Analyzing geomorphological and topographical controls for the heterogeneous glacier mass balance in the Sikkim Himalayas

Glacier response patterns at the catchment scale are highly heterogeneous and defined by a complex interplay of various dynamics and surface factors.Previous studies have explained heterogeneous responses in qualitative ways but quantitative assessment is lacking yet where an intrazone homogeneous climate assumption can be valid.Hence,in the current study,the reason for heterogeneous mass balance has been explained in quantitative methods using a multiple linear regression model in the Sikkim Himalayan region.At first,the topographical parameters are selected from previously published studies,then the most significant topographical and geomorphological parameters are selected with backward stepwise subset selection methods.Finally,the contributions of selected parameters are calculated by least square methods.The results show that,the magnitude of mass balance lies between-0.003±0.24 to-1.029±0.24 m.w.e.a^(-1) between 2000 and 2020 in the Sikkim Himalaya region.Also,the study shows that,out of the terminus type of the glacier,glacier area,debris cover,ice-mixed debris,slope,aspect,mean elevation,and snout elevation of the glaciers,only the terminus type and mean elevation of the glacier are significantly altering the glacier mass balance in the Sikkim Himalayan region.Mathematically,the mass loss is approximately 0.40 m.w.e.a^(-1) higher in the lake-terminating glaciers compared to the land-terminating glaciers in the same elevation zone.On the other hand,a thousand meters mean elevation drop is associated with 0.179 m.w.e.a-1of mass loss despite the terminus type of the glaciers.In the current study,the model using the terminus type of the glaciers and the mean elevation of the glaciers explains 76% of fluctuation of mass balance in the Sikkim Himalayan region.

Glacier mass balance and its impacts on streamflow in a typical inland river basin in the Tianshan Mountains, northwestern China

Glaciers are known as natural ’’solid reservoirs’ ’, and they play a dual role between the composition of water resources and the river runoff regulation in arid and semi-arid areas of China. In this study, we used in situ observation data from Urumqi Glacier No. 1, Xinjiang Uygur Autonomous Region, in combination with meteorological data from stations and a digital elevation model, to develop a distributed degree-day model for glaciers in the Urumqi River Basin to simulate glacier mass balance processes and quantify their effect on streamflow during 1980–2020. The results indicate that the mass loss and the equilibrium line altitude(ELA) of glaciers in the last 41 years had an increasing trend, with the average mass balance and ELA being-0.85(±0.32) m w.e./a(meter water-equivalent per year) and 4188 m a.s.l., respectively. The glacier mass loss has increased significantly during 1999–2020, mostly due to the increase in temperature and the extension of ablation season. During 1980–2011, the average annual glacier meltwater runoff in the Urumqi River Basin was 0.48×108 m3, accounting for 18.56% of the total streamflow. We found that the annual streamflow in different catchments in the Urumqi River Basin had a strong response to the changes in glacier mass balance, especially from July to August, and the glacier meltwater runoff increased significantly. In summary, it is quite possible that the results of this research can provide a reference for the study of glacier water resources in glacier-recharged basins in arid and semi-arid areas.

Study of annual mass balance(2011–2013) of Rikha Samba Glacier, Hidden Valley, Mustang, Nepal

Although Himalayan glaciers are of particular interest in terms of future water supplies, regional climate changes, andsea-level rises, little is known about them due to lack of reliable and consistent data. There is a need for monitoring theseglaciers to bridge this knowledge gap and to provide field measurements necessary to calibrate and validate the resultsfrom different remote sensing operations. Therefore, glaciological observations have been carried out by the CryosphereMonitoring Project （CMP） since September 2011 on Rikha Samba Glacier in Hidden valley, Mustang district in westernNepal in order to study its annual mass balance. This paper presents the first results of that study. There are 10 glaciers inHidden Valley, named G1, G2, G3, up to G10. Of these, G5 is the Rikha Samba Glacier, which has the largest area （5.37km2） in this valley and the highest and lowest altitudes （6,476 and 5,392 m a.s.l., respectively）. The glacier mass balancediscussed in this paper was calculated using the glaciological method and the equilibrium line altitude （ELA）. The glaciershowed a negative annual point mass balance along the longitudinal profile of its lower part from September 10, 2011 toOctober 3, 2012. Stake measurements from October 4, 2012 to September 30, 2013 indicated a negative areal average ofannual mass balance ？0.088±0.019 m w.e. for the whole glacier. Based on these observations, the ELA of the Rikha SambaGlacier is estimated at 5,800 m a.s.l. in 2013. This negative balance may be due to rising air temperatures in the region,which have been incrementally rising since 1980 accompanied by little or no significant increase in precipitation in thatperiod. The negative mass balance confirms the general shrinking trend of the glacier.

