Why do Arctic glaciers melt?

Due to the gradual warming of the global climate, the area and volume of glaciers around the world have obviously decreased, and some even disappeared. This phenomenon is particularly obvious in the middle and low latitudes.

Africa lost 92% of Mount Kenya glaciers, while Spain had 27 glaciers in 1980, and now it has been reduced to 13.

In the past century, the Alps in Europe have lost half of their glaciers. Since the summer of 2003, the heat wave sweeping across European countries has made the local temperature close to or exceed the historical record. In Switzerland, the temperature at the top of the 3,900-meter-high Fair Pecks Snow Mountain reached 5 degrees Celsius, and the glacier thickness there dropped to the lowest point in nearly 150 years.

In Tianshan Mountains, about 22% of the glacier volume has been gradually lost in the past 40 years. Tianshan Mountain is the largest glacier area in China, with more than 6,890 glaciers with a total area of about 9,500 square kilometers. Glaciers in northern and southern Xinjiang have been found to be shrinking, and glaciers have retreated to varying degrees. Urumqi River originates from Tiangeer Peak 1 glacier in Tianshan Mountain, with an annual runoff of 235 million cubic meters, which is the main water source in Urumqi. Glacier 1 has been in a state of retreat, and has retreated140m in the 30 years since 1962. In recent years, the glaciers in Qilian Mountain have shrunk, and the melt water has decreased by about 654.38+0 billion cubic meters compared with the 1970s. The snow line in some areas of the glacier is rising at an average annual rate of 2 to 6.5 meters, and the average annual increase rate in some areas is as high as 12.5 to 22.5 meters.

In the Himalayas, the largest glacier has been shortened by more than 300 meters since 1935. In recent years, the melting of the East Rongbu Glacier and the Middle Rongbu Glacier in the Everest region has intensified, resulting in obvious glacier retreat. In the early 1960 s, the tail of the glacier in the Everest region was over 5400 meters above sea level. In the 1980s, due to the opening of Mount Everest, the number of people climbing, exploring and traveling in this area increased rapidly, and the local people built yak passages at an altitude of 6,500 meters. A recent study by the International Snow and Ice Committee shows that glaciers in the Himalayas are melting at an accelerated pace, as evidenced by the rapid rise of water levels in nearly 50 glacial lakes in the Himalayas. Scientists predict that the Himalayan glaciers will shrink 1/5 in the next 35 years.

Scientists in the United States and Canada announced that Ward Hunt, the "boss" of the Arctic ice shelf 3,000 years ago, no longer exists near the north coast of ellesmere island, Nunavut, Canada. Through radar survey, they learned that in 2000, a small crack appeared in Wardhunt, with a size of 388.5 square kilometers. In 2002, the crack expanded to 77 meters, and some new cracks appeared beside it. An ice floe with a size of 6 square kilometers has been separated and floated near Ward Hunt. It is predicted that Ward Hunt will eventually split in two. Since 1993, the southern and eastern edges of the Arctic Greenland ice sheet have been thinning at the rate of 1 m per year.

The Antarctic ice sheet, which accounts for 9 1% of the world's ice reserves, disappeared from 1998, accounting for 1/7 of the total area. At the end of last year, the American Geographical Association reported that the three largest glaciers in Antarctica had thinned by 45 meters in ten years.

The rate at which glaciers shrink is really amazing. In Lima, Peru, glaciers are melting at a rate of 30 meters per year in recent years, while before 1990, the melting rate was only 3 meters per year. Scientists predict that by 2050, more than14 glaciers will disappear in the world. It may reach 50% by 2 100. By then, only Alaska, Patagonia Plateau, Himalayas and Central Asian mountains may have some large glacier distribution areas.

Influence of glacier retreat

The grim situation of accelerated melting of glaciers will inevitably bring the following serious consequences:

(1) sea level rise

Scientists believe that the melting of ice sheets and mountain glaciers in the past century is one of the reasons for the global sea level rise 10-25 cm. Nowadays, the value of sea level rise caused by melting glaciers is increasing. If the Antarctic ice sheet collapses, the global sea level will rise by nearly 6 meters. If the two ice sheets at the north and south poles all melt, the sea level will rise by nearly 70 meters.

