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Northwest China is much more sensitive to climate warming, and the climate has varied rapidly from warm and drought to warm and humid conditions. In addition, due to the complex terrain of Northwest China, the methods and parameterization schemes of different CMIP6 models, these models are mostly applied to arid areas in Northwest China or Central Asia, lacking climate data for plateau areas and eastern Lanzhou, specifically in filtering CMIP6 models and evaluating applicable models. In this paper, 34 CMIP6 climate models are used to evaluate and forecast future trends in Northwest China under the SSP126, SSP245 and SSP585 scenarios in the short, medium and long term. CMIP6 models of temperature and precipitation are identified by applying the interannual variability skill score (IVS) between CN05.1 datasets and historical CMIP6 models, which are suitable for Northwest China. Then, we assess the characteristics, warming and wetting deviations, and uncertainties in the prediction of climatic change according to CMIP6 models over Northwest China. The results show that CMIP6 models in precipitation and temperature applicable to Northwest China are AWI‐CM‐1‐1‐MR, BCC‐CSM2‐MR, FGOALS‐g3, INM‐CM4‐8, INM‐CM5‐0 and MRI‐ESM2‐0. The multi‐model ensemble mean (MMEM) has better capability than individual CMIP6 models in precipitation and temperature prediction. Spatiotemporal climatic change over Northwest China shows overall warming and wetting trends. The IVS provides the ability to estimate CMIP6 model simulation performance both temporally and spatially. The temperature simulation is quite good in the Tarim Basin and Hexi Corridor region, and the precipitation simulation is quite good in the plateau region, Altai Mountains, Tianshan Mountains and Hexi Corridor region. Cold and wet deviations occur in Northwest China due to the topography and few stations, which are common reasons. The main sources of uncertainties in temperature prediction during this century are model uncertainty (before the 2090s) and scenario variability (after the 2090s), and model uncertainty in precipitation for CMIP6 becomes the main source of uncertainty. [ABSTRACT FROM AUTHOR]

Transport of exogenous anthropogenic mercury (Hg) is an important source of Hg pollution in the Tibetan Plateau (TP) and its downstream water ecosystems, but the origins and contributions of Hg sources remain uncertain. Here, we investigate the concentrations and isotopic compositions of gaseous elemental mercury (GEM) at four rural sites in the TP and three urban sites surrounding the TP to quantify the sources of GEM in the TP. GEM concentrations in the surrounding cities (site‐specific means: 2.36–9.12 ng m−3) were highly elevated mainly due to strong local anthropogenic emissions as indicated by their negative δ202Hg and near zero Δ199Hg and Δ200Hg signatures. GEM isotopes indicate that GEM pollution in the TP, typically observed during the summer monsoon and the pre‐monsoon, were mainly caused by trans‐boundary transport of anthropogenic Hg from surroundings. Using an Hg isotope mixing model, we estimate that exogenous anthropogenic emissions on average contributed 26 ± 5% (1sd) to the GEM in the TP. Further analysis of the transport of anthropogenic Hg emissions based on the backward trajectory and gridded anthropogenic Hg emissions suggests that 16 ± 9% and 6 ± 13% of the GEM in the TP were derived from anthropogenic sources in South Asia and China, respectively. Our study suggests that anthropogenic Hg emissions in South Asia could be effectively transported to the TP across the Himalayan range. Future studies are needed to better assess the role of rapidly increasing anthropogenic Hg emissions in South Asia on the regional to global scale atmospheric Hg cycling. Plain Language Summary: Long‐range transport of air pollutants to the Tibetan Plateau (TP) are of particular concern for ecological and human health. Analysis of atmospheric gaseous elemental mercury (GEM) isotopes at multiple sites in the rural TP and surrounding urban sites revealed that transport of exogenous anthropogenic mercury (Hg) to the TP represents an important source of atmospheric GEM in the TP. Anthropogenic Hg emissions from South Asia could be effectively transported to the TP across the Himalayan range and subsequently represented the largest anthropogenic sources of GEM in the TP. This work highlights the need for assessing the role of rapidly increasing anthropogenic mercury emissions in South Asia on the atmospheric mercury cycle at regional and global scales. Key Points: Exogenous anthropogenic emissions on average contribute 26% of the atmospheric gaseous elemental mercury in the Tibetan Plateau (TP)Transport of anthropogenic mercury emissions to the TP can be intensified by Indian and East Asian summer monsoonAnthropogenic mercury emissions in South Asia can be effectively transported to the TP across the Himalayan range [ABSTRACT FROM AUTHOR]

This article discusses the lack of meteorological data and observations from the upper reaches of Mount Everest, emphasizing the importance of understanding high-altitude climates and their relation to freshwater storage and climate change. The authors present new winter weather observations from Mount Everest, including sublimation rates, wind chill temperatures, and frostbite risks. The data collected from the weather station network on Mount Everest provides valuable insights into climate conditions and mass loss from the highest glacier on Earth. The study reveals extremely cold temperatures and significant sublimation due to strong winds and low humidity. Further research on the impact of climate change on water resources in High Mountain Asia, including Mount Everest, is recommended. [Extracted from the article]

The climate change impacted glacio‐hydrological regime and thus the availability of water resources in arid region of Central Asia. The effects of climate change in the magnitude or seasonality of regional glacier runoff were still poorly understood in Central Asia. In this study, the glacier runoff, components of glacier runoff, equilibrium line altitude (ELA) and Glacier Mass Balance (GMB) during 1959–2017 are evaluated by elevation‐dependent Degree‐Day glacier melt model in eight sub‐basins of Tarim Basin over Central Asia. The impacts of climate change on glacier and hydrology are assessed. The results suggested that climatic regime shifted to more warm‐wet pattern on glacier zone after 1990 in study area. The ablation and accumulation of glaciers showed different patterns in eight sub‐basins. All sub‐basins showed a glacier mass deficit and GMB displayed a marked decreasing trend, but also exhibiting discrepancy. The mean ELA and rising rate of ELA were higher in the southern region. The glacier runoff increased significantly after 1990 in Tarim Basin, with obviously temporal and spatial variations in sub‐basins. The mean annual volume of glacier runoff was 175.8 × 108 m3. The ice melt was a larger component of glacial runoff in Tarim Basin. The influence of rainfall runoff on glacier runoff was more obviously than snow melt runoff as more precipitation fell as rain in northern region. The larger proportions of snow melt runoff imply more precipitation fell as snowfall in southern region. The elevation‐dependent contributions in glacier runoff showed differences in individual basins. Temperature and precipitation played different role for the glacier runoff increases among the sub‐basins. Differences in sensitivity of GMB and glacier runoff were distinct and vary considerably. A thorough assessment of the spatially and temporally varying melt water originated by glaciers is crucial for the success of water scarcity adaptation under climate change. [ABSTRACT FROM AUTHOR]

Indian monsoon circulation is the primary driver of the long‐range transboundary mercury (Hg) pollution from South Asia to the Himalayas and Tibet Plateau region, yet the northward extent of this transport remains unknown. In this study, a strong δ202Hg signature overlapping was found between Lake Gokyo and Indian anthropogenic sources, which is an indicative of the Hg source regions from South Asia. Most of the sediment samples were characterized with relatively large positive Δ199Hg values (mean = 0.07‰–0.44‰) and small positive Δ200Hg values (mean = 0.03‰–0.08‰). Notably, the Δ199Hg values in the lake sediments progressively increased from southwest to northeast. Moreover, the Δ199Hg values peaked at Lake Tanglha (mean = 0.44‰ ± 0.04‰) before decreased at Lake Qinghai that is under the influence of the westerlies. Our results suggest that transboundary atmospheric transport could transport Hg from South Asia northwards to at least the Tanglha Mountains in the northern Himalaya‐Tibet. Plain Language Summary: The fragile ecosystems of the Himalayas and Tibet Plateau region have been suffering transboundary Hg pollution from South Asia. However, the northward extent of this transport of atmospheric Hg pollution remains poorly understood. In our study, sediment core Hg isotope compositions from four lakes (Gokyo, Namco, and Tanglha in the south of the Tanglha Mountains and Qinghai in the north) along a southwest‐northeast transect in the region were combined to constrain the northward extent of transboundary Hg pollution by examining both mass‐dependent and mass‐independent fractionations. Our results suggest that transboundary atmospheric transport could transport Hg from South Asia northwards to at least the Tanglha Mountains in the northern Himalaya‐Tibet. Key Points: The δ202Hg signatures among the three lakes in the north are indistinguishable without spatial distribution differencesMost of sediment samples were characterized by positive Δ199Hg and Δ200Hg valuesThe northward extent of atmospheric mercury transboundary transport could be anchored by progressive shifts of Δ199Hg signatures [ABSTRACT FROM AUTHOR]

