Multi-decadal variations in glacier flow velocity and the influencing factors of Urumqi Glacier No.1 in Tianshan Mountains,Northwest China

Urumqi Glacier No. 1 is a representative glacier in the inland areas of Central Asia and is the only Chinese reference glacier in the World Glacier Monitoring Service. In this study, we explored multi-decadal variations in the flow velocity of the glacier and the influencing factors based on continuous field observations and path coefficient analysis. Results show that the glacier flow velocity decreased from 5.5 m/a in 1980/1981 to 3.3 m/a in 2010/2011. The annual variation in the direction of glacier flow velocity in the western branch and eastern branch was less than 1°–3°, and the change of glacier flow velocity in the western branch was more dramatic than that in the eastern branch. Glacier flow velocity was influenced by glacier morphology(including glacier area, glacier length, and ice thickness), glacier mass balance and local climate conditions(air temperature and precipitation), the glacier morphology being the leading factor. The long-term flow velocity data set of Urumqi Glacier No. 1 contributes to a better understanding of glacier dynamics within the context of climatic warming.     

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 altitude 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 increase 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 background of the increase in precipitation over the Tuyuksu Glacier.     

Long-term variations in runoff of the Syr Darya River Basin under climate change and human activities

In this study,we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930–2015 to investigate variations in river runoff and the impacts of climate change and human activities on river runoff.The Syr Darya River,which is supplied by snow and glacier meltwater upstream,is an important freshwater source for Central Asia,as nearly half of the population is concentrated in this area.River runoff in this arid region is sensitive to climate change and human activities.Therefore,estimation of the climatic and hydrological changes and the quantification of the impacts of climate change and human activities on river runoff are of great concern and important for regional water resources management.The long-term trends of hydrological time series from the selected 11 hydrological stations in the Syr Darya River Basin were examined by non-parametric methods,including the Pettitt change point test and Mann-Kendall trend tests.It was found that 8 out of 11 hydrological stations showed significant downward trends in river runof f.Change of river runoff variations occurred in the year around 1960.Moreover,during the study period(1930–2015),annual mean temperature,annual precipitation,and annual potential evapotranspiration in the river basin increased substantially.We employed hydrological sensitivity method to evaluate the impacts of climate change and human activities on river runoff based on precipitation and potential evapotranspiration.It was estimated that human activities accounted for over 82.6%–98.7%of the reduction in river runoff,mainly owing to water withdrawal for irrigation purpose.The observed variations in river runoff can subsequently lead to adverse ecological consequences from an ecological and regional water resources management perspective.     

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.     

夏季北极涛动与亚洲中部干湿状况关系研究

利用NCEP/NCAR全球再分析资料和NOAA北极涛动指数资料,采用相关分析、谱分析、小波分析等,对北极涛动(AO)与亚洲中部干旱区(ACA)的干湿变化关系进行分析.研究认为:夏季北极涛动指数和ACA相对湿度场存在显著反相关,尤其表现在年代际尺度上;两者都于20世纪70年代初发生显著突变,2年准周期贯穿过去50年,但5年左右的周期在70年代中期以后表现显著.结果表明:AO突变前后,ACA海平面高度场、对流低层风场都具有显著变化,但ACA东半部和西半部受作用的亚系统并不一致,认为夏季ACA干湿状况突变及其周期特点转变的主要原因之一是AO突变引起环流场变化所致.     

1959-2009年乌鲁木齐河源1号冰川零平衡线高度变化研究

基于1959-2009年间天山乌鲁木齐河源1号冰川观测资料,研究了该冰川零平衡线高度变化特征,并建立了零平衡线高度与夏季气温和夏季降水量之间的统计关系。研究表明:近51年来,1号冰川零平衡线高度呈缓慢上升、缓慢下降、急剧上升、急剧下降的变化趋势,但总体呈上升趋势,且该冰川零平衡线高度上升了约45m。1号冰川零平衡线高度和年净物质平衡有良好的线性关系,冰川处于稳定状态时的零平衡线高度为4018m。此外,对1号冰川零平衡线高度的气候敏感性研究表明,如果夏季气温升高(或降低)1℃,那么该冰川零平衡线高度将上升(或下降)约64m;如果夏季降水量增加(或减少)100mm,那么该冰川零平衡线高度将下降(上升)约21m,夏季气温是影响冰川零平衡线高度变化的主要气候因素。     