Sea level rise caused by melting glaciers will flood large coastal areas, making residents living in these areas, accounting for half of the world's population, restless. All coastal areas will become the sea of Wang Yang. Only the roofs of the United Nations building and several skyscrapers will remain in new york. Paris may only see the top of the Eiffel Tower, while dozens of low-lying countries such as the Netherlands and Britain will no longer exist.

China's coastline is more than 6,000 kilometers long, and hundreds of large and medium-sized cities along the coast are densely populated. Dalian, Tianjin, Qingdao, Shanghai, Hangzhou, Xiamen, Guangzhou, Hong Kong, Macao and Shenzhen are all within 20 meters above sea level. Even Beijing, Nanjing and Wuhan seem to have a certain distance from the ocean, but the altitude is in the melting of alpine glaciers and the "flooding" of polar ice sheets. What's more, besides the mainland, there are more than 5,000 islands in Hainan, Zhoushan and Taiwan Province.

(2) The global climate change is obvious.

Glaciers, especially large polar ice sheets, can reflect a lot of sunlight, thus helping the earth where humans live to keep the temperature from rising. However, when glaciers melt, the exposed land and water surface will absorb solar heat, leading to more ice melting, and the chain reaction will inevitably accelerate the process of ground warming and contribute to climate warming. However, the icy water after the excessive melting of Arctic ice will have a cooling effect on parts of Europe and the eastern United States. The inflow of ice water into the North Atlantic may destroy the ocean circulation model there, thus affecting global climate change.

Melting glaciers will bring disaster to the local area. If Himalayan glaciers melt like this, nearly 50 glacial lakes in Nepal and Bhutan will burst their banks and cause floods in 5 to 10 years. The rapid melting of glaciers in summer will also lead to rising water levels in the Indus and Ganges rivers in India, causing floods. On the contrary, with the retreat of glaciers, most areas with glacial meltwater as their water source will be seriously short of water, such as Peru and northern India, which are facing a water shortage crisis due to the accelerated melting of glaciers.

(3) the ecological environment is destroyed

Melting glaciers destroyed the living environment of some animals and plants, and also threatened the living environment of human beings. It has been reported that polar bears related to the change of ice sheet are difficult to find food and lose weight; Penguins and seals in Antarctica have also changed their living habits and breeding methods because of the decrease of sea ice and the increase of temperature. Microorganisms buried in the ice sheet hundreds to tens of thousands of years ago are exposed due to the melting of glaciers, and their diffusion will have a certain impact on human health.

In recent years, the glacier in Qilian Mountain is retreating at a rate of 2 meters to 16 meters per year, and its meltwater is about 10 billion cubic meters less than that in 1970s, which has seriously affected the natural ecological environment there. For example, in Minqin County, the annual runoff of Shiyang River, which originated from Qilian Mountain, dropped sharply, and deep wells had to be drilled, which led to the decline of groundwater level and the deterioration of water quality. 500,000 mu of desert plants died of thirst; 5 million mu of grassland degradation; The number of sandstorm days increased obviously. In the past 65,438+00 years, due to the reduction of water resources, the natural ecological environment there has deteriorated seriously. Coupled with the "narrow tube effect" caused by the southward strong cold air in the north, the Gobi and sandy land adjacent to Tengger and Badain Jaran deserts in the north, with an area of120,000 square kilometers, the Hexi Corridor area stretching over 1000 kilometers and the Alashan League area in Inner Mongolia, have become the strongest sources of sandstorms in northern China.

Causes of glacier retreat

(1) Climate warming

According to a research report of the United Nations Environment Programme, experts have observed 3,252 glaciers and 2,323 glacial lakes in Nepal and 677 glaciers and 2,674 glacial lakes in Bhutan through aerial survey, satellite observation and field investigation for three years. The results show that the temperature in these areas has increased by 1℃ compared with that in 1970s, and the fact that the melting speed of Himalayan glaciers has accelerated once again shows that global warming will be human in the coming decades. After photographing and analyzing 48 glaciers in New Zealand, scientists vividly compared them to "banks". In recent years, due to the prevalence of high pressure, the decrease of westerly winds, dry weather and obvious decrease of snowfall, the "bank" can't make ends meet, because glaciers are supplemented by natural snowfall, maintaining a dynamic balance, which reflects the balance of income and expenditure of glacier accumulation and melting. If the bad weather continues, the glaciers there will continue to shrink.

