The Tarim basin in China's northwestern Xinjiang province, which covers about 350,000 square miles, is one of the driest places you could imagine. Surrounded by mountains that block the passage of moist air from the ocean, it doesn't get much rainfall - less than 4 inches annually. And the shallow, silt-laden Tarim river doesn't provide much water, either.
Paradoxically, though, Chinese scientists have discovered that the Tarim basin actually has an enormous supply of water - 10 times the amount in all five of North America's Great Lakes combined, in fact. The problem is that the water in a gigantic aquifer that they describe as an underground ocean. It's too salty for the region's impoverished residents to use, but it apparently plays a role in helping to slow climate change.
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The findings were reported in a recent article in Geophysical Research Letters.
"This is a terrifying amount of water," professor Li Yan, who led the study at the Chinese Academy of Sciences' Xinjiang Institute of Ecology and Geography in Urumqi, the Xinjiang capital, told the South China Morning Post.
He added: "Our estimate is a conservative figure - the actual amount could be larger."
The scientists actually discovered the immense underground ocean while investigating carbon dioxide absorption by the region. A 2014 study in Nature Climate Change, which found that the Mojave Desert acts as a carbon sink, suggested that the world's deserts might play a role similar to oceans and forests in soaking up and storing some of the excess carbon emissions from human activity.
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The Chinese scientists obtained deep underground water samples from nearly 200 locations in the basin and measured the carbon dioxide in them, and then compared it to the levels in the snowmelt that gradually seeps into the ground from the surrounding mountains.
The area's alkaline soil helps the carbon dioxide to dissolve into the water, Li said.
Li described the carbon dioxide-rich water in the ground as "like a can of Coke." If the aquifer were somehow opened, "all the greenhouse gas will escape into the atmosphere."
A separate study by German scientists found that the region's underground water may actually be getting saltier, as a result of massive cotton farming in the region and resulting agricultural runoff.