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Glacier melting rings white alarm bell

发布时间:2019年12月24日16:55 Source: Xinhuanet Release time: 16:55, December 24, 2019
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Labula Glacier in Dongru Township, Ritu County, Ali District, Tibet. Xinhua News Agency

A scene of the Qionggangri Glacier, Guda Township, Dangxiong County, Tibet. Xinhua News Agency

Sap Snow Mountain and Glacier Lake are located in Naqu City, Tibet, such as Yangxiu Township. Xinhua News Agency

On November 4, the U.S. government formally notified the United Nations that it would withdraw from the Paris Agreement on global climate change.

Four months ago, Iceland lost the Oak Glacier. The locals gathered on a gravel slope and held a "funeral" for it. On the monument is a letter to the future: this is the first glacier to lose its status. For the next 200 years, all our glaciers will follow the same path of extinction ...

In fact, glacial funerals are not far away from us. In 2016, two ice avalanches occurred in the Aru Glacier in the Ali region of Tibet; in 2018, two ice avalanches occurred in the Sedongpu ditch of the Yarlung Zangbo River in southeast Tibet. According to China's two glacier catalog statistics, from around 1970 to 2010, the area of glaciers across the country decreased by 1,2442.4 square kilometers, accounting for 20.6% of the total area of glaciers.

1.One-fifth of glaciers in our country has melted away

Glaciers are recorders and early warning devices of climate change. China is the country with the most developed glaciers in the middle and low latitudes in the world. The third pole with the Qinghai-Tibet Plateau as the main body is the most important glacial enrichment area besides the north and south poles.

Guo Wanqin, an associate researcher at the State Key Laboratory of Cryosphere Science of the Northwest Institute of Ecological Resources of the Chinese Academy of Sciences, told reporters that the revised China's first catalog of glaciers showed that there were 48,410 glaciers in China, with a total area of 60,506 square kilometers. The latest edition of China's second glacier catalog shows that around 2010, China had a total of 53,778 glaciers with a total area of 4,8063.6 square kilometers. Over the past few decades, China's glaciers have shrunk as a whole by 1,2442.4 square kilometers, accounting for 20.6% of the total area, of which about 8,310 glaciers have completely disappeared. The largest reduction in glacier area is in the Tibet Autonomous Region. The overall area of glaciers has decreased by 7680.7 square kilometers, and the overall shrinkage has reached 27.7%. Yunnan Province is the province with the fastest rate of glaciers shrinking, with a total area of glaciers reduced by 28.2%.

Guo Wanqin said that the retreat of large glaciers is the main reason for the dramatic reduction in glaciers across the country. The 8310 disappearing glaciers are mainly small ice bucket glaciers and hanging glaciers. Most small ice bucket glaciers have only one branch, and they are mostly located in small valleys, similar in shape to dustpans. Hanging glaciers stick to steep slopes because of their shorter tongues and thinner thicknesses, ranging from a few meters to tens of meters, making them more susceptible to regional climate change.

Qi Guangjian, a researcher at the Qinghai-Tibet Plateau Research Institute of the Chinese Academy of Sciences, told reporters that the temperature of the Qinghai-Tibet Plateau has risen by an average of 0.4 ° C every 10 years, and the heating rate is twice the global average. Take the Azha Glacier in southeast Tibet as an example. This glacier is a marine glacier, and the end of the glacier is currently only about 2,700 meters above sea level. Observation records show that the end of the glacier retreats 30 to 60 meters per year.

"Human emissions of greenhouse gases that raise global temperatures are the main cause of glaciers melting," said Yang Wei, an associate researcher at the Institute of Tibetan Plateau, Chinese Academy of Sciences. The increase in temperature causes the melting and accumulation of the ice surface to increase, and at the same time, the ice temperature rises, ice cracks increase, glacial fragmentation increases, and the melting surface increases. Glacier retreat has also led to its "decomposition". For example, the Insugati Glacier in the Karakorum Mountains has been decomposed into five glaciers by 2010. This is why in the second glacier catalog, although the total area of glaciers decreased, the number of glaciers increased. The form of precipitation in glacial areas is generally solid, that is, snow, but as the temperature rises, the proportion of precipitation in glacial areas increases in low altitude areas. Latent heat released by rainfall has also accelerated the melting of glaciers.