Refractory black carbon (rBC) is an important climate‐forcing agent emitted by biomass burning and fossil fuel combustion. Antarctica can receive rBC aerosols emitted in Southern Hemisphere (SH) and preserve the history of emissions and atmospheric transport. Here, we present a high‐resolution record of rBC in an ice core (CA2016‐75) acquired from the coastal Eastern Antarctica, which accumulated during the past 100 years (1915–2015). The rBC concentration (0.030 ng g−1) and flux (7.22 μg m−2 yr−1) are both among the lowest values in Antarctic snow and ice. The rBC concentration reaches higher values on average in the period aligned with the austral Winter. The rBC concentrations show a long‐term descending trend during the period between 1950s and mid‐1990s, followed by an ascending trend to 2015. Back trajectory analysis indicates that the emissions resulting from the biomass burning and anthropogenic biofuel consumption in Southern America and Australia were the main sources for the rBC deposition. Wavelet spectral analysis and temporal correlation analysis on rBC deposition and the atmospheric circulation indices (El Niño–Southern Oscillation, Southern Annular Mode and Antarctic Oscillation) confirmed that the atmospheric circulations have certain influences on the rBC deposition, likely by their direct effects on rBC transport and on weather conditions driving the occurrence of fires and subsequent emissions in source regions. Key Points: Yearly resolution black carbon (BC) data during the past century in east Antarctica were presented and showed the lowest BC values over AntarcticaBC showed a decrease between 1980s and mid‐1990s and then an increase to 2015, the variation was associated with the BC emissions in Southern HemisphereSouthern America, Australia were the potential source regions and the El Niño–Southern Oscillation, Southern Annular Mode both had influences on BC transport and source emissions [ABSTRACT FROM AUTHOR]

Climate change is expected to result in more frequent and intense heat waves (HWs) in South Asia (SA). The simultaneous increases in temperature and population will exacerbate the population exposure to future HWs. Here we estimate the future population exposure to daytime and nighttime HWs in SA using the Coupled Model Intercomparison Project 6 (CMIP6) models under four Shared Socioeconomic Pathways (SSPs) during 2061–2100, relative to 1975–2014. The results show that the projected frequency and spatial extent of the daytime (nighttime) HWs will be higher under scenario SSP5‐8.5, followed by SSP2‐4.5, SSP3‐7.0, and SSP1‐2.6 (SSP5‐8.5, followed by SSP3‐7.0, SSP2‐4.5, and SSP1‐2.6), relative to the historical period. The approach presented here allows decomposing the effects of climate change and future population on the overall exposure. The results reveal that the compounding effects of projected trends in population and HWs will significantly escalate the population exposure to HWs. Under the selected SSPs, the total population exposure to daytime and nighttime HWs ranges from 185 to 492 and 204–555 million people‐event, respectively, with the maximum exposure occurring in the Indo‐Gigantic Plain. The wide range of exposed populations highlights the sensitivity of the overall exposure to our future socioeconomic pathway decisions, emphasizing the importance of curbing anthropogenic greenhouse gas emissions and adopting sustainable urban planning solutions to minimize the potential socioeconomic and health impacts of HWs. Plain Language Summary: Climate change will intensify the occurrence and intensity of heatwaves (HWs) in South Asia, with severe impacts on the population. Here we estimate the population exposure to daytime and nighttime HWs using the Coupled Model Intercomparison Project 6 (CMIP6) models under four Shared Socioeconomic Pathways (SSPs). The results show that the projected daytime and nighttime HWs will impact around 185–492 and 204–555 million people under the selected SSPs, respectively, with the maximum exposure occurring in the Indo‐Gigantic Plain. The wide range of populations under different SSPs highlights the sensitivity of the population to future SSP decisions. This emphasizes the importance of reducing greenhouse gas emissions and adopting sustainable urban planning solutions to minimize the potential socioeconomic and health impacts of HWs. Key Points: The number and extent of heat waves (HWs) are projected to increase under all the Shared Socioeconomic Pathways (SSPs)The population exposure to HWs ranges from 185 to 555 million people‐event with the highest exposure in the Indo‐Gigantic PlainCompounding effects of climate change and population increase substantially aggravate exposure to HWs [ABSTRACT FROM AUTHOR]

The Pan‐Third Pole contains the largest number of glaciers outside the polar region that plays a crucial role in atmospheric circulation and the hydrological cycle. However, this pristine region has undergone rapid change through complex interactions including the black carbon (BC) enhanced warming effect and glacier melting. Study shows, Weather Research and Forecasting coupled with Chemistry (WRF‐Chem) simulation is able to capture distinctive seasonal variability of BC. The result from our sensitivity experiments revealed that South Asia (SA; 60.7%) and East Asia (EA; 32.9%) contributed more toward the Tibetan Plateau (TP). Our analysis on aerosol‐boundary feedback interaction revealed BC expand planetary boundary layer height by 5.0% and 4.8% over SA and EA, respectively, which facilitates BC dispersion and transportation. Whereas, we also found that under the influence of different wind regimes the significant BC transport flux aloft over the TP and the upper troposphere and lower stratosphere. Additionally, mountain‐valley channel and synoptic and local meteorological processes also facilitated BC transport to the TP. This study also evaluated the effect of BC on direct radiative forcing and calculated subsequent temperature changes. A strong dimming effect of BC corroborated with the following negative surface temperature changes. However, enhanced BC concentration during winter and spring caused the increase in temperature over the TP. Here, the WRF‐Chem model, synergy on aerosol‐boundary feedback, BC transport flux, and source‐receptor methods confirmed the significant BC contribution and transportation, and notable BC‐induced warming over TP. Such trans‐Himalayan BC transport and associated warming could grim glacier melt and water availability in the region. Key Points: Trans‐Himalaya long‐range transport is evident with significant black carbon (BC) transport flux aloft above Himalayas and Tibetan Plateau and free troposphere from South Asia (SA) and East Asia (EA) regionSynergy on aerosol‐boundary feedback interaction manifested that BC expand planetary boundary layer height by 5.01% and 4.80% over SA and EA, respectivelyElevated BC caused notable warming over Tibetan Plateau that could pose a threat in the cryosphere over that region [ABSTRACT FROM AUTHOR]

