Search

Variations in glacier meltwater in the source regions of the Tibetan Plateau's (TP) largest lake (Selin Co) and China's longest river (Yangtze River) regulate the local and downstream water balance under the warming climate. However, the magnitude of their variations over the past four decades is still unknown. Here, we examine long-term changes in glacier mass balance over 1976–2017 using KH-9 and CoSSC-TanDEM-X data. We find that the mean rate of glacier mass loss (GML) has accelerated from −0.21 ± 0.11 m a–1 over 1976–2000, to −0.28 ± 0.14 m a–1 over 2000–11, and subsequently to −0.48 ± 0.10 m a–1 over 2011–17. Changes in temperature and precipitation are the major causes of GML. Over 1976–2017, the contribution of decadal GML to Tuotuohe sub-basin runoff ranges from 4.3 to 8.0%, while its contribution to increased lake volume change in Selin Co and Chibzhang Co-Dorsoidong Co ranges from 3.5 to 16.3% and 19.2 to 21.4%, respectively. The GML of source regions made relatively small contributions to river runoff and lake supply, but plays a vital role when precipitation decreases. The quantitative evaluation of the water balance for the sources of great rivers and lakes over the TP is therefore important for water resource management and hydrological cycle studies. [ABSTRACT FROM AUTHOR]

Elevational gradients are powerful 'natural laboratory' for testing the responses of microbes to geophysical influences. Microbial communities are normally composed of a few abundant and many rare taxa. Abundant and rare taxa play different ecological roles in kinds of environments, but how their diversity and composition patterns response to elevation gradients is still poorly elucidated. In this study, we investigated the elevational patterns of abundant and rare bacterial diversity and composition in a mountain stream from 712 to 3435 m at Gangrigabu Mountain on the Tibetan Plateau, China. Our results revealed abundant and rare bacteria had similar decreasing elevation trend of alpha diversity, and both of them showed a significant elevational distance-decay relationship. However, the turnover rate of the elevational distance-decay of rare bacteria was higher than that of abundant bacteria. The species-abundance distribution patterns of rare taxonomic composition were associated with the elevational gradient, while most of abundant bacterial clades did not display any relationships with elevation. Our results suggested that rare bacteria were more sensitive to changes in elevation gradient. [ABSTRACT FROM AUTHOR]

To further our understanding of the Asian monsoon system, particularly the onset dates of monsoon sub-systems over their respective East Asian domains, we present an 8-year (2007-2014) dataset of oxygen isotopes of precipitation (δ18Op) from three stations, Lulang and Nuxia in southeastern Tibetan Plateau (SETP) and Guangzhou in southeastern coastal China (SECN). The general agreement between isotopically identified monsoon onset dates with those identified by the meridional temperature gradient suggests that the initially sustained isotopic depletion is sensitive to the evolving thermal contrast between the Eurasian continent and the Indian Ocean. The 850 hPa meridional wind over nearby oceans is an efficient bridge linking isotopic variations in both regions with their respective monsoon sub-systems. The intensity of the South Asian High and tropical cyclone frequencies show stronger effects on isotopic depletion in the SECN than in the SETP and on monsoon onset timing over the South China Sea. Tibetan Plateau snow cover anomalies are significantly correlated with δ18Op in both regions on monthly timescales. [ABSTRACT FROM AUTHOR]

Since the late 1990s, lakes in the southern Tibetan Plateau (TP) have shrunk considerably, which contrasts with the rapid expansion of lakes in the interior TP. Although these spatial trends have been well documented, the underlying hydroclimatic mechanisms are not well understood. Since 2013, we have carried out comprehensive water budget observations at Paiku Co, an alpine lake in the central Himalayas. In this study, we investigate water storage and lake level changes on seasonal to decadal time scales based on extensive in-situ measurements and satellite observations. Bathymetric surveys show that Paiku Co has a mean and maximum water depth of 41.1 m and 72.8 m, respectively, and its water storage was estimated to be 109.3 × 10 8 m 3 in June 2016. On seasonal scale between 2013 and 2017, Paiku Co’s lake level decreased slowly between January and May, increased considerably between June and September, and then decreased rapidly between October and January. On decadal time scale, Paiku Co’s lake level decreased by 3.7 ± 0.3 m and water storage reduced by (10.2 ± 0.8) × 10 8 m 3 between 1972 and 2015, accounting for 8.5% of the total water storage in 1972. This change is consistent with a trend towards drier conditions in the Himalaya region during the recent decades. In contrast, glacial lakes within Paiku Co’s basin expanded rapidly, indicating that, unlike Paiku Co, glacial meltwater was sufficient to compensate the effect of the reduced precipitation. [ABSTRACT FROM AUTHOR]

Spatial and temporal variability in stable isotopic compositions (δ 18 O and δD) in river water of the Yarlungzangbo was investigated to identify major hydrological processes along the river channel and evaluate the isotopic response to discharge variation. The results show geographic, distinct isotopic evolutions in the Yarlungzangbo system. Along the main stem, river δ 18 O exhibits a decreasing trend from the headwaters to the middle reach but an increasing one from the middle to the lower reaches, and main flows demonstrate much greater δ 18 O-δD slope and intercept compared to the global meteoric water line (GMWL) and reported local meteoric water lines (LMWLs) for sites within the basin. These results are found to be consistent with the isotopic characteristics of stream and river waters collected across the entire drainage basin. Water mixing appears to be the dominant hydrological process along the Yarlungzangbo, and the pattern of isotopic change in individual river reaches closely reflects that of precipitation in corresponding part of the river basin. The isotopic variability along the main stem observed during the synoptic survey is evidenced to hold through time by a time-series investigation at three key hydrological stations. River water at such three stations shows a strong isotopic response to discharge variability. In general, river δ 18 O tends to be negatively correlated with discharge, highlighting a typical monsoon precipitation-driven isotope-discharge pattern. Specifically, we found their individual discharge-weighted average δ 18 O values likely vary in a similar rate with the ratio of mean discharge in monsoon season (JAS) to that in pre-monsoon season (MJ) on a yearly basis, indicating a specific relationship between average river isotopic composition and discharge seasonality throughout their drainage areas (i.e. the middle-lower Yarlungzangbo basin). This study thus demonstrates the usefulness of isotopic data for assessing hydrodynamics over a less explored, complex and high-altitude large river catchment. [ABSTRACT FROM AUTHOR]

Dyadobacter tibetensis Y620-1 is the type strain of the species Dyadobacter tibetensis, isolated from ice at a depth of 59 m from a high altitude glacier in China (5670 m above sea level). It is psychrotolerant with growth temperature ranges of 4 to 35°C. Here we describe the features of this organism, together with the draft genome sequence and annotation. The 5,313,963 bp long genome contains 4,828 protein-coding genes and 39 RNA genes. To the best of our knowledge, this is the first Dyadobacter strain that was isolated from glacial ice. This study provides genetic information of this organism to identify the genes linked to its specific mechanisms for adaption to extreme glacial environment. [ABSTRACT FROM AUTHOR]