Reconstructed annual glacier surface mass balance in theányêmaqên Mountains,Yellow River source,based on snow line altitude

Annual mass balance is an important factor that reflects glacier change and glacier meltwater resources.In this study,we analyzed the changes in glacier area,snow line altitude(SLA)and surface elevation in theányêmaqên Mountain region using multisource remote sensing data.Then,the annual mass balance of two glaciers was reconstructed by using SLA-mass-balance gradient method.The results showed that the glacier area in theányêmaqên Mountains decreased by 29.4 km2from 1985 to 2017.The average SLAs of the Halong Glacier and Yehelong Glacier were approximately 5290 m and 5188 m,respectively.The glacier mass balance for the two glaciers from 1990 to 2020 was-0.71 m w.e.a^(-1) and-0.63 m w.e.a^(-1),respectively.Our results indicate that SLA is an important indicator of glacier changes,and a long sequence of SLAs can more accurately reconstruct the glacier mass balance of the glacier.The mean annual glacial meltwater-fed streamflow is 1.45×10^(7)m^(3) and 1.12×10^(7)m^(3),respectively.Sensitivity analysis indicates that summer air temperature plays a leading role in regard to the influential climatic factors of glacial retreat in theányêmaqên Mountains.This highlights the potential of the methodology for application on reconstructing annual glacier surface mass balance at larger scales without direct measurements.

Applicability of an ultra-long-range terrestrial laser scanner to monitor the mass balance of Muz Taw Glacier,Sawir Mountains,China

Glacier mass balance is a key component of glacier monitoring programs. Information on the mass balance of Sawir Mountains is poor due to a dearth of in-situ measurements. This paper introduces the applicability of an ultra-long-range terrestrial laser scanner(TLS) to monitor the mass balance of Muz Taw Glacier, Sawir Mountains, China. The Riegl VZ?-6000 TLS is exceptionally well-suited for measuring snowy and icy terrain. Here, we use TLS to create repeated high spatiotemporal resolution DEMs, focusing on the annual mass balance(June 2, 2015 to July 25, 2016). According to TLS-derived high spatial resolution point clouds, the front variation(glacier retreat) of Muz Taw Glacier was 9.3 m. The mean geodetic elevation change was 4.55 m at the ablation area. By comparing with glaciological measurements, the glaciological elevation change of individual stakes and the TLS-derived geodetic elevation change of corresponding points matched closely, and the calculated balance was-3.864±0.378 m w.e.. This data indicates that TLS provides accurate results and is therefore suitable to monitor mass balance evolution of Muz Taw Glacier.

A STUDY ON MASS BALANCE OF HIGH ASIAN GLACIERS

Glaciers play an important role in the global water cycling especially in the balance of fresh water on our planet, which exhibits a significant impact on global changes. This paper describes the role of glaciers in the water cycle and global changes and that of High Asian glaciers and their fluctuations, and introduces the global monitoring project on glacier mass balance and the progress in corresponding research in China.