In addition, industrial pollution such as black carbon aerosols settles on the surface of glaciers, which reduces the albedo of glaciers and makes it easier to absorb solar radiation, which accelerates the melting of glaciers to a certain extent. The melting of glaciers will cause black carbon to accumulate on the surface of the glaciers and absorb more heat.

2. Serious water crisis in arid regions of Northwest China after glaciers disappear

"The shrinking glacier area is only a superficial phenomenon. In fact, changes in ice volume reflect the loss of glacial water resources." Said Chen Rensheng, a researcher at the Northwest Institute of Ecological Resources of the Chinese Academy of Sciences. Glacier is a "solid reservoir", which plays an important role in supplementing and regulating river runoff. China's cryosphere is the birthplace of important rivers and rivers in China and neighboring countries, and it is also a water tower in the arid inland river basins of the “Belt and Road”, which nourish a large number of people in the basin. In the context of global warming, rapid changes in the cryosphere have a greater impact on hydrological processes and water resources in China, especially in the western region.

Chen Rensheng said that over the past few decades, rapid changes in the cryosphere have led to changes in river basin runoff, and the inflection point of the "glacial melt water first increase and then decrease" has or will soon appear. By the end of the 20th century, China's glacial meltwater will be significantly reduced, among which the Qilian Mountains will be reduced by more than 80%, the eastern and southern Qinghai-Tibet Plateau will be reduced by about 50% to 90%, and the Tianshan region will be reduced by about 30% to 50%.

From the perspective of a single glacier, the inflow point of the meltwater of most small glaciers in China is likely to have reached an inflection point, such as the Ningchan River No. 3 glacier in Qilian Mountains. And relatively large glaciers are likely to have peak runoff recently, such as Qiyi Glacier in Qilian Mountains.

On a river basin scale, the inflection point of “glacial melt water first increases and then decreases” has emerged in basins with low glacier coverage and small glaciers, such as the Shiyang River Basin and Westerly Belt in the Hexi Corridor, which is greatly affected by the East Asian monsoon. The Manas and Hutubi river basins on the northern slope of the Tianshan Mountains and the Nu, Yellow and Lancang sources of the Qinghai-Tibet Plateau. In some river basins, inflection points of glacial melting water will appear in the next 10 to 20 years, such as the Kuqa River and Muzart River on the southern slope of the Tianshan Mountains, the Heihe and Shule Rivers of the Qilian Mountains, and the source of the Yangtze River on the Tibetan Plateau. With large glaciers, the turning point of glacial meltwater appears later.

On the mountain scale, the glacial meltwater runoff is likely to have peaked around 2000 in the Qilian Mountains, which are dominated by small glaciers. At present, the glacial meltwater runoff has shown a decreasing trend, while the eastern Kunlun Mountains may be around 2040. Only reached the peak of melt water runoff.

In the medium emission scenario, when the global average temperature rises by 2 ° C, the runoff will reach its peak. After that, the runoff in some river basins can be reduced by more than 50%, which will cause some small rivers and rivers that used to be mainly supplied by glacial meltwater to be cut off. The runoff of rivers will change significantly, and local floods and droughts will intensify. A regional water crisis may occur in season or year.

After most glaciers disappear, once precipitation decreases and the climate dries out, there will be a regional long-term water crisis in the arid regions of the northwest. Therefore, controlling emissions in a medium-emission scenario and controlling global temperatures to within 2 ° C is the key to ensuring the stability of river runoff in the arid regions of the northwest.

3. Glacier disasters on the Tibetan Plateau are increasing

In 2016 and 2018, a number of ice avalanches occurred in the Tibetan region of China, which sounded the white alarm bell in response to the melting of glaciers. The Qinghai-Tibet Plateau Institute of the Chinese Academy of Sciences has participated in the emergency investigation of these ice avalanches. According to Jian Guangjian, glaciers in China are widely distributed, with different types and properties of glaciers. The Aru Glacier, which experienced an avalanche in 2016, is a polar continental glacier, while the glaciers in Southeast Tibet, which experienced an avalanche in 2018, are marine glaciers. Both types of glaciers have experienced ice avalanches, which may indicate that the glaciers on the Qinghai-Tibet Plateau are in an unstable state as a whole, and the scope of glacial disasters is gradually expanding.

