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In order to provide more conclusive evidence of monsoon-driven transport of persistent organic pollutants (POPs) to the Tibetan Plateau (TP) and assess the potential influence of forests on the fate of these pollutants, passive air samplers were consecutively deployed during 2008–2011 on Sygera Mountain (3800 m–4400 m). Higher DDTs levels were observed in the monsoon season (20.5–57.4 pg m −3 ) than the non-monsoon season (9.2–27.4 pg m −3 ), which confirmed that the Indian monsoon plays a key role in driving the atmospheric transport of DDTs to the TP. The similar DDT isomer ratios to the South Asia further suggested that Sygera Mountain is likely a receptor region of Indian subcontinent. By comparing the difference in concentrations between forest and clearing sites, it was found that the forest canopy can reduce airborne DDTs by a factor of 2, indicating strong absorption of DDTs by the Tibetan forest. [ABSTRACT FROM AUTHOR]

Hydrological processes of lakes in the Tibetan Plateau are an important indicator of climate change. Due to the high elevation, inaccessibility and limited availability of historical observations, water budget evaluation of typical lake basins has been inadequate. In this study, stable isotopes are used to trace the multiple water sources contributing to two adjacent lakes on the north slope of the Himalayas, Gongmo-tso and Drem-tso. The two lakes have nearly the same elevation, lake area and climatic condition. However, the isotopic composition of the two lakes presents significant differences. Qualitative observations attribute the differences to hydrological discrepancies: Gongmo-tso is a through-flow lake, whereas Drem-tso is a terminal lake. Quantitative analyses, including water and isotope mass balance modelling, clarify the fluxes and isotopic compositions among the various hydrological elements. The isotopic composition of input water, calculated as the summation of rainfall and upstream runoff, is estimated using the local meteoric water line (LMWL) combined with the time series of lake water isotope values. The isotopic composition of evaporation is calculated with a linear resistance model using local meteorological data. The results show that Drem-tso is a closed lake in a hydrological steady state with relatively more enriched lake water isotope values resulting mainly from evaporation. In contrast, through-flow accounts for more than 88% of the water input into Gongmo-tso. The large amount of upstream runoff with lower isotopic composition and enrichment due to evaporation are the major contributions to the observed lake water isotope values. Isotopic modelling of the two neighbouring lakes is effective for isotopic and hydrological research in this region with limited in situ observations. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

δ18O measurements based on systematic sampling and isotopic modeling have been adopted to study the controls of stable isotopes in lakewater in two lake basins (lakes Yamdrok-tso and Puma Yumtso) at two different elevations on the southern Tibetan Plateau. Temporally, d18O values in precipitation and lake water display a seasonal fluctuation in both lakes. Spatially, δ18O values in the two lake basins increase by 10%from the termini of glaciers to the lake shores, by ~1% from the lake shores to the lake center and by 0.4% from the water surface to depth in these lakes. The clear annual δ18O variations indicate that lake water mixes sufficiently in a short time. Model results show that glacial meltwater and surface lake-water temperature are not the dominant factors in the balance process of stable isotopes in lake water. Equilibrium d18O values decrease by 0.8%for Yamdrok-tso lake and 0.6% for Puma Yum-tso lake when glacial meltwater contributions to these lakes shrink by 60%. δ18O ratios increase rapidly during the initial stages and take a longer time to approach the equilibrium value. [ABSTRACT FROM AUTHOR]

Temperature signals in ice-core δ18O on the Tibetan Plateau (TP), particularly in the central and southern parts, continue to be debated because of the large scale of atmospheric circulation. This study presents ten ice-core δ18O records at an annual resolution, with four (Malan, Muztagata, Guliya, and Dunde) in the northern, three (Puruogangri, Geladaindong, Tanggula) in the central and three (Noijin Kangsang, Dasuopu, East Rongbuk) in the southern TP. Integration shows commonly increasing trends in δ18O in the past century, featuring the largest one in the northern, a moderate one in the central and the smallest one in the southern TP, which are all consistent with ground-based measurements of temperature. The influence of atmospheric circulation on isotopic signals in the past century was discussed through the analysis of El Niño/Southern Oscillation (ENSO), and of possible connections between sea surface temperature (SST) and the different increasing trends in both ice-core δ18O and temperature. Particularly, El Niño and the corresponding warm Bay of Bengal (BOB) SST enhance the TP ice-core isotopic enrichment, while La Niña, or corresponding cold BOB SST, causes depletion. This thus suggests a potential for reconstructing the ENSO history from the TP ice-core δ18O. [ABSTRACT FROM AUTHOR]

