Australian-Chinese research finds deep ocean marine heatwaves underreported

CANBERRA, Oct. 17 (Xinhua) -- A world-first research by Australia's national science agency and the Chinese Academy of Sciences (CAS) has found that marine heatwaves in the deep ocean are underreported.

According to the research published on Thursday, 80 percent of marine heatwaves that occur at depths below 100 meters do not concur with surface events.

Marine heatwaves, which are prolonged temperature events that can cause severe damage to marine habitats, have been traditionally tracked by satellite data that focuses on surface temperatures.

The new research by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and CAS indicated that deep-water heatwaves could be significantly underreported.

"Our research reveals that marine heatwaves are often hidden below the surface and occur separately from those on the surface," Ming Feng, a co-author of the study from the CSIRO, said in a media release.

"These findings deepen our understanding of the frequency and intensity of extreme temperature events under the ocean surface, and possible implications."

The world-first global analysis of subsurface marine heatwaves and marine cold spells used long-term temperature observations from eight mooring sites in various ocean basins and over 2 million global historical temperature-profile measurements.

It found that ocean eddies, a type of circular current, have a crucial role in driving and intensifying subsurface marine heatwaves and marine cold spells.

Feng said the research found that marine heatwaves at deeper depths are often associated with eddies and that global warming has intensified temperature extremes in eddies in the past decades, which could result in more severe subsurface marine heatwaves.

The researchers said that better understanding of the drivers of marine heatwaves below the surface will help predict them in the future.