Marine heatwaves are getting hotter, longer and more frequent

"There was a clear relationship between the rise in global average sea-surface temperatures and the increase in marine heatwaves," researcher Neil Holbrook said.
By Brooks Hays  |  April 10, 2018 at 3:36 PM
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April 10 (UPI) -- Heatwaves are most frequently thought of as affecting land, but the prolonged periods of extremely high temperatures are impacting the ocean, too.

New research suggests marine heatwaves are getting longer and hotter -- and are happening more frequently.

When scientists in Australia and Canada analyzed marine heatwave patterns between 1925 and 2016, they found a 34 percent increase in the frequency of heatwaves across the world's oceans. They also found modern heatwaves are 17 percent longer than a century ago.

"Our research also found that from 1982 there was a noticeable acceleration of the trend in marine heatwaves," Eric Oliver, a researcher at Dalhousie University in Canada, said in a news release. "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."

In 2011, prolonged heat transformed an ecosystem along the Australian coast to one dominated by kelp to one dominated by seaweed. Even after temperatures normalized, the shift in vegetation remained.

Unusually warm water in the Pacific between 2014 and 2016 led to mass stranding and deaths of marine mammals along the coasts of Northern California and the Pacific Northwest. Animals were found in places they're rarely seen, fisheries were closed and harmful algae blooms persisted for weeks at a time.

In 2016, heatwaves led to a record coral bleaching event on the Great Barrier Reef.

Scientists used a combination of satellite data and temperature measurements taken from research vessels and various land-based measuring stations to plot marine heatwave events over the last several decades. The researchers used statistical analysis to account for the influence of climate patterns like El Nino Southern Oscillation, the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation.

Scientists published their findings this week in the journal Nature Communications.

"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 Neil Holbrook, a researcher at the University of Tasmania.

Scientists expect 90 percent of the increase in heat from global warming to be absorbed by the planet's oceans. As such, marine heatwaves are likely to continue, significantly altering marine ecosystems.

"The next key stage for our research is to quantify exactly how much they may change," Holbrook said. "The results of these projections are likely to have significant implications for how our environment and economies adapt to this changing world."

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