Lake level and area variations are sensitive to regional climate changes and can be used to indirectly estimate water balances of lakes. In this study, 10 of the largest lakes in China, ∼1000 km or larger, are examined to determine changes in lake level and area derived respectively from ICESat and Landsat data recorded between 2003 and 2009. The time series of lake level and area of Selin Co, Nam Co, and Qinghai Lake in the Tibetan Plateau (TP) and Xingkai Lake in northeastern China exhibit an increasing trend, with Selin Co showing the fastest rise in lake level (0.69 m/a), area (32.59 km/a), and volume (1.25 km/a) among the 10 examined lakes. Bosten and Hulun lakes in the arid and semiarid region of northern China show a decline in both lake level and area, with Bosten Lake showing the largest decrease in lake level (−0.43 m/a) and Hulun Lake showing the largest area shrinkage (−35.56 km/a). However, Dongting, Poyang, Taihu, and Hongze lakes in the mid-lower reaches of the Yangtze River basin present seasonal variability without any apparent tendencies. The lake level and area show strong correlations for Selin Co, Nam Co, Qinghai, Poyang, Hulun, and Bosten lakes ( R >0.80) and for Taihu, Hongze, and Xingkai lakes (∼0.70) and weak correlation for East Dongting Lake (0.37). The lake level changes and water volume changes are in very good agreement for all lakes ( R > 0.98). Water balances of the 10 lakes are derived on the basis of both lake level and area changes, with Selin Co, Nam Co, Qinghai, and Xingkai lakes showing positive water budgets of 9.08, 4.07, 2.88, and 1.09 km, respectively. Bosten and Hulun lakes show negative budgets of −3.01 and −4.73 km, respectively, and the four lakes along the Yangtze River show no obvious variations. Possible explanations for the lake level and area changes in these four lakes are also discussed. This study suggests that satellite remote sensing could serve as a fast and effective tool for estimating lake water balance. [ABSTRACT FROM AUTHOR]

Glaciers on the Tibetan Plateau are undergoing an accelerating retreat under climatic warming, with the immediate result of glacial lake outburst floods (GLOFs) becoming increasingly frequent. Glacial lakes in the southeast of the Tibetan Plateau are densely distributed. Due to the difficulties associated with field investigations of glacial lakes, including remote locations and harsh weather conditions, methods which combine remote sensing, geographic information systems and hydrodynamic modeling (HEC-RAS) with field investigation were developed to assess regional glacial lake variation and hazard. The methods can be divided into three levels. At the first level, multi-temporal satellite images were used to (1) study the variation of glacial lakes for the whole region during recent decades, as well as (2) qualitatively identify potentially dangerous glacial lakes (PDGLs). The second level is an in-depth evaluation of the degree of danger for selected PDGLs by ground-based surveys, and then verification of the first-level results. At the third level, the one-dimensional (1D) hydrodynamic model HEC-RAS was used to simulate the inundation characteristics of hypothetical outburst of PDGLs. The three levels downscale from the whole study area to individual PDGLs, and thus assess the hazard of glacial lakes progressively. The methods were then applied to a region of southeastern Tibet-the Boshula mountain range-to analyze the variation of glacial lakes and assess potential hazards posed by GLOFs. Since these methods employ easily accessible data and instruments, the application in other regions is promising. [ABSTRACT FROM AUTHOR]

Abstract: 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−1 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 explore the culturable microbial diversity in ice core by combining the approaches of both direct and enrichment cultivation. [Copyright &y& Elsevier]

Dissolved inorganic carbon isotope (δ13CDIC) is an important tool to reveal the carbon cycle in lake systems. However, there are only few studies focusing on the spatial variation of δ13CDIC of closed lakes. Here we analyze the characteristics of δ13CDIC of 24 sampled lakes (mainly closed lakes) across the Qiangtang Plateau (QTP) and identify the driving factors for its spatial variation. The δ13CDIC value of these observed lakes varies in the range of − 15·0 to 3·2‰, with an average value of − 1·2‰. The δ13CDIC value of closed lakes is close to the atmospheric isotopic equilibrium value, much higher than that in rivers and freshwater lakes reported before. The high δ13CDIC value of closed lakes is mainly attributed to the significant contribution of carbonate weathering in the catchment and the evasion of dissolved CO2 induced by the strong evaporation of lake water. The δ13CDIC value of closed lakes has a logarithmic correlation with water chemistry (TDS, DIC and pCO2), also suggesting that the evapo-concentration of lake water can influence the δ13CDIC value. The δ13CDIC value shows two opposite logarithmic correlations with lake size depending on the δ13CDIC range. This study suggests that the δ13C in carbonates in lacustrine sediments can be taken as an indicator of lake volume variation in closed lakes on QTP. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The resolution and accuracy of digital elevation models (DEMs) can affect the hydraulic simulation results for predicting the effects of glacial lake outburst floods (GLOFs). However, for the Tibetan Plateau, high-quality DEM data are often not available, leaving researchers with near-global, freely available DEMs, such as the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) and the Shuttle Radar Topography Mission data (SRTM) for hydraulic modelling. This study explores the suitability of these two freely available DEMs for hydraulic modelling of GLOFs. Our study focused on the flood plain of a potentially dangerous glacial lake in southeastern Tibet, to evaluate the elevation accuracy of ASTER GDEM and SRTM, and their suitability for hydraulic modelling of GLOFs. The elevation accuracies of ASTER GDEM and SRTM were first validated against field global position system (GPS) survey points, and then evaluated with reference to the relatively high precision of 1:50 000 scale DEM (DEM5) constructed from aerial photography. Moreover, the DEM5, ASTER GDEM and SRTM were used as basic topographic data to simulate peak discharge propagation, as well as flood inundation extent and depth in the Hydrologic Engineering Center's River Analysis System one-dimensional hydraulic model. Results of the three DEM predictions were compared to evaluate the suitability of ASTER GDEM and SRTM for GLOF hydraulic modelling. Comparisons of ASTER GDEM and SRTM each with DEM5 in the flood plain area show root-mean-square errors between the former two as ± 15·4 m and between the latter two as ± 13·5 m. Although SRTM overestimates and ASTER GDEM underestimates valley floor elevations, both DEMs can be used to extract the elevations of required geometric data, i.e. stream centre lines, bank lines and cross sections, for flood modelling. However, small errors still exist in the cross sections that may influence the propagation of peak discharge. The flood inundation extent and mean water depths derived from ASTER GDEM predictions are only 2·2% larger and 2·3-m deeper than that of the DEM5 predictions, whereas the SRTM yields a flood zone extent 6·8% larger than the DEM5 prediction and a mean water depth 2·4-m shallower than the DEM5 prediction. The modelling shows that, in the absence of high-precision DEM data, ASTER GDEM or SRTM DEM can be relied on for simulating extreme GLOFs in southeast Tibet. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This research aimed to identify and characterize individual spherical fly ash particles extracted from surface snow at Urumqi Glacier No.1 (UG1), Eastern Tien Shan, central Asia. Characterization of the spherical particles (i.e. morphology, chemical composition and genesis) was obtained by scanning electron microscopy coupled with energy dispersive X-ray spectrometer (SEM-EDX). This method enabled the characterization of submicroscopic spherical particles, which were present in very small quantities. Spherical particles and agglomerates were identified according to their morphology in five snow samples. Prevalent particle types in all samples were granular spherical particles, hollow spherical particles, irregularly shaped carbonaceous particles and agglomerates. The vast majority of spherical particles in our samples had mostly smooth and glossy surfaces, although these particles varied in diameter and elemental composition. The diameter of fly ash particles ranged from 0.76 to 16.7 μm, with an average of 3.79 μm (median: 3.21 μm). Individual particle analyses of elemental composition showed that particles formed in combustion were mainly composed of carbon, silicon, aluminum and trace elements (e.g. Na, K, Ca, Fe). Some spherical fly ash particles contained toxic heavy metals (e.g. Pb, Cr, As, Zn), and indicated that fly ash particles acted as the main possible carriers of toxic heavy metals deposited in snow and ice of glaciers in high altitudes of central Asia. On the basis of chemical information obtained from EDX, the fly ash particles deposited in the snow could be classified into four types. Namely, Si-dominant particles, with average diameters of 3.24 μm were formed by industrial coal combustion via high temperature processes in typical coal-fired heating stations and thermal power plants. Moreover, Fe-dominant particles, with average diameters of 3.82 μm, and Ti-dominant spherical particles formed by lower temperature processes in foundry and iron or steel plants. In addition, C-dominant particles, with average diameters of 8.43 μm, formed from unburned coal. Fe-dominant particles had larger average diameters than Sidominant particles, indicating that the former were easier to form and developed earlier in the furnace because of their differential melting points of compositional oxide. Backward air mass trajectory analysis suggests that the developed urban regions of central Asia contributed the primary fly ash particles from industrial combustion to the study site through the high-level westerlies jet steam. [ABSTRACT FROM AUTHOR]