(2) Human causes

After studying the glaciers in Qilian Mountains, China scholars pointed out that besides the natural climatic factors, another main reason for glacier retreat is population expansion, overgrazing, over-reclamation, deforestation, indiscriminate excavation of Chinese herbal medicines and indiscriminate exploitation of groundwater. In the past 50 years, the population of Gansu has more than doubled, while the cultivated land has only increased by 4%. In the 20 years since the founding of New China, northwest China has successively carried out three large-scale deforestation and land reclamation. By the end of 1990s, the area of soil erosion in Gansu Province accounted for 85.6% of the total area, and sandstorms increased significantly, which further aggravated the glacier shrinkage.

Warning of glacier retreat

Tepfer, Executive Director of the United Nations Environment Programme, profoundly pointed out that the research results of the accelerated melting of Himalayan glaciers have issued a new warning to the whole world: saving glaciers can save lives. Faced with the amazing speed of glacier change and the severe challenge of global warming, human beings have the obligation and responsibility to take prompt measures to reduce the emission of greenhouse gases such as carbon dioxide, so as to slow down the rate of glacier retreat.

In Gansu, China, the slogan of protecting glaciers was clearly put forward. The person in charge of the relevant departments stressed that in order to control desertification in Hexi Corridor, the Qilian Mountains glacier must be protected. We should take practical measures and respect the laws of science and nature. We can neither blindly open up wasteland nor blindly expand the scale of afforestation. We should adjust measures to local conditions, develop moderately, and curb the deterioration trend of the environment around Qilian Mountain, thus helping to protect the lifeline of Hexi Corridor-Qilian Mountain Glacier.

1. With the accelerated melting of Canadian glaciers, the unique biological dependence of the largest frozen lake in the northern hemisphere is threatened: during the two years from 2000 to 2002, the Wardhunt ice sheet in ellesmere island, northern Canada, broke, and the huge ice sheet split in two, threatening the strange biological phenomenon of Disraeli Fjord, the largest frozen lake in the northern hemisphere. In this 3000-year-old fjord, marine microorganisms at the bottom of the water coexist harmoniously with freshwater organisms under water ice, forming a strange phenomenon of symbiosis between freshwater organisms and marine organisms. However, due to the melting of the ice sheet, this strange low salinity seawater is slowly disappearing. By 2002, 96% of low salinity habitats had disappeared.

2. Glacier melting affects water resources: With the retreat of mountain glaciers, there will be a serious water shortage crisis in most areas where glacier runoff is the source of water supply. The Quelcaya ice cap is a traditional water source in Ma Lili, Peru. Now the glacier is retreating at a rate of 30 meters per year. Before 1990, the rate of glacier retreat was only 3 meters per year, which threatened the water use of tens of thousands of residents in the city. Most areas of Ecuador, Peru and Bolivia rely on meltwater from glaciers in the Andes to provide urban water and hydropower. However, the accelerated retreat of glaciers is constantly threatening the normal life of residents here, and water shortage and water disputes have begun to appear in some areas.

3. The accelerated melting of glaciers caused large chunks of ice to fall into glacial lakes, which burst into floods. Due to the retreat of glaciers in the Himalayas, the glacial lakes in Langmochi, Nepal burst into crevasses at 1985, flooding cultivated land, destroying bridge houses and a hydropower station to be built soon, resulting in casualties and property losses.

4. Potential threat of glacier melting: Glacier melting will expose microorganisms buried in the ice sheet for hundreds or even tens of thousands of years in the north, and the spread of microorganisms will affect human health. Organic pesticides were widely used in the middle of last century. Although many kinds of pesticides are restricted now, many pesticide residues are found in glaciers. Harmful substances are brought to cold places with the flow of air, and harmful substances are often compressed and stored in glaciers. Melting glaciers will make these toxic and harmful substances leak out, which will have a great impact on lakes and rivers around glaciers.