Pu Jianchen

Recent glacial retreat in High Asia in China and its impact on water resource in Northwest China

Under the impact of climatic warming, the glaciers in the High Asia in China have been retreating continuously with negative glacial mass balance in recent several decades. The retreat became more intensive in the past 10 years. The spatial pattern of the glacial retreat in the High Asia in China is that the smallest magnitude of retreat is in the inland of the Tibetan Plateau, the magnitude increases from the inland to the margin of the Tibetan Plateau, and the largest magnitude at the margin of the Tibetan Plateau. The glacial retreat in the High Asia in China has an important impact on the water resource of the arid regions in Northwest China. This study shows that the glacial retreat in the 1990s has caused an increase of 5.5% in river runoff in Northwest China. In the Tarim River basin, the increase of river runoff is higher than 5.5%.

Superimposed ice in glacier mass balance on the Tibetan Plateau

The relations betw een mass bal ance and meltwater refre ezing were examined on the basis of glac iolo gical obse rvations carried out in summer 1993 on Xiao Dongkemadi Glacier, Tanggula Mountai ns, central Tibetan Plateau. On this glacier, a part of melt water refreezes at the snovv/ice int erface as superimp osed ice. The amount of supe rimp osed ice formation was determ ined by both meltw ater supply and temperat ure condit ion of the glaci er. Snow-lay er thic kness on the glacier ice body is less than 2 m, even in the higher accu mulat ion zone. About 60% of meltw ater generate d in the accumula tion zone for the period ?v1ay-September was trapped at the snow/ice interface by refre ezing , and was not dis charged out of the glacie r. About 26% of accumulated snow to the glacier surface was repl aced on the snow/ice interface by refreez ing in the accumulation zone. These facts indicate that superim posed ice formation is quit e signifi cant for water retention in glaciers unde r low-pre cipitation conditions.

Mass balance of Xiao Dongkemadi glacier on the central Tibetan Plateau from 1989 to 1995

Abstract Data on the mass balance of Xiao Dongkemadi glacier in the Tanggula mountains, central Tibetan Plateau, were obtained over 5 5 years from 1989 to 1995. These are the first continuous mass-balance data for a continental-type glacier on the Tibetan Plateau, where the glacier accumulates during the summer monsoon (summer-accumulation-type glacier). Mass-balance vs altitude profiles were steeper in the negative than in the positive mass-balance years. This is considered to have resulted from the effect of summer accumulation. The annual mass balance is compared with air temperature, precipitation, and black-body temperature in the area including the glacier, which is calculated from infrared radiation observations by theJapanese Geostationary Meteorological Satellite. It was found that the interannual variation in the glacier mass balance was not closely related to maximum monthly mean air temperature, while it did have a relatively good correlation with maximum monthly mean black-body temperature.

Temperature and methane changes over the past 1000 years recorded in Dasuopu glacier (central Himalaya) ice core

Abstract In 1997, three ice cores were recovered from Dasuopu glacier on the northern slope of the central Himalaya. the first core, 159.9 m long, was drilled at 7000ma.s.l. down the flowline from the top of the col. the second core, 149.2m long, was drilled on the col at 7200ma.s.l. the third core, 167.7 m long, was also drilled on the col at 7200ma.s.l., 100 maway from the second core. the present paper discusses the δ18O and methane results reconstructed for the past 1000 years based on the second core. the δ18O can be interpreted as an air-temperature signal. the methane concentration is mainly representative of atmospheric methane concentration. Both δ18O and methane records show an obvious increasing trend in the past 1000 years. Methane concentration in the record is similar to the fluctuations of δ18O, decreasing during cold periods and increasing during warm periods. the Little Ice Age was well recorded in the core by both δ18O and methane. the coldest period appeared in the late 18th century, accompanied by a decrease in methane concentration. the abrupt methane-concentration increase starting after the 18th century is no doubt due to anthropogenic input. the observed methane-concentration decrease during World Wars I and II clearly demonstrates the importance of the anthropogenic input to atmospheric methane concentration if further measurements prove that it is a true atmospheric signal.

Climatic and environmental changes over the last millennium recorded in the Malan ice core from the northern Tibetan Plateau

In this paper, climatic and environmental changes were reconstructed since 1129A.D. based on the Malan ice core from Hol Xil, the northern Tibetan Plateau. The record of δ18O in the Malan ice core indicated that the warm-season air temperature variations displayed a general increase trend, the 20th-century warming was within the range of natural climate variability, and the warmest century was the 17th century while the warmest decade was the 1610s, over the entire study period. The “Medieval Warm Epoch” and “Little Ice Age” were also reflected by the ice core record. The dust ratio in the Malan ice core is a good proxy for dust event frequency. The 870-year record of the dust ratio showed that dust events occurred much frequently in the 19th century. Comparing the variations of δ18O and the dust ratio, it is found that there was a strong negative correlation between them on the time scales of 101–102 years. By analyses of all the climatic records of ice cores and tree rings from the northern Tibetan Plateau, it was revealed that dust events were more frequent in the cold and dry periods than in the warm and wet periods.

Climatic changes on orbital and sub-orbital time scale recorded by the Guliya ice core in Tibetan Plateau

Based on ice core records in the Tibetan Plateau and Greenland, the features and possible causes of climatic changes on orbital and sub-orbital time scale were discussed. Orbital time scale climatic change recorded in ice core from the Tibetan Plateau is typically ahead of that from polar regions, which indicates that climatic change in the Tibetan Plateau might be earlier than polar regions. The solar radiation change is a major factor that dominates the climatic change on orbital time scale. However, climatic events on sub-orbital time scale occurred later in the Tibetan Plateau than in the Arctic Region, indicating a different mechanism. For example, the Younger Dryas and Heinrich events took place earlier in Greenland ice core record than in Guliya ice core record. It is reasonable to propose the hypothesis that these climatic events were affected possibly by the Laurentide Ice Sheet. Therefore, ice sheet is critically important to climatic change on sub-orbital time scale in some ice ages.Based on ice core records in the Tibetan Plateau and Greenland, the features and possible causes of climatic changes on orbital and sub-orbital time scale were discussed. Orbital time scale climatic change recorded in ice core from the Tibetan Plateau is typically ahead of that from polar regions, which indicates that climatic change in the Tibetan Plateau might be earlier than polar regions. The solar radiation change is a major factor that dominates the climatic change on orbital time scale. However, climatic events on sub-orbital time scale occurred later in the Tibetan Plateau than in the Arctic Region, indicating a different mechanism. For example, the Younger Dryas and Heinrich events took place earlier in Greenland ice core record than in Guliya ice core record. It is reasonable to propose the hypothesis that these climatic events were affected possibly by the Laurentide Ice Sheet. Therefore, ice sheet is critically important to climatic change on sub-orbital time scale in some ice ages.