One-fifth of China’s glaciers have melted, sounding the white alarm

On November 4th the US government formally notified the UNITED Nations of its request to withdraw from the Paris Agreement, which addresses global climate change. Four months ago, Iceland lost the Oak Glacier. Locals gathered on a gravel slope for a “funeral” for it. The monument is engraved with a letter to the future: this is the first glacier to lose its glacier status. For the next 200 years, all of our glaciers will follow the same path of extinction…

In fact, glacier funerals are not far away. In 2016, there were two ice avalanches on the Ayu Glacier in the Ali region of Tibet, and in 2018, two ice-breaking events occurred in the East Pugou of the Yalu-Zangbu River in southeastern Tibet. According to China’s two glacier catalog statistics, from around 1970 to 2010, the national glacier area decreased by 12442.4 square kilometers, accounting for 20.6% of the total area of the glacier.

One-fifth of China's glaciers have melted, sounding the white alarm

The Labra Glacier in Dongyu Township, Nitou County, Ali District, Tibet. Xinhua News Agency

1. One fifth of China’s glaciers have melted

Glaciers are the recorders and early warning devices for climate change. China is the most developed low-to-medium-latitude glacier in the world, of which the third pole with the Qinghai-Tibet Plateau as the main body is the most important glacier-rich area except the north and south poles.

Guo Wanqin, an associate researcher at the National Key Laboratory of Frozen Circle Science at the Northwest Institute of Ecological Resources of the Chinese Academy of Sciences, told reporters that the revised catalog of China’s first glaciers shows that China has a total of 48,410 glaciers, with a total area of 60,506 square kilometers. According to the latest edition of China’s second glacier catalog, around 2010, China had a total of 53,778 glaciers, with a total area of 48063.6 square kilometers. Over the past few decades, China’s glaciers have shrunk by 12442.4 square kilometers, accounting for 20.6% of the total area, of which about 8310 glaciers have completely disappeared. The largest contraction in the area of glaciers was in the Tibet Autonomous Region, which decreased by 7680.7 square kilometers as a whole, and the overall contraction reached 27.7%. Yunnan Province, the province with the fastest rate of glacier shrinkage, saw its total glacier area decrease by 28.2%.

Guo Wanqin said the retreat of large glaciers is the main reason for the significant reduction in the size of the country’s glaciers. The 8310 lost glaciers are dominated by small ice bucket glaciers and suspended glaciers. Most of the small ice-bucket glaciers have only one branch, mostly located in small valleys, shaped like bumps. Hanging glaciers are attached to steep slopes because of their shorter, thin, only a few to tens of meters, and are more susceptible to regional climate change.

The recent temperature of the Qinghai-Tibet Plateau has risen by an average of 0.4 degrees Celsius per decade, twice the global average heating rate, said Yan Guangjian, a researcher at the Qinghai-Tibet Plateau Research Institute of the Chinese Academy of Sciences. Take the Aza Glacier in southeast Tibet as an example, which belongs to the ocean-type glacier, which is only about 2,700 meters above sea level at the end of the glacier. Observations show that the end of the glacier retreats by 30 to 60 metres per year.

“The rise in global temperatures caused by human emissions of greenhouse gases is the main cause of melting glaciers. Yang Wei, an associate researcher at the Qinghai-Tibet Plateau Institute of the Chinese Academy of Sciences, said. The increase in temperature leads to the increase of ice melting and the decrease of accumulation, while causing the ice temperature to rise, the ice crack increases, the glacier fragmentation increases, the melting surface increases, and the melting surface increases. Glacier retreats have also led to its “decomposition”, such as the Ninsughetti glacier in the Karakoram Mountains, which had broken down into five glaciers by 2010. This is also the reason why, in the second glacier catalog, although the overall area of the glacier decreased, the number of glacier strips increased. Precipitation in glacial areas is generally in the form of solid, i.e. snowfall, but as temperatures rise, the proportion of precipitation in glacial areas increases at low altitudes. The latent heat released by rainfall also accelerates the melting of glaciers.

