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Study: Pace of Warming is Set to Accelerate in the Deep Ocean

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Mesopelagic fish, including lanternfish and hatchetfish species (file image courtesy NOAA)

By The Maritime Executive 06-08-2020 06:58:16

A new study published in Nature Climate Change suggests that the deep ocean may not be as invulnerable to warming as once thought. By looking at the pace and horizontal movement of temperature rise over time (climate velocity), a team led by Isaac Brito-Morales of the University of Queensland predicted that life in the deep ocean will experience accelerated change in the second half of this century, even under a best-case climate action scenario. 

According to the study, the mesopelagic - the region between 200-1000 meters in depth - will be most affected, especially in high latitudes. This band could experience temperature changes at a rate four times higher than surface waters by the century's end, likely resulting in "dramatic distribution changes" as deep ocean species move geographically to follow the water conditions that they prefer. Long-term fishery surveys indicate that those changes are already well under way at the surface. 

The study's most concerning finding is that these deep-ocean temperature shifts will likely occur even if society takes aggressive climate action in line with the Paris Climate Accord. 

"The deep ocean and biodiversity below the surface of the ocean, no matter what we do, it's going to be impacted by climate change," Brito-Morales told CBS.

The mesopelagic is the realm of the lanternfish, one of the most abundant classes of vertebrates on earth and a key food source for surface species like salmon, tuna, whales and halibut. This family of "forage fish" accounts for an estimated 65 percent of all deep sea fish biomass, and it may become a commercial fishing target to meet demand for feed for aquaculture, pigs and chickens.

As a measure to mitigate the impact of temperature change for these and other key species, the research team advised creating tailored marine protected areas (MPAs). "To optimize opportunities for climate adaptation among deep-ocean communities, future open-ocean protected areas must be designed to retain species moving at different speeds at different depths under climate change while managing non-climate threats, such as fishing and mining," the team concluded.