Picture: supplied
THE impact of deep-water marine heatwaves may be significantly underestimated, according to a new report.
The research was conducted by the CSIRO and Chinese Academy of Sciences and published today in Nature, the prestigious scientific journal.
A CSIRO statement says that while marine heatwaves (MHWs) at the sea surface have been studied for more than a decade, 80 per cent of MHWs below 100 metres are independent of surface events.
The CSIRO says MHWs can cause severe damage to marine habitats, such as coral reefs, and even species displacement.
These events are becoming more frequent due to global warming, it adds, such as events off Australia’s east coast and Tasmania, the northeast Pacific coast and North Atlantic.
CSIRO oceanographer Dr Ming Feng says knowledge about subsurface events has been limited – until now.
“Our research reveals that MHWs are often hidden below the surface and occur separately to those on the surface,” he says.
“The deep ocean is home to a range of marine life, including plankton and fish species.
“These findings deepen our understanding of the frequency and intensity of extreme temperature events under the ocean surface, and possible implications.”
The CSIRO says traditionally, MHWs are tracked via satellite data focusing on surface temperatures.
The organisation says new research indicates that deep-water heatwaves may be significantly under-reported.
Marine heatwaves can cause species displacement, says the CSIRO. Picture: supplied
OCEAN CURRENTS
The research also highlights the influence of ocean currents, particularly eddies, on MHWs, indicating they are a key driver of subsurface events.
“Eddies are swirling currents that alter the uptake, redistribution and storage of heat in the ocean. They play an important role in temperature variability,” Dr Feng says.
“Our findings show that MHWs at deeper depths are often associated with ocean eddies.
“Global warming has intensified temperature extremes in eddies in our oceans in the past decades, mostly due to an increase in energy residing in eddies. This could result in more frequent and severe MHWs below the surface.
“In the East Australian Current region, data from Australia’s Integrated Marine Observing System reveals more than 70 per cent of MHWs below the surface occur in ocean eddies,” Dr Feng says.
Ocean eddies can impact acidification, oxygen levels and nutrient concentrations in the ocean.
Understanding the drivers of subsurface MHWs, such as eddies, will help to better assess and predict them, and to better understand their impact on marine life.