Fully physics-based, process-level, distributed fluid flow and reactive transport hydrological models are rarely used in practice until recent years. These models are useful tools to help understand the fundamental physical, chemical, and biological processes that take place in nature. In this study, sensitivity analyses based on a mountain area river basin modelling study are performed to investigate the effect of river channel geometric characteristics on downstream water flow. Numerical experiments show that reduction in the river channel geometric measurement interval may not significantly affect the downstream water stage simulation as long as measurement accuracy at special nodes is guaranteed. The special upstream nodes include but are not limited to 1) nodes located close to the observation station, 2) nodes near the borders of different land covers with considerable riverbed roughness changes, 3) nodes at entering points of tributaries causing discharge jump and 4) nodes with a narrow cross-section width that may control the flow conditions. This information provides guidelines for field investigation to efficiently obtain necessary geometric data for physics-based hydrological modelling. It is especially useful in alpine areas such as the Tibetan Plateau where field investigation capability is limited under severe topography and climate condition. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article presents a study which describes the ice-core evidence of westerly and monsoon atmospheric moisture contributions in the Tanggula Mountains in the central Tibetan Plateau. The researchers have compared the annual accummulated isotope values with climate indices, local station temperature records and monsoon precipitation in northern India. The study indicates that the annual average d-excess values reveal a significant negative correlation with the Dipole Mode Index, suggesting a greater contribution of westerly-dominated continental moisture.

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: The Tibetan Plateau and surrounding mountains represent one of the largest ice masses of the Earth. The region, referred to by scientists as the Third Pole, covering 5 million km2 with an average elevation of >4000m and including more than 100,000km2 of glaciers, is the most sensitive and readily visible indicator of climate change. The area also demonstrates considerable feedbacks to global environmental changes. The unique interactions among the atmosphere, cryosphere, hydrosphere and biosphere on the Third Pole ensure permanent flow of Asia''s major rivers, thus significantly influencing social and economic development of China, India, Nepal, Tajikistan, Pakistan, Afghanistan and Bhutan where a fifth of the world''s population lives. Like Antarctica and the Arctic, a series of observations and monitoring activities in the Third Pole region have been widely implemented. Yet for a comprehensive understanding of the Third Pole, current observational resources need to be integrated and perfected, and research goals and approaches need to be updated and identified. The Third Pole Environment (TPE) program aims to attract relevant research institutions and academic talents to focus on a theme of ‘water–ice–air–ecosystem–human’ interactions, to reveal environmental change processes and mechanisms on the Third Pole and their influences on and responses to global changes, and thus to serve for enhancement of human adaptation to the changing environment and realization of human–nature harmony. [Copyright &y& Elsevier]

The long range atmospheric transport of Polycyclic Aromatic Hydrocarbons (PAHs) from heavily polluted regions to remote areas has been well-known. However, there are limited studies focussing on the Tibetan Plateau (TP). To assess the temporal transport patterns of PAHs and particulate matters (PMs), a ground-based observation program (2008–2011) was conducted in the southeast TP. Relatively high atmospheric concentrations of particulate-PAHs (0.2–5.0 ng m −3 , sum of 15 compounds) and Total suspended Particles (TSP, 4.1–46.7 μg m −3 ) were observed. Concentrations of particulate-PAHs/TSP exhibited seasonality with higher levels in the winter–spring season and lower levels in summer. Using the potential source contribution function model, the source region of both particulate-PAHs and particles was attributed to the Indo-Gangetic Plain (IGP), suggesting the co-transport of particulate-PAHs and aerosols. The aerosol incursion, penetrating the Himalayas and reaching the TP was further captured by Moderate Resolution Imaging Spectroradiometer and Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations. [ABSTRACT FROM AUTHOR]

