Variation of culturable bacteria along depth in the East Rongbuk ice core,Mt.Everest

Ice melt water from a 22.27 m ice core which was drilled from the East Rongbuk Glacier, Mt. Everest was incubation in two incubation ways： plate melt water directly and enrichment melt water prior plate, respectively. The abundance of cultivable bacteria ranged from 0-295 CFU mL-I to 0--1720 CFU mL-1 in two incubations with a total of 1385 isolates obtained. Comparing to direct cultivation, enrichment cultivation recovered more bacteria. Pigment-producing bacteria accounted for an average of 84.9% of total isolates. Such high percentage suggested that pigment production may be an adaptive physiological feature for the bacteria in ice core to cope with strong ultraviolet radiation on the glacier. The abundances of cultivable bacteria and pigment-producing isolates varied synchronously along depth： higher abundance in the middle and lower at the top and bottom. It indicated that the middle part of the ice core was hospitable for the microbial survival. Based on the physiological properties of the colonies, eighty-nine isolates were selected for phylogenetic analysis. Obtained 16S rRNA gene sequences fell into four groups： Firmicutes, Alpha-Proteobacteria, Gamma-Proteobacteria, and Actinobacteria, with the Firmicutes being dominant. Microbial compositions derived from direct and enrichment cultivations were not overlapped. We suggest that it is a better way to explorethe culturable microbial diversity in ice core by combining the approaches of both direct and enrichment cultivation.

Amount and temperature effects responsible for precipitation isotope variation in the southern slope of Himalayas

Seasonal variation of stable isotopes in precipitation of Kathmandu Valley on the southem slope of Himalaya was carried out to understand the controlling mechanism of amount and temperature effect on the basis of one year stable isotope data from 2010 to 2011. Highly depleted isotope values in major rainy period are obtained just after the onset of precipitation in summer, which ac- counts for ＂amount effect＂ due to saturation isotopic compositions in high moisture condition, whereas, the higher values in winter are indicative to regional vapors （temperature effect） recycling of various sources. An abrupt depletion of isotope values in mid- June, indicates the onset date of monsoon precipitation, by the replacement of winter air mass with southem monsoon. Thus, pre- cipitation isotopes are a tool revealing the onset date of summer monsoon and temporal features of variability, in local and regional monsoons precipitations. A comparison of long term monthly values of 5180, temperature, and precipitation with GNIP 6180 data shows the temporal variations of stable isotopes are mostly controlled by amount and temperature effects. During summer mon- soon, the amount effects are stronger for high values of precipitation （R=0.7） and altitude effect appears for low moisture in late rainy season, thus from December to June （winter to pre-monsoon） the controlling features of isotopes remains under the temper- ature effect. A temporal rate of temperature effect is derived as 0.04%0 per year which indicates a dry signal of atmospheric condition and a temperature relation 5180=（0.371±0.08）T＋（0.156±0.05） is obtained from this analysis. The meteoric water lines of Kathmandu before and after monsoon onset of 2011, are found as 5D=（4.36±0.3）5180＋（15.66±1.2） and 5D=（6.91±0.2）S180-（7.92±2.26） from lab samples result, and 5D=9.25180＋11.725 and 5D=8.535180＋16.65 from GNIP data, which lacks the consistency both for slopes and intercepts values for the study period. The mean lapse rate values of δ18O and δD from GNIP data are obtained as -0.002‰/m and -0.015 ‰/m, which indicate the altitudinal effects in regional precipitation of the southern slope of Himalayas. This study estimates new stable isotopes data in recent precipitation using simple methodology which can be important for regional precipitation monitoring systems, environmental change and paleo-climatic studies.

Climatic changes have led to significant expansion of endorheic lakes in Xizang (Tibet) since 1995

Robust climate warming has led to significant expansion of lakes in the central Tibetan Plateau. Using remote sensing data, our quantitative analysis indicates that Siling Co, a saline lake in a characteristic endorheic basin in the central region of the Plateau, has expanded more than 600 km2 in area since 1976. Particularly since 1995, the lake has signif- icantly expanded in response to increasing precipitation, decreasing water surface evaporation caused by weaker winds and less solar radiation, and increased glacier meltwater draining to the lake. Glacie^lake interactions are important in governing lake expansion and are also part of a feedback loop that influences the local climate. Worsening climatic conditions （decreased precipitation and increased temperatures） that could have caused the lake to shrink during 1976-1994 were offset by increasing glacier meltwater feeding the lake, which made the lake nearly stable. We demonstrate that this pattern changed during 1995-2009, when glacier meltwater actually decreased but participation runoff increased and evaporation decreased, leading to expansion of the lake. If climatic conditions became suitable for further lake development, which would be indicated by expansion in lake area, glacier meltwater could be saved in a stable reservoir.