We present a field investigation over a melting valley glacier on the Tibetan Plateau. In the ablation zone, aerodynamic roughness lengths ( z) vary on the order of 10-10 m, whose evolution corresponds to three melt phases with distinct surface cover and moisture exchange: snow (sublimation/evaporation), bare ice (deposition/condensation), and ice hummocks (sublimation/evaporation). Bowen-ratio similarity is validated in the stably stratified katabatic winds, which suggests a useful means for data quality check. A roughness sublayer is regarded as irrelevant to the present ablation season, because selected characteristics of scalar turbulence over smooth snow are quite similar to those over hummocky ice. We evaluate three parametrizations of the scalar roughness lengths ( z for temperature and z for humidity), viz. key factors for the accurate estimation of sensible heat and latent heat fluxes using the bulk aerodynamic method. The first approach is based on surface-renewal models and has been widely applied in glaciated areas; the second has never received application over an ice/snow surface, despite its validity in (semi-)arid regions; the third, a derivative of the first, is proposed for use specifically over rough ice defined as z > 10 m or so. This empirical z threshold value is deemed of general relevance to glaciated areas (e.g. ice sheet/cap and valley/outlet glaciers), above which the first approach gives notably underestimated z. The first and the third approaches tend to underestimate and overestimate turbulent heat/moisture exchange, respectively, frequently leading to relative errors higher than 30%. Comparatively, the second approach produces fairly low errors in energy flux estimates both in individual melt phases and over the whole ablation season; it thus emerges as a practically useful choice to parametrize z in glaciated areas. Moreover, we find all three candidate parametrizations unable to predict diurnal variations in the excess resistances to humidity transfer, thus encouraging more efforts for improvement. [ABSTRACT FROM AUTHOR]

Bacterial abundances and diversity in the surface water of Lake Namco, the largest oligosaline lake on the Tibetan Plateau, were examined using flow cytometry approach and constructing 16S rRNA gene clone libraries. Bacterial abundances were from 0.08 × 106 to 1.6 × 106 cells mL-1, and were in the reported range of other lakes of the Tibetan Plateau and high mountain regions. Bacterial abundances were significantly correlated with the concentrations of chlorophyll a (chl a), but showed no significant relationship with the dissolved organic carbon (DOC), which suggested that the amount of DOC released by algae was the key factor determining the bacterial abundance rather than the total DOC. The total trace elements concentrations also obviously connected with bacterial abundances, and 9 of 20 elements showed significant relationship. Bacterial 16S rRNA gene clone sequences were affiliated to the α-, β-, γ-, δ-, and ε-Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Acidobacteria, Planctomycetes, Verrucomicrobia, Candidate division OD1, or unclassified, and among these the β-Proteobacteria dominated. Bacteria in Lake Namco were most closely related to those retrieved from freshwater habitats. Relatively few sequences were closely related to those recovered from saline habitats. Eleven of 34 typical freshwater bacterial clusters were detected in the oligosaline Lake Namco. Bacterial diversity within the lake varied and was connected with the concentrations of DOC and chl a. [ABSTRACT FROM AUTHOR]

Sediments from a remote lake of northeastern Tibetan Plateau were analyzed for polycyclic aromatic hydrocarbons (PAHs) and trace metals. USEPA priority PAHs, ranged from 11 in 1860 to 279 ng g−1 in 2002, while, the deposition fluxes were in the range of 0.2–11.4 ng cm−2 yr−1. Similarly, from 1860 to 2002, an increased trend of Hg flux was observed (0.5–3.2 ng cm−2 yr−1). Remarkable increase of PAHs and Hg concentration began from 1970, nearly the same period of the “Reform and Open” Policy had been embarked (1978) in China. Good correlations were found between concentrations of Pb, Zn, Cd, As, Hg, and PAHs, which suggested the sources of these chemicals in the sediment is analogous, likely from anthropogenic sources. Based on isomer ratios, PAHs in core were dominantly from the incomplete combustion of coal. Owing to the proximity to dust source area (Qaidam Basin) and the close association between PAHs, Hg, Pb, and particle matters, atmospheric dust-transport and deposition might be the main pathways that pollutants enter into Qinghai Lake. [Copyright &y& Elsevier]