To characterize the spatiotemporal variations of glacier surface speed on the Kenai Peninsula, Alaska (∼3,900 km2), we derived 92 surface speed fields between October 2014 and December 2019 using intensity offset tracking on Sentinel‐1 data. On average, speeds are 50% greater in spring (March‐May) than the annual mean (69 m a−1) while winter speeds are close to the annual mean. While marine‐terminating glaciers have their maximum speed near the terminus, both land‐ and lake‐terminating glaciers flow fastest around the median glacier elevation. On average, the lake‐terminating and tidewater glaciers flow 1.7 and 2.3 times faster than the land‐terminating glaciers, respectively. Monthly variations over the 5‐year period are strikingly synchronous regardless of terminus type suggesting that regional‐scale meteorological drivers govern the temporal variability. Mean annual speeds fluctuate roughly ±10% of the period mean without an apparent trend. At lake‐terminating Bear Glacier, a short‐term tripling in ice speed in fall 2019 over the area below an ice‐dammed lake coincides with an observed glacier lake outburst flood (GLOF). An earlier GLOF caused a persistent breach of the beach barrier between the proglacial lake and ocean which likely led to overall speed‐up of the lower glacier part throughout 2019. A significant speedup was also observed at the lower part of the lake‐terminating Ellsworth Glacier and attributed to rapid glacier retreat and lake expansion, probably further amplified by the terminus area becoming buoyant and a large tabular iceberg breaking off. Our results highlight the impact of GLOFs and proglacial characteristics in spatial and temporal glacier speed variations. Plain Language Summary: Glaciers constantly move but the speed varies with time and space. We use satellite data to calculate the surface ice speed variations of all glaciers on the Kenai Peninsula, Alaska (∼3,900 km2), between October 2014 and December 2019. On average, the glacier speed is 50% higher in spring than the annual average. Overall, the lake‐terminating glaciers flow 70% faster, and marine‐terminating glaciers more than 100% faster than the land‐terminating glaciers. Over the 5‐year period, all glaciers regardless of terminus type tended to speed up or slow down simultaneously, probably driven by large‐scale variations in weather governing the water supply to the drainage system. The lower part of Bear Glacier tripled in speed in fall 2019 when an ice‐dammed lake suddenly drained through the glacier. Another glacier outburst flood in 2018 led to a breach of the beach barrier between the large lake at the glacier terminus and the ocean which might have caused the considerable speedup of the lower glacier part throughout 2019. Key Points: Lake‐terminating glaciers flow 1.7 times and tidewater glaciers 2.3 times faster than the land‐terminating glaciersMonthly ice speed variations are largely synchronous across the Peninsula irrespective of terminus typeA glacier outburst flood at Bear Glacier caused both a short‐term and a longer‐term speed‐up of the glacier's lower part [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) has received wide scientific concern in recent decades owing to its important impacts on regional climatic and cryospheric changes, hydrological cycles, and environments. However, our understanding of the spatial distribution of the chemical and optical properties of aerosols is still limited based on prior single‐site observations. In this study, aerosol light absorptions from black carbon (BC) and brown carbon (BrC) were explored and compared among three remote TP sites, including Qomolangma Station (QOMS) on the southern TP, Nam Co Station (NamCo) on the central TP, and Waliguan Observatory on the northeastern TP. Although the aerosol mass concentration at QOMS was less than half of that at Waliguan, the light absorption coefficient of aerosols at QOMS was nearly 5 times higher than that at Waliguan, mainly as a result of more light‐absorbing carbonaceous aerosols on the southern TP due to long‐range transported biomass burning emissions. Specifically, BC dominated aerosol light absorption at all wavelengths, whereas BrC contributed ∼30% of the light absorption at 370 nm at QOMS and ∼20% at Waliguan and NamCo. A major contributor to BrC light absorption at QOMS was biomass burning‐related organic aerosols apportioned from aerosol mass spectrometry measurements. Understanding the significant regional differences in aerosol light absorption properties on the TP is useful for evaluating the regional climatic and environmental effects and validating the model results on aerosol radiative forcing. Plain Language Summary: Brown carbon (BrC) is a group of organic compounds that preferentially absorbs solar light at short wavelengths and has raised wide scientific concerns. However, understanding the physicochemical and optical properties of BrC is still limited, especially in remote regions. Combining two online instruments and adopting a novel approach, our study focuses on the absorption properties of BrC on the Tibetan Plateau (TP), which should be considered carefully in future climate models for evaluating the radiant energy budget and potential impacts on climatic and cryospheric changes over the TP. Key Points: The aerosol light absorption coefficient in the southern region of the Tibetan Plateau (TP) was much higher than that in the northeastern TPBrown carbon contributed significantly to light absorption in the southern TP and was mainly related to biomass burning emissions [ABSTRACT FROM AUTHOR]

The Himalayas and Tibetan Plateau, identified as the Third Pole (TP), is a unique region because of its insertion into global environmental and climatic changes. Deposition of atmospheric nitrate in this region is one of the most important sources of reactive nitrogen to glacial‐hydrologic system and ecosystems. The isotopic composition of atmospherically deposited nitrate preserved in ice bodies plays a central role in delineating environmental and climatic changes, present, and past. Here, we provide an overview of the complete isotopic compositions (δ15N, δ18O, and Δ17O) of nitrate in aerosol, snow, ice, and water samples (n = 46) collected across the Southern, Southeastern, Central, and Northern TP to constrain complex nitrogen cycles of the atmosphere, cryosphere, hydrosphere, and, potentially, the biosphere. A large variability of snow nitrate isotopic compositions is observed across the TP at different spatial scales (from a single glacier to the entire plateau), likely due to the complex landscape and relevant physical and chemical processes across the TP. Large nitrate Δ17O values are observed in water samples collected from the Mt. Everest region, highlighting the considerable fraction (up to 45%) of atmospheric nitrate to the nitrate load in this Himalayan hydrologic system. Our work reveals the complex chemical, depositional, and postdepositional processes over the TP that are greater than previously thought and identifies further comprehensive investigations, which entail using nitrate isotopic compositions as an identifier for nitrate source apportionment in various ecosystems and understanding past atmospheric and climatic conditions in this region. Key Points: Complete isotopic compositions of nitrate in aerosol, snow, ice, and water samples collected across the Tibetan Plateau were measuredNitrate isotopic compositions in the cryosphere over the Tibetan Plateau is spatially highly heterogeneousContribution of atmospheric nitrates to the hydrologic system is high at Himalayas [ABSTRACT FROM AUTHOR]

Changes in the hydrological regimes of Arctic rivers could affect the thermohaline circulation of the Arctic Ocean. In this study, we analysed spatiotemporal variations in temperature and precipitation in the Ob River Basin regions during 1936–2017 based on data from the Global Precipitation Climatology Center. Changes in discharge and response to climate change were examined based on monthly observed data during the same period. It is indicated the Ob River Basin experienced significant overall rapid warming and wetting (increased precipitation) in the study period, with average rates of 0.20°C (10 year−1) and 5.3 mm (10 year−1), respectively. The annual spatial variations of temperature and precipitation showed different scales in different regions. The discharge in spring and winter significantly increased at a rate of 384.1 and 173.1 m3/s (10 year−1), respectively. Hydrograph separation indicated infiltration and supported that deep flow paths increased the contribution of groundwater to base flow. Meanwhile, the variation of the ratio of Qmax/Qmin suggested that the basin storage and the mechanism of discharge generation have significantly changed. The hydrological processes were influenced by changes of permafrost in a certain in the Ob River Basin. An increase in the recession coefficient (RC) implies that the permafrost degradation in the basin due to climate warming affected hydrological processes in winter. Permafrost degradation affected the Qmax/Qmin more significantly in the warm season than RC due to the enhanced infiltration that converted more surface water into groundwater in the cold season. The impact of precipitation on discharge, including surface flow and base flow, was more significant than temperature at the annual and seasonal scales in the Ob River Basin. The base flow was more obviously influenced by temperature than surface flow. The results of this study are significant for analyses of the basin water budget and freshwater input to the Arctic Ocean. [ABSTRACT FROM AUTHOR]

Temporal variation of runoff chemistry and its seasonal controls relating to chemical weathering processes and drainage system evolution were examined at Urumqi Glacier No.1 in Xinjiang, China, over a full melt season. The dominant ions in meltwater runoff are HCO3−, Ca2+, and SO42−; and Fe, Sr, and Al are dominant elements. Concentrations of major ions and some elements show periodic variations with seasons and negatively correlate with discharge, whereas other elements (e.g., Al, Ni, Cu, Zn, Cd, and Pb) show a random change, providing insights into the hydrological and physicochemical controls. HCO3− and Ca2+ are primarily derived from calcite, SO42− and Fe mainly come from pyrite, and Sr and Al principally originate from silicate. Hydrochemical fluxes of solutes exhibit strong seasonality but are positively related to discharge, suggesting an increasing release of solutes during higher flow conditions. Solute yields, cation denudation rate, and chemical weathering intensity observed at Urumqi Glacier No.1 are higher than those at most basins worldwide. This suggests that chemical weathering in central Asia may be stronger than at other glacial basins with similar specific discharge. Concentrations of some elements (e.g., Fe, Al, As, Pb, and Zn) are close to or exceed the guidelines for drinking water standards in meltwater‐fed rivers. These rivers may face future challenges of water quality degradation, and relationships between changing flow and water quality conditions should be established soon, given that development of channelized flow is expected to be earlier over a melt season in a warming climate. [ABSTRACT FROM AUTHOR]