Effects of atmospheric circulation on summertime precipitation variability and glacier mass balance over the Tuyuksu Glacier in Tianshan Mountains, Kazakhstan

The amount and the form of precipitation have significant effects on glacier mass balances in high al- titude mountain areas by controlling the accumulation, the ablation and the energy balance of a glacier through impact on the surface albedo. The liquid precipitation has negative effects on glacier accumulation and may in- crease the ablation of surface ice through the heat input for melting. The timing and the forms of precipitation over glacierized regions depend on the weather processes both locally and regionally. Early studies showed that regional to large-scale atmospheric circulation processes play a key role in affecting the precipitation events over glaciers. This paper analyzed the relationship between the inter-annual variability of the summertime precipitation over the Tuyuksu Glacier and the atmospheric circulation types, which related to various atmospheric circulation types in the Northern Hemisphere. Results indicated that the decrease in the duration of zonal processes and the increase in the meridional northern processes were observed in the last decade. The total summer precipitation associated with these processes also increased along with an increase of summertime solid precipitation. Although the decadal fluctuation of glaciological parameters were found in dependent of the above large-scale atmospheric circulation processes, global warming was a dominant factor leading to the mass loss in the recent decades under the back- ground of the increase in precipitation over the Tuyuksu Glacier.

An investigation on changes in glacier mass balance and hypsometry for a small mountainous glacier in the northeastern Tibetan Plateau

Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the ablation zone of Shuiguan Glacier No.4, Qilian Mountains, China, combined with the balance ratio between accumulation and ablation, we established a linear relation between mass balance and altitude. The results show that the mean annual mass balance of this glacier was ~510 mm w.e. from 2010 to 2013. The uncertainty in the balance ratio value does not lead to a significant difference in the mass balance. The equilibrium-line altitude rose by 180 m from 1972 to 2013, while the accumulation–area ratio decreased from 0.68 to 0.25. These variations may be caused by changes in air temperature. Meanwhile, the glacier is at present not in a steady state, and it may continue to shrink by a further ~900 m, even without further climate warming. In the western Lenglongling Mountains, assuming that the glaciers are in a steady state and the Equilibrium-line altitudes(ELAs)remain similar, there will be only 46 glaciers left, covering a total area of 19.2 km^2, in other words, only 22.3% of the glaciers area in 1972.

Glacier mass balance in High Mountain Asia inferred from a GRACE release-6 gravity solution for the period 2002–2016

We provide estimates of glacier mass changes in the High Mountain Asia (HMA) area from April2002 to August 2016 by employing a new version of gravity solutions of the Gravity Recovery and ClimateExperiment (GRACE) twin-satellite mission. We find a total mass loss trend of the HMA glaciers at a rateof –22.17 (±1.96) Gt/a. The largest mass loss rates of –7.02 (±0.94) and –6.73 (±0.78) Gt/a are found forthe glaciers in Nyainqentanglha Mountains and Eastern Himalayas, respectively. Although most glaciers inthe HMA area show a mass loss, we find a small glacier mass gain of 1.19 (±0.55) and 0.77 (±0.37) Gt/a inKarakoram Mountains and Western Kunlun Mountains, respectively. There is also a nearly zero massbalance in Pamirs. Our estimates of glacier mass change trends confirm previous results from the analysisof altimetry data of the ICESat (ICE, Cloud and Land Elevation Satellite) and ASTER (AdvancedSpaceborne Thermal Emission and Reflection Radiometer) DEM (Digital Elevation Model) satellites inmost of the selected glacier areas. However, they largely differ to previous GRACE-based studies which weattribute to our different post-processing techniques of the newer GRACE data. In addition, we explicitlyshow regional mass change features for both the interannual glacier mass changes and the 14-a averagedseasonal glacier mass changes. These changes can be explained in parts by total net precipitation (netsnowfall and net rainfall) and net snowfall, but mostly by total net radiation energy when compared to datafrom the ERA5-Land meteorological reanalysis. Moreover, nearly all the non-trend interannual masschanges and most seasonal mass changes can be explained by the total net radiation energy data. The massloss trends could be partly related to a heat effect due to increased net rainfall in Tianshan Mountains, QilianMountains, Nyainqentanglha Mountains and Eastern Himalayas. Our new results for the glacier mass changein this study could help improve the understanding of glacier variation in the HMA area and contribute tothe study of global change. They could also serve the utilization of water resources there and in neighboringareas.