Vegetation dynamics and its response to climate change in Central Asia

The plant ecosystems are particularly sensitive to climate change in arid and semi-arid regions. However, the responses of vegetation dynamics to climate change in Central Asia are still unclear. In this study, we used the normalized difference vegetation index(NDVI) data to analyze the spatial-temporal changes of vegetation and the correlation of vegetation and climatic variables over the period of 1982–2012 in Central Asia by using the empirical orthogonal function and least square methods. The results showed that the annual NDVI in Central Asia experienced a weak increasing trend overall during the study period. Specifically, the annual NDVI showed a significant increasing trend between1982 and 1994, and exhibited a decreasing trend since 1994. The regions where the annual NDVI decreased were mainly distributed in western Central Asia, which may be caused by the decreased precipitation. The NDVI exhibited a larger increasing trend in spring than in the other three seasons. In mountainous areas, the NDVI had a significant increasing trend at the annual and seasonal scales; further, the largest increasing trend of NDVI mainly appeared in the middle mountain belt(1,700–2,650 m asl). The annual NDVI was positively correlated with annual precipitation in Central Asia, and there was a weak negative correlation between annual NDVI and temperature. Moreover, a one-month time lag was found in the response of NDVI to temperature from June to September in Central Asia during 1982–2012.     

基于CRU资料的中亚地区气候特征

基于中亚地区1971-2000年的CRU资料,利用一元线性回归法,分析中亚地区30 a的气候变化特征。结果表明：土库曼斯坦和乌兹别克斯坦的沙漠地区是中亚最为干旱的地区,也是气温最高的地区。塔吉克斯坦和吉尔吉斯斯坦冬季和春季降水多,夏季和秋季降水少,气温变化幅度相对较小。哈萨克斯坦的降水呈现西多东少,且主要集中在夏季,气温变化幅度较大,且西暖东冷。中亚地区气温年较差较小。新疆与中亚五国的气候有明显差异,新疆降水主要集中在夏季的天山山区,气温增暖明显,最高和最低气温与中亚西部的变化趋势相反。     

影响柴达木盆地降水量变化的主要天气动力因素

为了解柴达木盆地内近57 a来降水量变化与太阳黑子、北极涛动(AO)和厄尔尼诺-南方涛动(ENSO)等因素间的关系,运用线性趋势法、Mann-Kendall检验法和小波分析法等对盆地内8个气象站的降水量进行了分析。发现近57 a来盆地内降水量年平均增加0.628 mm,夏季增加0.423 mm,夏季降水占全年总增加量的67%,年降水量存在2~3 a和1 a的显著周期。降水量与太阳黑子相对数存在近似正相关的8~12 a的主共振周期,降水量滞后1.2~1.8 a。年降水量与AO主要存在近似正相关的2~3 a和1~2 a的共振周期。年降水量与ENSO存在近似负相关的3 a和近似正相关的5~6 a的共振周期。表明盆地内降水与其天气动力因素在不同的周期尺度上存在不同的相关性。     

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.     

Precipitation trends and variability from 1950 to 2000 in arid lands of Central Asia

Climate warming will cause differences in precipitation distribution and changes in hydrological cycle both at regional and global scales. Arid lands of Central Asia(ALCA), one of the largest arid regions at the middle latitudes in the world, is likely to be strongly influenced by climate warming. Understanding the precipitation variations in the past is an important prerequisite for predicting future precipitation trends and thus managing regional water resources in such an arid region. In this study, we used run theory, displacement, extreme deviation theory, precipitation concentration index(PCI), Mann-Kendall rank correlation and climatic trend coefficient methods to analyze the precipitation in wet and dry years, changes in precipitation over multiple-time scales, variability of precipitation and its rate of change based on the monthly precipitation data during 1950–2000 from 344 meteorological stations in the ALCA. The occurrence probability of a single year with abundant precipitation was higher than that of a single year with less precipitation. The average duration of extreme drought in the entire area was 5 years, with an average annual water deficit of 34.6 mm(accounting for 11.2% of the average annual precipitation over the duration). The occurrence probability of a single wet year was slightly higher than that of a single dry year. The occurrence probability of more than 5 consecutive wet years was 5.8%, while the occurrence probability of more than 5 consecutive dry years was 6.2%. In the center of the study area, the distribution of precipitation was stable at an intra-annual timescale, with small changes at an inter-annual timescale. In the western part of the study area, the monthly variation of precipitation was high at an inter-annual timescale. There were clear seasonal changes in precipitation(PCI=12–36) in the ALCA. Precipitation in spring and winter accounted for 37.7% and 24.4% of the annual precipitation, respectively. There was a significant inter-annual change in precipitation in the arid Northwest China(PCI=24–34). Annual precipitation increased significantly(P=0.05) in 17.4% of all the meteorological stations over the study period. The probability of an increase in annual precipitation was 75.6%, with this increase being significant(P=0.05) at 34.0% of all the meteorological stations. The average increasing rate in annual precipitation was 3.9 mm/10a(P=0.01) in the ALCA. There were significant increasing trends(P=0.01) in precipitation in Kazakhstan, Kyrgyzstan and Tajikistan, with rates of 2.6, 3.1 and 3.7 mm/10 a, respectively.     

