Study region: Urumqi River headwater region in eastern Tianshan, central Asia. Study focus: Climate change is anticipated to accelerate glacier shrinkage and alter hydrological conditions, causing variations in the runoff patterns in the catchment and significantly threatening the regional water resources. However, few models exhibit adequate performance to simulate both surface alterations and glacier/snow runoff. Therefore, this study combined the glacier module with the Soil and Water Assessment Tool (SWAT) model to estimate the effect of climate change on the streamflow in the Urumqi River headwater region. The Urumqi River Headwater region is representative because of its long data series, viatal location, and local water availability, and it contains the longest-observed reference glacier (Urumqi Glacier No.1) in China, which spans the period from 1958 to the present. New hydrological insights for the region: The SWAT model performed satisfactorily for both calibration (1983-2005) and validation (2006-2016) periods with a Nash-Sutcliffe efficiency (NSE) greater than 0.80. The water balance analysis suggested that the snow/glacier melt contributed approximately 25% to the water yield. At the end of the 21st century, the temperature would increase by 2.4-3.8 degrees C while the precipitation would decrease by 1-2% under two future scenarios (ssp245 and ssp585). Thus, a 34-36% reduction in streamflow was projected due to above climate change impacts. This information would contribute to the development of adaptation strategies for sustainable water resource management.

Glacial landforms formed by multiple glaciations are well-preserved in the valleys around Karlik Mountain in the easternmost Tianshan range, Central Asia. These landforms are direct imprints of palaeoglaciers and represent important archives of past climatic and environmental conditions. Dating these landforms contributes to understanding the spatiotemporal variations of past glaciers and provides key information for reconstructing the palaeoclimate and palaeoenvironment in Central Asia. In this study, thirty-two boulder and bedrock samples were collected from two glaciated valleys on the southern slope of Karlik Mountain for terrestrial in situ cosmogenic nuclides (TCN)10Be surface exposure dating. Based on the geomorphic relationships and dating results, the innermost MS1 moraine complex was deposited during the Little Ice Age (LIA); the MS2 moraine complex was formed during the Late -glacial; the MS3 moraine complex was deposited during the global Last Glacial Maximum (LGMG); the MS4 moraine complex, which is the largest moraine complex, is marine oxygen isotope stage (MIS) 4 in ages; and the MS5 moraine complex, which is only preserved at the interfluve ridges, has a similar age to MS4. The age of MS4 demonstrates that the largest local last glacial maximum (LGML) occurred during the early part of the last glacial cycle rather than during the LGMG. The MS4 and MS5 glacial complexes imply that a large ice cap with outlet valley glaciers developed on the whole of Karlik Mountain during MIS 4. These ages, combined with previous landform mapping and dating on the northern slope of the mountain, show that glacial advances since MIS 4 in this mountainous area were restricted to the valleys, rather than large ice cap scale, which is consistent with moraine records in the other valleys across the Tianshan range. The pattern and nearly synchronous timing of palaeoglacier fluctuations during the last glaciation in arid Central Asia imply that the main determinant for glacier fluctuations in this region has been changes in precipitation brought by the westerlies during periods of low temperature.(c) 2023 Elsevier Ltd. All rights reserved.

Worldwide examination of glacier change is based on detailed observations from only a small number of glaciers. The ground-based detailed individual glacier monitoring is of strong need and extremely important in both regional and global scales. A long-term integrated multi-level monitoring has been carried out on Urumqi Glacier No. 1 (UG1) at the headwaters of the Urumqi River in the eastern Tianshan Mountains of Central Asia since 1959 by the Tianshan Glaciological Station, Chinese Acamedey of Sciences (CAS), and the glaciological datasets promise to be the best in China. The boundaries of all glacier zones moved up, resulting in a shrunk accumulation area. The stratigraphy features of the snowpack on the glacier were found to be significantly altered by climate warming. Mass balances of UG1 show accelerated mass loss since 1960, which were attributed to three mechanisms. The glacier has been contracting at an accelerated rate since 1962, resulting in a total reduction of 0.37 km(2) or 19.3% from 1962 to 2018. Glacier runoff measured at the UG1 hydrometeoro-logical station demonstrates a significant increase from 1959 to 2018 with a large interannual fluctuation, which is inversely correlated with the glacier's mass balance. This study analyzes on the changes in glacier zones, mass balance, area and length, and streamflow in the nival glacial catchment over the past 60 years. It provides critical insight into the processes and mechanisms of glacier recession in response to climate change. The results are not only representative of those glaciers in the Tianshan mountains, but also for the continental-type throughout the world. The direct observation data form an essential basis for evaluating mountain glacier changes and the impact of glacier shrinkage on water resources in the interior drainage rivers within the vast arid and semi-arid land in northwestern China as well as Central Asia.

