The third-largest region of ice on the planet is located on the Tibetan Plateau and Himalaya-Hindu Kush mountains, also known as the Third Pole. As the polar regions, the glaciers in this third region are shrinking. The difference is that the Third Pole is especially vulnerable to pollution due to its close proximity to densely populated and industrialized regions. New research is shedding light on these effects and potential ways to mitigate the disappearance of glacial ice.

In Western China alone, which consists of 48,571 glaciers with an area of 51,840 sq km (20,015 sq miles), there has been an 18 percent decrease in its glaciers over the last 30-50 years according to a study by the Chinese Academy of Sciences' Institute of Tibetan Plateau Research. This shrinkage is especially concerning since over a billion people in the region rely, some indirectly, on the melt water that feeds the region's waterways, such as the Indus River.

Map showing the sources of black carbon around the Third Pole(Credit: Chaoliu Li, Carme Bosch, Shichang Kang et. al. / Nature Communications (CC 4.0))

In the new study funded by the National Natural Science Foundation of China and other institutions, researchers used a special chemical process to fingerprint the source and details of the air pollution, which can be differentiated between South Asia and East Asia. Samples of black carbon (soot) were collected throughout the Third Pole, in the air and on the ground, to determine the type of burning that produced them and where they came from.

Because black carbon is the most heavily light-absorbing component of particulate matter, it can cause temporary warming in the region by absorbing sunlight. In addition, when found atop snow and ice it can darken surfaces, which leads to the absorption of sunlight (and heat), and thus faster melting.

For the Himalayas region, the researchers found evidence of the burning of both fossil fuels and biomass, which includes plants and animal dung, coming from northern India's Indo-Gangetic Plain. Black carbon from the northern Tibetan Plateau came mostly from fossil fuel burned in China. But the researchers discovered that black carbon in the central Tibetan Plateau came primarily from biomass; meaning the daily routine of burning yak dung for cooking and home heating contributed significantly to the region's air pollution.

The information is important for creating and adjusting policies that could cut pollution sources that directly affect melting ice. In the case of the Tibetan Plateau, substituting efficient stoves and clean energy sources for yak dung could slow the rate of glacial ice melt. Policies such as China's three-year moratorium on new coal mine approvals could also help reduce black carbon air pollution.

Source: Nature Communications

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