Climate change

The deep ocean is warming, research finds

written by Oceanographic Staff

An international study led by the University of Queensland (UQ) has found that the planet’s deep oceans are warming, albeit at a slower rate than the surface, while examining how ocean life is responding to climate change.

Using a metric known as climate velocity, which defines the likely speed and direction a species shifts as the ocean warms, the team calculated the climate velocity throughout the ocean for the past 50 years and then for the rest of this century using data from 11 different climate models.

climate velocity deep ocean

“This allowed us to compare climate velocity in four ocean depth zones – assessing in which zones biodiversity could shift their distribution the most in response to climate change,” said UQ PhD student Isaac Brito-Morales, who led the study.

The researchers found climate velocity is currently twice as fast at the surface because of greater surface warming, and as a result deeper-living species are less likely to be at risk from climate change than those at the surface.

“However by the end of the century, assuming we have a high-emissions future, there is not only much greater surface warming, but also this warmth will penetrate deeper,” Mr Brito-Morales said. “In waters between a depth of 200 and 1000 metres, our research showed climate velocities accelerated to 11 times the present rate. And in an interesting twist, not only is climate velocity moving at different speeds at different depths in the ocean, but also in different directions which poses huge challenges to the ways we design protected areas.”

The whole team have stated that action must be taken to aggressively manage carbon emissions in order to help take control of climate velocities in the surface layers of the ocean by 2100.

“Because of the immense size and depth of the ocean, warming already absorbed at the ocean surface will mix into deeper waters,” said Professor Anthony Richardson, a senior researcher at UQ. “This means that marine life in the deep ocean will face escalating threats from ocean warming until the end of the century, no matter what we do now. This leaves only one option – act urgently to alleviate other human-generated threats to deep-sea life, including seabed mining and deep-sea bottom fishing.”

Richardson adds that the most effective way to achieve this would be to declare large, new protected areas in the deep ocean where damage to ocean life is prohibited, or at the very least, strictly managed.

The global team included UQ’s Dr Carissa Klein, UQ PhD candidate Mr Nur Arafeh-Dalmau, Professor David Schoeman from the University of the Sunshine Coast, Hokkaido University’s Assistant Professor Jorge García Molinos, and Professor Michael Burrows from the Scottish Association for Marine Science.  Additional collaborators included members of the AquaMaps team.

To read the full study, “Climate velocity reveals increasing exposure of deep-ocean biodiversity to future warming”, click here.

Photograph by the Schmidt Ocean Institute, courtesy of The University of Queensland.

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