Australia’s most famous coral resides on its Pacific coast. The Great Barrier Reef is amazing, to be sure, and a bellwether of how climate change is impacting reefs around the world.

But there’s a reef hidden in the depths of the Southern Ocean off Australia’s south coast that could unlock a much more profound secret about climate change and the entire ocean. And until recently, it remained completely unexplored.

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Over the course of a month, a team of researchers probed the deep-sea canyons that jut out from Australia’s southern continental shelf like fingers plunging into the chilly Southern Ocean. Delicate corals exist in the waters that may only reach 10 degrees Celsius (50 degrees Fahrenheit), clinging to the walls of the canyons and crawling over plateaus. The researchers on the R/V Falkor sent a remote operated vehicle (ROV) down to those depths to collect samples of both living and fossil corals while capturing stunning 4K video from the deep sea. Researchers had a good guess these unique ecosystems were sitting at the bottom of the sea in the area after a 2015 expedition in somewhat nearby Perth Canyon, but it was a crapshoot of just what exactly they would find.

“It could [have] been just a fizzle,” Julie Trotter, a geochemist at the University of Western Australia, told Earther.

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Instead, the trip yielded a wide array of coral samples that could help Trotter and her colleagues understand this part of the ocean and the waters that flow through it. While there was plenty of live coral to be found, the team also found a coral graveyard spanning an entire plateau. And they found numerous fossilized coral that could date back thousands of years to the Last Glacial Maximum when ice covered much of the Northern Hemisphere before rapidly (by geological standards) receding. What happened then as well as a few other moments throughout history is particularly interesting to climate researchers as they try to figure out what the fate humanity will look like. And the coral samples the team brought up with the ROV could provide clues.

That’s because corals act as little time capsules. Like trees, corals essentially have growth rings. But rather than revealing disturbances like fire or drought on the landscape, a core from a coral can reveal how the chemistry of the waters around has changed over time.

Trotter and her team can sync the data they pull about the ocean chemistry with data from other so-called proxy sources of data like tree rings, stalagmites, and ice cores to better understand the climate of the past. And that, in turn, can help us better understand our present climate and where we may be headed thanks to humanity’s little experiment to pump carbon into the atmosphere at unprecedented rates.

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Knowing the ways in which water wends its way from Antarctica slowly north on a current across the Southern Ocean can also help them understand the whole system. In an era of climate change, oceans are taking up 90 percent of all excess heat that carbon pollution traps and also sequestering massive amounts of said carbon (which, FYI, is driving ocean acidification). And of all the oceans, the Southern Ocean is perhaps the most important, sucking up 40 percent of all of humanity’s emissions each year. Because the waters the deep-sea corals inhabit are more corrosive than surface waters, Trotter said, the research could also help other coral researchers looking at how to conserve warm water corals in more acidic oceans.

“From our perspective, we’d like to work on not just in our local backyard,” Malcolm McCulloch, another ocean researcher from the University of Western Australia who was on the cruise, told Earther. “But we try to use information from the Southern Ocean [because] it has global importance.”

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Managing editor, Earther

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