The processes and characteristics of mass balance on the Urumqi Glacier No. 1 during 1958-2009

As a solid reservoir, a glacier can regulate regional water resources. The annual net mass balance directly reflects the fluctuation of the glacier and climate variability. Based on 51 years of mass balance observation data, the mass balance of Tianshan Mountains Urumqi Glacier No. 1 experienced a nine times positive balance fluctuation and nine times negative balance fluctuation. There were 35 and 16 negative and positive balance years, respectively. From 1996/97 to 2008/09, 12 consecutive negative balance years were observed at Tianshan Mountains Urumqi Glacier No. 1. These results demon- strate that the Urumqi Glacier No. 1 is experiencing a strong negative balance, and the strongest negative balance, -931 mm w.e. （mm water equivalent）, during the observation period occurred in 2008. In addition, the cumulative mass balance reached 13,709 mm w.e. in 2008. However, in 2009, the mass balance was positive at 63 mm w.e. The equilibrium-line al- titude changes with the fluctuation in the mass balance, and the effective mass balance gradient is 7.4 mrn/m. In this paper, the headwaters of the Urumqi River were analyzed using meteorological data from 1958 to 2009, including the average seasonal temperature and precipitation. The results showed that the main factor associated with the mass balance variation of Glacier No. 1 is the fluctuation in the summer air temperature, followed by changes in the precipitation.

Comparative study on observed mass balance between East and West Branch of Urumqi Glacier No. 1, Eastern Tianshan, China

This paper is based on observed mass balance between East and West Branch of Urumqi Glacier No. l, meteorological data dur- ing 1988-2010, comparative studies the mass balance variations, and analyses the mass balance sensitivity to climate change. Re- sults show that average mass balance of East and West Branch was -532 mm/a and 435 mm/a, cumulative mass balance was 12,227 mm （ice thinned by 13.6 m） and -10,001 mm （ice thinned by 11.1 m）, respectively, and mass loss of East Branch was 97 mm/a larger than West Branch. The East and West Branch ELA （equilibrium line altitude） ascended about 176 m and 154 m, analysis shows the steady-state ELA0 was 3,942 m a.s.1, and 4,011 m a.s.1., and when East and West Branch mass balance de- creased by 100 ram, ELA ascended 20 m and 23 m, respectively. The AAR （accumulation area ratio） of East and West Branch presented an obviously decreasing trend of 34.5% and 23%, equilibrium-state AAR0 was 65% and 66%, when East and West Branch mass balance increased by 100 mm, AAR ascended 4.6% and 4.2%, respectively. Glacier mass balance was sensitive to change of net ablation, net ablation of East and West Branch increased 10x 104 m3, and mass balance decreased 110 mm and 214 mm, respectively. By analyzing mass balance sensitivity to climate change, results suggest that East and West Branch mass bal- ance decreased （increased） 463 mm and 388 mm when ablation period temperature increased （decreased） by 1 ~C, East and West Branch mass balance increased （decreased） 140 mm and 158 mm when annual precipitation increased （decreased） by 100 mm, and sensitivity of East Branch mass balance to climate change was more intense than that of West Branch.

Spatial variability between glacier mass balance and environmental factors in the High Mountain Asia

