Glacier Melting Simulation Based On Energy Balance Model Of Xiaodongkemadi Glacier In The Qinghai-tibetan Plateau

Glaciers in the Qinghai-Tibetan Plateau experienced accelerated melting in the past decades under the context of global climate changes,which also had a significant impact on the regional water cycle system.Terrestrial water storage is an important indicator to show the state of the water cycle.The reduction of solid water storage caused by glacier melting had a profound impact on terrestrial water storage.Thus,it is important to investigate the trend of terrestrial water in the Qinghai-Tibetan Plateau under climate changes.In addition,understanding the mechanisms of accelerated glacier melting is critical to water security risk estimation.Current studies which focus on terrestrial water storage were mostly based on Gravity Recovery and Climate Experiment（GRACE）data,the long-term changes in terrestrial water storage in the Qinghai-Tibetan Plateau were still unclear due to the limitation of data duration.Glacier melting simulation had been considered by part of hydrological models.However,most hydrological models simulated glacier melting based on the degree-day factor method,which lacks the simulation and analysis of the mass and energy processes simulation.To address the above problems,the long-term changes in terrestrial water storage in the Qinghai-Tibetan Plateau were analyzed by integrating satellite observation data and model simulation data,and the impact of climate change s on terrestrial water storage was also explored.A glacier melting model based on the mass-energy balance was built.Based on the model,the mass-energy processes in a typical glacier were simulated,and the mechanisms of the influence of different climate factor changes on the glacier mass balance were investigated.The trend of glacier mass balance under different climate scenarios in the future was predicted by the mode l.The main research results were as follows:Based on GRACE data and Intersectoral Impact Model Intercomparison Program（ISIMIP）multi-model simulation data,the long-term trend of terrestrial water storage and the impact of climate changes were explored by combining different socioeconomic and radiation forcing scenarios.The results showed that from 1861 to2005,the terrestrial water storage in the Qinghai-Tibetan Plateau showed an increasing trend under both the pre-industrial scenario（PIC）and the historical scenario（HIST）,and climate changes reduced the increase rate(0.50 km³ a^-1).From2006 to 2099,the terrestrial water storage in the Qinghai-Tibetan plateau showed an increasing trend under the PIC scenario and showed decreasing trends under RCP2.6,RCP6.0,and RCP8.5 scenarios.Climate changes changed the trend of terrestrial water storage in the Qinghai-Tibetan Plateau.The analysis based on glacier elevation data and GRACE data indicated that the solid water storage loss caused by glacier melting was the main reason for the decrease in terrestrial water storage in the Qinghai-Tibetan Plateau since 2003.A glacier melting simulation model was developed based on mass and energy balance in the glacier surface,which described the mass and energy processes between the atmosphere,glacier surface,and glacier interior.This model was used to simulate the glacier mass balance in the Xiaodongkemadi glacier in two mass balance years from 2012 to 2014.The results showed that the Xiaodongkemadi glacier was in a state of mass loss in both two mass balance years,the mass balance value s for two years were-682.08 mm w.e.and-574.85 mm w.e.,respectively.The simulation results of the mass-energy process showed that glacier melting mainly occurs in the warm season,and the intense melting made the glacier present a negative mass balance stat e.Net radiation dominated the energy process in the warm season and it was the main source of melting energy.Sensitivity experiments of climatic factors on glacier mass balance showed that air temperature changes mainly affect the energy balance processe s of glaciers by changing the net radiation and affecting the mass balance through the amount of glacier melting.Precipitation changes mainly affect the mass balance of glaciers by changing snowfall.The sensitivity of the mass balance to temperature increase by1°C was higher than that of a temperature decrease by 1°C in Xiaodongkemadi glacier,which means that the glacier mass loss caused by global warming cannot be compensated by a temperature decrease at the same extent.Temperature rise was the most important reason for the glacier mass loss in the Qinghai-Tibetan Plateau,and the key to slowing down the glacier recreation was to control the global warming level.Based on CMIP6 simulation data,the future climate change in the Qinghai-Tibetan Plateau was projected.From 2015 to 2100,the annual mean temperature rise rate in the Qinghai-Tibetan Plateau under the SSP2-4.5 scenario and the SSP5-8.5scenario were 0.034℃a^-1 and 0.070℃a^-1,respectively.The annual average precipitation showed significant increase trends under both SSP2-4.5 and SSP5-8.5scenarios in the Qinghai-Tibetan Plateau.The future climate in the Qinghai-Tibetan Plateau will towards the direction of“warming”and“wetting”.The simulation of the future mass balance change in the Xiaodongkemadi glacier showed a decreasing trend under both SSP2-4.5 and SSP5-8.5 scenarios,and the glacier mass loss rate showed an accelerated state in the future.However,the rate of mass loss in Xiaodongkemadi glacier under SSP5-8.5 scenario was higher than that under SSP2-4.5 scenario.To sum up,this paper analyzed the trends of terrestrial water storage under different climate scenarios in the Qinghai-Tibetan Plateau,and revealed the impact of climate changes on terrestrial water storage and its components.A mass-energy balance based glacier melting model was constructed to simulate the mass balance changes in a typical glacier.Based on the model,the energy mechanisms of glacier melting acceleration under global warming were revealed.This research provided an effective tool for hydrological simulation in alpine basins.Fu rthermore,this study provides a scientific basis for further understanding the response mechanism of glaciers to climate changes,it also provides a theoretical basis for the development of water resources management.