Study finds remote climate ‘events’ can drive marine heatwaves

Impact of 2011 marine heatwave in Kalbarri

A new international study involving The University of Western Australia has found marine heatwaves can be influenced by climate ‘events’ that take place thousands of kilometres away.

The research, published today in Nature Communications, is the first global assessment of the major drivers of marine heatwaves, which can have devastating effects on ocean ecosystems, fisheries and tourism.

Co-author Dr Thomas Wernberg, from UWA’s Oceans Institute and School of Biological Sciences, said while the frequency of marine heatwave days had increased across the globe by more than 50 per cent over the past century, the ability to predict them had been limited.

“Despite their serious consequences, our understanding of their drivers has been largely based on isolated case studies until now,” Dr Wernberg said.

The new study looked at marine heatwaves and their drivers in 22 regions across four oceans and climate zones, based on published papers since 1950.

Researchers also examined relationships between marine heatwaves and nine known climate oscillations or patterns such as El Niño, and used satellite records to estimate the intensities, durations and extents of the heatwaves.

“We found marine heatwaves may be influenced by several factors in combination, and from processes that might be local, or remote, to the events,” Dr Wernberg said.

The El Niño – Southern Oscillation, for example, was found to not only influence marine heatwaves in the Pacific Ocean but also the Indian Ocean and played a strong role in the extreme marine heatwave known as the Ningaloo Niño in Western Australia in 2011.

Other climate phenomena such as the Indian Ocean Dipole and North Atlantic Oscillation were also found to influence the likelihood of marine heatwaves occurring.

The global assessment also revealed some surprising extreme marine heatwave records.

The most intense heatwave the scientists found was in the north-west Atlantic Ocean during 2012, where the temperature peaked at 10.3°C degrees above average for that time of year.

Dr Wernberg said the baseline knowledge from this study regarding the important drivers of marine heatwaves across the globe would be invaluable to researchers for many years to come.

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