In addition, industrial pollution such as black carbon aerosols settles on the surface of glaciers, resulting in a decrease in the albedo of glaciers and easier absorption of solar radiation, which accelerates the melting of glaciers to a certain extent. The melting of the glacier smelts black carbon on the surface of the glacier, absorbing more heat.

One-fifth of China's glaciers have melted, sounding the white alarm

A view of the Qionggang Day Glacier in Geda Township, Dangxiong County, Tibet. Xinhua News Agency

2. Water crisis in northwest arid region is severe after glacier sluice

“The shrinking area of glaciers is only a superficial phenomenon. In fact, changes in ice volume reflect the loss of glacier water resources. Chen Rensheng, a researcher at the Northwest Institute of Ecological Resources of the Chinese Academy of Sciences, said. Glacier is a “solid reservoir” which plays an important role in supplementing and regulating river runoff. China’s frozen circle is the birthplace of important rivers and rivers in China and neighboring countries, and it is the water tower of the arid inland river basin of “Belt and Road”, nourishing the large population in the basin. Under the background of global warming, the rapid change of the frozen circle has a great influence on the hydrological process and water resources in China, especially in the western region.

Chen Rensheng said that in the past few decades, the rapid changes in the frozen circle led to changes in the runoff of the basin, the glacier melt “first increase and then decrease” inflection point has been or is about to appear. By the end of the 20th century, China’s glacial meltwater will be significantly reduced, including more than 80% in the mountains, about 50% to 90% in the eastern and southern parts of the Qinghai-Tibet Plateau, and about 30% to 50% in Tianshan.

From the single glacier, most of China’s small glaciers, the flow of meltwater is likely to have turned a corner, such as the Yanlian Shanning River No. 3 glacier. The relatively large glaciers are likely to experience recent runoff peaks, such as the 71 glaciers in Lulian Mountains.

On the basin scale, the basin with low glacier coverage and the xiaobing river,”zone” inflection point of “first increase and decrease” of glacial melt water has appeared, such as the Shiyang River basin in the Hexi Corridor, which is greatly affected by the East Asian monsoon, the Manas river and The Hutubi river basin on the northern slope of Tianshan in the west wind belt, and the source of the Nujiang River in the Qinghai-Tibet Plateau, the source of the Yellow River and the source of the Lancang River. Some basins will have glacier melting water inflection points in the next 10 to 20 years, such as the Kucar River and Muzat River on the southern slope of Tianshan, the Heihe and Shule Rivers of Yanlianshan, and the yangtze River source of the Qinghai-Tibet Plateau. In the basin with large glaciers, the inflection point of glacier melt water appears late.

On the mountain scale, in the mountainous area of Lilian, which is dominated by small glaciers, the glacier meltwater runoff is likely to have peaked around 2000, and the current glacier meltwater runoff has shown a decreasing trend, while the eastern part of Kunlun Mountain may reach the peak of the flow of meltwater around 2040.

In a medium-emission scenario, runoff peaks when the global average temperature rises by 2 degrees Celsius. After that, the reduction of runoff in some basins can reach more than 50%, which will lead to the break-off of some small rivers and rivers that used to be mainly replenished by glacial meltwater, the rapid and dry changes of river runoff are obvious, local floodand disasters are intensified, regional water crises may occur in dry season or years.

After most glaciers disappear, once precipitation decreases and the climate dries, there will be a regional long-term water crisis in the northwest arid region. Therefore, to control emissions within the medium emission scenario and the global temperature to be controlled within 2 degrees Celsius is the key to ensure the stability of river runoff in the northwest arid region.

One-fifth of China's glaciers have melted, sounding the white alarm

Located in naqu city in Tibet, such as the county sheep show village of sapp snow mountain and glacial lake. Xinhua News Agency

3. Glacier disasters in the Qinghai-Tibet Plateau are increasing

In 2016 and 2018, a number of ice avalanches occurred in Tibet, China, sounding a white alarm about the melting of glaciers. The Qinghai-Tibet Plateau of the Chinese Academy of Sciences participated in the emergency investigation of these ice avalancheevents, and Yan Guangjian introduced that China’s glaciers are widely distributed and the types and nature of glaciers are different. The Ayu glacier, which experienced an ice avalanche in 2016, is a continental glacier, while the glaciers in southeastern Tibet, where the avalanche occurred in 2018, are offshore glaciers. Both types of different glaciers have experienced ice avalancheevents, which may well indicate that the glaciers in the Qinghai-Tibet Plateau are in an unstable state as a whole, while the scope of glacial disasters is gradually expanding.