Abstract: Event-based rain and snow samples were collected from May 2009 to April 2010 at Madoi in the eastern Tibetan Plateau, and the stable isotopic compositions (δ18O and δD) of these samples were analyzed. The local meteoric water lines (LMWLs) based on individual samples and monthly weighted means were δD = 8.37δ18O + 11.86 (R 2 = 0.97, n = 175) and δD = 8.80δ18O + 20.16 (R 2 = 0.98, n = 11), respectively. Although fluctuations of the isotopic compositions in precipitation throughout the year were high, monthly amount-weighted means revealed seasonal signals. According to the monthly averaged data, the δ18O values decreased distinctly from June to July, indicating that summer monsoon circulation can significantly influence precipitation in this region. The high d-excess values from May to June and from October to November were probably the result of local moisture recycling. Apart from moisture sources, the δ18O and d-excess values in precipitation were also affected by subcloud evaporation/sublimation, which could be inferred from their relationships with different temperature and relative humidity ranges. The results of this study augment the understanding of the water cycle in the eastern Tibetan Plateau. [Copyright &y& Elsevier]

Highlights: [•] First detailed long-term water balance observations on a large Tibetan lake. [•] Two catchment runoff coefficients and two glacial runoff depths were obtained. [•] First solid result demonstrating the existence of Tibetan lake water seepage. [•] Results significantly affect environmental studies on Tibet and the surrounding areas. [Copyright &y& Elsevier]

Due to the influence of the Indian monsoon system, air mass transport in and to the Tibetan Plateau shows obvious seasonality. In order to assess the responses of atmospheric concentrations of persistent organic pollutants (POPs) to the Indian Monsoon fluctuation patterns, a three year air monitoring program (2008-2011) was conducted in an observation station close to the Yarlung Tsangpo Grand Canyon, southeastern Tibetan Plateau. The air concentrations of polychlorinated biphenyls (PCBs) and hexachlorocyclohexanes (HCHs) are generally comparable to those of other remote regions, whereas the concentrations of DDTs are much higher than reported for the polar regions, the North American Rocky Mountains, and the European Alps. The concentrations of DDTs and PCBs were strongly linked to the cyclic patterns of the Indian monsoon, displaying higher values in the monsoon season (May-September) and lower values in the nonmonsoon season (November-March). A "bimodal" pattern was observed for α- and γ-HCH, with higher concentrations in spring and autumn and lower concentrations in the summer (monsoon season). Rain scavenging in the monsoon season likely resulted in the lower HCH concentrations in the atmosphere. This paper sheds lights on the role the Indian monsoon plays on the atmospheric transport of POPs to the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Summary: Alpine meadow soil is an important ecosystem component of the Qinghai-Tibetan Plateau. However, the alpine meadow soil is undergoing serious degradation mainly due to global climate change, overgrazing, human activities and rodents. In this paper, spatial sequencing was chosen over time succession sequencing to study the changes of soil hydraulic properties under different degrees of alpine meadow degradation. Soil saturated hydraulic conductivity (Ks) and Gardner α both at the surface and at 40–50cm depth were investigated in the field using tension infiltrometers. Soil physical and chemical properties, together with the root index at 0–10cm and 40–50cm soil layer depths were also analyzed. Pearson correlations were adopted to study the relationships among the investigated factors and principal component analysis was performed to identify the dominant factor. Results show that with increasing degree of degradation, soil sand content increased while soil Ks and Gardner α as well as soil clay content, soil porosity decreased in the 0–10cm soil layers, and organic matter and root gravimetric density decreased in both the 0–10cm and 40–50cm soil layers. However, soil moisture showed no significant changes with increasing degradation. With decreasing pressure head, soil unsaturated hydraulic conductivity reduced more slowly under degraded conditions than non-degraded conditions. Soil Ks and Gardner α were significantly correlated (P =0.01) with bulk density, soil porosity, soil organic matter and root gravimetric density. Among these, soil porosity is the dominant factor explaining about 90% of the variability in total infiltration flow. Under non-degraded conditions, the infiltration flow principally depended on the presence of macropores. With increasing degree of degradation, soil macropores quickly changed to mesopores or micropores. The proportion of total infiltration flow through macropores and mesopores significantly decreased with the most substantial decrease observed for the macropores in the 0–10cm soil layer. The substantial decrease of macropores caused a cut in soil moisture and hydraulic conductivity. This study improves the understanding and prediction of alpine meadow soil and ecosystem changes and provides guidelines for improving water flow modeling under the background of global climate change over the Qinghai-Tibetan Plateau and similar regions. [Copyright &y& Elsevier]

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]