High Mountain Asia(HMA) region contains the world’s highest peaks and the largest concentration of glaciers except for the polar regions, making it sensitive to global climate change. In the context of global warming, most glaciers in the HMA show various degrees of negative mass balance,while some show positive or near-neutral balance. Many studies have reported that spatial heterogeneity in glacier mass balance is strongly related to a combination of climate parameters. However, this spatial heterogeneity may vary according to the dynamic patterns of climate change at regional or continental scale. The reasons for this may be related to non-climatic factors. To understand the mechanisms by which spatial heterogeneity forms, it is necessary to establish the relationships between glacier mass balance and environmental factors related to topography and morphology. In this study, climate, topography,morphology, and other environmental factors are investigated. Geodetector and linear regression analysis were used to explore the driving factors of spatial variability of glacier mass balance in the HMA by using elevation change data during 2000–2016. The results show that the coverage of supraglacial debris is an essential factor affecting the spatial heterogeneity of glacier mass balance, followed by climatic factors and topographic factors, especially the median elevation and slope in the HMA. There are some differences among mountain regions and the explanatory power of climatic factors on the spatial differentiation of glacier mass balance in each mountain region is weak, indicating that climatic background of each mountain region is similar. Therefore, under similar climatic backgrounds, the median elevation and slope are most correlated with glacier mass balance. The interaction of various factors is enhanced, but no unified interaction factor plays a primary role. Topographic and morphological factors also control the spatial heterogeneity of glacier mass balance by influencing its sensitivity to climate change. In conclusion,geodetector method provides an objective framework for revealing the factors controlling glacier mass balance.

Surface mass balance and ice flow of the glaciers Austre Lovenbreen and Pedersenbreen,Svalbard,Arctic

The glaciers Austre Lovenbreen and Pedersenbreen are located at Ny-（？）lesund. Svalbard.The surface mass balance and ice flow velocity of both glaciers have been determined from the first year of observations（2005/2006）.while the front edge of Austre Lovenbreen was also surveyed.The results are as follows： （1） The net mass balances of Austre Lovenbreen and Pedersenbreen are—0.44 and—0.20 m w.e.,the annual ablation is—0.99 and—0.91 m w.e.. and the corresponding equilibrium line altitudes are 178.10 and 494.87 m.respectively. （2） Austre Lovenbreen and Pedersenbreen are characterized as ice flow models of surge-type glaciers in Svalbard.The horizontal vectors of the ice flow velocities are parallel or converge to the central lines of both glaciers,with lower velocities in the lower ablation areas and higher velocities in the middle and upper reaches of the glaciers.The vertical vectors of ice flow velocities show that there is a mass loss in the ablation areas,which reduces with increasing altitude, while there is a mass gain near the equilibrium line of Austre Lovenbreen.（3） The front edge of Austre Lovenbreen receded at an average rate of 21.83 m·a^（-1）,with remarkable variability-a maximum rate of 77.30 m·a^（-1） and a minimum rate of 2.76 m·a^（-1）.

Study on mass balance and sensitivity to climate change in summer on the Qiyi Glacier,Qilian Mountains

Based on the glacier mass balance and meteorological data of air temperature and precipitation on the Qiyi Glacier from June 30 to September 5, 2010, we used a degree-day mass balance model to simulate the change of mass balance during this period. Our results indicate that the current value of the mass balance is -856.2 mm w.e. Subjected to the strong influences of air temperature and precipitation, the mass balance process can be divided into three stages： accumulating exiguously ~ melting intensively melting exiguously. The variation trends of the mass balance according to the degree-day mass balance model and the observed values are similar and wholly reflect the spatial distribution characteristics of the glacier mass balance, which increases with the increase of altitude. Our experiment on climate sensitivity of the mass balance showed that mass balance was very sensitive to the change of temperature; air temperature is the key factor which influences mass balance; and a slight increase in precipitation will have a negligible effect on mass balance when the air temperature increases continuously.

Long-term glacier variations and the response to climate fluctuation in Qilian Mountains,China