The loss of stability of glaciers under gravity is the direct cause of the avalanche, and the deeper reason is that the warming climate has changed the geometry, physical properties, thermodynamic structure and liquid water content of glaciers, thus increasing the instability of glaciers as a whole. Yan Guangjian told reporters that glaciers have been changing, the reason for the more attention now is because global warming accelerates the change of glaciers, and makes the glacier disaster increased. In addition to ice avalanches, glacial disasters include glacier jumps, glacial mudslides, and ice lake burst floods. Disasters often do not occur simply, they tend to induce a variety of secondary disasters, the formation of a disaster chain, thus prolonging the disaster time and amplifying the consequences of disasters.

At present, the research on glacier disaster in China is still relatively weak, which is also one of the important contents of the second Qinghai-Tibet Plateau science examination. First of all, He said, we should do a good job of census, collect and organize the records of past glacier disasters, and clarify the regional distribution characteristics and occurrence of glacier disasters. Secondly, the study of glacier change and monitoring should be strengthened. Through remote sensing images of the disaster occurred in the key areas of the census, to identify the key objects prone to glacial disasters, regular “medical examination” of these glaciers, carry out detailed field visits and monitoring, the risk of disaster-prone glaciers, including the speed of glacier movement, annual losses, accumulation, and meteorological data around the glacier. Thus, the process of glacier change and glacier disaster is simulated, and the mechanism of glacier disaster is revealed. Finally, a perfect early warning system for glacier disaster monitoring and early warning should be established.

4. Explore the path to adapt to the changes in the frozen circle

“The frozen circle is the most sensitive and most directly feedbacked ring in the climate system. Yang Wei said. The fifth assessment report of the United Nations Intergovernmental Panel on Climate Change noted that, as a result of warming, glaciers around the world continue to retreat and permafrost degrade. In many regions, the melting of the frozen rings is changing the hydrological system in the region, affecting the amount of local water resources and the quality of water. In semi-arid areas and areas replenished by glacial meltwater, floods and landslides will be threatened.

Simulations suggest that the loss of the ice sheet could lead to large-scale, irreversible sea level rise. Changes in glaciers (ice sheets), permafrost, fresh water and marine conditions in the polar regions put local freshwater resources and terrestrial and marine ecosystems at risk, affecting species habitats, quantities, conditions and fertility. Permafrost degradation has led to the destruction of infrastructure such as land transportation facilities and buildings, and the melting of sea ice poses a greater risk of storms for Arctic coastal residents. These changes in the frozen circle are or are about to pose a significant threat to the global ecological and socio-economic systems.

There is growing evidence that, beginning in the 1970s, global warming has continued to increase in scope and extent of impact, resulting in increased frequency, intensity and loss of frozen ring disasters. The rapid change of china’s frozen circle has a wide and profound negative impact on the regional social and economic system, mainly reflected in the arid oasis agriculture, the major projects in the cold zone, the cold zone animal husbandry, the snow and ice tourism industry and so on. China’s frozen circle is mainly in the western region, the economic level is relatively backward, the ability to cope with the changes in the frozen circle capacity. At present, adaptation is still the main way to cope with changes in the frozen circle. The comprehensive influence analysis of the change of the frozen circle on the social and economic system is the basis for adapting to the rapid change of the frozen circle, and its adaptive management strategy is the ultimate goal of reducing the adverse effects of the rapid change of the frozen circle, reducing the loss of natural and social economic system, and thus reducing its adverse effects.

Under the background of global warming, the rapid change of the frozen circle and its interaction with the biosphere, lithosphere, hydrosphere, atmospheric circle and human circle are increasing day by day, especially on the sustainable development of hydrologic water resources, ecosystems and human economy and society. In the future, it is urgent to carry out system integration research on the disaster-causing effect struck by China’s frozen circle, disaster prevention and mitigation measures, risk assessment and function services of the frozen ring.

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