between the rise in global average sea-surface temperatures and the increase in marine heatwaves, much the same as we see increases in extreme heat events related to the increase in global average temperatures,” said co-author Professor Neil Holbrook.

“With more than 90% of the heat from human caused global warming going into our oceans, it is likely marine heatwaves will continue to increase. The next key stage for our research is to quantify exactly how much they may change.”

“The results of these projections are likely to have significant implications for how our environment and economies adapt to this changing world.”

The study is published in Nature Communications.

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By Chrissy Sexton, Earth.com Staff Writer

Image Credit: Daniel Hjalmarsson/Unsplash.com