Decades of data shows marine heatwaves have increased in number, length and intensity as a result of warming oceans.

A new study has found that from 1925-2016, the frequency of marine heatwaves had increased by about 34 per cent, and the length of each heatwave had increased by 17 per cent.

This means there has been a 54 per cent 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 from Dalhousie University, Canada.

“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.”

The researchers used a variety of observational datasets to reveal the trend of increasing marine heatwaves, combining satellite data with a range of century-long datasets taken from ships and various land-based measuring stations. 

They then removed the influences of natural variability caused by the El Nino Southern Oscillation, the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation to find 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 Prof Neil Holbrook from IMAS at the University of Tasmania.

“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 accessible here.