In this study, a decade long measurement of aerosol optical properties at two AERONET stations (Nam Co during 2006–2016 and QOMS during 2009–2017) in the Tibetan Plateau (TP), a region sensitive to climate change and human perturbation, is presented. The baseline value of aerosol optical depth (AOD) was 0.029 and 0.027 at Nam Co and QOMS, respectively, which are comparable to or even lower than those at some Arctic and remote ocean locations. The seasonality of AOD values were the order of spring > summer > winter > autumn. Based on AOD and Ångström exponent (α), major aerosol types over the TP were further identified as continental background, biomass burning, and dust. Although continental background aerosol was the main feature in remote areas of TP, biomass burning plumes frequently occurred, especially during spring (March–April). In one of such biomass burning event in April 2014, MODIS observations demonstrated that intensive open fires occurred in South Asia, covering the foothills of Himalayas and Indo‐Gangetic Plain. The air mass back trajectories and CALIOP observations further revealed that biomass burning plume could be uplifted to higher altitudes and reach the Himalayas. Moreover, an occasional dust event detected in April 2008 over the TP demonstrated that the dust from Taklamakan Desert may impact the main body of TP episodically, although the local dust from the inside of TP cannot be excluded and warrants further study. Key Points: The baseline value of AOD in Tibetan Plateau is comparable to or even lower than that at Arctic and remote ocean locationsMajor aerosol types over the Tibetan Plateau were identified as continental background, biomass burning, and dustBiomass burning emissions in South Asia and dust from Taklamakan Desert could impact Tibetan Plateau episodically [ABSTRACT FROM AUTHOR]

In the current study, psychrophilic, endolithic, and epilithic bacterial strains were isolated and characterized from the nonpolar Laohugou glacier (LHG) no. 12, the largest valley glacier in the western Qilian Mts. located on the northeastern edge of the Tibetan Plateau. Five different types of samples, rocks, soil, glacial water, ice/snow, and cryoconite, were collected. A total of 48 bacterial strains were isolated by using the R2A bacterial cultural medium. The findings revealed that the Gram‐positive bacteria 41 (85.4%) dominated the Gram‐negative bacteria 7 (14.6%) in this extremely harsh environment. Molecular characterization based on 16S ribosomal RNA gene sequencing exhibited that the obtained isolates belong to four phyla, among which the diversity of Firmicutes (58.33%) was higher followed by Actinobacteria (23.0%), Proteobacteria (14.6%), and least diversity was reported in Euryarchaeota (4.2%). The bacterial communities were most dominant in soil samples followed by cryoconite sample and least dominant in the ice and snow samples. Moreover, the obtained bacterial isolates were found resistant to high concentrations of heavy metals (Cr3+, Cd2+, Hg2+, and Ar3+) and sodium chloride, and, therefore, exhibited polyextremophilic characteristics. LHG no. 12 is rich in bacterial and archaeal diversities and provides a potentially curious site for further in‐depth exploration of microbial diversity and their biotechnological applications. [ABSTRACT FROM AUTHOR]

Ice sheets have been shown to deliver large amounts of labile iron (Fe) to aquatic ecosystems; however, the role of glaciers distinct from ice sheets in supplying labile Fe to downstream ecosystems is less well understood despite their rapid volume loss globally. Direct and continuous measurements of Fe from glaciers throughout an entire melt season are very limited to date. Here we present extensive seasonal data on 0.45‐μm‐filtered Fe (dFe) from three glaciers in Asia. Concentrations of dFe are negatively correlated with glacier discharge, and dFe yields are closely related to specific discharge. Based on our study and previously published dFe data, we estimate the release of dFe from Asian glaciers to be 23.8±14.1 Gg/a. We further compile a global data set of dFe from more than 12 glaciers, which, when combined with data on glacier discharge, suggest that the release of dFe from glaciers globally is on the order of 185±172 Gg/a. This finding suggests that glaciers may provide a substantial, but largely unrecognized source of potentially labile Fe, and may become increasingly important for the Fe biogeochemical cycle in a warming climate. Key Points: This study presents data of dFe from three glaciers in Asia over a full melt season and compiles a global dataset of dFe from over 12 glaciersRelease of dFe from Asian glaciers is 23.7 Gg/a, and from global glaciers is 185 Gg/a, which is 4–10 times higher than from ice sheetsGlaciers may provide a substantial but largely unrecognized source of potentially labile Fe and become increasingly important for global Fe cycle [ABSTRACT FROM AUTHOR]

Carbonaceous matter in the atmosphere has an important influence on climate change. Currently, the deposition of carbonaceous matter is one of the largest uncertainties in the climate system. This phenomenon is common in remote regions, such as the Himalayas and Tibetan Plateau. In this study, for the first time, we reported in situ measurements of wet and dry deposition rates of carbonaceous matter at three remote stations: Nam Co, Lulang, and Everest. The results showed that the annual wet deposition rates of water‐insoluble organic carbon (WIOC) and black carbon (BC) were 60.2 and 5.8 mg·m−2·year−1, 330 and 34.6 mg·m−2·year−1, and 47.0 and 2.6 mg·m−2·year−1 at the Nam Co, Lulang, and Everest stations, respectively. Seasonal variations in the wet deposition rates of WIOC and BC were controlled by precipitation amount and their atmospheric concentrations. In addition, the wet scavenging ratios of WIOC and BC at Nam Co Station were close to those observed in other remote areas. The total BC deposition at Nam Co Station (15.3 mg·m−2·year−1) was higher than that from chemical transport models, implying a dominant role of dry deposition of BC in the total deposition at this station and an urgent need to improve the aerosol deposition in models for the Himalayas and Tibetan Plateau. It was found that the deposition rates of carbonaceous matter in the Himalayas and Tibetan Plateau had large spatial variation; thus, high‐resolution models need to be applied in the future. Key Points: Large spatial variations in WIOC and BC deposition rates were found among three study stations due to complex local factorsIn situ BC dry/wet deposition rates at study station were much higher than those from the CAM5 model due to the influence of mineral dustDry deposition rates of WIOC and BC were comparable or even higher than their wet deposition rates at the study stations [ABSTRACT FROM AUTHOR]

Research has revealed systematic changes in warming rates with elevation (EDW) in mountain regions. However, weather stations on the Tibetan plateau are mostly located at lower elevations (3,000‐4,000 m) and are nonexistent above 5,000 m, leaving critical temperature changes unknown. Satellite LST (Land Surface Temperature) can fill this gap but needs calibrating against in situ air temperatures (Tair). We develop a novel statistical model to convert LST to Tair, developed at 87 high‐elevation Chinese Meteorological Administration stations. Tair (daily maximum/minimum temperatures) is compared with Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua LST (1330 and 0130 local time) for 8‐day composites during 2002‐2017. Typically, 80‐95% of the difference between LST and Tair (ΔT) is explained using predictors including LST diurnal range, morning heating/nighttime cooling rates, the number of cloud free days/nights, and season (solar angle). LST is corrected to more closely represent Tair by subtracting modeled ΔT. We validate the model using an AWS on Zhadang Glacier (5800 m). Trend analysis at the 87 stations (2002‐2017) shows corrected LST trends to be similar to original Tair trends. To examine regional contrasts in EDW patterns, elevation profiles of corrected LST trends are derived for three ranges (Qilian Mountains, NyenchenTanglha, and Himalaya). There is limited EDW in the Qilian mountains. Maximum warming is observed around 4,500‐5,500 m in NyenchenTanglha, consistent with snowline retreat. In common with other studies, there is stabilization of warming at very high elevations in the Himalaya, including absolute cooling above 6,000 m, but data there are compromised by frequent cloud. Key Points: High mountains above 4,000 m are thought to be warming more rapidly than the global mean, but there is very little station data to prove thisWe correct satellite land surface temperature to more closely represent air temperatures up to 8,000 m where there is currently no dataEnhanced daytime warming occurs at current snowline (3,500‐5,000 m). However, cooling is seen at highest elevations >6,000 m in the Himalaya [ABSTRACT FROM AUTHOR]