Hydrological and climatological glaciers observation 20 years on Tanggula Pass of Tibetan Plateau: its significance and contribution

Two decades have passed since China and Japan jointly launched hydrological ＆ climatological observations on the glaciers in Tanggula Pass, Tibetan Plateau. Although the research institutions involved have been either restructured or renamed, their work, between 1989 and 1993, was ground-breaking and remains significant even to this day. Some observation sites established at that time are still utilized for large-scaled projects sponsored by GAME/Tibet, NSFC （Natural Science Foundation of China） and the Major State Basic Research Development Program of China （973 Program）. Recently, a glacier monitoring system has been established on the cap of Dongkemadi Glacier, and is expected to make further contributions to research on the change of the cryospheric and climatic environment in the area.

Glacier in the upstream Manla Reservoir in the Nianchu River Basin,Tibet:shrinkage and impacts

Glaciers in the upstream Mania Reservoir in the Nianchu River Basin are crucial for agriculture and hydropower in the ＂One River and Two Streams＂ area. Rising temperature has caused widespread retreat of glaciers on the Tibetan Plateau during the last few decades. In this study, glacier variations under climate change in the Nianchu River Basin are quantified and their influence are evaluated by analyzing 1980 aerial topographic maps, 1990 Landsat TM, 2000 Landsat ETM＋, and 2005 CBERS remotely sensed images. It is found that from 1980 to 2005, the debris-free glacier area shrank by 7.3% （13.42 kin2）. Glacier shrinkage will have a positive effect on agriculture, hydropower and eco-environment in the near future. However, because the large number of small glaciers （〈2 km2） will rapidly retreat and disappear in future years, melt water will decrease, ultimately resulting in a long term water shortage. Glacial lakes exhibited rapid expansion due to accelerating glacier retreat during 19802005, increasing the possibility of glacial lake outbtwst floods.

青藏高原地表变暗与北极气候变化间的共振

The Tibetan Plateau(TP)exerts a profound influence on global climate over million-year timescales due to its past uplift.However,whether the ongoing climate changes over the TP,particularly the persistent reduction in its local albedo(referred to as“TP surface darkening”),can exert global impacts remains elusive.In this study,a state-of-the-art coupled land–atmosphere global climate model has been employed to scrutinize the impact of TP darkening on polar climate changes.Results indicate that the projected TP darkening has the potential to generate a stationary Rossby wave train,thereby modulating the atmospheric circulation in the high-latitudes of the Northern Hemisphere and instigating a dipole-like surface air temperature anomaly pattern around the Arctic region.An additional experiment suggests that the projected Arctic warming may in return warm the TP,thus forming a bi-directional linkage between these two climate systems.Given their association with vast ice reservoirs,the elucidation of this mechanism in our study is crucial in advancing our comprehension of Earth system climate projections.

Human activity over natural inputs determines the bacterial community in an ice core from the Muztag ata glacier

Ice core provides a valuable vertical timeline of past climates and anthropogenic activities.Environmental proxies have been widely used in these studies,but there are few biological indicators available.To address this gap,we investigated the bacterial community from a 74 m ice core of Muztag ata glacier on the Tibetan Plateau to link biological indicators with past climate and anthropogenic activities.By analyzing the portion of the ice core with environmental proxies available(corresponding to 1907 to 1991),we observed an increase in bacterial richness throughout the ice core,which was associated with higher NH_(4)^(+),an indicator of agricultural development.The bacterial community was jointly determined by human activity,natural input,and air temperature,with a strong human influence after the 1950s.Furthermore,the relative abundance of animal gut-associated bacteria,including Aerococcaceae,Nocardiaceae,Muribaculaceae,and Lachnospiraceae,was associated with livestock number changes in the Central Asian region.Together with other bacterial lineages,they jointly explained 59.8%of the livestock number changes.This study provides quantitative evidence of the associations between bacterial indicators and past climate and human activities,highlighting the potential of using bacterial proxies for ice core studies.

