Catchment-scale Reconstruction Of Glacier Mass Balance And Its Affecting Factors Between 1990 And 2018 In The Kanchenjunga Basin

Under the background of climate warming,the global glaciers are generally retreating with their mass budget in an accelerated loss state,which has an important influence on the regional downstream water resources and causes glacial disasters such as glacial lake outburst floods and glacier-induced debris flows that seriously threaten the lives and property safety of downstream residents.The Kanchenjunga Basin is located in the central Himalayas,where is a highly glacierized catchment that has several types of glaciers.Reconstructing and analyzing the history and future mass balance of glaciers in the Kanchenjunga Basin is conducive to understanding the glaciers in response to climate change under different impacts,such as glacial lakes and debris-cover,which can provide support and reference data for the study of global-scale or regional-scale glacier mass loss and its impact on glacial disasters.In this study,the China meteorological forcing dataset was used as the meteorological forcing parameter,and the mass balance of the Kanchenjunga Basin from 1990 to 2018 was reconstructed by using the glacier energy and mass balance model.In addition,the influence of climate factors,debris-cover,and proglacial lake distribution on the characteristics and changes of glacier mass balance is analyzed and discussed.Driven by the CMIP6 future scenario model data,the glacier change trend of the glacier mass balance in the Kanchenjunga Basin under different radiation intensity paths was discussed.The main conclusions of this study are as follows:（1）From 1990 to 2018,more than 80%of the years in the Kanchenjunga Basin showed a negative mass balance with an average mass balance of-0.35 m w.e.a^-1 and a cumulative mass balance of-10.70 m w.e.;In the past 29 years,the equilibrium-line altitude of glaciers in the Kanchenjunga Basin range between 5 817 and 6 282 m a.s.l.with an average altitude of 6 030m;The months when the glacier mass balance is positive are mainly from March to May,while the months when the glacier mass balance is negative are mainly from June to October within the July and August are the most negative months.（2）In the Kanchenjunga Basin,temperature and precipitation is the main factor affecting the glacier mass balance.An increase of 1°C annual average temperature will lead to mass loss in 0.35 m w.e.with 113.7 m of ELA uplift,while a 100 mm increase of annual precipitation will lead to mass loss in 0.3 m w.e.,in the meantime will cause 77.0 m of ELA decrease.In addition,the glacier mass balance is most sensitive to summer average temperature and winter precipitation,while is the least sensitive to winter average temperature and summer precipitation.（3）The debris cover in the Kanchenjunga Basin generally promoted the glacier melt,and we found a 20.2%decrease in glacier melt with an assumption of no debris cover on the glaciers compared to the real surface condition.In addition,it was found that when the debris thermal resistance increased to 200%,the ablation rate was comparable to that without the debris cover.In the Kanchenjunga Basin,the rate of mass loss of lake-terminating glaciers is faster.（4）In the future,the glaciers’mass loss in the Kanchenjunga Basin will be continued and accelerated.Under the SSP126 pathway,the glacier mass balance will change small compared with the baseline term（1990-2018）,while the glacier mass balance will be in an accelerated loss situation under SSP245,SSP370,and SSP585 three pathways.Compared with 2019 with10.8766 Gt,by 2050 and 2099 glacial volume will be reduced by～36%and～53%respectively,and under the SSP585 pathway,ice volume will decrease by～40%and～88%respectively.The results of the paper show that during the past 29 years,the glaciers in the Kanchenjunga Basin have experienced severe mass loss with an average mass balance of-0.35m w.e.a-1,which is more negative than the 1975-2015 average mass balance in the Himalayas(-0.32 m w.e.a^-1).The glacier mass loss is more sensitive to changes in summer mean temperature and winter precipitation.In addition,debris-cover and proglacial lake are also important affects that accelerate the rate of glaciers mass loss.The total glacier volume will decrease by～36%and～53%in 2050 and 2099（under SSP126）compared with 2019,respectively,with rates reaching～40%and～88%in extreme situation（under SSP585）.