Cold and Arid Regions Environmental and Engineering Research Institute,
Chinese Academy of Sciences, Lanzhou 730000, China
Ice and snow covers are the basic components of cryosphere. The studies of ice and snow in China have been developed rapidly in recent 40 years. At the same time, the studies also contribute to resources development, environment protection and hazard prevention in the cold regions of China.
China is the country occupying the most continental glaciers in mid-low latitudes in the world, and there are about 45375 Glaciers in China, the total area is about 58728 km2 and 51 percent of that in Mid-Asia according to the last statistics data of the Glacier Inventory of China (Wang, 1989). Chinese scientists have worked on the Glacier Inventory of China since 1958 and finished in 1990, which linked with the World Glacier Inventory. Based on glacier studies in several ten years, Chinese scientists have published a monograph of Glacier Conspectus of China (Shi et al., 1988).
Chinese glaciologists have done a lot of studies on glacier growth conditions, snow line distribution, ice formation, mass balance, glacier movement, glacier temperature and glacier classification etc. This indicated that Chinese glaciology matured and reached to the international level. One example is the forecast and mechanism study of The Batuola Glacier led by Professor Shi (Batoula Glacier Investigation Team, Glaciology and Geocryology Institute of Chinese Academe Science, 1978). The results of flow deformation and internal movement of the continental glacier by Chinese glaciologists cooperating with American was also successful (Huang et al., 1987)
The relations between glaciology and climate have been more and more recognized. The glacial fluctuations in the past 100 years were as follow: Glaciers advanced or comparatively stabled before 1930s, retreated quickly between 1940s and 1960s, advanced in a short time or retreated very slowly from about 1970s to earlier 1980s, and then, retreated a little more quickly during middle 1980s (Zhang, 1997), glacier retreating was more intensive in the 1990s. In the 1970s, the retreat velocity of glaciers in central West Qilian Mountains was slow corresponding to the temperature decrease during 1960s and 1970s (Xie et al., 1982). Glacier measurements show that Qiyi glacier and Laohugou glacier were in a state of positive mass balance (Liu et al., 1992). According to our recent studies, all these glaciers are retreating now.
The Tianshan Glaciological Station or The Glacier No. 1 is a long and continuous monitoring station. The glacial study at the Tianshan Glaciological Station has achieved many developments, for example, the studies of glaciological physical, mass balance, hydrological and meteorological and effects of glacier on ecology.
The Quaternary glaciology in China faces two important problems. One is whether there were ancient glaciers during the Quaternary period in East China. This problem urged scientists to study deeply in different aspects including the formation of glaciers, the causes of matrix deposits, conditions of glaciers growth etc. Based on the studies, they published a monograph named Questions of Quaternary Glacier and Environment in East China. The other problem is whether there was a largest ice sheet over the Qinghai-Tibetan Plateau. The studies of Quaternary glaciers in West China are progressing (Shi et al., 1992).
After 1980s, snow cover in China has been studied by remote sensing and field investigation. The snow cover area in China was about 9´106 km2, of which the snow cover area with snow cover days more than 30 days was 56% of the total area. The seasonal snow cover in China is 3.4518 ´ 1011 m3.
The Antarctic Ice Sheet covers an area of 1.4´ 107 km2, 86% of the total area of global glaciers. The mean depth of the Antarctic ice sheet is about 2450 m. The volume of ice is about 3.0´ 107 km3 and 85% of the global freshwater resources. The Antarctic Ice Sheet has an important influence on the changes of global climate and sea surface level. Moreover, the Antarctic Ice Sheet preserves a lot of information reflecting the changes of global climate and environment.
In 1981, Xie firstly made a winter investigation at the Kaixi Station of Australia in Antarctica. He measured particularly the fabric of ice core, and found that the ice between 250 m and 300 m deep corresponding to the last glacial maximum was characterized by “single maximum” (Xie, 1985). Since then, there were about 30 Chinese glaciologists had arrived to Antarctic to make investigation. Li et al. (1988) studied the mechanism of the “single maximum” of crystals in Antarctic Ice Sheets. Huang et al. (1988) studied the multi-maximum at the bottom of the ice sheet.