Glacial retreat and the thawing of permafrost due to climate warming have altered the hydrological cycle in cryospheric‐dominated watersheds. In this study, we analysed the impacts of climate change on the water budget for the upstream of the Shule River Basin on the northeast Tibetan Plateau. The results showed that temperature and precipitation increased significantly during 1957–2010 in the study area. The hydrological cycle in the study area has intensified and accelerated under recent climate change. The average increasing rate of discharge in the upstream of the Shule River Basin was 7.9 × 106 m3/year during 1957–2010. As the mean annual glacier mass balance lost −62.4 mm/year, the impact of glacier discharge on river flow has increased, especially after the 2000s. The contribution of glacier melt to discharge was approximately 187.99 × 108 m3 or 33.4% of the total discharge over the study period. The results suggested that the impact of warming overcome the effect of precipitation increase on run‐off increase during the study period. The evapotranspiration (ET) increased during 1957–2010 with a rate of 13.4 mm/10 years. On the basis of water balance and the Gravity Recovery and Climate Experiment and the Global Land Data Assimilation System data, the total water storage change showed a decreasing trend, whereas groundwater increased dramatically after 2006. As permafrost has degraded under climate warming, surface water can infiltrate deep into the ground, thus changing both the watershed storage and the mechanisms of discharge generation. Both the change in terrestrial water storage and changes in groundwater have had a strong control on surface discharge in the upstream of the Shule River Basin. Future trends in run‐off are forecasted based on climate scenarios. It is suggested that the impact of warming will overcome the effect of precipitation increase on run‐off in the study area. Further studies such as this will improve understanding of water balance in cold high‐elevation regions. [ABSTRACT FROM AUTHOR]

Ice sheets and glaciers have been shown to deliver large amounts of labile dissolved organic carbon (DOC) to downstream aquatic ecosystems, but recent studies may underestimate the release of DOC from mountain glaciers. To date, continuous measurements of DOC from mountain glaciers throughout entire glacier melt season are very limited. Here we present high‐density data on DOC from two Asian mountain glaciers over a full melt season in 2013 and compile a global data set of DOC from 42 mountain glaciers. Based on our study and previously published DOC data, we estimate the storage and release of DOC associated with Asian mountain glaciers to be 8.8 to 13.8 Tg C and 0.19 Tg C/a, respectively. Rough extrapolation of glacier runoff to a global scale suggests that DOC release from mountain glaciers is on the order of 0.8 Tg C/a, which is 1.4 times higher than the most current estimates. The current release of DOC from mountain glaciers is therefore far more significant than previously thought and should be considered in future evaluation of the global carbon cycle. Key Points: Data on DOC from two Asian glaciers have been collected, and a global data set of DOC from worldwide mountain glaciers have been compiledStorage of DOC in Asian glaciers is 8.8 to 13.8 Tg C, and release of DOC from mountain glaciers worldwide is on the order of 0.8 Tg C/aCurrent release of DOC from mountain glaciers is far more significant than previously thought and should be considered in future evaluation of the global carbon cycle [ABSTRACT FROM AUTHOR]

Abstract: We present data of 129I deposition in fresh snow in the Laohugou glacier basin, northeast Tibetan Plateau, in summer 2016 and 2017, and trace its source and elevational distribution in the troposphere. Our results show that the 129I/127I atomic ratios in the fresh snow on the glacier surface are about 2 orders of magnitude larger than those in the Antarctic fresh snow and 4 orders the prenuclear level, indicating a predominantly anthropogenic source of the 129I in the mountain glacier environment of northeast Tibetan Plateau. The 129I level in the Laohugou glacier basin is 1–2 orders of magnitude lower than at representative European locations, and not significantly higher than that observed at other sites in Asia. The 129I/127I atomic ratio and 129I level show clear increases with elevation from 4,300 to 5,100 m above sea level. The 129I in the Laohugou glacier basin is probably deposited from the upper troposphere where there exists a local maximum of 129I. A conceptual model for interpretation of the observed 129I concentration and profile in Laohugou is provided. Thus, this work is of importance in providing a more complete view on the transport, dispersion, and removal of 129I in the atmosphere. [ABSTRACT FROM AUTHOR]

Abstract: This study presents the Hf‐Nd‐Sr isotopic compositions of eolian dust deposited on glacier snowpacks along a longitude transect on the eastern Tibetan Plateau, in order to trace its source areas and the provenance of long‐range transported (LRT) Asian dust on the eastern margin of Tibetan Plateau. Most of the glacier snowpack samples from northern locations (Qiyi and Lenglongling Glaciers) indicated similar Hf‐Nd‐Sr isotopic ratios with that of large central Asian deserts. However, the southern locations (Dagu, Hailuogou, and Baishui Glaciers) showed dramatic difference in the Hf‐Nd‐Sr isotopic ratios of snowpack dust compared with those of large Asian deserts, but were more similar to that of Tibetan Plateau surface crust. Hf‐Nd isotopes indicated that the southern Tibetan Plateau locations are hardly influenced by central Asian dust, but probably influenced by southward dust transport from the Loess Plateau, in addition to the arid deserts on the Tibetan Plateau surface. Meteorological data and aerosol optical depth also demonstrated the potential differences of eolian dust transport and input between the north and south locations. Loess Plateau is even in today's climate a dust sink, but dust emission from the Loess Plateau is also possible. The influence of the Tibetan Plateau and southwest vortex of China to atmospheric circulation may have caused such eolian transport, in particular for LRT eolian dust transport to southeastern Tibetan Plateau glaicers. This study is also of importance in that the Hf‐Nd isotopic fingerprinting could provide new evidences for LRT dust deposition on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: Lakes play an important role in the global carbon cycle, and littoral zones of lakes are potential hotspots of greenhouse gas production. In this study, we measured the partial pressures of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in the littoral zones of 17 lakes on the Tibetan Plateau. The littoral zones of lakes on the Tibetan Plateau were supersaturated and acted as sources of CO2, CH4, and N2O to the atmosphere. The average partial pressures of CO2, CH4, and N2O in the surface lake water were 664.8 ± 182.5, 139.8 ± 335.6, and 0.3 ± 0.1 μatm, respectively. The average diffusive fluxes (and uncentainty intervals) of these three gases were 73.7 (0.9–295.3) mmol · m−2 · day−1, 5.2 (0.0008–45.9) mmol · m−2 · day−1, and 6.5 (0.07–20.9) μmol · m−2 · day−1, respectively. The diffusive fluxes of CO2 in lakes were significantly correlated with dissolved organic carbon, dissolved organic nitrogen, salinity, and water temperature. The diffusive fluxes of N2O were significantly correlated with lake water depth. However, no relationships were found between environmental factors and the CH4 diffusive flux at the scale of this study. CO2 exchange with the atmosphere from saline lakes was found to be higher than from freshwater lakes with equivalent CO2 concentrations by a factor of 2.5 due to chemical enhancement of the gas transfer velocity. Therefore, further study with enhanced spatiotemporal resolution and breadth is needed to better understand the important role played by lakes on the Tibetan Plateau in both regional and global carbon cycles. [ABSTRACT FROM AUTHOR]

Abstract: The dissolved organic carbon in precipitation (water‐soluble organic carbon, WSOC) can provide a carbon subsidy to receiving ecosystems. The concentrations, isotopic signatures (δ13C/Δ14C), and molecular signatures (transform ion cyclotron mass spectrometry) of WSOC being delivered to Nam Co—a remote site on the inland Tibetan Plateau (TP)—were compared to those of WSOC in the snowpack, and in wet deposition from urban cities fringing the TP. The average WSOC concentration at Nam Co (1.0 ± 0.9 mg C L−1) was lower than for the large cities (1.6 to 2.3 mg C L−1) but higher than in the snowpack samples (0.26 ± 0.09 mg C L−1). Based upon radiocarbon data, it is estimated that 15 ± 6% of Nam Co WSOC was fossil derived, increasing to 20 ± 8% for snowpack WSOC, 29 ± 4% for Lhasa WSOC, and 34 ± 8% for the three cities. Transform ion cyclotron mass spectrometry results revealed that the abundance of dissolved black carbon and sulfur‐containing molecules of WSOC increased in the order Nam Co < snow pack < urban. The enrichment in 14C and depletion in dissolved black carbon and sulfurous organic molecules of Nam Co WSOC was suggestive of low, but still detectable inputs of fossil‐derived organics to WSOC on the remote TP. Backward air mass trajectories for the precipitation events at Nam Co suggested that the fossil fuel contributions to WSOC in Nam Co region originated mainly from South Asia. This study provides novel radiocarbon age, chemistry, and source evidence that anthropogenic WSOC is delivered to the remote TP, one of the most remote regions on Earth. [ABSTRACT FROM AUTHOR]