Many temperate glaciers in the southeast Tibetan Plateau are covered by supraglacial debris in the ablation area. To evaluate the effect of such debris on summer ablation and mass balance, the surface ablation on the 24K Glacier was measured in the summer of 2008. Mean ablation rates varied from 10 to 52 mm/day, strongly correlated to debris thickness. Synchronous observations of air temperature allowed application of a simple degree-day model to calculate ablation rates. Maximum values of both ablation rate and degree-day factors appeared in the middle area of the glacier where the debris layer thickness was about 1 cm. The simulated daily ablation obtained from the degree-day approach showed that the debris layers significantly affected the total summer ablation. The calculated ablation would be increased by 36% of the total ablation with the actual surface debris cover if glacier surface had been assumed to be entirely debris free. If completely covered by 65 cm thick debris in the ablation area, the glacier would experience a 59% decrease in summer ablation. The presence of a debris cover also leads to a change in the ablation gradient in the ablation zone. [ABSTRACT FROM AUTHOR]

Glaciers in the Yarlung Zangbo River witness severe glacial retreat nowadays, which gives important influence on lake processes in the region. We have studied glacial distribution, glacial mass balance and found large deficit in glacial mass and its impact in the region. Our study also integrated the variation in glacial-fed lakes of the Nam Co and Ranwu Lake, and presented an initial assessment of the impact of glacial mass balance on lakes. The study has shown a significant contribution of glacial melting to recent lake expansion and lake level rising. [ABSTRACT FROM AUTHOR]

Abstract: A 32.4m shallow ice core was recovered from a site at 5743m above sea level on the Mt. Tanggula in the central Qinghai-Tibetan Plateau in August 2005. A total of 630 samples were analyzed for major ions (Na+, NH4 +, K+, Mg2+, Ca2+, Cl−, SO4 2 − and NO3 −) and stable oxygen isotope ratios (δ 18O). The ion chemistry of the upper 14.5m, covering the last 55years, is characterized by mineral dust (HCO3 −, Ca2+, SO4 2 −, Na+, Cl− and K+), anthropogenic species (SO4 2 −, NH4 + and NO3 −) and soil and biogenic emissions (NO3 − and NH4 +). Ca2+ is the dominant cation in the core with a medium value of 33.5μeqL− 1, accounting for 64.5% of the total cations, and HCO3 − is the predominant anion, accounting for 80.2% of the total anions. Compared with ice core records from Altai and Himalayas, at the northern and southern margin of the Qinghai-Tibetan Plateau, respectively, major ion concentrations (except SO4 2 −, NH4 + and NO3 −) in Tanggula ice core are much higher due to pronounced regional crustal aerosol inputs. Increasing SO4 2 − concentrations in the most recent 50years are attributed to anthropogenic contributions; but mineral dust is still the major sources for SO4 2 − in the central Qinghai-Tibetan Plateau. The notable relationship between increasing Northern Hemisphere temperature and NO3 − and NH4 + concentrations suggests that recent temperature increase in Qinghai-Tibetan Plateau may be enhancing biological activity and associated NO3 − and NH4 + emissions from the regional terrestrial ecosystems. [Copyright &y& Elsevier]

Bacterial community in the water of Lake Puma Yumco, a freshwater alpine lake on the Tibetan Plateau was studied for the first time using an integrated approach including water chemistry and culture-dependent and -independent methods. Microbial abundance in the lake water was from 1.59 × 105 to 3.37 × 105 cells mL- 1, and bacteria were evenly distributed in the lake due to its uniform water physical-chemistry. Obtained isolates were affiliated with α-, β- and γ-Proteobacteria, Actinobacteria and Bacteroidetes, among which γ-Proteobacteria isolates were dominant. Retrieved bacterial 16S rRNA gene clones fell into α-, β- and γ-Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Planctomycetes, Verrucomicrobia and Chloroflexi. Bacterial diversity in Lake Puma Yumco was higher than that in other Tibetan lakes at levels of both phyla and clusters. A half of total clones in Lake Puma Yumco were members of the widespread typical freshwater bacterial clusters. The low temperature of Lake Puma Yumco also made it possess unique freshwater bacteria members. [ABSTRACT FROM AUTHOR]

The article focuses on the simplification of heat balance calculation to simulate discharge fluctuations from the July 1st Glacier in China since 1930s. It notes the estimation of the relative humidity and downward solar radiation from precipitation. It mentions that the computation of the daily discharge for the 2002 melting had produced a better simulation than those using the positive degree-day method. It states the calculation of the glacier runoff and mass balance at the July 1st Glacier since 1935. It also mentions the utilization of three patterns of daily temperature and precipitation to estimate meteorological data.

Culturable bacteria in the glacial meltwater in the ablation zones of glacier at high altitude (6,350 m) on Mt Everest were isolated and identified by 16S rRNA amplification and sequencing. The obtained sequences revealed the presence of members of α, β, and γ-Proteobacteria, Actinobacteria, and Firmicutes, with the Actinobacteria dominant in the studied habitat. All 16S rRNA sequences were similar to previously determined sequences, ranging from 97 to 99% identical values. The strains isolated from meltwater were distinctly different from those recovered from a cryoconite hole and under glacier habitat. The majority of the isolates’ nearest neighbors were from the permafrost, dust, soil, plant, and aqueous environments. The Biolog bioassay and growth test under different temperatures suggested that the culturable bacteria in glacial meltwater could be divided into three categories in terms of their survival strategies: Group I sensitive to temperature change but versatile in utilization of carbon substrates (capable of utilization of about 70% of the Biolog carbon substrates); Group II tolerant to variable temperature and less capable of carbon utilization (less than half of the Biolog carbon species can be used); Group III slow in growth and weak in carbon utilization (only a few Biolog carbon substrates can be used). [ABSTRACT FROM AUTHOR]

Geographic variations in summer (July-August) precipitation data for the northern Qinghai-Xizang (Tibetan) Plateau, collected during the lOP (Intense Observation Period) of GAME-Tibet, were examined. Results indicated that, basically, the daily precipitation amount consistently varies temporally at all sites. An increase in precipitation amount is evident from north to south. The distribution of summer monsoon precipitation is affected by latitude, altitude, and other factors (i.e. atmosphere circulation, water vapor transportation). The latitude effect of precipitation in July and August was significant. August precipitation varied with both latitude and altitude. The site with higher elevation received more precipitation. Topoclimatic controls operating over precipitation on slopes include elevation. The distribution of the precipitation during July-August mainly showed the effects of latitude, but this was modified by the altitude effect. Redistribution processes caused by topography induce increased precipitation with altitude at some sites. Owing to the complexity of surface conditions on the Qinghai-Xizang (Tibetan) Plateau, precipitation is controlled by many factors simultaneously. Without benefit of an expanded observation network, it is difficult to separate the effects of the many factors influencing the distribution of precipitation in the region. [ABSTRACT FROM AUTHOR]