Impacts of land surface darkening on frozen ground and ecosystems over the Tibetan Plateau

Tibetan Plateau(TP) is known as the “Third Pole” of the Earth. Any changes in land surface processes on the TP can have an unneglectable impact on regional and global climate. With the warming and wetting climate, the land surface of the TP saw a darkening trend featured by decreasing surface albedo over the past decades, primarily due to the melting of glaciers, snow,and greening vegetation. Recent studies have investigated the effects of the TP land surface darkening on the field of climate, but these assessments only address one aspect of the feedback loop. How do these darkening-induced climate changes affect the frozen ground and ecosystems on the TP? In this study, we investigated the impact of TP land surface darkening on regional frozen ground and ecosystems using the state-of-the-art land surface model ORCHIDEE-MICT. Our model results show that darkening-induced climate changes on the TP will lead to a reduction in the area of regional frozen ground by 1.1×10~4±0.019×10~4km~2, a deepening of the regional permafrost active layer by 0.06±0.0004 m, and a decrease in the maximum freezing depth of regional seasonal frozen ground by 0.06±0.0016 m compared to the scenario without TP land surface darkening.Furthermore, the darkening-induced climate change on the TP will result in an increase in the regional leaf area index and an enhancement in the regional gross primary productivity, ultimately leading to an increase in regional terrestrial carbon stock by0.81±0.001 PgC. This study addresses the remaining piece of the puzzle in the feedback loop of TP land surface darkening, and improves our understanding of interactions across multiple spheres on the TP. The exacerbated regional permafrost degradation and increasing regional terrestrial carbon stock induced by TP land surface darkening should be considered in the development of national ecological security barrier.

Overflow of Siling Co on the central Tibetan Plateau and its environmental impacts

The Tibetan Plateau(TP)and its surroundings are also referred to as“Asian Water Tower”,which is the headwater of ten major rivers in Asia and provides ecosystem service for nearly two billion people[1].The interior TP boasts the greatest concentration of high-latitude inland lakes in the world,providing essential water resources,regulating regional climate and maintaining ecological balance.Over the past 50 years,the TP has experienced rapid climate warming and overall wetting,which has led to glacier mass loss,thawing of permafrost,reduction in snow cover,and shortening of lake ice duration[1].Changes in lake water storage provide a means of assessing the regional hydrological response to recent climate change in this sparsely populated region.

气候变化下多年冻土融水对青藏高原径流影响评估

青藏高原约40%的面积分布有多年冻土,相比冰川积雪融水得到的广泛关注,冻土融水对径流的影响仍有待评估.本研究基于耦合冰冻圈过程的分布式水文模型GBEHM(Geomorphology-based Ecohydrological Model),在区域尺度量化了多年冻土融水对径流的影响.研究结果表明:(1)过去40年间,青藏高原多年冻土面积下降13.9%,地下冰储量减少约401.1 Gt,约为同期冰川储量减少量的2倍;(2)多年冻土融水对全青藏高原总径流贡献相对较小(约0.5%),但在某些区域(如黄河上游、长江上游)和高程范围(如河西走廊4000m高程附近),地下冰融水对径流的贡献超过冰川融水贡献,其影响不可忽略;(3)气候变化背景下,地下冰融水径流在未来不可持续,澜沧江、怒江等区域历史阶段已经达到峰值,而对全青藏高原,融水径流拐点预计将在21世纪20年代(SSP1-2.6)、50年代(SSP2-4.5)或90年代(SSP5-8.5)达到.