Abstract: High altitude ecosystems have important natural ecological functions but are under increasing impacts from human activities and climate change. A detailed analysis of the water chemistry of Lake Rara, a high mountain lake in western Nepal, was carried out in October 2015 and April 2016. A total of 31 water samples were collected. Major ions (Ca2+, Mg2+, Na+, K+, SO42−, NO3− and Cl−) were analysed by ion chromatography. Si and PO43− were analysed following the standard protocols. Conductivity, pH, total dissolved solids (TDS), turbidity and dissolved oxygen (DO) were measured on‐site. The lake is oligotrophic characterized by low PO43− concentration (0.06 ± 0.01 mg/L), high DO values (6.73 ± 0.06 and 10.89 ± 0.86 mg/L), alkaline pH (8.42 ± 0.3 and 8.32 ± 0.23) and low conductivity (189.93 ± 5.3 and 189.22 ± 5.8 μS/cm). The concentrations of the major cations were in the order of Ca2+ > Mg2+ > K+ > Na+ (during both seasons), and for anions, it was HCO3− > SO42− > Cl− > NO3− and HCO3− > Cl− > NO3− > SO42− during postmonsoon and premonsoon, respectively. One‐way ANOVA revealed significant seasonal variations (p < 0.05) in most of the physicochemical parameters. The increased concentrations of most of the ions in the premonsoon time probably reflect long‐range transport of materials through dry deposition, whereas higher concentrations of NO3− and Cl− in some sites possibly reflect the localized impacts of settlement and grazing. The lake water was classified as Ca(Mg)HCO3. High (Ca2+ + Mg2+)/Tz+ ratio (0.97 in postmonsoon and 0.95 in premonsoon) and low (Na+ + K+)/Tz+ ratio (0.03 in postmonsoon and 0.04 in premonsoon) confirm carbonate weathering as the principal source of major ions with bedrock geology governing the water chemistry. The findings of this study build on the baseline dataset for assessing future anthropogenic influence on the lake and subsequent development for future lake management strategies. [ABSTRACT FROM AUTHOR]

Abstract: Black carbon (BC) in snow/ice induces enhanced snow and glacier melting. As over 60% of atmospheric BC is emitted from anthropogenic sources, which directly impacts the distribution and concentration of BC in snow/ice, it is essential to assess the origin of anthropogenic BC transported to the Tibetan Plateau (TP) where there are few direct emissions attributable to local human activities. In this study, we used a regional climate‐atmospheric chemistry model and a set of BC scenarios for quantitative evaluation of the impact of anthropogenic BC from various sources and its climate effects over the TP in 2013. The results showed that the model performed well in terms of climatology, aerosol optical properties, and near‐surface concentrations, which indicates that this modeling framework is appropriate to characterize anthropogenic BC source‐receptor relationships over the TP. The simulated surface concentration associated with the anthropogenic sources showed seasonal differences. In the monsoon season, the contribution of anthropogenic BC was less than in the nonmonsoon season. In the nonmonsoon season, westerly winds prevailed and transported BC from central Asia and north India to the western TP. In the monsoon season, BC aerosol was transported to the middle‐upper troposphere over the Indo‐Gangetic Plain and crossed the Himalayas via southwesterly winds. The majority of anthropogenic BC over the TP was transported from South Asia, which contributed to 40%–80% (mean of 61.3%) of surface BC in the nonmonsoon season, and 10%–50% (mean of 19.4%) in the monsoon season. For the northeastern TP, anthropogenic BC from eastern China accounted for less than 10% of the total in the nonmonsoon season but can be up to 50% in the monsoon season. Averaged over the TP, the eastern China anthropogenic sources accounted for 6.2% and 8.4% of surface BC in the nonmonsoon and monsoon seasons, respectively. The anthropogenic BC induced negative radiative forcing and cooling effects at the near surface over the TP. [ABSTRACT FROM AUTHOR]

The Tianshan Mountains represent an important water source for the arid and semi-arid regions of Central Asia. The discharge and glacier mass balance (GMB) in the Tianshan Mountains are sensitive to changes in climate. In this study, the changes in temperature, precipitation, and discharge of six glacierized watersheds of Tianshan Mountains were explored using non-parametric tests and wavelet transforms during 1957-2004. On the basis of the statistical mechanics and maximum entropy principle model, the GMB at the watershed scale were reconstructed for the study period. The discharge and GMB responses to climate change were examined in different watersheds. The results showed that regional climate warming was obvious, especially after 1996. The warming trend increased gradually from east to west, and the increase in temperature was greater on the north slope than on the south slope. The changing trends in precipitation increased from eastern region to central region, and then, the trend decreased in the western region, although the value was higher than that in the eastern region. The discharge presented significant periods of 2.7-5.4 years and increased from east to west. Significant periodicity indicated that the discharge in the different watersheds exhibited obviously different patterns. The GMB losses were larger in south and east than in north. The large glaciers had more stable interannual variations in discharge, and large fluctuations in discharge will be observed as the glacier areas shrink. Precipitation was the dominant factor for discharge during the study period, although the influence of increasing temperatures on hydrological regimes should not be neglected in the long term. Systematic differences in discharge and the GMB in glacierized watersheds in response to climate change are apparent in the Tianshan Mountains. [ABSTRACT FROM AUTHOR]

Snow and glaciers are known to be important sources for freshwater; nevertheless, our understanding of the hydrological functioning of glacial catchments remains limited when compared with lower altitude catchments. In this study, a temperate glacial region located in the southeast margin of the Tibetan Plateau is selected to analyse the characteristics of δ18O and δD in different water sources and the contribution of glacier-snow meltwater to streamflow. The results indicate that the δ18O of river water ranges from −16.2‰ to −10.2‰ with a mean of −14.1‰ and that the δD values range from −117.0‰ to −68.0‰ with a mean of −103.1‰. These values are more negative than those of glacier-snow meltwater but less negative than those of precipitation. The d-excess values are found to decrease from meltwater to river to lake/reservoir water as a result of evaporation. On the basis of hydrograph separation, glacier-snow meltwater accounts for 51.5% of river water in the Baishui catchment in the melting season. In the Yanggong catchment, snow meltwater contributes 47.9% to river water in the premonsoon period, and glacier meltwater contributes only 6.8% in the monsoon period. The uncertainty in hydrograph separation is sensitive to the variation of tracer concentrations of streamflow components. The input of meltwater to a water system varies with local climate and glacier changes. The results confirm that hydrograph separation using water isotopes is valuable for evaluating the recharge sources of rivers, especially in ungauged glacial regions. This study provides insights into the hydrological processes of glacial catchments on the Tibetan Plateau, which is important for water resource management. [ABSTRACT FROM AUTHOR]

