An ocean beneath the Sea of Death
The Taklamakan Desert, covering 337,000 square kilometers of the Tarim Basin, is one of the world's largest and driest shifting sand deserts. Its Uyghur name is often translated as "Place of No Return" or "Sea of Death," showing its hostile environment with annual precipitation as low as 1 to 4 centimeters. Bounded by the Tian Shan, Kunlun, and Pamir mountain ranges, the desert sits in a rain shadow that blocks most moisture.
Beneath this hyper-arid surface, is an enormous secret. Researchers investigating "missing" atmospheric carbon in the Tarim Basin unexpectedly discovered a vast underground water system. Estimates suggest the aquifer could hold more water than all of North America's Great Lakes combined. This subterranean reservoir is fed by meltwater from the glaciers of the surrounding mountain ranges, which seeps deep underground through the porous sand. The water collected over millennia, forming a large hidden reservoir.
Ancient water and a modern carbon sink
The discovery of the water led to another question: how old is it? Isotope dating techniques provided the answer. While traditional radiocarbon dating is effective for water up to about 40,000 years old, newer methods using noble gas isotopes like krypton-81 can date water up to a million years old. Analysis of the Taklamakan's groundwater indicates much of it fell as rain and snow during a wetter climatic period at the end of the last ice age, tens of thousands of years ago.
This ancient water is not sitting idle. The basin is is a massive carbon sink. As meltwater and irrigation water percolate down, they carry dissolved carbon dioxide from the atmosphere. The alkaline soils of the region aid this process, and the carbon becomes trapped in the deep, saline aquifers. Scientists estimate the basin may be absorbing billions of pounds of carbon dioxide annually. Separately, China's "Great Green Wall" project, an ambitious afforestation effort started in 1978 to plant billions of trees along the desert's edge, has also turned the desert's periphery into a measurable carbon sink by increasing photosynthesis.