Qin had collected large quantities of snow and ice samples, completed glaciological studies and the basic physical characteristics of surface snow in Antarctica during International Trans-Antarctic Expedition in 1990 (Qin et al., 1991). Fruitful results were achieved from this expedition, which include the characteristics of distribution of the stable isotopic, concentration of main anions and cations and heavy metals (Qin et al., 1992). Furthermore, the studies of Antarctic ice cores (Yao et al., 1992a; Han et al., 1994) and investigations on the Nelson Island and ice caps of the King George Island (Ren, 1988) have also achieved a series of results. Glaciological and meteorological evidences show opposite trends on temperature and precipitation history between eastern and western sides of the Lambert Glacier Basin (LGB) for the past 50 years.
For the past decade, observations of surface accumulation, meridional moisture fluxes as well as d18O in surface snow and their relationships with mean annual temperature were carried out at the eastern and western sides of LGB. These observations indicate that there exists a clockwise circulation of air masses, which lead to a remarkable difference in spatial distribution of these parameters between the two areas. Opposite trends on stable isotopic temperature and accumulation variation for the past 50 years between the two sides are also yielded by the records from the firn cores. These trends have also been evidenced by the relevant meteorological parameters observed at Davis (east LGB) and Mawson (west LGB) Stations since 1950s.The changed circulation patterns in the coastal Antarctica during the past decades can explain such patterns over the LGB. It was shown that there is an important role in the location of the circum-polar pressure trough (CPT) and timing of its contraction and expansion in the year. The results of the CPT activities in the past decades are in quantitative agreement with our results.
This study reveals that the local circulation, mainly the semi-annual oscillation (SAO), could alter at least the annual to decadal time-scale climate records, and may result in completely different climate histories between even adjacent areas.
The Qinghai-Tibetan Plateau, often called as the ‘Third Pole' of the Earth, is as important as the Polar Regions for ice core study. In the mid-1980s, Chinese glaciologists carried out ice core studies on the Dunde Ice Cap in the Qilian Mountains cooperated with Americans, and drilled 3 ice cores with depths of 140 m at 5325 m a.s.l., which indicated the beginning of ice-core study in China. Since then, scientists have achieved ice core studies on the Guliya Ice Cap in the West Kunlun Mountain, on the Dongkemadi Glacier in the Tanggula Mountain, on the Dasuopu Glacier in the Xixiabanma Mountain, on the Puruogangri Icefield in the West Tanggula Mountain. So far, we have drilled and analyzed several ice cores over the Tibetan Plateau. One of the most important ice core records is the temperature change reconstruction in the past 100000 years. Based on a comparison between Guliya record over the Tibetan Plateau and Vostok and GISP2 in the Polar Regions, we can clearly recognize an important feature: our climate is not stable (Yao et al., 1999). Also it is evident that the major climatic events are similar in the studied three regions. In other words, the major climatic events are global.
Why the major climatic events in different regions follow a common pattern? We found that sun radiation is mainly responsible for this. The black line here represents insolation at 65 degree north. We found that the cold periods coincide with low insolation periods, and warm periods coincide with high insolation periods.
An interesting advance in ice core climatic study is that we found the climatic changes in the past might be very fast some times, we call it abrupt climatic change. Concerning temperature, it can rise or drop 10 °C in 50 or 60 years. The abrupt climatic change is more frequent from 18000 to 32000 years before present. There were 22 warming events with temperature rising more than 10 °C, and 20 cooling events with temperature dropping more than 10 °C. Abrupt climatic changes with temperature rising or dropping over 5 °C were as many as 100 times over this period. It was also found that the stage 3 was abnormally warming. This period was even warmer than Holocence and similar to the Last Interglacial (Shi et al., 2000; Yao, et al., 1997).The last largest abrupt climatic change occurred between 11000 and 12300 years before present. We call this event as Younger Dryas. Dust concentration is an indicator of dust storm. The Younger Dryas cold event occurred 12300 years ago. The Younger Dryas cold reversal was well recorded over the Qinghai-Tibetan Plateau by ice-core records. It reached to the coldest period through three steps. We described here as Step A, Step B and Step C. With climatic cooling, the dust concentration was getting higher and higher through three steps. It is therefore concluded that the dust concentration recorded in ice core increased with climatic cooling, and decreased with climatic warming. So the High Asia might be an important source region of dust concentration (Yao et al., 1996a)The past 2000 years are characterized by human activities. It is more important to understand climatic changes over this period. By ice core climatic record, we can reconstruct climatic changes year by year. Therefore, climatic changes can be studied with high resolution. Even in the past 2000 years, there were abrupt climatic changes. There were several abrupt cooling events, occurred in 100 AD, 300 AD, 1200 AD, and 1500 AD and 1200 AD respectively. The abrupt warming occurred in 500 AD (Yao et al., 1991a, 1991b, 1996b, 1996c, 1996d).The ice core record is up to 1990. If we add the temperature increase in the last 10 years, the present climatic warming is another abrupt climatic event.
