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.

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.

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.

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.

Mass balance and near-surface ice temperature structure of Baishui Glacier No.1 in Mt. Yulong

The accumulation and ablation of a glacier directly reflect its mass income and wastage, and ice temperature indicates glacier＇s climatic and dynamic conditions. Glaciological studies at Baishui Glacier No.1 in Mt. Yulong are important for estimating recent changes of the cryosphere in Hengduan Mountains. Increased glacier ablation and higher ice temperatures can cause the incidents of icefall. Therefore, it is important to conduct the study of glacier mass balance and ice temperature, but there are few studies in relation to glacier＇s mass balance and active-layer temperature in China＇s monsoonal temperate glacier region. Based on the field observations of mass balance and glacier temperature at Baishui Glacier No.1, its accumulation, ablation, net balance and near-surface ice temperature structure were analyzed and studied in this paper. Results showed that the accumulation period was ranged from October to the following mid-May, and the ablation period occurred from mid-May to October, suggesting that the ablation period of temperate glacier began about 15 days earlier than that of continental glaciers, while the accumulation period began about 15 days later. The glacier ablation rate was 6.47 cm d 1 at an elevation of 4600 m between June 23 and August 30, and it was 7.4 cm d 1 at 4800 m between June 26 and July 11 in 1982, moreover, they respectively increased to 9.2 cm d 1 and 10.8 cm d 1 in the corresponding period and altitude in 2009, indicating that glacier ablation has greatly intensified in the past years. The temperature of the main glacier body was close to melting point in summer, and it dropped from the glacier surface and reached a minimum value at a depth of 4-6 m in the ablation zone. The temperature then rose to around melting point with the depth increment. In winter, the ice temperature rose gradually with the increasing depth, and close to melting point at the depth of 10 m. Compared with the data from 1982, the glacier temperature has risen in the ablation zone in recent decades.

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.

Application of a Degree-Day Model for Determination of Mass Balance of Urumqi Glacier No. 1, Eastern Tianshan, China

In order to verify the feasibility and stability of a degree-day model on simulating the long time series of glacier mass balance, we apply a degree-day model to simulate the mass balance of Urumqi Glacier No. 1 for the period 1987/1988-2007/2008 based on temperature and precipitation data from a nearby climate station. The model is calibrated by simulating point measurements of mass bal- ance, mass balance profiles, and mean specific mass balance during 1987/1988-1996/1997. The opti- mized parameters are obtained by using a least square method to make the model fit the measured mass balance through the model calibration. The model validation （1997/1998-2007/2008） indicates that the modeled results are in good agreement with the observations. The static mass balance sensitiv- ity of Urumqi Glacier No. 1 is analyzed by computing the mass balance of the glacier for a temperature increase of 1℃, with and without a 5% precipitation increase, and the values for the east branch are -0.80 and -0.87 m w.e. a-1℃-1, respectively, and for the west branch, the values are -0.68 and -0.74 m w.e. a-1℃-1, respectively. Moreover, the analysis of the parameter stability indicates that the parame- ters in the model determined from the current climate condition can be applied in the prediction of the future mass balance changes for the glacier and provide a reference for extending the model to other small glaciers in western China.

MASS BALANCE SENSITIVITY TO CLIMATE CHANGE: A CASE STUDY OF GLACIER NO. 1 AT URUMQI RIVERHEAD, TIANSHAN MOUNTAINS, CHINA

In this paper the degree day mass balance model is applied to the sensitivity test of mass balance/ELA(equilibrium line altitude) to climate change of Glacier No.1 at Urumqi Riverhead, the Tianshan Mountains, China. The results demonstrate that the mass balance of Glacier No.1, which is of continental type and accumulates in warm seasons, is less sensitive than that of a maritime glacier. On Glacier No.1, air temperature rise of 1℃ or precipitation increase by 20% can cause the ELA shift 81 m up or 31 m down respectively. Air temperature and precipitation play the different roles in the mass balance formation, in which the mass balance hypsometry follows the temperature variations by the means of rotation against the elevation axis and it shifts in parallel with precipitation change. Assuming a future temperature rise of 2 ℃ the mass losing trend on Glacier No.1 can not be radically alleviated even if there is a precipitation increase by 30%.