In this work, the decomposition characteristics of compound additive (NaCl and Na2SO4) were investigated by thermogravimetry-differential scanning calorimetry-mass spectrometry coupling techniques. The results showed that the decomposition of NaCl was prior to that of Na2SO4 and the chlorine was generated during roasting. When the chlorine concentration is more than 2%, the phenomenon of vanadium volatilization becomes obvious in the process of roasting of stone coal. However, the chlorine concentration is less than 50 p.p.m. for the compound additive roasting, which would not cause the vanadium emission. The oxygen concentration of more than 5% is sufficient for oxidizing V(III) in the stone coal to water soluble V(V). Copyright © 2017 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The diurnal temperature range (DTR), defined as the difference between the maximum and minimum temperature, is a useful diagnostic index for evaluating global climate models. In this study, the DTR from 17 GCMs available in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) is evaluated on the Tibetan Plateau (TP) by comparison with the observations during 1961-2005. During the studied period, the observed maximum/minimum temperatures on the TP show statistically increasing trends with the annual rates of 0.19/0.36 °C decade−1, respectively, leading to the reduction of DTR (−0.22 °C decade−1). Compared with the observed DTR, most CMIP5 models generally underestimate DTR, with absolute error ranging from −4.58 °C (GFDL-ESM2M) to −1.36 °C (CESM1-BGC). Fifteen CMIP5 models have reproduced the overall negative trends of DTR on the TP, but their trend magnitudes are smaller. Furthermore, the CMIP5 model biases in DTR are investigated by means of correlative approach, to reveal the dominant variables. The differences between the surface downwelling short-wave radiation (SDSR) with clear skies (SDSRcs) and the SDSR can be used to describe the surface short-wave cloud radiative effect. Similarly, the differences between the surface downwelling long-wave radiation (SDLR) and the SDLR with clear skies (SDLRcs) are defined to address the surface long-wave cloud radiative effect. It is found that the mean DTR in the CMIP5 models has significantly negative correlations with both SDLR-SDLRcs and SDSRcs-SDSR, suggesting that the model differences in DTR on the TP are probably determined by radiation variables and total cloud fraction in the CMIP5 models. [ABSTRACT FROM AUTHOR]

During post-monsoon 2013, surface water samples were collected form 34 sites from the Bagmati River and its tributaries within the Kathmandu Valley to assess the river water quality. The physical parameters were measured on site and major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, SO42-, and NO3-) and 17 elements in water were analyzed in the laboratory. Conductivity ranged from 21.92 to 846 μS/cm, while turbidity ranged from 2.52 to 223 NTU and dissolved oxygen (DO) ranged from 0.04 to 8.98 mg/L. The ionic and elemental concentrations were higher in the lower section where the population density is high compared to the headwaters. The large input of wastewater and organic load created anoxic condition by consuming dissolved oxygen along the lower belt of the river. The concentration of the elements was found to be in the order of Mn > Zn > Ti > Rb > Cr > Cu > Sc > Ni > V > Li > Co > Mo > Cd > Y > Ga > Be > Nb. The concentration of Mn, Cd, Cr, Co, and Zn was particularly higher in urban and semiurban sections. Enrichment factor (EF) calculations for Cd, Co, and Zn showed their highly enriched values indicating that these elements originated from anthropogenic sources. Preliminary risk assessments were determined by the hazard quotient (HQ) calculations in order to evaluate the health risk of the metals. The HQingestion values of elements were found to be in the order Sb > Mn > Cr > V > Co > Cd > Cu > Zn > Ni > Li > Mo with all averaged HQ values less than 1, indicating no or limited health risk of metals from the river to the local residence. However the values of Sb in some parts of the Bagmati were close to unity indicating its possible threat. Anthropogenic activities like industrial activities, municipal waste water, and road construction besides the river appear to control the chemical constituent of the river water. Overall the river was highly polluted with elevated concentrations of major ions and elements and there is a need for restoration projects. [ABSTRACT FROM AUTHOR]

Climate change and anthropogenic factors can alter biodiversity and can lead to changes in community structure and function. Despite the potential impacts, no long-term records of climatic influences on microbial communities exist. The Tibetan Plateau is a highly sensitive region that is currently undergoing significant alteration resulting from both climate change and increased human activity. Ice cores from glaciers in this region serve as unique natural archives of bacterial abundance and community composition, and contain concomitant records of climate and environmental change. We report high-resolution profiles of bacterial density and community composition over the past half century in ice cores from three glaciers on the Tibetan Plateau. Statistical analysis showed that the bacterial community composition in the three ice cores converged starting in the 1990s. Changes in bacterial community composition were related to changing precipitation, increasing air temperature and anthropogenic activities in the vicinity of the plateau. Collectively, our ice core data on bacteria in concert with environmental and anthropogenic proxies indicate that the convergence of bacterial communities deposited on glaciers across a wide geographical area and situated in diverse habitat types was likely induced by climatic and anthropogenic drivers. [ABSTRACT FROM AUTHOR]

ABSTRACT On the basis of mean temperature, maximum temperature and minimum temperature from the updated China Homogenized Historical Temperature Data Sets, the recent warming in the Tibetan Plateau ( TP) during 1961-2005 and global warming hiatus period are examined. During 1961-2005, the mean temperature, maximum temperature and minimum temperature in the whole TP show a statistically increasing trend especially after the 1980s, with the annual rates of 0.27, 0.19 and 0.36 °C decade−1, respectively. The performance of 26 general circulation models ( GCMs) available in the fifth phase of the Coupled Model Intercomparison Project ( CMIP5) is evaluated in the TP by comparison with the observations during 1961-2005. Most CMIP5 GCMs can capture the decadal variations of the observed mean temperature, maximum temperature and minimum temperature, and have significant positive correlations with observations ( R > 0.5), with root mean squared error <1 °C. This suggests that CMIP5 GCMs can reproduce the recent temperature evolution in the TP, but with cold biases. However, most CMIP5 GCMs underestimate the observed warming rates, especially the CNRM-CM5, GISS-E2-H and MRI-CGCM3 models. There are significant positive correlations between the trend magnitudes and the anomaly of the mean temperature, maximum temperature and minimum temperature, with correlations of 0.85, 0.86 and 0.87, respectively. The warming from the observations and CMIP5 mean in the TP is significant during the global hiatus period, consistent with decreasing snow cover and albedo in the region. This study suggests that positive snow/ice-albedo feedback processes may account for ongoing surface warming in the TP despite the pause in global mean surface warming. [ABSTRACT FROM AUTHOR]

ABSTRACT Spatial and temporal variabilities of long-term (1961-2013) diurnal temperature range ( DTR) are examined in the Tibetan Plateau ( TP) based on the 71 observational stations. The relative regional contributions to DTR in the TP are studied among maximum temperature, minimum temperature, total cloud cover ( TCC), and atmospheric teleconnections. The regional annual mean DTR (average of the 71 stations) is 14.17 °C, with a clear maximum in winter (16.35 °C) and minimum in summer (12.62 °C). During 1961-2013, the DTR in the TP declines before the 1980s and shows mute change afterwards, with an annual rate of −0.20 °C decade−1 calculated by the Mann-Kendall method. The trend in DTR is primarily a consequence of greater warming in minimum temperature than maximum temperature. In summer, there are significant negative correlations between the TCC and DTR in the TP, suggesting that the decreases in the DTR are associated with variations of TCC in the region. The atmospheric circulation composite analysis between strongly positive and negative DTR in summer in the TP reveals that during the low DTR period the TP has more water vapour flux, stronger temperature advection, and strengthened southerly wind. This suggests that the atmospheric circulations have contributed to the trends in the DTR, but it is difficult to account for the specific contributions. Further investigations of the impact of global warming on the DTR in the TP are still required. [ABSTRACT FROM AUTHOR]

Changes in permafrost influence water balance exchanges in watersheds of cryosphere. Water storage change (WSC) is an important factor in water cycle. We used Gravity Recovery and Climate Experiment (GRACE) satellite data to retrieve WSC in the Three-River Source Region and subregions. WSC in four types of permafrost (continuous, seasonal, island, and patchy permafrost) was analyzed during 2003–2010. The result showed that WSC had significant change; it increased by 9.06±0.01 mm/a (21.89±0.02×109 m3) over the Three-River Source Region during the study period. The most significant changes of WSC were in continuous permafrost zone, with a total amount of about 13.94±0.48×109 m3. The spatial distribution of WSC was in state of gain in the continuous permafrost zone, whereas it was in a state of loss in the other permafrost zones. Little changes of precipitation and runoff occurred in study area, but the WSC increased significantly, according to water balance equation, the changes of runoff and water storage were subtracted from changes of precipitation, and the result showed that changes of evaporation is minus which means the evaporation decreased in the Three-River Source Region during 2003–2010. [ABSTRACT FROM AUTHOR]