One of the major climatic events we studied is E1 Nino event. Talking about El Nino event, perhaps everybody knows it. Climatic disasters accompanied with this event are tremendous. Droughts, floods, forest fires, we can hear all these terrible words very frequently during El Nino years. We studied precipitation feature during El Nino year. Our study found that precipitation decreased during El Nino year. We also studied the temperature feature during El Nino Year. We found that temperature also decreased during El Nino year. So we concluded that the El Nino year over the Tibetan Plateau is characterized with low precipitation and low temperature.Our major challenge both in climate and environment is that greenhouse gases, such as CO2, CH4, are possibly amplifying global warming. But we are still not sure at what degree the greenhouse gases are impacting climate. One of the ways to understand greenhouse gases is to reconstruct the past greenhouse gases recorded in ice. By the way, ice core record is the only way to extract greenhouse gases in the past (Xu et al., 1999). In 1997, we drilled an ice core from 7100 m a.s.l. in the Himalayas to reconstruct methane record. This is methane record versus depth for the ice core. Based on the depth profile, we found seasonal cycles of methane. The methane concentration is high in summer, which means more emissions of methane from wet land in summer. Based on seasonal cycles, we can reconstruct in detail the methane fluctuation in the past 500 years. There are several features in the methane fluctuations in the past 500 years: The most prominent feature is the abrupt increase since 1850 AD. This is closely related to industrial revolution. Secondly, we can observe sudden decrease in methane concentration during the World War I and World War II. It implies that human activities already controlled atmospheric greenhouse gases 80 years ago. Thirdly, we found that the average methane concentration in the Tibetan ice core is higher than polar region ice core, indicating that the low latitude wet land is a major natural source of atmospheric methane.
We also compared methane fluctuations in the past 500 years with temperature. It is clear that there is a good positive relationship between methane concentration and temperature. The low methane concentration corresponds to low temperature, and high concentration corresponds to high temperature.
Yang (1991) summarized the results of glacier water resource studies and published a book, Glacier Water Resources in China. She also calculated the glacier meltwater runoff in detail, she estimated that the sum of the glacier meltwater runoff in China was about 5.64´1010 m3, in which 58% is in Tibet and 33% in Xinjiang.
In order to calculate the river water resources in mountains, precipitation observation methods were improved (Yang et al., 1992). Major effort was also put in the study of glacier energy balance and runoff formation process (Kang et al., 1992), river ice and its effects on the spring-time runoff formation process (Zhang et al., 1992), evaporation calculating of riverhead regions (Zhang et al., 1992) and valley evaporation estimation (Zhang et al., 1992) and so on. Kang et al. (1994), combined with energy balance and valley water balance, have established a model linked with the processes of atmosphere and valley hydrology.
In order to discuss the processes of hydrology, the mechanism of runoff formation and the characteristics of runoff producing in high mountainous cold regions, Yang et al. (1992) made observation of hydrology in cold regions at the Binggou Station in the upper reaches of the Heihe River in the Qilian Mountains. The results suggested that it was feasible to calculate runoff by mathematical model in cold and high elevation regions, and the runoff was a result of the transformation between surface water and water in permafrost (Yang et al., 1996a). In addition, the phenomenon of “element pulse” in the snowmelt runoff was found in the chemical studies of snow-melt runoff in the Urumqi (Liu et al., 1997).