Glaciers are considered to be‘climate-sensitive indicators'and‘solid reservoirs',and their changes significantly impact regional water security.The mass balance(MB)from 2011 to 2020 of the Qiyi Glacier in the northeast Tibetan Plateau is presented based on field observations.The glacier showed a persistent negative balance over 9 years of in-situ observations,with a mean MB of-0.51 m w.e.yr^(-1).The distributed energy-mass balance model was used for glacier MB reconstruction from 1980 to 2020.The daily meteorological data used in the model were from HAR v2 reanalysis data,with automatic weather stations located in the middle and upper parts of the glacier used for deviation correction.The average MB over the past 40 years of the Qiyi Glacier was -0.36 m w.e.yr^(-1)with the mass losses since the beginning of the 21st century,being greater than those in the past.The glacier runoff shows a significant increasing trend,contributing~81% of the downstream river runoff.The albedo disparity indicates that the net shortwave radiation is much higher in the ablation zone than in the accumulation zone,accelerating ablation-area expansion and glacier mass depletion.The MB of the Qiyi Glacier is more sensitive to temperature and incoming shortwave radiation variation than precipitation.The MB presented a non-linear reaction to the temperature and incoming shortwave radiation.Under future climate warming,the Qiyi Glacier will be increasingly likely to deviate from the equilibrium state,thereby exacerbating regional water balance risks.It is found that the mass losses of eastern glaciers are higher than those of western glaciers,indicating significant spatial heterogeneity that may be attributable to the lower altitude and smaller area distribution of the eastern glaciers.

Geotextile protection of glacier:Observed and simulated impacts on energy and mass balance

The detailed physical processes involved in slowing glacier ablation by material cover remain poorly understood so far.In the present study,using the snow cover model SNOWPACK,the effect of geotextile cover on the energy and mass balance at the tongue of the Urumqi Glacier No.1(Chinese Tien Shan)was simulated between July 12,2022 and August 31,2022.The mass changes and the energy fluxes with and without material cover were compared.The results indicated that the geotextile covering reduced glacier ablation by approximately 68%compared to the ablation in the uncovered regions.The high solar reflectivity of the geotextile reduced the net short-wave radiation energy available for the melt by 45%.Thermal insulation of the geotextile reduced the sensible heat flux by 15%.In addition,the wet geotextile exerted a cooling effect through long-wave radiation and negative latent heat flux.This cooling effect reduced the energy available for ablation by 20%.Consequently,only 37%of the energy was used for melting compared to that used in the uncovered regions(67%).Sensitivity experiments revealed that the geotextile cover used at a thickness range of 0.045-0.090 m reduced the ice loss by approximately 68%-72%,and a further increase in the thickness of the geotextile cover led to little improvements.A higher temperature and greater wind speed increased glacier ablation,although their effects were small.When the precipitation was set to zero,it led to a significantly increased melt.Overall,the geotextile effectively protected the glacier tongue from rapid melting,and the observed results have provided inspiration for developing an effective and sustainable approach to protect the glaciers using geotextile cover.

Spatiotemporal variations in surface albedo during the ablation season and linkages with the annual mass balance on Muz Taw Glacier,Altai Mountains

Melt-albedo feedback on glaciers is recognized as important processes for understanding glacier behavior and its sensitivity to climate change.This study selected the Muz Taw Glacier in the Altai Mountains to investigate the spatiotemporal variations in albedo and their linkages with mass balance,which will improve our knowledge of the recent acceleration of regional glacier shrinkage.Based on the Landsat-derived albedo,the spatial distribution of ablation-period albedo was characterized by a general increase with elevation,and significant east–west differences at the same elevation.The gap-filling MODIS values captured a nonsignificant negative trend of mean ablation-period albedo since 2000,with a total decrease of approximately 4.2%.From May to September,glacier-wide albedo exhibited pronounced V-shaped seasonal variability.A significant decrease in annual minimum albedo was found from 2000 to 2021,with the rate of approximately−0.30%yr−1 at the 99%confidence level.The bivariate relationship demonstrated that the change of ablation-period albedo explained 82%of the annual mass-balance variability.We applied the albedo method to estimate annual mass balance over the period 2000–2015.Combined with observed values,the average mass balance was−0.82±0.32 m w.e.yr−1 between 2000 and 2020,with accelerated mass loss.