Glaciers retreating due to global warming create important new habitats, particularly suitable for studying ecosystem development where nitrogen is a limiting factor. Nitrogen availability mainly results from microbial decomposition and transformation processes, including nitrification. AOA and AOB perform the first and rate-limiting step of nitrification. Investigating the abundance and diversity of AOA and AOB is essential for understanding early ecosystem development. The dynamics of AOA and AOB community structure along a soil chronosequence in Tianshan No. 1 Glacier foreland were analyzed using qPCR and clone library methods. The results consistently showed low quantities of both AOA and AOB throughout the chronosequence. Initially, the copy numbers of AOB were higher than those of AOA, but they decreased in later stages. The AOB community was dominated by Nitrosospira cluster ME, while the AOA community was dominated by the soil and sediment 1. Both communities were potentially connected to supra- and subglacial microbial communities during early stages. Correlation analysis revealed a significant positive correlation between the ratios of AOA and AOB with soil ammonium and total nitrogen levels. These results suggest that variations in abundance and diversity of AOA and AOB along the chronosequences were influenced by ammonium availability during glacier retreat.

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 re-lationships 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.

The glacier is a crucial freshwater resource in arid and semiarid regions, and the vulnerability of the glacier change is intimately linked to regional ecological services and socio-economic sustainability. Taking the Tianshan Mountains region in China as an example, a basic framework for studying the vulnerability of glacier change was constructed so as to address factors such as physical geography, population status, socio-economic level, agricultural development, and social services. The framework was based on key dimensions, that is, exposure, sensitivity, and adaptability, and this constituted a targeted evaluation index system. We examined the spatial structure and spatial autocorrelation of the glacier change vulnerability using ArcGIS and GeoDa software. The influence and interaction of natural, social, economic, population and other factors on glacier change adaptability was examined using the GeoDetector model. The results suggested the following: (1) The vulnerability level decreased from the western region to the eastern region with significant differences between the two regions. The eastern region had the lowest vulnerability, followed by the central region, and then western region which had the highest vulnerability. (2) Significant positive and negative correlations were found between exposure, sensitivity, and adaptability, indicating that the areas with high exposure and high sensitivity to glacier change tended to have a low adaptive capacity, which led to high vulnerability, and vice versa. (3) The spatial heterogeneity regarding the ability to cope with glacier change reflected the combined effects of the natural, social, economic, and demographic factors. Among them, factors such as the production value of secondary and tertiary industries, the urban population, urban fixed-asset investment, and the number of employees played major roles regarding the spatial heterogeneity of glacier change.

The impact of climate change on glaciers and the hydrological processes in the easternmost end of the eastern Tianshan Mountains has yet to be understood. This study investigated the glacier change (area, surface elevation and volume change) and analyzed the variation of the observed runoff series over the past four decades in the Yushugou Basin, Eastern Tianshan Mountains. The hydrological processes were also simulated through the HBV-light model to quantify the impact of climate change on the glacier and runoff. The results showed that the glacier area has decreased by 13% and the total volume has decreased by 0.018 km(3) over the past four decades. A significant increasing trend (p < 0.01) was detected for the annual runoff and monthly runoff (May to September; p < 0.01). The simulation results revealed that the Yushugou River was highly recharged by glacial runoff and a negative tendency was found for the glacier mass balance on the basin scale over the past 38 years. As a region with an extremely dry climate and the lowest precipitation in the Tianshan Mountains, the observation and simulation of glaciers is critical to the security assessment of local water resources.

