Change Of Glacier Mass Balance Based On Multi-source Remote Sensing Data In Tianshan Mountains,China

Glacier mass balance(GMB)is a bridge between climate change and runoff response.Melting water from mountain glaciers plays an important role in supplying and regulating river runoff in arid areas,which is crucial to maintaining regional ecological stability and human social development.Tianshan Mountains is a natural “wet island” in Xinjiang and even in Central Asia.However,most data of the GMB in mountain areas are scarce or blank.In addition,the simulation study of the GMB in Tianshan Mountains is limited to a single glacier or a few watersheds,which limits the detailed assessment of glacier water resources in Tianshan Mountains and the study of spatial differentiation of mass balance.Based on MOD11C3,TRMM3B43 and other multi-source remote sensing data,the OLS-downscaling model of temperature and precipitation is constructed to accurately depict the spatio-temporal variation characteristics of temperature and precipitation in the runoff producing area of the Tianshan Mountains.The distributed degree-day model is driven to simulate the mass balance changes of the Tianshan Mountains glaciers from 2000 to 2018 a.The spatio-temporal variation law of the GMB and its influencing factors in various drainage areas of the Tianshan Mountains are further analyzed,and the change of glacier melt water and its replenishment characteristics to river runoff are attempted to be explored.The results show that:(1)During the study period,the temperature changes in the runoff producing areas of each basin are different and show a warming trend.The temperature tendency rates in Turpan-Hami Basin,Tarim River Basin,Yili River Basin and Dzungaria Basin are 0.47,0.35,0.24 and 0.21?/10 a respectively.The vertical variation of air temperature shows that the vertical decreasing rate of air temperature in Tarim River Basin and Turpan-Hami Basin is higher,which is-0.58,-0.57?/100 m respectively.However,the vertical decline rate of air temperature in Yili River Basin and Dzungaria Basin is lower,which is-0.48,-0.47?/100 m respectively.The changes of temperature in runoff producing areas in Tianshan Mountains indicate that the geographical location,topography,average altitude,etc.of the basins may be important factors affecting the temporal and spatial differences of temperature.(2)The spatio-temporal distribution of precipitation in runoff producing areas of each basin is different during the study period.The precipitation in Yili River Basin is decreasing while that in other basins is increasing.The precipitation change rates in Yili River Basin,Dzungaria Basin,Tarim River Basin and Turpan-Hami Basin are-4.72,16.23,13.27 and 4.02mm/10 a respectively.The vertical variation of precipitation shows that the vertical increase of precipitation in Turpan-Hami Basin is the most obvious,13.28mm/100mm;The second is Tarim River Basin and Dzungaria Basin,which are 8.63mm/100 m and7.99mm/100 m respectively.However,the vertical increase of precipitation in Yili River Basin is weak,4.57mm/100 m m.The precipitation distribution in runoff-producing areas of the Tianshan Mountains is more significant in “west to east” than in “north to south”.Water vapor sources,topography and altitude have significant effects on the precipitation distribution.Combined with the trend of temperature growth,it is found that the Tianshan Mountains climate as a whole presents the characteristics of warm and humid.(3)During the study period,the Tianshan Mountains glacier as a whole showed a negative balance of continuous melting and strengthening,with continuous strengthening from 2000—2010a and weakened volatility from 2010 to 2018 a.According to the spatio-temporal differentiation characteristics of mass balance,the glacier losses in the Turpan-Hami Basin and Tarim River Basin are strong,at-498.35,-458.29 mm w.e.;The glacier losses in Dzungaria Basin and YIli River Basin are relatively weak,at-199.49and-331.10 mm w.e.,respectively.the mass balance gradients in Turpan-Hami Basin,Dzungaria Basin,YIli River Basin and Tarim River Basin are-9.17,-6.45,-4.16 and-3.28 mm w.e./a respectively.According to the law of mass balance change,the annual average mass balance value of a single glacier in Tianshanmountain changes from-4222.83 to 260.31 mm w.e.,which generally follows the model of “exponential accumulation and logarithmic ablation”.From the site conditions of mass balance,the temperature and precipitation are at-6.82 ~-1.82?,354.38 ~ 432.97 mm,the slope within 0 ~ 8.54°,the slope direction to the north,which has the most significant impact on the mass balance.In addition,the GMB will continue to increase with the elevation,thus finding that the GMB is affected by different climatic and topographic factors.(4)During the study period,glacier melt water in all river basins has obvious recharge to river runoff,and the recharge rate of melt water in Tarim River Basin is the most obvious,reaching 26.16%;the second is Dzungaria Basin and YIli River Basin,with 13.46% and 13.45% respectively.However,the Turpan-Hami Basin has a slightly weak supply of 10.05%.The recharge characteristics of glacier melt water to river runoff also show that,except the sensitivity of mass balance to climate change,the quantity and scale of glaciers in various watersheds also have great influence on runoff recharge rate.