Influence of Degree-Day Factor Variation on the Mass Balance of Glacier No. 1 at the Headwaters of ürümqi River,China

The degree-day factor （DDF） is a key parameter in the degree-day model, and the varia- tions in DDF have the significant effects on the accuracy of glacier mass balance modeling. In this study, Glacier No. 1 at the headwaters of Uriimqi （-~O）~Z~=） River in China was selected, and the estimated DDF by stakes-observed mass balance and meteorological data from 1983-2006 was used to analyze the spatio-temporal variability of DDF and its influencing factors, such as climate condition, surface fea- ture, and topography. Then, the ablations from the 1980s to 2000s were estimated using the degree-day modei, and the ablation change from the 1980s to 2000s was divided into the changes caused by climate change and by the ice-surface feature. The following results were obtained： （1） The annual change in DDF for snow was not obvious, whereas that for ice increased, and the increasing trend on the lower glacier was more significant than that on the upper glacier because of decreased albedo caused by vari- ations in ice-surface feature; （2） The DDF for ice clearly decreased with altitude by approximately 0.046 and 0.043 mm.＇C-l-d-Lm-1 on the east and west branches, respectively, and the DDF of the west branch was obviously larger than that of the east branch in the same altitude belt; （3） the changes in mass balance in the summers from the 1980s to 2000s were -391 and -467 mm on the east and west branches, respectively. Among the total changes, the components directly caused by climate change were -193 and -198 mm, whereas those indirectly caused by ice-surface feature change were -198 and -269 mm on the east and west branches, respectively.

Glacier Mass-Balance Variation in China during the Past Half Century

The aim of this study is to investigate the impact of temperature trend on glacier-mass balance, snow density, snowmelt, snow depth and runoff by using observations of nine glacier stations that covered most of the China over the period of 1979-2013. Trend analysis showed an increasing trend of temperature on all of the selected stations. On an average, temperature was increasing at the rate of 0.46/10a. The increasing trend of temperature showed a negative relationship with annual glacier-mass balance on most of the stations and caused a decrease in annual balance. Results of Pearson’s correlation analysis showed a highly significant negative correlation between temperature and snow density (correlation coefficient (CC = -0.661 at 0.01 significance level). There was a significant positive correlation between temperature and snowmelt (CC = 0.532 at 0.01 significance level). There was a significant negative correlation between temperature and snow depth (correlation coefficient (CC = -0.342 at 0.05 significance level). Moreover, there was a significant positive correlation between temperature and runoff (CC = 0.586 at 0.01 significance level). Increasing trend of temperature caused an increasing trend of annual snowmelt and runoff anomaly% at the rate of 24.82/10a and 9.87/10a, respectively. On the other hand, a declining trend in annual snow density and snow depth anomaly% was found at a rate of -5.32/10a and -1.93/10a, respectively. We concluded that the snow density, snowmelt and runoff are significantly sensitive to temperature in China. This contribution has provided information for further understanding of glacier variation and its influencing factors.

Changes in climate extremes in a typical glacierized region in central Eastern Tianshan Mountains and their relationship with observed glacier mass balance

As an icon of anthropogenic climate change,alpine glaciers are highly sensitive to climate change.However,there remain research gaps regarding trends in climate extremes in glacierized regions and their relationship with local glacier mass balance.In this study,these relationships and their underlying links were explored in a typical glacierized region in the Eastern Tianshan Mountains,China,from 1959 to 2018.All warm extremes exhibited increasing trends that intensified dramatically from the 1990s.Meanwhile,decreasing trends were found for all cold extremes except for the temperatures of the coldest days and coldest nights.All of the precipitation extremes demonstrated increasing trends,except for consecutive dry days and consecutive wet days.Statistically significant positive/negative correlations were detected between glacier mass balance and six warm extremes(TN90p,TX90p,SU99p,TR95p,TXx,and TNx)/four cold extremes(TN10p,TX10p,FD0,and ID0).Simulation results showed that the impact of the intensity/frequency of the warm extremes(TN90p,TX90p,SU99p,and TR95p)on glacier ablation was remarkable and the effect of the cold extremes(FD0 and ID0)on accumulation was also significant.Additionally,the increases in the intensity and frequency of most climate extremes seemed more remarkable in glacierized regions than in non-glacierized regions.Hence,studies on glacier-climate interactions should focus greater attention on the impacts of climate extremes on glacier evolution.