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NASA landsat photo of the Tarim Basin.

Carbon sink found hidden “in the most unlikely place on earth”.

Chinese scientists have published findings an oceanic sink, absorbing large amounts of harmful carbon from the atmosphere, created unknowingly by millennial farming practices, beneath the arid Tarim Basin, of Xinjiang province, northern China. 

The study begun in earnest about 10 years ago when the team, based out of the Chinese Academy of Sciences’ Xinjiang Institute of Ecology and Geography in the capital, Urumqi, became aware carbon dioxide was disappearing in Tarim.

The basin is as a mouth, 906,500 km2 (350,000 sq mi) in the Taklakmakan Desert, with the Tian Shan mountains along its upper jaw, in the north, and the Kunlun, along its lower, in the south.

A cooperation of Baker Hughes and PetroChina agreed in 2010 to drill following an exploration by the China National Petroleum Corporation, – begun 1989, concluded 1995 – which identified 26 oil- and gas-bearing structures or pockets.

It is arid land but there is water, the snows of K2 form glaciers, which melt in the valleys of the Karokorum range and, as rivers, flow down to the basin, never to reach the ocean, slipping instead beneath.

By measuring the carbon content of water samples in the basin and then the rivers that flow there, dammed to irrigate local farms, they were able to establish the existence of a carbon sink.

For the basin is endorehic – allowing no outflow to other external bodies of water such as rivers or oceans.

As the paper in question, Hidden carbon sink beneath desert, makes note: “rivers in closed (terminal) arid basins have no outlet and no hydrological connection to the oceans, creating aquifers isolated from the river-ocean system.”

Aquifers are bodies of permeable rock.

“Saline aquifers function as the “ocean” for these inland river-aquifer hydrological systems. The only difference is that this ocean is covered by a thick layer of sandy soil.”

Speaking to Stephen Chen of the South China Morning Post, Yan Li lead author of the paper, said: “This is a terrifying amount of water”.

The desert biogeochemist added: “Never before have people dared to imagine so much water under the sand. Our definition of desert may have to change.”

Evaporation is greater in the basin than precipitation meaning it is arid and saline land. This is crucial in the creation of a carbon sink, as the paper, co-authored by Yu-Gang Wang, R.A. Loughton and Li-Song Yang, describes:

“CO2 solubility in saline/alkaline water is much higher than in pure or acidic water, the solubility increases linearly with electric conductivity and exponentially with alkalinity (pH) of the soil solution [Lindsay, 1979].”

Added to this, Xinjiang is the largest cotton producer of the provinces. The crop is grown on small Uyghur minority farms and large scale Han-Chinese populated state or “regimented” farms, part of the Xinjiang Production and Construction Corps (XPCC). As per the 6311 campaign, initiated 2006-7, fruit and nut trees were also planted, by the hundred-thousand-acre-square, and there was an expansion of grain production promoted through subsidies.

These operations are characterised by extensive agricultural land reclamation and, more importantly, water use. – Such is the scale that in recent decades it has resulted in degradation of ecosystems along the Tarim River. – The salinity of the soil demands an agricultural practice of overirrigation to leach, that is to drain, the salt downward, where it wells in the aquifers.

This has been going on, progressively to greater extent, ever since man begun farming this land.

Troops of the Han Dynasty are known to have driven northern tribesmen from their oases in the first millennium, establishing the Northern Silk Road and safe passage for merchants through the basin.

There follows the long and bloody history of the basin but of relevance are the Uyghur People,  Turkic speaking Muslim farmers, professing links to the Tarim mummies, buried there since 1800 BC. Ancestrally Mongoloid, the Uyghur migrated to the basin with the fall of the Uyghur Khaganate in 842. They call it Altishahr, there 80% remain. There were over 10,000,000 Uyghur living in China as of a 2010 census.

And so, for millennia the farmers grow plants, the plants absorb the carbon, releasing some into the earth where it would escape but for the the aridity of the soil and resulting practice of overirrigation. The overirrigation dissolves the CO2, depositing it in the aquifer below, where it remains, – as it is an endorehic basin, allowing no outflow – overtime, creating a carbon sink.

According to Tim Appenzeller’s The Case of the Missing Carbon, published in National Geographic: “Each year humanity dumps roughly 8.8 billion tons (8 metric tons) of carbon into the atmosphere, 6.5 billion tons (5.9 metric tons) from fossil fuels and 1.5 billion (1.4 metric) from deforestation. But less than half that total, 3.2 billion tons (2.9 metric tons), remains in the atmosphere to warm the planet.”

The findings of Li et al, published in AGU journal Geophysical Research Letters, are therefore significant because they account for, in part, the missing carbon.

– And a larger part of the remaining 5.6 billion tons than that of the Tarim Basin alone, representative as it may be of other deserts, previously negated in the search.

Carbon – contained in coal, oil and natural gas – was breathed in millions of years ago by plants. Now all the exhaust pipes and dark satanic mills of industry, as well as other natural occurrences, breathe carbon back into the atmosphere, up where the air was clear. Carbon is one of the greenhouse gasses, absorbing infrared radiation, trapping heat in the atmosphere. Compounded by deforestation, this is believed to cause a greenhouse effect and global warming, springtime in winter and ice caps falling into the sea.

So, if other such caches are confirmed, this research may represent a way of realigning our seasons by hiding carbon the same way it has been hidden in the Tarim Basin.

Then again, it may represent a sleeping dragon, which would return to darken our skies were it awakened. As the paper states: “It could be argued that pumping of groundwater for irrigation will release DIC [dissolved inorganic carbon] back into atmosphere.”

However, as this would come about through large scale use of saline/alkaline water for irrigation, it is unlikely because, to paraphrase the paper, saline/alkaline water is not usable by crop plants.

You can find the paper Hidden carbon sink beneath desert, here: http://onlinelibrary.wiley.com/doi/10.1002/2015GL064222/full?campaign=wlytk-41855.5282060185

 

By Harrison Drury.

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