Study on the glacier variation and its runoff responses in the arid region of Northwest China

The glaciers in the arid region of Northwest China are viewed as an independent system, and glacier variation and mass balance fluctuation since the Little Ice Age and in the recent decades are estimated. Based on the estimation, the threshold time of glacier runoff against the backgrounds of the current and future varying climate conditions is simulated.

CLIMATIC TREND INDICATED BY VARIATIONS OF GLACIERS AND LAKES IN THE TIANSHAN MOUNTAINS

Under the control of geographical environment and the influence ofmodified west air mass, the mass balance of glaciers in the Tianshan Mountains hascontinously decreased since the 1970s. However, the lake level has increased gradually duo to the increase of precipitation. The interaction between temperature andprecipitation resulted in a normal and slightly more total amount of water resources inthe areas of the Tianshan Mountains. It is estimated that this climatic trend will lastto the early stage of the next century.

天山乌鲁木齐河源1号冰川径流对气候变化的响应分析

利用天山乌鲁木齐河源1号冰川1959—2006年的气象、冰川物质平衡和1980—2006年的水文资料,分析了其冰川径流的变化.结果表明:由于1996年以来的显著升温,导致了1号冰川水文点径流主要受夏季气温变化的控制,冰川物质损失对径流的补给作用已超过了降水的作用.1996—2006年与1980—1995年相比,夏季气温升高了0.9℃,降水增加了84.8mm(18.1%),冰川径流增加256.6mm(37.3%),其中约12.3%来自降水增加,约26.9%来自冰川物质的加速消融.对1980—1995年和1996—2006年两个时间段的气温和径流变化进行比较,并考虑到冰川区降水主要为降雪,折合夏季气温升高1℃将导致冰川径流增加470mm.夏季气温与冰川物质平衡和冰川径流的统计分析亦得出同样的结果.

天山乌鲁木齐河源1号冰川1959-2009年物质平衡变化过程及特征研究

以天山乌鲁木齐河源1号冰川1958/1959—2008/2009年度物质平衡资料为基础,研究了冰川的物质平衡变化过程及特征.结果表明:51a来1号冰川物质平衡经历了9次负平衡波动和9次正平衡波动,负平衡年与正平衡年之比为35∶16,负平衡年平均物质平衡-450mm,正平衡年平均物质平衡130mm,多年平均物质平衡-267mm.1997—2008年,该冰川连续12a的物质平衡观测结果均为负平衡年,并且总体上处于数值很大的强负平衡,直至2008年出现了历史上最大的负平衡,物质平衡量为-999mm.1959—2009年,累积亏损达-13 646mm(约-2 402.6×104 m3),即冰川平均较之1959年减薄了15.2m,这种长时期连续物质亏损状态对1号冰川是一个严峻的考验.

天山乌鲁木齐河源1号冰川物质平衡对气候变化的敏感性研究

应用度日物质平衡模式对天山乌鲁木齐河源１号冰川物质平衡及平衡线高度对气候变化的敏感性进行了研究．结果表明，位于大陆性气候区且具有暖季补给特征的乌鲁木齐河源１号冰川物质平衡对气候变化的敏感性要小于海洋性冰川，升温１℃或增加２０％的降水可引起平衡线上升８１ｍ或下降３１ｍ．此外，气温与降水在物质平衡形成过程中的作用是不同的，气温引起物质平衡剖面以旋转方式变化，而降水可导致其平移方式的响应．若未来升温２℃时，即使降水增加３０％，１号冰川向负平衡变化仍然不能得到遏制．

天山乌鲁木齐河源1号冰川物质平衡特征

统计了天山乌鲁木齐河源 1号冰川自 1980年以来冰川表面的单点物质平衡,分析了不同季节物质平衡及其冰川变化特征。研究表明, 1号冰川厚度较之 1959年平均减薄了 9 599mm;1997—2002年为实际观测以来连续的强负物质平衡时段,平均物质平衡为 -739. 6mm /a。物质平衡与气温、降水的相关分析显示: 1号冰川物质平衡主要取决于夏季平均气温的高低,二者具有较好的反相关关系(相关系数为-0. 72),而与降水的关系相对较差。20世纪 80年代末以来, 1号冰川退缩速度明显增大,尤以 2000—2002年为甚,西支冰川退缩速度为连续的高值(退缩速度分别为 6. 92m/a、6. 95m/a和 6. 25m/a);东支冰川的退缩速度与高度大于 4 200m的高度带区间的平均物质平衡值有较好的相关关系(相关系数为 0. 65),表明了 1号冰川进退的动力主要源于冰川积累区的物质平衡大小。