托木尔峰地区神奇峰冰川3950m处物质平衡与气象要素关系分析

2008年夏季,中国科学院天山冰川观测试验站科研人员对天山托木尔峰地区神奇峰冰川(也称青冰滩72号冰川)进行了大规模综合性的野外科考活动,获得了2008年7月30日至8月31日期间的冰川海拔3950m处的实测气象资料,包括气温、降水等。文中将这些气象资料与物质平衡数据相结合,对它们的关系进行了分析。2008年夏季青冰滩72号冰川野外观测资料分析结果表明:研究时段内,冰川日平均气温在0℃以上的天数达到了96%,冰川基本上处于消融状态;降水前后伴随的气温变化幅度大;基于观测数据,对气温和物质平衡进行了回归分析,回归系数为0.631;并利用灰熵关联度分析了降水和物质平衡之间的关系,它们之间的关联度系数为0.497。     

大气红外探测器（AIRS）资料揭示的中亚地区上对流层水汽时空变化特征

水资源纠纷已成为当前威胁中亚地区国家安全与稳定的主要因素，而上对流层水汽作为全球水循环的重要组成部分，其空间分布和变化过程对中亚地区水资源分配具有重要科学价值。利用最新的AIRS水汽质量混合比数据，分析了中亚地区2003-2011年上对流层水汽的时空变化及其异常特征，揭示了其与青藏高原、热带季风区等受亚洲夏季风影响区域的显著差异。研究表明：就整个亚洲中低纬地区而言，中亚地区全年上对流层水汽偏少，且年内变化相对稳定，逐月波动不大。与夏季青藏高原南部及热带季风区北部的水汽大值区相比，在黑海-里海以东至我国新疆西部之间的中亚地区上对流层为显著的水汽含量低值区。近9 a中亚地区上对流层水汽整体呈微弱的增加趋势，且具有较强的波动性：水汽最小、最大值分别出现在2009年、2010年，这一显著振荡对近9 a水汽的线性变化趋势影响较大。就季节变化而言，春、夏季分别呈微弱的下降、上升趋势，秋季上升趋势显著，冬季在2~3 a波动变化特征明显。     

Spatiotemporal changes in water,land use,and ecosystem services in Central Asia considering climate changes and human activities

Central Asia is located in the hinterland of Eurasia, comprising Kazakhstan, Uzbekistan, Kyrgyzstan, Turkmenistan, and Tajikistan; over 93.00% of the total area is dryland. Temperature rise and human activities have severe impacts on the fragile ecosystems. Since the 1970s, nearly half the great lakes in Central Asia have shrunk and rivers are drying rapidly owing to climate changes and human activities. Water shortage and ecological crisis have attracted extensive international attention. In general, ecosystem services in Central Asia are declining, particularly with respect to biodiversity, water, and soil conservation. Furthermore, the annual average temperature and annual precipitation in Central Asia increased by 0.30°C/decade and 6.9 mm/decade in recent decades, respectively. Temperature rise significantly affected glacier retreat in the Tianshan Mountains and Pamir Mountains, which may intensify water shortage in the 21^st century. The increase in precipitation cannot counterbalance the aggravation of water shortage caused by the temperature rise and human activities in Central Asia. The population of Central Asia is growing gradually, and its economy is increasing steadily. Moreover, the agricultural land has not been expended in the last two decades. Thus, water and ecological crises, such as the Aral Sea shrinkage in the 21^st century, cannot be attributed to agriculture extension any longer. Unbalanced regional development and water interception/transfer have led to the irrational exploitation of water resources in some watersheds, inducing downstream water shortage and ecological degradation. In addition, accelerated industrialization and urbanization have intensified this process. Therefore, all Central Asian countries must urgently reach a consensus and adopt common measures for water and ecological protection.     