The Gravity Recovery and Climate Experiment (GRACE) satellite mission provides measurements of Earth’s static and time-variable gravity fields with monthly resolution. In this study, changes of water storage in northwestern China were determined by GRACE monthly gravity field data obtained from 2003 to 2010. Comparisons of water storage change (WSC) simulated by a four-dimensional assimilation model (Noah) and observed by GRACE revealed similar patterns of change and a correlation coefficient of 0.71 (P<0.05). Trend analysis indicated significant changes in the spatiotemporal variation of WSC in northwestern China during the 8-year study period, which were stronger in the east than in the west and more pronounced in the south than in the north. The most pronounced increase in water storage occurred in Gansu and Qinghai provinces, but, overall, water storage increased by 0.61 mm/a over northwestern China during the study period. Clear seasonal variations of WSC and precipitation were found, because glacial meltwater and precipitation are the main sources of water in the hydrosphere; meanwhile, the distributions of glaciers and permafrost also affect the spatial distribution of WSC. [ABSTRACT FROM AUTHOR]

ABSTRACT Based on intersatellite-calibrated high-resolution infrared radiation sounder (HIRS) upper tropospheric water vapour (UTWV) brightness temperatures, the width of the tropical belt is defined as the distance between the latitudes at which maximum HIRS UTWV brightness temperatures are recorded in both hemispheres. Poleward expansion of the tropical belt is evident during 1979-2013 on an annual basis, with an average global magnitude of 1.57° latitude per decade. Most rapid widening is evident in the west Pacific, in agreement with the strengthening of the Walker Circulation over time. This research suggests that the HIRS UTWV brightness temperatures are a good proxy to investigate the expansion of the tropical circulation in low latitudes. [ABSTRACT FROM AUTHOR]

ABSTRACT Extreme climate events over China at the end of the 21st century (2080-2099) are investigated using the regional climate model RegCM4. Model performance is validated through comparison between observations and simulations over the period 1985-2005. The results show that RegCM4 can satisfactorily reproduce the spatial distribution of extreme climate events over China. The model simulates temperature extremes more accurately than precipitation. Under the RCP8.5 (high emission) scenario, the number of frost days decreases, and both the heat wave duration index and the growing season length increase dramatically towards the end of the 21st century. Changes in extreme temperature become increasingly pronounced from South to North China, with the most significant changes occurring on the Tibetan Plateau ( TP). The proportion of heavy precipitation generally increases, except on the southern TP. The number of very heavy precipitation days increases by 25-50% in Northwest and East China. In winter, the number of consecutive dry days ( CDD) decreases in North China and increases in South China. The greatest increases in CDD are found in June, July and August ( JJA) in Southwest China. In a future that follows this scenario, drought events may be aggravated in Southwest China, and decrease in North China. In contrast, when repeating these projections under the assumption of the RCP4.5 scenario for emissions, the frequency of extreme climate events is reduced. These results suggest that reductions in greenhouse gas emissions may mitigate the effects of climate change over the coming decades. [ABSTRACT FROM AUTHOR]

The annual and seasonal total cloud cover (TCC) variations in the eastern and central Tibetan Plateau (TP) during 1961-2005 are analysed using 71 surface observational stations. The mean TCC decreases from the southeastern to the northwestern TP, consistent with the patterns of atmospheric moisture in the region. The annual mean TCC shows a significant decreasing trend of -0.09 percent decade-1, mainly contributed by winter. About 65% of the stations show significant downward trends on the annual basis with large trend magnitudes occurring in the central TP. The seasonal patterns confirm the annual patterns in most cases. Compared with the surface observations, both National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis (NCEP/NCAR) (1961-2005) and ERA-40 (1961-2001) can reproduce the decreasing TCC trends. The shift of TCC before and after the mid-1980s is obvious in observations and both reanalyses, reflecting the changes of large-scale atmospheric circulation. However, NCEP/NCAR underestimates and ERA-40 overestimates observations on the annual and seasonal basis, presumably caused by the different cloud parameterization schemes. A Taylor diagram diagnose summarizes the discrepancies between observations and reanalyses. [ABSTRACT FROM AUTHOR]

ABSTRACT Climate warming on the Tibetan Plateau ( TP) potentially influences many climate parameters other than temperature including wind speed, cloudiness and precipitation. Temporal trends of surface wind speed at 71 stations above 2000 m above sea level in the TP are examined during 1980-2005. To uncover causes of observed trends in wind speed, relationships with surface temperature, a TP index and sunshine duration are also analysed. The TP index is calculated as the accumulated 500 hPa geopotential height above 5000 m over the region of 30°N-40°N, 75°E-105°E from NCEP/ NCAR reanalysis. The annual mean wind speed patterns during 1980-2005 are similar to those in different seasons, with higher wind speeds in the northern and western parts of the TP. Highest mean wind speeds occur in spring and lowest in autumn. During 1980-2005, annual and seasonal mean wind speeds show statistically decreasing trends at most stations. The mean trend magnitude for annual mean wind speed is −0.24 m s−1 decade−1, with the maximum decline in spring (−0.29 m s−1 decade−1) and minimum in autumn (−0.19 m s−1 decade−1). Both annually and in different seasons, wind speed is significantly negatively correlated with mean temperature, minimum temperature, maximum temperature, and the TP index, but significantly positively correlated with sunshine duration. Wind speed trends fail to show a simple elevation dependency but speeds are positively correlated with meridional surface temperature/pressure gradients. Warming in the TP may weaken the latitudinal gradients of both regional temperature and surface pressure, thus altering the regional atmospheric circulation and accounting in part for the observed decline of wind speed. [ABSTRACT FROM AUTHOR]

Cold and warm temperature extremes predominantly occurring in winter gained much more attention than mean temperatures. On the basis of daily maximum and minimum surface air temperature records at 303 meteorological stations in China, the spatial and temporal distributions of five indices for winter (DJF: December, subsequent January and February) temperature extremes are analysed during 1961-2003. For the majority of stations, the frequency of cold days/nights decreases by − 1.33/− 2.98 and warm days/nights increases by 0.92/2.35 d/decade, respectively. Cold days/nights are significantly negatively correlated with the Arctic Oscillation (AO) index, while warm days/nights are positively correlated with the AO. The diurnal temperature range (DTR) has a declining trend with rate of − 0.25 °C/decade and positive correlation with the AO index. Compared with other regions in China, stations in the northern China have larger trend magnitudes and stronger correlations with the AO index, and the AO can explain more than 50% of winter temperature extreme change in China. Compared with the annual basis, the winter temperature extremes have larger trend magnitudes, which reflect the rapid warming. During strongly positive AO index years, enhanced contrast tropospheric temperature (defined as the average of air temperature vertically integrated between 200 hPa and 1000 hPa based on the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis) between the north of China and the southern China weakens the East Asian winter monsoon which in turn reduces cold outbreaks in the northern and eastern China. The composites of large-scale atmospheric circulation are consistent with the asymmetrical changes of the geopotential height, zonal and meridional winds at high and mid latitudes at troposphere. Meanwhile, the linkage between the AO and solar activity also modulates the winter temperature extremes, while the mechanism needs to be investigated. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) with an average elevation of over 4000 m a.s.l. is the world's highest and most extensive highland. The scarcity of climatic observations limits our understanding of surface air temperature change in the region. Thus, we compare temperatures and their trends from 71 homogenized surface stations (with elevations above 2000 m a.s.l.) with National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis (NCEP/NCAR hereafter) and European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40 hereafter) in the eastern and central TP during 1961-2004. For current climatology, ERA-40 is more similar to the surface stations than NCEP/NCAR. Compared with surface stations, both NCEP/NCAR and ERA-40 reanalyses have cold biases, which are mainly a result of differences in topographical height, and station aspect and slope. Warming trends at the surface stations are on average stronger than in both reanalyses, but ERA-40 captures the surface warming more clearly than NCEP/NCAR on an annual and seasonal basis. Since ERA-40 more closely represents the surface temperatures and their trends in the central and eastern TP, ERA-40 predictions are selected to examine change in the western TP where there are few surface stations. NCEP/NCAR, on the other hand, is more representative of free air temperature conditions. The 'observation minus reanalysis' (OMR) method can be used to estimate the impact of surface changes on climate by computing the difference between surface observations and NCEP/NCAR (which only contains the forcing influencing the assimilated atmospheric trends). The OMR trend is significantly increasing but the extent to which the changes in local environment are responsible needs further study. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]