天山乌鲁木齐河源1号冰川物质平衡过程研究

天山乌鲁木齐河源１号冰川１９５８－１９５９～１９９１－１９９２年度，以负物质平衡状态为主，累积负平衡量达８５１．９×１０４ｍ３，冰川平均亏损４５６２ｍｍ水层，与中亚山地冰川物质平衡的变化趋势相似，均是由夏季平均气温升高和年降水量减少引起的。分析１７ａ的物质平衡实测资料表明，净物质平衡与平衡线高度，以及平衡线高度与夏季平均气温和年降水量存在着密切关系，夏季平均气温变化１℃，平衡线高度变化１０２ｍ，年降水量变化１００ｍｍ，平衡线高度波动５８ｍ。

天山乌鲁木齐河源1号冰川面积变化对物质平衡计算的影响

应用天山乌鲁木齐河源1号冰川8期不同时期测绘的冰川地形图,结合冰川物质平衡的实测资料,研究了1号冰川的面积变化及其对物质平衡计算的影响.结果表明:自1962年以来,1号冰川面积处于持续的退缩状态.到2008年8月为止,1号冰川东、西支已经分别退缩了208.2m和110.5m,同时冰川面积退缩为1.645km2,比1962年的冰川面积减小了0.305km2,即15.6%.结果显示,冰川面积的变化不仅表现在冰川末端退缩引起的面积减小上,而且还表现在表面高程下降引起的不同高度带冰川面积的重新分布上,即冰川的表面形态也发生了较大的变化.当不考虑冰川面积变化时,所计算的物质平衡值可能偏大,即高估了物质平衡的变化.计算结果表明,1988/1989年度—2005/2006年度间,1号冰川面积变化对物质平衡计算影响最大为4.5%,最小为2%,平均为3.5%.总之,冰川面积或表面形态变化不大时,对物质平衡的计算影响较小,反之,则影响较大.

乌鲁木齐河源1号冰川2009年出现物质正平衡

自1997年以来,乌鲁木齐河源1号冰川消融极为强烈,物质平衡呈大幅度亏损,连续12 a都处于强负平衡状态,平均物质平衡达-708 mm,且在2008年物质平衡达到历史最低值-999 mm,然而2009年出现了物质正平衡,物质平衡63 mm,年际变化量达1 062 mm。以2008-2009年物质平衡实测资料为基础,根据该地区的气温和降水资料分析,结果表明,造成这种现象的主要原因是夏季气温(5～8月)的降低,较2008年低1.8℃,致使冰川消融期的开始时间推迟至了7月份,结束时间提前到8月份,大大削弱了冰川的消融强度,其次是2005年以来逐渐增多的连续性降水,增加了冰川的积累量。

中国西部大陆性冰川与海洋性冰川物质平衡变化及其对气候响应——以乌源1号冰川和帕隆94号冰川为例

为认识全球变暖背景下中国西部大陆性冰川与海洋性冰川物质平衡变化及其对气候响应,以天山乌鲁木齐河源1号冰川和藏东南帕隆94号冰川为例,结合大西沟与察隅站气象资料,对1980—2015年两条冰川的物质平衡变化特征及差异进行了分析。结果表明:36 a来乌源1号冰川与帕隆94号冰川物质平衡总体上均呈下降趋势,累积物质平衡达-17 102 mm w. e.与-8 159 mm w. e.,相当于冰川厚度减薄19 m与9. 01 m,且分别于1996、2004年左右发生突变。同期两条冰川所处区域年均温呈显著上升趋势,而降水量却表现出不同的变化态势;二者年内气温分配相仿,但降水分配差异较大。初步分析认为气温上升是导致乌源1号冰川与帕隆94号冰川物质亏损的主要原因,冰川区气温和降水变化幅度的差异和地性因子(坡度、冰川面积)的不同使得乌源1号冰川对气候变化响应的敏感性高于帕隆94号冰川,由于目前海洋性冰川物质平衡监测时段相对较短,为深入研究中国西部冰川物质平衡变化及过程仍需加强对冰川的持续观测。