Glaciers Change Of Urumqi River Watershed From Little Ice Age

Glaciers are solid reservoir,which is made of precipitation,snowfall and other solid precipitation.Glaciers can achieve solid precipitation from atmosphere.The glaciers melt water can increase stream runoff.So glaciers are exchange atmosphere with mass and energy,and rivers water resource.The glaciers in western of China is retreating in different degree because of the world warming.Urumqi River Watershed is located in the middle of Tianshan,and there are 107 glaciers on it(2014).Glaciers are main water source of the Urumqi River system and Dongshan River system,at the same time,it is the Urumqi‘s water source.Research glaciers change in this area from the Little Ice Age,is very important to us comprehend the history and now of the glaciers,and prevent the glaciers disaster happen.The Urumqi River Watershed Urumqi Glacier NO.1(here after this text will be abbreviated as the Urumqi Glacier NO.1)in this Watershed is the only one glacier in WGMS of China.It has observation a long time and more data.It is important to study the Urumqi Glacier NO.1.The Urumqi Glacier NO.1 has developed many observation project,such as the length of the glacier,area change,the speed of glacier movement and glacier reserves.Studies of glaciers in the Urumqi River Watershed are mainly focused on the change of them in the past 50 years,and studies of glaciers change since the Little Ice Age are relatively rare.Thus this paper mainly studies the characteristics of glaciers change in the Urumqi River Watershed from the Little Ice Age.This paper consists of two parts:Firstly,spot5,Google Earth and field measurement are used by the artificial visual interpretation method to study the changes of Urumqi Glacier No.1 in length and area since the LIA,and the length and area change are validated with field measured data.Ice storage of Urumqi Glacier No.1 are also studied.Secondly,the changes of 73 glaciers with recognizable marginal moraines in Urumqi Watershed since the Little Ice Age are studied,including area,length,orientation,area changes at different elevation and other comparison and analysis of mountain glacier retreat.During the period of the LIA,there were three glacier advances of the Urumqi Glacier No.1,leaving three terminal moraines.From the field measure and RS sensing data,During LIA,Urumqi Glacier No.1 area decreased from 2.48 km~2 in 1538±20 to2.15 km~2 in 1871±20 with area retreat rate of 13.31%,Urumqi Glacier No.1 area decreased from 1.95 km~2 in 1964 to 1.56 km~2 in 2014 with area retreat rate of 25%.The glacier area was retreat slowly in LIA.In 1964 to 2014,the glacier retreat speed up,espencially from 1989.The Urumqi Glacier No.1 length decreased from 2760.59 m in 1538±20 to2608.33 m in 1871±20 with length retreat rate of 5.51%.The Urumqi Glacier No.1length decreased from 1964 to 2014 retreat 274.14m with length retreat rate of14.20%.The Urumqi Glacier No.1 length retreat 1103.75 m in total.The Urumqi Glacier No.1 ice storge is not invitable in LIA,decreased from 0.136 km~3 in 1538±20to 0.112 km~3 in 1871±20 with ice storage retreat rate of 21.43%.In the late of LIA to2014 ice storage is decreased 0.039 km~3,with ice storage retreat rate of 26.26%.So it is obviously that in recent 50 years the glacier retreat more quickly than LIA.The results are compared with the measured cumulative retreat length and the area of the glacier measured using stereoscopic photogrammetry,and the accordance of the results demonstrates the accuracy of the proposed glaciers changes extracting method using remote sensing.The study of the 73 glaciers in the Urumqi River Watershed with recognizable marginal moraines comes to the following conclusions:The area of glaciers decreased from the Little Ice Age to 2014 with obvious retreat;From maximum of Little Ice Age to 2014,the area retreated 37.22 km~2 with a retreat rate of 64.84%,and the total length retreated 52878.67 m,with a retreat rate of 49.83%.Since the Little Ice Age,with the global warming,glacier melting increased,and glacier retreats are more intense.With 100 m as the altitude gradient,glacier change characteristics of different altitude are analyzed,and it‘s found that the most significant area retreats originated from the glaciers with altitude between 3400~4000 m.The glaciers terminal in the Watershed rises as a whole,and glaciers between altitude 3400~3600 m disappeared.The analysis of the glaciers orientation shows that the glacier retreat rate of different orientation from high to low are:E(86.98%),ES(83.11%),EN(75.74%),W(73.20%),S(71.61%),WN(75.94%),N(54.47%),WS(53.97%).The first condition of glacier development is the abundant precipitation,and the southwest direction is in the direction of water vapor transport of westerlies,thus,the area changes of glacier in this direction is smaller than that in other directions.Glacier area retreated the most in the east direction,and the watershed glaciers are mostly in the north direction.The number of glaciers with area less than 1 km~2 of the Urumqi River Watershed in the maximum of Little Ice Age is 55,and the glaciers in this watershed are significantly retreated because the small glaciers are more sensitive to climate change than the big ones.The glacier changes of Urumqi River Watershed are also compared with the glacier changes of 5 watershed in western Qilian Mountains studied by other researchers with the same study period since the Little Ice Age.It‘s found that the glacier changes in the Urumqi River Watershed are larger than those in other watershed.