The maritime glaciers are sensitive to climate change because of high annual precipitation and high air temperature in the region. A combined comprehensive study was carried out based on glacier mass balance observation, GPS-based glacier terminus position survey, glacier Ground Penetrating Radar, topography maps and RS satellite images in the Kangri Karpo Mountains, Southeast Tibet. The study revealed a strong ice mass loss and quick glacier retreat since the 1970s. Ata Glacier, one glacier from the south slope of the Kangri Karpo Mountains, has formed a 6-km-long terminal moraine zone at the end of the glacier since the 1970s, and the accelerating retreat is largely due to the strong glacier surface melting. Mass balance study on the other four glaciers on the northern side of the Kangri Karpo Mountains shows that they are in large negative mass balance and the glaciers had retreated 15-19 m from May 2006 to May 2007. The in-situ glacier observation also shows that the glacier retreat is more obvious in small glaciers. The enhanced ice mass deficit caused by climate warming and the ongoing extinction of many small glaciers in this region could seriously affect the water resources, environments, local climate and regional sustainable development in the near future. [ABSTRACT FROM AUTHOR]

Bacterial abundance in surface snow between 6600 and 8000 m a.s.l. on the northern slope of Mt. Everest was investigated by flow cytometry. Bacterial diversity in serac ice at 6000 m a.s.l., glacier melt-water at 6350 m, and surface snow at 6600 m a.s.l. was examined by constructing a 16S rRNA gene clone library. Bacterial abundance in snow was higher than that in the Antarctic but similar to other mountain regions in the world. Bacterial abundance in surface snow increased with altitude but showed no correlation with chemical parameters. Bacteria in the cryosphere on Mt. Everest were closely related to those isolated from soil, aquatic environments, plants, animals, humans and other frozen environments. Bacterial community structures in major habitats above 6000 m were variable. The Cytophaga-Flavobacterium-Bacteroides (CFB) group absolutely dominated in glacial meltwater, while ß-Proteobacteria and the CFB group dominated in serac ice, and ß-Proteobacteria and Actinobacteria dominated in surface snow. The remarkable differences among the habitats were most likely due to the bacterial post-deposition changes during acclimation processes. [ABSTRACT FROM AUTHOR]

The total activity variation with depth from a 41.6 m Muztagata ice core drilled at 7010 m, recorded not only the 1963 radioactive layer due to the thermonuclear test, but also clearly the radioactive peak released by the Chernobyl accident in 1986. This finding indicates that the Chernobyl nuclear accident was clearly recorded in alpine glaciers in the Pamirs of west China, and the layer can be potentially used for ice core dating in other high alpine glaciers in the surrounding regions. [ABSTRACT FROM AUTHOR]

High mountains may serve as a condenser for persistent organic pollutants. In the present study, soil and grass samples from Mt. Qomolangma region, China were collected from 4600 to 5620 m a.s.l and were analyzed for polycyclic aromatic hydrocarbons (PAHs) to determine if they are concentrated at colder, more elevated sites and to evaluate their possible resources and fractionation. The total PAHs concentration in soil samples was < 600 ng g-1, the critical value to differentiate PAHs levels in remote and urban regions. This implied the PAHs levels at Mt. Qomolangma are relatively low and what one might expect in such a remote region of the world. These low values may represent a soil background for mid-latitude Northern Hemisphere soils away from the direct influence of an anthropogenic source. As for the distribution pattern, the low molecular weight PAHs were prone to accumulate at higher altitude, while the high molecular weight PAHs inversely related or unrelated with elevation. Based on high concentration of phenanthrene at elevated sample site and the ratios of individual PAHs, we deduced that home-heating combustion and vehicle emission may result in the constitution trait of PAHs in this mountain region. Monsoon traveling over India, Pakistan and other countries with dense population may carry contaminant to Mt. Qomolangma region. [ABSTRACT FROM AUTHOR]

Abstract: Recently, several ice cores were drilled on the Tibetan Plateau to examine climate and environmental changes. Based on the temperature proxy records in the Guliya ice core, climate oscillations over the past 120kyr were examined using wavelet analysis and singular spectrum analysis methods. The results showed two main Milankovitch-type oscillatory modes, 22 and 44kyr. The 22kyr period corresponds to the precession period and 44kyr period corresponds to the Earth axis''s obliquity inclination period. The two periods combined explain ∼43% of the variance. In addition, there are millennial and 10 thousand years time scales periods, which may be related to the Dansgaard–Oeschger (D–O) cycles and the Heinrich (H) events. [Copyright &y& Elsevier]

The bacterial diversity and abundance in the snow of East Rongbuk glacier, Mt. Everest were examined through 16S rRNA gene clone library and flow cytometry approaches. In total, 35 16S rRNA gene sequences were obtained, which belong to a, β, γ-Proteobacteria, Actinobacteria, Firmicutes, CFB, Cyanobacteria, Eukaryotic chloroplast, and TM7 candidate phylum respectively. γ-Proteobacteria was the dominant bacterial group in this region, while the genera Acinetobacter and Leclercia were dominant on the genus level. The community structure varied seasonally. The bacterial abundance in summer snow was higher than that in winter. Moreover, the snow bacterial community structures in both seasons were diverse, with not only common species but season-specific species. The common species most likely originated from the Tibet Plateau. Bacteria in summer snow are affiliated with marine environment, whereas bacteria in winter snow are closely related to more diverse environments and show the feature of resistance to cold. Seasonal variations of abundance and bacterial diversity were most probably due to the seasonal characteristics of climate and atmospheric circulation in Mt. Everest. [ABSTRACT FROM AUTHOR]

In order to understand the relationship between the community structure of bacteria in ice core and the past climate and environment, we initiated the study on the microorganisms in the three selected ice samples from the Malan ice core drilled from the Tibetan Plateau. The 16S ribosomal DNA (rDNA) molecules were directly amplified from the melt water samples, and three 16S rDNA clone libraries were established. Among 94 positive clones, eleven clones with unique restriction pattern were used for partial sequence and compared with eight reported sequences from the same ice core. The phylotypes were divided into 5 groups: alpha, beta, gamma proteobacteria; CFB, and other eubacteria group. Among them, there were many ‘typical Malan glacial bacteria’ pertaining to psychrophilies and new bacteria found in the ice core. At a longer time scale, the concentration distribution of '‘typical Malan glacial bacteria’ with depth showed negative correlation with temperature variations and was coincident with dirty layer. It implied the influence of temperature on the microbial record through impact on the concentrations of the '‘typical Malan glacial bacteria’. In addition, the nutrition contained in ice was another important factor controlling the distribution of microbial population in ice core section. Moreover, the result displayed an apparent layer distribution of bacterial community in the ice core section, which reflected the microbial response to the past climatic and environmental conditions at the time of deposition. [ABSTRACT FROM AUTHOR]