A program titled as ‘Impacts of Climatic Change on Water Resources in Northwest China and Trends Estimation' led by Shi studied the water resources in Northwest China regions in different ways, such as the paleoclimte information recorded by ice core, the changes and trends of glaciers, seasonal snow covers, rives and plains runoffs, and lakes etc. (Shi, 1995a). The regional runoff change distributions have been clarified, and the climatic change impacts on the runoff in high mountainous regions have been simulated (Lai et al., 1995). Water mass balance model has been used to simulate the changes of runoff in different background climate in the Tianshan Urumqi River valley (Lai et al., 1991) and Ili River valley (Ye et al., 1996). And the forecast of the future climatic changes impacts on the water resources in the arid regions in northwest China has been done based on these studies (Shi et al., 1995b).
Through another program titled as ‘Cryosphere Response to Climatic Change and Its Impacts on Environment in High Asian Area', the water runoff model with water energy and flux balance has been used to simulate glacier system and possible change following the climate change in north slope of the Tianshan Mountains (Kang, 1996). The response of hydrology to climate change in cold regions in north slope of the Qilian Mountains has been studied, and the runoff flux and the environment change in cold regions have been forecast (Yang et al., 1996b). At the same time, the impacts of climate change on the runoff of large rivers and lakes in the Qinghai-Tibetan Plateau have also been estimated (Lai, 1996). In addition, climatic impacts on water flux balance and its future trends were forecast for the Qinghai Lake basin (Ding et al., 1995).
4.5 GLACIAL DISASTER
Glacial advance and retreat and ice melt-water channel changes are important disasters to roads and bridges. Expeditions and studies had been done for the Batuora Glacier in Karakoram between1974—1975. The advance in the end of this century and retread in the next century of the Batuora Glacier had been forecast. The two re-observations in 1978 and 1980a suggested that the previous forecasts were mostly correct (Shi, 1980).
The glacial outburst floods of Yarkant Lake in the Xinjiang Autonomous Region are more dangerous and frequent. A study between 1985—1987 suggested that the floods were caused by glacial outburst. And the modes of glacial outburst were the water channel under fast ice expanding. It was forecasted that the glacial outburst floods in the Yarkant Lake would decrease gradually in the future (Zhang et al., 1989a, b).
4.5.3 Moraine Outburst Floods
The glacial outburst floods and the glacial debris-flow in Boqu and Pengqu Rivers in the Himalayan Mountains, cause a series of disasters. In 1987, scientists studied the moraine outburst floods, analyzed the mechanism of moraine outburst floods, and revealed glacial debris-flow formation and movement process (Xu, 1987).
Based on the studies, Ding et al. (1992) pointed out that the outburst of the moraine lake mainly related to icefall. Liu et al. (1998) studied the Maicibahe glacial lake outburst floods and suggested that the flux of the glacial-lake and the runoff increased year by year, which were related to regional warming in the Tianshan region.
The first blowing snow station was established at the source area of the Künes River in the West Tianshan Mountains during 1967—1977. The wind tunnel simulation laboratory is used to combine with the field laboratory. Blowing-snow disaster prevention engineering was designed in the South Xinjiang in 1975. Since 1978, blowing snow had been studied on the Qinghai-Tibetan Road and Xinjinag. The principle of the prevention of blowing snow disaster was summarized (Wang et al., 1980, 1982). The practice proved that the blowing snow disaster prevention engineering designed in the South Xinjiang Railway were correct.
The design of Tianshan road avalanche prevention engineering started in 1976 was completed at the Avalanche Study Station at the source area of the Künes River, Xinjiang, which secured the transportation in winter and spring on the road (Zhang, 1986). The study of avalanche and its prevention in the Hengduan Mountains since 1980s had classified the avalanche regions based on seasonal snow cover, and completed the avalanche maps in west Szechwan, North Yunnan and Southeast Tibet (Wang et al., 1986; Wang, 1992).
Snow disaster in pasturing area is one of the main factors restricting the economy development in some areas. In recent years, several serous snow disasters have happened in Ngari and Nagqu in Tibet, Altay in Xinjiang, Yushu in Qinghai and A'ba in Szechwan etc. Scientists have studied the snow cover distribution and snow disaster area of China (Li, 1993). Since the 1990s, scientists have used the advanced remote sensing technique to inspect and estimate the snow disaster in pasturing area, and put forward a classification index system of snow disaster in pasturing area, made Snow Cover Strength Estimation Map of China and Snow Disaster Degree Map of China (Feng et al., 1997).
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