The accumulation and ablation processes of seasonal snow significantly affect the land surface phenology in a mountainous ecosystem. However, the ability of snow to regulate the alpine land surface phenology in the arid regions is not well described in the context of climate change. The impact of snowpack changes on land surface phenology and its driving factors were investigated in the Tianshan Mountains using the land surface phenology metrics derived from satellited products and a snow dataset from downscaled regional climate model simulations covering the period from 1983 to 2015. The results demonstrated that the annual mean start of growing season (SOS) and length of growing season (LOS) experienced a significant (p < 0.05) decrease and increase with a rate of -2.45 days/decade and 2.98 days/decade, respectively. The significantly advanced SOS and increased LOS were mainly seen in the Western Tianshan Mountains and Ili Valley regions with elevations from 2500 to 3500 m a.s.l and below 3000 m a.s.l, respectively. During the early spring, the significant decline in snow cover fraction (SCF) could advance the SOS. In contrast, snowmelt amount and annual maximum snow water equivalent (SWE) have an almost equally substantial positive correlation with annual maximum vegetation greenness. In particular, the SOS of grassland was the most sensitive to variations of snow cover fraction during early spring than that of other vegetation types, and their strong relationship was mainly located at elevations from 1500 to 2500 m a.s.l. Its greenness was significantly controlled by the annual maximum snow water equivalent in all elevation bands. Both decreased SCF and increased temperature in the early spring caused a significant advance of the SOS, consequently prolonging the LOS. Meanwhile, more SWE and snowmelt amount could significantly promote vegetation greenness by regulating the soil moisture. The results can improve the understanding of the snow ecosystem services in the alpine regions under climate change.

Study region: The upstream reaches of Manas River Basin (UMNS), and Muzati River Basin (UMZT) Study focus: Glaciers, as solid reservoirs, substantially regulate runoff abundance and depletion through peak shaving and valley filling. The regulations of glaciers in hydrological cycles are crucial to the arid regions. We aim to quantify the dynamics of the glaciers' hydrological regulating function in the UMNS and UMZT from 1971 to 2100 using a glacier hydrological regulation index (GlacierR). New hydrological insights for the region: Our results indicate that the glacier runoff in both basins showed a decreasing trend in the past four decades and will continue decreasing in the future under three shared socioeconomic pathways (SSPs): SSP1-2.6, SSP2-4.5, and SSP5-8.5. The UMZT has a stronger regulating function of glacial runoff than the UMNS. In contrast, the tipping point of the glaciers' hydrological regulating function in the UMNS occurred ten years earlier than in the UMZT. Under the three SSPs, the glaciers' hydrological regulation function on the north -and south-facing slopes of the Tianshan Mountains will show a weakening trend. The weakness trend is more notable in UMZT, where the glaciers' hydrological regulation function will decrease by 66.9 % between 2061 and 2100 under SSP1-2.6. Thus, it sets alarm bells for the rational use of water resources in glacier-covered arid regions.

Mountains form distinct geographical units with complex topographic and climatic features. Mountain ecosystems, especially those in arid and semi-arid regions, are likely to be strongly influenced by climate change. The NDVI-based vegetation response to climate change was analyzed in the Tianshan Mountains in China, one of the largest mountain systems of central Asia. Datasets, including the Normalized Difference Vegetation Index (NDVI), precipitation, soil moisture, and snow cover, were used to analyze spatial patterns of NDVI during 2001-2013. A trend test and correlation analysis were used to verify the results. Results showed that: (1) Spatial patterns of NDVI in the Tianshan Mountains revealed significant differences during 2001-2013. A decreasing trend appeared mainly in the Ili River Valley (<-0.005 NDVI/year), the Kaidu River (-0.01 to -0.005 NDVI/year), and Bogda Shan (-0.005 to 0 NDVI/year). NDVI in the western Tianshan Mountains, eastern and western Bogda Shan showed an increasing trend. (2) Spring NDVI in the Tianshan Mountains decreased, while summer NDVI increased during 2001-2013. (3) Spatial variations in vegetation dynamics were attributed to the interaction of the four spheres of the earth's system, hydrosphere-pedosphere-atmosphere-biosphere. The main contributors including temperature, precipitation, and soil moisture had a notable effect on variations in vegetation. (4) The snow cover in the mountains was crucial for vegetation growth, especially in the winter half of the year. Understanding the spatial characteristics of NDVI in mountains under the effects of climate change will underpin further study in this ecological environment.