黄河流域夏季降水与亚州季风的关系

利用1951-2009年600、850hPa 2.5°×2.5°NCEP/NCAR再分析资料和中国气象局整编的160站的降水资料,计算和分析了反映亚洲地区各个季风特征的指数序列及年代际变化。结果表明:夏季黄河流域降水与印度季风和高原季风关系密切,而与西北太平洋季风的关系不显著;印度季风偏强的年份,黄河流域降水偏多,而在印度季风偏弱的年份,黄河流域降水偏少;近59年来,印度季风指数与黄河流域降水同样具有2～3年、9～10年和21～22年的周期变化。     

Effect of topography on the changes of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains

Topography plays an important role in determining the glacier changes. However, topography has often been oversimplified in the studies of the glacier changes. No systematic studies have been conducted to evaluate the relationship between the glacier changes and topographic features. The present study provided a detailed insight into the changes in the two branches (east branch and west branch) of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains since 1993 and systematically discussed the effect of topography on the glacier parameters. This study analyzed comprehensive recently observed data (from 1992/1993 to 2018/2019), including mass balance, ice thickness, surface elevation, ice velocity, terminus, and area, and then determined the differences in the changes of the two branches and explored the effect of topography on the glacier changes. We also applied a topographic solar radiation model to analyze the influence of topography on the incoming shortwave radiation (SW_in) across the entire glacier, focusing on the difference in the SW_in between the two branches. The glacier mass balance of the east branch was more negative than that of the west branch from 1992/1993 to 2018/2019, and this was mainly attributed to the lower average altitude of the east branch. Compared with the west branch, the decrease rate of the ice velocity was lower in the east branch owing to its relatively increased slope. The narrow shape of the west branch and its southeast aspect in the earlier period resulted in a larger glacier terminus retreat of the west branch. The spatial variability of the SW_in across the glacier surface became much larger as altitude increased. The SW_in received by the east branch was slightly larger than that received by the west branch, and the northern aspect could receive more SW_in, leading to glacier melting. In the future, the difference of the glacier changes between the two branches will continue to exist due to their topographic differences. This work is fundamental to understanding how topographic features affect the glacier changes, and provides information for building different types of relationship between the glacier area and ice volume to promote further studies on the basin-scale glacier classification.     

近20 a中国天山东段典型冰川变化及其气候响应

冰川作为重要的淡水资源的存储体,也是气候变化的敏感"指示器"。在干旱半干旱区,冰川变化对人们的生产、生活和生态产生重要的影响。本文基于1990—2015年Landsat TM及ETM+遥感影像数据,利用雪盖指数法(NDSI)和阈值法,分析博格达峰及喀尔力克山的冰川面积变化,结合长时间序列的气温、降水数据分析天山东段典型冰川的气候响应。结果表明:(1)博格达峰与喀尔力克山的冰川均呈现退缩趋势,与气温和降水的变化趋势一致。(2)博格达峰和喀尔力克山冰川面积变化在东南坡向有波动增加趋势,其他坡向则未出现该现象。(3)从两个冰川不同坡向的面积和面积重心分布变化分析,博格达峰冰川面积在东坡方向退缩速率最大,而喀尔力克山的冰川在东北坡方向退缩速率最大。(4)根据栅格气象资料分析,近四五十年博格达地区冰川面积退缩速率大于喀尔力克山地区,并且博格达峰降水量的增加对冰川的退缩起到的作用不大,喀尔力克山的降水量对冰川面积的退缩起到了一定的抑制作用。(5)通过对博格达峰地区和喀尔力克山地区不同坡向的冰川面积与年均气温、年均降水量进行Person相关性分析,博格达峰地区、喀尔力克山地区各个坡向的冰川面积变化与降水相关系数均很小。但博格达峰地区北、东北、东南坡向的冰川面积与区域气温变化相关系数较高,喀尔力克山地区东南、东北坡向的冰川面积与区域气温的相关系数高且显著性明显。分析其原因,在年内尺度上,博格达峰地区、喀尔力克山地区是湿季气温升高所致,干湿两季降水量的增多,并没有使得冰川整体的退缩有所减缓。     

Impact of climate change on the streamflow in the glacierized Chu River Basin,Central Asia