青藏高原及周边地区近期冰川状态失常与灾变风险

青藏高原及周边地区是除南、北极地区之外全球最重要的冰川资源富集地.近百年来,青藏高原及周边地区冰川整体处于缓慢退缩状态,但20世纪90年代以来,这种状态发生了根本变化.以东帕米尔-喀喇昆仑-西昆仑地区冰川相对稳定甚至部分冰川前进为特征的'喀喇昆仑异常'是青藏高原及周边地区冰川状态失常的一种表现形式;而青藏高原东南地区冰川加速退缩则是这一地区冰川失常的另一种表现形式.高海拔地区的异常升温是青藏高原及周边地区冰川状态失常的重要驱动力.另外,这种冰川状态失常还与气候变暖背景下的西风和季风大气环流过程有关.随着全球变暖的加剧,冰川状态失常直接导致冰崩、冰湖溃决等灾变风险的增加.应对青藏高原及周边地区冰川状态失常的不利影响,需要进一步加强冰川变化监测与研究,加大冰川灾害防范力度.

拉萨河流域典型区域保护、修复、治理技术示范体系

青藏高原是世界屋脊、亚洲水塔,是地球第三极,是我国重要的生态安全屏障[1],是地球上最独特的地质-地理-生态单元,是开展地球与生命演化、圈层相互作用及人地关系研究的天然实验室[2].近50年,青藏高原自然与社会环境发生了剧烈变化,气候变暖幅度约是同期全球平均值的2倍[3],是全球变暖背景下环境变化不确定性最大的地区。

青藏高原大气水汽稳定同位素三维观测体系

青藏高原是南北极之外冰雪储量最大的地区,也是亚洲10条大江大河的发源地,其水循环变化会影响全球近五分之一人口的生存和发展.水汽传输是青藏高原水循环的关键过程.大气水汽稳定同位素是研究水汽传输过程和机制的新指标.本文回顾了大气水汽稳定同位素垂直剖面观测研究的发展历程和青藏高原大气水汽稳定同位素研究现状,重点介绍了自第二次青藏高原综合科学考察研究启动以来,本研究团队建成的全球最大的同类地表水汽稳定同位素观测网,及结合浮空艇技术,开展的国际前沿大气水汽稳定同位素三维传输过程观测研究新进展.今后,我们将通过多学科交叉,继续拓展高精度三维(地-空)水汽稳定同位素多尺度连续观测,并结合地球系统模型,从而全面、准确地认知全球变暖背景下的青藏高原水汽传输过程和水循环变化机制,以服务于青藏高原和周边地区的水安全战略和水资源管理.

第三极西风和季风主导流域源区降水呈现不同梯度特征

利用位于第三极东南部受季风主导的长江、黄河、澜沧江、怒江上游和雅鲁藏布江流域,以及位于西部受西风主导的叶尔羌河、印度河、阿姆河和锡尔河上游流域源区256个气象站的降水数据,分析了各流域降水随海拔变化的梯度关系;基于ERA5数据,通过分析水汽含量、对流有效势能和抬升凝结高度与各流域内海拔的变化关系,探讨了不同气候系统主导的流域呈现不同梯度特征的原因;通过水文模型模拟径流反向验证降水梯度校正方法在推算高海拔山区降水时的可行性.结果表明:(1)位于季风区的长江上游、黄河上游、澜沧江、怒江和雅鲁藏布江流域降水随海拔增加而降低(17~128 mm/100 m),地形效应仅在小尺度呈现;西风主导的叶尔羌河、印度河、阿姆河和锡尔河上游流域降水随海拔增加而增加(5~64 mm/100 m),地形效应明显.(2)ERA5与气象站观测降水数据在不同流域源区表现出一致的降水梯度特征.季风区流域降水随海拔增加而减少,主要由水汽含量随海拔增加而减少所致,地形效应在局地尺度依然有所反映;西风区流域降水随海拔增加而增加,主要受抬升凝结高度降低和对流有效势能增加的影响.(3)陆面水文模型反向验证结果表明,在降水地形效应明显的流域,对低海拔站点降水进行地形校正是提高通过降水变率推算高海拔区域降水可靠性、提高水文模拟精度的一个有效途径.研究结果对第三极流域高海拔山区降水数据的地形校正有参考价值;对第二次青藏高原综合科学考察中降水观测的选点有指导意义.

Tackling on environmental changes in Tibetan Plateau with focus on water, ecosystem and adaptation

The Tibetan Plateau represents a unique landform with an average elevation that is higher than 4,000 m above sea level. Also known as the roof of the world and the Asian Water Tower, this topography preserves the largest ice mass as the solid water outside the Arctic and Antarctica. The Tibetan Plateau is a natural laboratory for research on multi-sphere interactions and for the study of humannature relationship. China conducted the first large and longstanding scientific expedition to this area between the 1970s and the 1990s and achieved fruitful scientific results.

