青藏高原东部发育冰川临界海拔的影响因素研究

Impact factors of the threshold altitude for glacier development on the eastern Tibetan Plateau

基于冰川-气候模型,青藏高原东部的布尔汗布达山北坡、布尔汗布达山南坡、达里加山、拉脊山、贡嘎山东坡、贡嘎山西坡和海子山发育冰川临界海拔与物质平衡线高度的差值(Δh)分别为89 m、85 m、4 m、24 m、16 m、29 m和8 m。研究区5个山体地形、气候和地势的对比分析表明,研究区不同山体间Δh的差异受控于山体平衡线高度(ELA)处的年降水量和ELA以上区域的坡度,布尔汗布达山ELA处极低的降水使得其Δh最大,达里加山ELA处较为丰沛的降水和较为平缓的坡度使得其Δh最小。气候是影响冰川发育最重要的因素,应进一步探寻气候波动下山体发育冰川临界海拔的变化规律。

Elevation is a very important factor for glacier development on the Tibetan Plateau and the glacier equilibrium line altitude(ELA)is the lowest limit for glacier development.However,on the Tibetan Plateau,previous studies about how many meters above the ELA of mountains can develop glacier is still scarce.Based on the glacier-climate model,the threshold altitude for glacier development(H_(t))in the north and south slope of Burhan Budai Mountain,Dalijia Mountain,La Ji Mountain,east and west slope of Gongga Mountain,and Haizi Mountain on the eastern Tibetan Plateau are 5320 m,5390 m,4740 m,4881 m,4894 m,5114 m and 5414 m,respectively and the ELA of these mountains are 5231 m,5305 m,4736 m,4793 m,4878 m,5085 m and 5406 m respectively.Thus,the difference(Δh)between the H_(t)and ELA of these mountains are 89 m,85 m,4 m,24 m,16 m,29 m and 8 m,respectively.Based on the comparative analysis of the topography,climate and relief of the five mountains in the study area,our results indicate that the changes in ice volumes on the Gongga Mountain and Burhan Budai Mountain are consistent with their positive difference of glaciation.With greater positive difference of glaciation,the size of glaciers in Gongga Mountain is larger than that of Burhan Budai Mountain.Generally speaking,the difference in slope above ELA during last glacial maximum(SELA)makes theΔh of Dalijia Mountain and Haizi Mountain,which were occupied by ice cap during late Quaternary,smaller than that of Burhan Budai Mountain,La Ji Mountain and Gongga Mountain,which mainly developed valley glaciers since the late Quaternary.Compared with other mountains in the study area,the extremely low annual precipitation at the ELA of Burhan Budai Mountain makes itsΔh the largest.TheΔh of the Dalijia Mountain is the smallest due to the relatively abundant annual precipitation at ELA and the relatively gentle S_(ELA).In the marine glacial area,the lower average summer temperature at ELA and the gentler S_(ELA)make itsΔh smaller than that of Gongga Mountain.The differences ofΔh between east and west slope of Gongga Mountain are mainly affected by their annual precipitation at ELA.In continental glacial area,the differences ofΔh between Burhan Budai Mountain,La Ji Mountain and Dalijia Mountain are dominated by the changes in annual precipitation at ELA.As a consequence,the differences ofΔh between different mountains in the study area are controlled by changes in annual precipitation at ELA and SELA.This article preliminarily researches the impact of climate differences(or changes)onΔh based on the comparison of different mountains.Climate is the greatest factors impacted on the development of glaciers.Changes in climate will cause changes in the surface environment of earth and this will introduce errors for model because of our simulation commonly based on modern conditions.In addition,quantitative paleoclimatic reconstructions are scarce in glaciated areas,which restrict the application of the model.Further research should be applied to explore the changes in H_(t)under climate fluctuations based on more robust paleoclimate data.