Formate and acetate concentrations are measured in a 22.56 m-depth ice core recovered in Mt. Muztagata Glacier, northwest Tibetan Plateau. The mean concentrations for formate and acetate in this ice core are 186.6±160.1 and 136.4±133.9 ng/g, respectively. Study shows that there is a positive correlation between formate and nitrate, suggesting both continental origins. However, no significant relationship has been found between formate and acetate, though they both have obvious periodical variations. Because Mr. Muztagata lies in the mid-latitude and is correlative to the nearby human activities, formate and acetate concentrations are higher than those in Greenland and Antarctica. During recent decades, the increase of formate concentration in the Muztagata ice core and formaldehyde production shows a close correlation. We preliminarily presume that the high formate concentration in the Muztagata ice core is concerned with the thriving of house decoration in which excess formaldehyde was used. [ABSTRACT FROM AUTHOR]

Examines the diversity of bacteria in Malan Glacier ice at the Qinghai-Tibetan Plateau. 16S rDNA sequencing; Molecular microbiology; Factors influencing the distribution of microorganisms in ice.

The soil energy–water distribution and freezing–thawing processes varied at different sites in the northern part of the Qinghai–Xizang (Tibetan) Plateau. The temporal and spatial variations of the soil moisture content were more complex than those of temperature. At the observation site, the soil moisture content increases with depth in certain layers but decreases in other layers. The freezing/thawing processes and the temperature distribution were strongly influenced by soil moisture content. During the summer monsoon period, the soil moisture contents at a depth of 10 cm for all sites were relatively high but differed spatially. In general, the shallow layers started to freeze in October and thaw in April at all sites, with a freezing period of about 6 months. However, the onset of freezing/thawing varied at different sites.The results suggest that the freezing process may prevent the soil moisture from evaporating. Although there is low precipitation in winter (freezing period), the soil moisture content is high when the soil begins to thaw. The abrupt increase/decrease of net atmospheric heating synchronized with the thawing/freezing of soil indicates that these processes may strongly influence the seasonal transition on the Qinghai–Xizang (Tibetan) Plateau. [Copyright &y& Elsevier]

Focuses on cold events in the early Holocene era and evidence provided from the circum-North Atlantic area. Discusion of the "8.2 ka cold event" and evidence from the Guliya ice core in the northwest Tibetan Plateau; The peak cooling in this ice core, about 7.8-10°C, which was larger than the cooling in the North Atlantic region; Idea that the events were caused by diminished solar activity and weakened thermohaline circulation; The weak cold event, centered about 9.4 ka, recorded in the Guliya ice core record; Indication these two cold events happened at the same time as the ice-rafting episodes in the North Atlantic; Implication the millennial-scale climatic cyclicity exists in the Tibetan Plateau and the North Atlantic.

Presents information on a study which investigated the El Nino and Southern Oscillation (ENSO) teleconnection based on the ENSO chronology and climatic information recovered from the Guliya ice core in the Tibetan Plateau of China. Background of ENSO events; Description of the Guliya ice core; Results and discussion.

Presents information on a study which discussed the problems related to the sensitivity of temporal and spatial changes of the climate in high-altitude regions, particularly in the Qinghai-Tibetan (Q-T) Plateau in China. Background of the study; Data and methodology used; Amplitude of climatic changes in different periods in the Q-T Plateau; Possible mechanism of large amplitude of climatic oscillations in the Q-T Plateau.

Based on the Guliya ice core records, the precipitation in the past 400 years was retrieved. Its relations with other regions were also analyzed. The results demonstrated that there were two high-precipitation periods and two low-precipitation periods in Guliya ice core since 1571 AD. The average precipitation in the two high-precipitation periods was 42 mm (21%) higher than that in the two low-precipitation periods. The precipitation recorded in the ' Guliya ice core was consistent with that in Dunde ice core. The variation trends of precipitation in the Guliya ice core and the northern hemisphere are similar. During the extremely wet years in the northern hemisphere, the precipitation recorded in the Guliya ice core was two times the long-term average. However, the annual precipitation was 38% less than that of the long-term average in extremely dry years. Based on the Guliya ice core records, the precipitation in the past 400 years was retrieved. Its relations with other regions were also analyzed. The results demonstrated that there were two high-precipitation periods and two low-precipitation periods in Guliya ice core since 1571 AD. The average precipitation in the two high-precipitation periods was 42 mm (21%) higher than that in the two low-precipitation periods. The precipitation recorded in the ' Guliya ice core was consistent with that in Dunde ice core. The variation trends of precipitation in the Guliya ice core and the northern hemisphere are similar. During the extremely wet years in the northern hemisphere, the precipitation recorded in the Guliya ice core was two times the long-term average. However, the annual precipitation was 38% less than that of the long-term average in extremely dry years. [ABSTRACT FROM AUTHOR]

Examines the variations of nitrate concentration in the Guliya ice core in the Qinghau-Xizang Plateau in China. Reconstruction of the variations; Spectrum analysis; Correlation between the variations in nitrate concentration and solar activity.

• The CO 2 fluxes in winter were three times higher than in other seasons. • Glacier meltwater altered the diel pattern of CO 2 fluxes. • The total CO 2 fluxes from the headwaters were 39.57 (30.04–50.21) Gg C yr−1, ignoring the diurnal variation overestimated the CO 2 fluxes. • The CO 2 fluxes from 1st and 2nd order streams accounted for 77% of the headwaters. Rivers are important sources of the carbon dioxide (CO 2) released into the atmosphere; however, research on CO 2 emission from riverine headwater regions is sparse, particularly from rivers in the Tibetan Plateau (TP) region, which has large area of glaciers and permafrost. We conducted a three-year (2020–2022) observational study of CO 2 flux rates from the riverine headwater region of the Qilian Mountains (QLMs) to determine diel and seasonal CO 2 variations and flux rates. Our results revealed that the annual average CO 2 emission was 0.45 (0.03–1.60) kg CO 2 m−2 yr−1, with the highest flux rates observed in winter [0.87 (0.08–2.67) μmol CO 2 m−2 s−1], which was approximately three times higher than flux rates in other seasons. Glacier meltwater altered the diel pattern of riverine CO 2 flux rates by diluting CO 2 and dissolved inorganic carbon. Meanwhile, CO 2 release from rivers in the permafrost region was dictated by stream order, with a linear decrease as stream order increased. Considering diel variations, the total CO 2 fluxes from the headwater regions of the QLMs were approximately 32.70 (25.00–41.28) Gg C/yr, representing 76 % of the pre-calibration total CO 2 fluxes ignoring diel variations. This study provides essential insights into CO 2 release from headwaters, which have substantial implications for understanding CO 2 outgassing. [ABSTRACT FROM AUTHOR]

Provides environmental information recorded in shallow ice core of Dasuopu glacier in the Qanghai-Tibetan Plateau. Character of ion distribution; Relationship between ion concentration and precipitation.