The loss of stability of glaciers under gravity is the direct cause of ice avalanches, and the deeper cause is that climate warming has changed the geometry, physical properties, thermodynamic structure, and liquid water content of glaciers, thereby increasing the overall glacial instability. stability. Xu Guangjian told reporters that glaciers have been changing. The reason why they are more concerned now is that global warming has accelerated changes in glaciers and increased glacial disasters. In addition to ice avalanches, glacial disasters also include glacial leaps, glacial mudslides, and glacial lake burst floods. Disasters often do not simply occur. They can easily induce multiple secondary disasters and form a disaster chain, thereby extending the disaster time and amplifying the consequences of the disaster.

At present, the research on glacial disasters in China is still relatively weak, which is also one of the important contents of the second scientific investigation on the Qinghai-Tibet Plateau. Wu Guangjian believes that, first of all, it is necessary to do a good census, collect and sort out past glacial disaster records, and clarify the regional distribution characteristics and occurrence rules of glacial disasters. Second, research on glacial changes and monitoring should be strengthened. Conduct a general survey of key disaster areas through remote sensing images, identify key objects prone to glacial disasters, regularly perform "physical examinations" on these glaciers, conduct detailed field surveys and monitoring, and measure disaster-prone glaciers, including glacier movement Speed, annual losses, accumulations, and meteorological data around glaciers. Therefore, the glacial change and glacial disaster process are simulated, and the mechanism of glacial disaster is revealed. Finally, it is necessary to establish a comprehensive monitoring and early warning system for glacier disasters.

4. Exploring the path to adapt to changes in the cryosphere

"The cryosphere is the most sensitive and most direct feedback zone in the climate system," Yang Wei said. The Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change pointed out that global glaciers have continued to shrink due to warming and permafrost has deteriorated. In many regions, cryosphere ablation is changing hydrological systems within the region, affecting local water resources and water quality. In semi-arid areas and areas recharged by glacial meltwater, they will be threatened by floods and landslides.

Simulation estimates suggest that the loss of ice sheets could lead to large-scale, irreversible sea-level rise. Changes in glaciers (ice caps), permafrost, freshwater and marine conditions in polar regions have put local freshwater resources and terrestrial ecosystems and marine ecosystems at risk, affecting species habitats, numbers, phenology and fertility. Deterioration of permafrost has caused damage to infrastructure such as land transportation facilities and buildings, and the melting of sea ice has brought more storms to the Arctic coastal residents. These changes in the cryosphere are or will soon pose a huge threat to the global ecological and socio-economic systems.

More and more evidence shows that since the 1970s, global warming has continued to affect its scope and extent, and the resulting cryosphere disasters have an increasing trend in frequency, intensity and loss. The rapid changes in China's cryosphere have had a broad and profound negative impact on the regional socio-economic system, which is mainly reflected in the comprehensive impact on oasis agriculture in the arid regions, major projects in the cold regions, animal husbandry in the cold regions, and snow and ice tourism. China's cryosphere is mainly located in the western region, its economic level is relatively backward, and its ability to respond to changes in the cryosphere is limited. At present, adaptation is still the main way to deal with changes in the cryosphere. The analysis of the comprehensive impact of the changes in the cryosphere on the socioeconomic system is the basis for adapting to the rapid changes in the cryosphere. The adaptive management strategy is to reduce the adverse effects of rapid changes in the cryosphere, reduce the loss of natural and socioeconomic systems, and then mitigate their adverse effects. The ultimate goal.

In the context of global warming, the rapid changes of the cryosphere and its interaction with the biosphere, lithosphere, hydrosphere, atmosphere, and human circle are increasingly intensified, especially for the sustainable development of hydrological water resources, ecosystems, and human economy and society. Development has a broad and profound impact. In the future, it is urgent to carry out system integration research on the disaster-to-benefit effects of China's cryosphere, disaster prevention and mitigation measures, risk assessment and cryosphere function services.

(Source: Xinhua Author: Reporter correspondent Liu Xiaoqian group Song hi Editor: Shen Min Xia)

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