2050年前气候变暖冰川萎缩对水资源影响情景预估

Estimation of the Water Resources Affected by Climatic Warming and Glacier Shrinkage before 2050 in West China

根据有不确定性的综合预测 ,到 2 0 5 0年左右青藏高原温度可比 2 0世纪末升高 2 .5℃左右 ,其导致冰川强烈消融的夏季升温为 1.4℃ ,将使平衡线上升 10 0m以上 .冰舌区消融冰量超过积累区冰运动来的冰量 ,冰川出现变薄后退 ,初期以变薄为主融水量增加 ,后期冰川面积大幅度减少 ,融水量衰退 ,至冰川消亡而停止 .考虑冰川大小 ,冰川类型响应气候变暖的敏感性有重大差别 ,应用新编中国冰川目录的统计数据 ,选择若干区域 ,预估 2 0 5 0年前冰川萎缩对水资源影响情景 .祁连山北麓河西地区 ,天山北麓准噶尔盆地南缘 ,天山南麓吐鲁番 哈密盆地的多数出山河流的冰川 ,以面积小于 2km2 者占绝对优势 ,对气候变暖最为敏感 ,衰退迅速 ,本世纪初期出现融水量高峰 ,中期融水量减少 ,对每条河流的影响以 10 6～ 10 7m3 ·a-1计 .少数流域如疏勒河、玛纳斯河等 ,冰川融水量占河川径流 1/ 3以上 ,有若干 5～ 30km2 左右中等规模冰川存在 ,预期至本世纪中期才出现融水高峰 ,融水增加值以 10 8m3 ·a-1计 .塔里木盆地周围高山冰川总面积达 2 2 0 0 9km2 ,有面积超过 10 0km2 、冰舌为厚表覆盖的大冰川 2 2条 ,退缩缓慢 ,冰川融水量在叶尔羌河、玉龙喀什河与阿克苏河等占 5 0 %～ 80 % .

According to a comprehensive prediction with some uncertainties, temperature of the Tibetan Plateau may rise by 2.5 ℃ by 2050 or so as compared to that at the end of the 20th century. It is very likely that the summer temperature, which causes intense ablation of glaciers, will rise by 1.4 ℃. As a result, the equilibrium line altitude will rise more than 100 m; the ablation in the tongue zone will exceed the ice amount moved from the accumulation zone; and glaciers will thin and retreat. In the earlier stage, thinning prevails and meltwater increases. While in the later stage, glacier largely shrinks, meltwater decreases and some glaciers will disappear. There is a large difference in the sensitivity of response of glaciers to climate warming, depending on the size and type of glaciers. Using the statistical data of China's glacier inventory, several regions were selected to make a prediction of the water resources affected by glacier shrinkage before 2050. In some regions, such as the Hexi Region in the north slopes of the Qilian Mountains, southern margin of the Junggar Basin in the north slopes of the Tianshan Mountains and the Hami-Turpan Basin in the south slopes of the Tianshan Mountains, glaciers, most of them have an area less than 2 km 2,are sensitive to the climate warming and hence ablation increases. At the beginning of this century meltwater will reach its peak value, and by the middle part of this century meltwater will decrease. The impact on runoff of different rivers is estimated to be in the order of 10 6～10 7 m 3·a -1 . Some basins, such as the Shule River Basin in the Qilian Mountains and the Manas River Basin in the Tianshan Mountains, meltwater can account for one-third or more of the river runoff. It is predicted that several medium-sized glaciers of 5～30 km 2 will reach their meltwater peak value by the middle part of this century and their meltwater will increase in the order of 10 8 m 3·a -1 . In the mountain regions around the Tarim Basin there are totally 22 009 km 2 of glaciers, 22 larger ones of which have an area exceeding 100 km 2,with their tongues covered by thick debris mantle. Therefore, these glaciers will retreat slowly. Glacier meltwater occupies 50%～80% of the discharge of the Yarkant River, Yurunkax River and Aksu River. At present the main stem of the Tarim River is mainly fed by meltwater of glaciers in the southwest part of the Tianshan Mountains via the Aksu River. It is predicted that glacier meltwater will continue to increase before 2050, the increased volume may reach about 25%～50% more than that at the beginning of this century, and annual increased discharge of 7 major rivers of the Tarim Basin is estimated to be in the order of 10 8 m 3·a -1 . In order to effectively utilize the increased meltwater, it is necessary to construct mountain reservoirs to increase energy output and irrigation effect. Inland watersheds in the Qaidam Basin and the Tibetan Plateau are dominated by extreme continental type glaciers with lower temperature and slow retreat velocity. Temperature rise and meltwater increase during the first half of this century are favorable to the development of animal husbandry and economic growth. However, in the maritime-type glacier regions at the southeast part of the Tibetan Plateau and the Hengduan Mountains, where precipitation is more and ice temperature is higher, the temperature rise will quicken ablation and retreat of glaciers, perhaps thus causing frequent flood and debris flow disasters.