Focuses on the glaciological investment on the Dasuopu Glacier in Xixabangma in China from July to October 1997. Drilling of three ice cores from a glacier; Collection of surface meteorological data; Accumulation, movement and temperature of the glacier.

Summary A Snowmelt Runoff Model (SRM) is used to simulate streamflow from snowmelt in the Buha watershed within the Qinghai Lake basin for the hydrologic years 2003–2009 (from September to August). Two different precipitation products are used as inputs to examine the model and their performances: station measured precipitation and gridded APHRODITE-precipitation, with two different snow cover products, namely, flexible multiday combined MODIS Terra–Aqua (MODISMC) maps, and the standard MODIS/Terra 8-day composite (MOD10A2) product. Results show that the MODISMC product with a higher temporal resolution of 2.2 days obtains slightly small bias in runoff volumes than MOD10A2 does for basin- and zone-wide simulations. The average Nash–Sutcliffe coefficient of determination ( R 2 ) is 0.73 (0.70–0.75) for basin- and zone-wide simulations. The simulated runoff with APHRODITE-precipitation is well correlated with measured runoffs ( R 2 = 0.76). The multivariate regression analysis indicates that lake level changes are significantly associated (95% level) with the following single variables: measured runoff discharge from the Buha watershed ( R m ), simulated runoff ( R s ), simulated runoff fraction from rainfall ( R s -rainfall), the snow cover area at zone B of the Buha watershed, or with a combination of multivariates: R s -rainfall + P L (precipitation over the lake) and R m + P L + Evaporation. These results suggest that precipitation plays a dominant role in lake level variations. Snowmelt contributed runoff shows no significant contribution to lake level variation (13% of the total runoff). This study suggests that APHRODITE-precipitation data can be used for snowmelt simulations and water resource management on the Tibetan Plateau where precipitation gauges are limited, and that the SRM is an effective tool for estimating snowmelt discharge and water resource management in high mountain regions. [ABSTRACT FROM AUTHOR]

Desertification in Qinghai-Xizang (Tibet) Plateau is part of Chinese desertification. In the past decades, due to the climate warming, the climate condition in Qinghai-Xizang (Tibet) Plateau has been relatively dry. This has resulted in permafrost degradation and other environmental problems. In addition, the vegetation and the soil layer were also destroyed by unreasonable economic activities. Cultivated and grassland lands have become deserted. Nowadays, the desertification is still expending. In this paper, the factors affecting the desertification in Qinghai-Xizang (Tibet) Plateau were examined, and the desertification as well as its relationship with permafrost degradation was also discussed. [Copyright &y& Elsevier]

China has the largest area of glaciers situated within the middle- and low-latitude areas worldwide. Rapid changes in mountain glaciers across western China in the last decades have not only affected glacial runoff and hazards but also had profound impacts on ecosystems and socioeconomic activities in the extensive cold and arid regions of Asia and even beyond. Therefore, research on glacier change is of significant importance for regional sustainability. This study re-analyzes the first and second Chinese Glacier Inventories (CGI-1 and CGI-2) and summarizes available in-situ observation-based studies on glacier mass balance and length to provide a spatially explicit and coherent national-scale assessment of glacier changes and associated influencing factors in recent decades. We connect the glaciers between CGI-1 (from the 1950s to the 1980s) and CGI-2 (from the 2000s to the 2010s) one by one to explore the area, volume, and Equilibrium Line Altitude (ELA) changes at both the individual glacier and river basin scales for the first time. The results show that the long-term area and volume changes in China's glaciers during the area-weighted average period from CGI-1 (around 1969) to CGI-2 (around 2008) were − 5.6%/decade and − 5.3%/decade, respectively, with a mean ELA change of 12.5 m/decade. Approximately 17.2% of the total number of glaciers in CGI-1 disappeared, only 5.5% of the glaciers advanced, and the majority of glaciers decreased in size during the period between CGI-1 and CGI-2, which was characterized by a shrinkage in area and volume and a rise in ELA or division into multiple branches. In-situ observation-based analysis shows that glacier length has reduced since at least the 1960s on average, and their trends have accelerated since the 1990s. The negative trend of mass balance was slightly larger than that of the reference glaciers globally during 1960–2019, while the mean mass loss in any given decade was lower than that of the global mean. The changes have different regional characteristics. Overall, the shrinkage increased from the interior to the southeast in the Tibetan Plateau and decreased from the northeast to the southwest in northern Xinjiang, including the Chinese Tien Shan Mountains. Climatic conditions, as reflected in annual mean temperature and precipitation, are the primary causes of different spatiotemporal patterns of glacier change. A significant positive correlation is observed between annual absolute area/volume changes and snowfall variations, and a significant negative correlation is found with rainfall variations, but there is no significant correlation between the indicators of air temperature and glacial changes at the river basin scale. Additionally, other local-scale factors, such as glacial morphology and topographic conditions, have exerted profound impacts on glacier retreat for individual glaciers. • A spatially explicit national-scale assessment of China's glacier changes over the past several decades was conducted. • Out of the 34,578 glaciers examined, of which 17.2% disappeared, 5.5% expanded, and the majority decreased in size. • The glacier area, volume, and ELA changes were quantified at both the individual glacier and river basin scales. • The area and ELA change rates were -5.6%/decade and 12.5 m/decade, averaged over all China's glaciers during 1970–2009. • In-situ observed and reconstructed glacier mass balance showed an increasingly more negative trend during 1961–2019. • In-situ observation-based glacier length has decreased since the 1960s, and the trend has accelerated since the 1990s. • Climatic and topographic conditions, and glacial morphology were analysed as main influencing factors for glacier changes. [ABSTRACT FROM AUTHOR]

Abstract: The dustiness on the remote Tibetan Plateau and its trend within the ongoing global warming perspective are not well understood. In this study, we present the detailed dust history from 1850 to 2004 AD on an annual timescale from a shallow ice core from Tanggula, central Tibetan Plateau. Two periods of strong dustiness, one at the end of the Little Ice Age (1860–1874) and the other during the period 1930–1954, occurred during low oxygen isotope stage, which is correlated with temperature on multi-year and decadal timescales. The extremely high level of dust flux between 1860 and 1874 was unique – this level has not occurred again during the past century, and the 1930s'' dustiness was characterized more by strong wind and dust storms rather than drought, as shown by great grain size but low dust flux. We have used the composite analysis of modern meteorological data to study the possible dustiness mechanism and found that strengthened high-level westerlies over the Tibetan Plateau and intensified low pressure activities in the upward potential source regions, such as Tarim Basin, are the possible causes for high dust flux in Tanggula. Those results have revealed that although the dustiness on the Tibetan Plateau normally occurs in cold conditions, pronounced warming since the 1960s can change the dust pattern and strengthen the dustiness in this remote and high-altitude region, and can thus induce associated environmental issues by creating dustier conditions. [Copyright &y& Elsevier]