Potentially dangerous glacial lakes across the Tibetan Plateau revealed using a large-scale automated assessment approach

Glacial lake outburst floods(GLOFs) are a major concern in the Himalaya and on the Tibetan Plateau(TP),where several disasters occurring over the past century have caused significant loss of life and damage to infrastructure. This study responds directly to the needs of local authorities to provide guidance on the most dangerous glacial lakes across TP where local monitoring and other risk reduction strategies can subsequently be targeted. Specifically, the study aims to establish a first comprehensive prioritisation ranking of lake danger for TP, considering both the likelihood and possible magnitude of any outburst event(hazard), and the exposure of downstream communities. A composite inventory of 1,291 glacial lakes(>0.1 km^2) was derived from recent remote sensing studies, and a fully automated and object assessment scheme was implemented using customised GIS tools. Based on four core determinates of GLOF hazard(lake size, watershed area, topographic potential for ice/rock avalanching, and dam steepness), the scheme accurately distinguishes the high to very high hazard level of 19 out of 20 lakes that have previously generated GLOFs. Notably, 16% of all glacial lakes threaten human settlements, with a hotspot of GLOF danger identified in the central Himalayan counties of Jilong, Nyalam, and Dingri, where the potential trans-boundary threat to communities located downstream in Nepal is also recognised. The results provide an important and object scientific basis for decision-making, and the methodological approach is ideally suited for replication across other mountainous regions where such first-order studies are lacking.

Recent change of the ice core accumulation rates on the Qinghai-Tibetan Plateau

Three ice cores recovered from the Himalayas (i.e. the East Rongbuk Glacier and the Far East Rongbuk Glacier at Mt. Qomolangma (Everest), and the Dasuopu Glacier at Xixiabangma) show a sharp decline in the accumulation rates since the 1950s, which is consistent with the precipitation fluctuation over India and the low northern latitude zone (5°-35癗). Correspondingly, an increasing trend is observed for the ice core accumulations from the central and northern Qinghai-Tibetan Plateau (i.e. the Xiao Dongkemadi Glacier in the central Tanggula Mountains, the Guliya Ice Cap in the western Kunlun Mountains, and the Dunde Ice Cap in the Qilian Mountains) since the 1950s, which is consistent with the precipitation fluctuation over the middle-high northern latitude zone (35°-70°N). However, the variation magnitude of the high-elevation ice core accumulations is more significant than that of precipitation at the low-eleva- tion places, suggesting its extra sensitivity of high-elevation areas to climatic change.

Quantifying the major drivers for the expanding lakes in the interior Tibetan Plateau

自20世纪90年代中期以来,青藏高原内流区的湖泊呈现显著扩张趋势.气候变化和加剧的冰冻圈融化推动了湖泊的扩张,然而由于高海拔地区不同因素复杂的相互作用,目前对湖泊流域的潜在水文过程和冰冻圈要素变化的作用仍然缺少了解.借助于冰冻圈-水文模型(WEB-DHM-SF),本研究以内流区10个大型湖泊(面积大于500 km^(2))为例,对湖泊水储量变化开展了长期(1979-2016年)模拟和综合评估,定量探讨了不同驱动因素的影响.结果表明,到2016年10个湖泊总水量增加了58.5 km^(3),并且在1995年左右(转折年)显著增加.降雨是湖泊扩张的主要驱动因素,但冰雪融水的贡献在转折年后显著增加,不同因素的贡献呈现出一定的区域差异.研究结果为了解流域水文过程和冰冻圈变化在湖泊扩张中的作用提供了定量评估.

The Tibetan Plateau as the engine for Asian environmental change:the Tibetan Plateau Earth system research into a new era

The Tibetan Plateau(TP),as the world’s highest plateau,has almost all the key elements of the entire Earth system,including interconnected lithosphere,atmosphere,cryosphere,biosphere and anthroposphere[1-3].This completeness makes the TP an ideal natural laboratory for studying multispheric interactions within the Earth system,and for cultivating key breakthroughs in geoscience of the 21st century[2,3].