The Tarim basin in Xinjiang, China is a valley the size of Venezuela; bigger than California, New Mexico and Florida put together. On the surface it is home to Taklimakan, China’s biggest desert, but deep beneath lies a hidden ‘ocean’ that is thought to contain up to ten times more water than all the Great Lakes combined, storing more carbon than all the plants on the planet put together. While more water may sound like a good thing, researchers believe that if this carbon were to escape into the atmosphere, we would be in serious, serious trouble.

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“Never before have people dared to imagine so much water under the sand. Our definition of desert may have to change,” he told the South China Morning Post. “We were after carbon, not water,” Li explained. For ten years he has been studying the phenomenon of “missing carbon” in the atmosphere in the Tarim basin: the carbon seems to vanish into thin air and the scientists have spent years trying to figure out where it goes. “This is a terrifying amount of water, our estimate is a conservative figure — the actual amount could be larger”, said Professor Li Yan, who leads a research team at the Xinjiang Institute of Ecology and Geography in Urumqi, the Xinjiang capital.

Li may have been searching for carbon, but it seems that the water holds the answer to the mystery. The alkaline soil on the surface of the desert helps to dissolve carbon which is carried underground by rainwater, meltwater from the surrounding mountains, and irrigation from farming. Cavernous chambers store the carbon-filled water in an immense underground ‘ocean’ from which it cannot escape, acting as a giant ‘carbon sink’. The combination of the alkaline sands on the surface and saline water deep beneath create the perfect conditions for carbon capture.

Related: Sea Urchins’ Nickel Nanoparticles Could Hold the Key to Carbon Capture

Forests and oceans have been traditionally considered the world’s largest carbon processors, but Li’s research, published in the journal Geophysical Research Letters, appears to show that, paradoxically, the driest places on earth may be hiding massive water reserves which serve as enormous liquid carbon sinks. Li explained that “It’s like a can of coke. If it is opened all the greenhouse gas will escape into the atmosphere”. These desert waters may contain more carbon than all the plants on the planet combined.

Fascinatingly, when Li’s team took samples of the water from a variety of locations and used a process of carbon dating they “recorded a jump of ‘carbon sinking’ after the opening of the ancient Silk Road more than two thousand years ago.” Meaning that the natural world began dealing with human excess long before we ever imagined. “CCS [carbon capture and storage] is a 21st century idea, but our ancestors may have been doing it unconsciously for thousands of years,” he said.

The big question now is whether other deserts in the world harbor watery secrets on a similar scale. There is some scientific excitement about the likelihood of a “trillion tons” of carbon contained in subterranean desert aquifers worldwide, a figure that matches the “missing carbon” on the planet, according to scientific calculations.

+ Geophysical Research Letters

Via Discovery

Photos via NASA and Li Yan