Abstract: This study investigates the distribution of modern pollen assemblages in the Qinghai-Tibetan Plateau, China, based on surface soil samples collected at 1202 sites along an altitudinal gradient of 10–5500 m asl, where mean annual precipitation (MAP) ranges from 12 to 1840 mm and mean annual temperature (MAT) from −7 to 21.5 °C. A total of 153 pollen taxa were found with relative abundances greater than 1% in at least two samples. Canonical correspondence analysis (CCA) was used to determine the main environmental variables influencing pollen distributions. The results reveal that MAP is the most significant dominant variable. However, MAT, altitude (ALT), July temperature (MT7), and relative humidity (HHH) are also significant variables that clearly follow the gradients in the CCA ordination, suggesting that pollen assemblages probably not only reflect a single climatic parameter, but also a variety of other climatic inter-related parameters. Transfer functions, based on locally weighted weighted averaging (LWWA), were developed for MAP (R2-boot = 0.89, RMSEP = 109 mm), MAT (R2-boot = 0.78, RMSEP = 2.3 °C), ALT (R2-boot = 0.73, RMSEP = 597 m), HHH (R2-boot = 0.82, RMSEP = 4.5%), and July mean precipitation (MP7) (R2-boot = 0.87, RMSEP = 23 mm). Overall, our results confirm that pollen can provide reliable estimates of the primary climatic parameters. The application of the LWWA model to the fossil records of Chen Co Lake allowed quantitative inferences to be made about Holocene climatic changes in the southern Tibetan Plateau, suggesting that LWWA is a robust calibration method for quantitative palaeo-environmental reconstruction based on pollen data in the regions. [Copyright &y& Elsevier]

Abstract: While pollen is used as a palaeoenvironmental proxy, as of now there are no continuous in situ airborne pollen observations in the Tibetan Plateau. Here we present the first data of airborne pollen collected from September 2005 to August 2006 using a Burkard trap in the Nam Co Basin in central Tibet. The airborne pollen assemblage is dominated by local herbaceous Cyperaceae and Artemisia pollen, and Sabina pollen is the major arboreal taxon. Betulaceae, particularly Alnus, and Pinaceae were the dominant wind-transported pollen over long distances. Seasonal variations in the differences in amounts and taxa over time are evident. There are three clear pollen concentration peaks, in spring, summer, and early autumn, dominated by Sabina, Cyperaceae, and Artemisia, respectively. Consequently the record of pollen deposition is consistent with respective flowering periods, which are mainly a function of climate factors, especially air temperature. Backward air mass trajectory analysis suggests that non-native Alnus pollen may originate in southwestern Tibet or nearby areas. Airborne pollen data will contribute to the knowledge of modern pollen distribution and its relationship to vegetation and climate, and are useful for interpreting fossil pollen records and understanding vegetation response to climate change in the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: This study presents the Sr and Nd isotopic composition of dust from a shallow Dunde ice core (38°06′N, 96°24′E, 5325m a.s.l.), Northern China, in order to trace its source regions and the provenance of long-range transported (LRT) Asian dust. Dunde dust samples show similar Sr (87Sr/86Sr averages 0.719982 and varies between 0.715220 and 0.721874) and Nd (εNd(0) averages −10.6 and ranges from −11.1 to −9.9) isotopic composition to desert sand from Taklimakan and Qaidam, revealing that the Tarim and Qaidam Basins are the most possible source areas for Dunde dust, while the contribution from Badain Jaran and Tengger seems very small or unlikely. Our results indicate that materials from Taklimakan can be entrained from the Tarim Basin and transported to Qilian Shan by Westerlies under the present climate. The Sr–Nd isotopic composition of Dunde dust, which is a good analogue for the long-range transported Asian dust, resembles that of North Pacific and Greenland dust, indicating that the important provenance of end members of the Asian dust seems to be Taklimakan on a regional scale. [ABSTRACT FROM AUTHOR]

Abstract: Monsoon transport is an important process that influences the global transport of persistent organic pollutants. Only a few studies focused on the influence of monsoon on organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) levels in the Tibetan Plateau. In this study, 19 samples were collected in Lhasa, the capital of Tibet Autonomous Region, using a high-volume air sampler. The average concentrations of α-HCH, γ-HCH, p-p′-DDT, p-p′-DDE, o-p′-DDT, α-endosulfan, β-endosulfan and PCBs (including PCB-28, 101, and 118) were 2.3, 10.3, 3.2, 2.9, 5.8, 6.3, 2.2, and 10.6 pg m−3, respectively. The weak correlation coefficients between lnp (natural logarithm of partial pressure) and 1/T (reciprocal temperature) were obtained for DDTs and β-endosulfan (r 2 values ranged from 0.13 to 0.41). However, no significant correlations were obtained for HCHs and PCBs. These results suggested that both local emission and long-range atmospheric transport (monsoon) may influence the distribution of OCPs at Lhasa. In this study, peak concentrations of DDTs, endosulfans and PCBs were found in August, when Eastern Monsoon system occurred. However, the maximum concentrations of HCHs appeared in June (Indian Monsoon is the dominant air circulation pattern). Monthly variation of OCP/PCB levels was likely associated with the different air sources of monsoon system. [Copyright &y& Elsevier]

Abstract: A drill core (1.8m; 34 samples) was taken out of a swamp near Nam Co (Tibet, China) for palynological analysis. C14-Dating of the cores sediment at 3 different layers led to an numerical core age of about 8000BP and the palynomorph content of prepared samples enabled reconstruction of the vegetation and climatic history of Nam Co Area. Pollen of Alpine Steppe elements together with Cyperaceae dominates the palynoflora reflecting the existing vegetation units around the lake throughout the investigated time span. Due to availability of water/precipitation, the different vegetation units extended or had to retreat, and hence the amount of their pollen increased or decreased. The presence of arboreal plants, verified by charcoal particles, suggest the existence of woodlands in the lake''s surrounding area until possibly human made fires changed the environment over time. Holocene climate history around Nam Co shows several phases of a strengthening/weakening or even an interruption of monsoonal activity. Changing conditions between dry and humid evolved from 8017BP until 4800BP. A mostly humid and relative stable system occurred from 4800 until 700BP whereas the last 700 years are characterized by drier conditions according to fluctuating monsoonal activity. Humid or arid periods have been different in duration and intensity. The interaction of both parts of the monsoonal system, the South Asian Monsoon and the East Asian Monsoon, influenced the climatic conditions around Nam Co. [Copyright &y& Elsevier]