Catchments dominated by meltwater runoff are sensitive to climate change as changes in precipitation and temperature inevitably affect the characteristics of glaciermelt/snowmelt, hydrologic circle and water resources. This study simulated the impact of climate change on the runoff generation and streamflow of Chu River Basin(CRB), a glacierized basin in Central Asia using the enhanced Soil and Water Assessment Tool(SWAT). The model was calibrated and validated using the measured monthly streamflow data from three discharge gauge stations in CRB for the period 1961–1985 and was subsequently driven by downscaled future climate projections of five Global Circulation Models(GCMs) in Coupled Model Inter-comparison Project Phase 5(CMIP5) under three radiative forcing scenarios(RCP2.6, RCP4.5 and RCP8.5). In this study, the period 1966–1995 was used as the baseline period, while 2016–2045 and 2066–2095 as the near-future and far-future period, respectively. As projected, the climate would become warmer and drier under all scenarios in the future, and the future climate would be characterized by larger seasonal and annual variations under higher RCP. A general decreasing trend was identified in the average annual runoff in glacier(–26.6% to –1.0%), snow(–21.4% to +1.1%) and streamflow(–27.7% to –6.6%) for most of the future scenario periods. The projected maximum streamflow in each of the two future scenarios occurred one month earlier than that in the baseline period because of the reduced streamflow in summer months. Results of this study are expected to arouse the serious concern about water resource availability in the headwater region of CRB under the continuously warming climate. Changes in simulated hydrologic outputs underscored the significance of lowering the uncertainties in temperature and precipitation projection.     

Glacier variations and their response to climate change in an arid inland river basin of Northwest China

Glaciers are a critical freshwater resource of river recharge in arid areas around the world. In recent decades, glaciers have shown evidence of retreat due to climate change, and the accelerated ablation of glaciers and associated impacts on water resources have received widespread attention. Glacier variations result from climate change, so they can serve as an indicator of climate change. Considering the climatic differences in different elevation ranges, it is worthwhile to explore whether different responses exist between glacier area and air temperature in each elevation zone. In this study, we selected a typical arid inland river basin(Sugan Lake Basin) in the western Qilian Mountains of Northwest China to analyze the glacier variations and their response to climate change. The glacier area data from 1989 to 2016 were delineated using Landsat Thematic Mapper(TM), Enhanced TM+(ETM+) and Operational Land Imager(OLI) images. We compared the relationships between glacier area and air temperature at seven meteorological stations in the glacier-covered areas and in the Sugan Lake Basin, and further analyzed the relationship between glacier area and mean air temperature of the glacier surfaces in July–August in the elevation range of 4700–5500 m a.s.l. by the linear regression method and correlation analysis. In addition, based on the linear regression relationship established between glacier area and air temperature in each elevation zone, we predicted glacier areas under future climate scenarios during the periods of 2046–2065 and 2081–2100. The results indicate that the glaciers experienced a remarkable shrinkage from 1989 to 2016 with a shrinkage rate of –1.61 km2/a(–0.5%/a), and the rising temperature is the decisive factor dominating glacial retreat; there is a significant negative linear correlation between glacier area and mean air temperature of the glacier surfaces in July–August in each elevation zone from 1989 to 2016. The variations in glaciers are far less sensitive to changes in precipitation than to changes in air temperature. Due to the influence of climate and topographic conditions, the distribution of glacier area and the rate of glacier ablation first increased and then decreased in different elevation zones. The trend in glacier shrinkage will continue because air temperature will continue to increase in the future, and the result of glacier retreat in each elevation zone will be slightly slower than that in the entire study area. Quantitative glacier research can more accurately reflect the response of glacier variations to climate change, and the regression relationship can be used to predict the areas of glaciers under future climate scenarios. These conclusions can offer effective references for assessing glacier variations and their response to climate change in arid inland river basins in Northwest China as well as other similar regions in the world.     

利用树轮重建玛纳斯河流域过去289 a降水变化

利用采自天山北坡中部玛纳斯河流域的树轮样本,建立了玛纳斯河流域合成的区域标准化年表。树轮-气候响应分析表明,玛纳斯河流域树木径向生长的主要限制性因子是上年7月至当年6月降水量。进一步利用该年表重建了玛纳斯河流域过去289 a的降水变化。历史降水变化特征分析表明,过去289 a的降水经历6干6湿的阶段变化,并存在着1810、1823、1824、1885、1910、1944、1945年和1977年8个干旱年;具有2.0~2.4 a、3.3~3.8 a、17.4 a、48.0 a和64.0 a变化准周期,并在1780年前后发生了由少到多的突变,在1807年前后与1830年前后发生了由多到少的突变;重建的过去289 a玛纳斯河流域降水变化与天山山区历史气候变化序列有较好的一致性,并且能够代表新疆北部和中亚大部分区域历史降水变化。