Interior Of Tibetan Plateau Research Articles

Unveiling Cloud Vertical Structures over the Interior Tibetan Plateau through Anomaly Detection in Synergetic Lidar and Radar Observations

Unveiling Cloud Vertical Structures over the Interior Tibetan Plateau through Anomaly Detection in Synergetic Lidar and Radar Observations

Catastrophic outburst floods along the middle Yarlung Tsangpo River: Responses to coupled fault and glacial activity on the Southern Tibetan Plateau

The immense outburst floods that have occurred on the Tibetan Plateau during the Late Quaternary are closely linked to tectonic and climatic factors. These floods likely induced very rapid, short-term geomorphic impacts on the evolution of mountain drainage systems and patterns of sedimentary movement. In this study, four glacially-dammed lake outburst flood events that occurred along the middle reaches of the Yarlung Tsangpo River since the Middle Pleistocene were reconstructed by combining comprehensive geomorphic, stratigraphic and geochronologic investigations. The most recent outburst flood sequence occurred at ∼10.5 ka, with a peak discharge of ∼5 × 105 m3/s. The tilted uplift of the Cona Normal Fault has resulted in localized topographic lift and the formation of river knickpoints, contributing to the development and stabilization of glacial dams. River damming and outburst events have also been influenced by glacial-interglacial climate fluctuations since the Middle Pleistocene. The focused erosion and extensive mobilization of sediment by these low-frequency, high-energy floods have resulted in a repeated pattern of material transport and deposition from the Tibetan Plateau interior to its exterior. Coupled with glacial activity, the primary factor impacting the sustained stability of knickpoints on the Yarlung Tsangpo River along the Tibetan plateau's southern margin has been differential rock uplift, which results in a distinct geomorphic pattern characterized by knickpoints, glacial dams and alternating wide valleys and deep gorges.

Sedimentation history linked to global change in the alpine Damqu Wetland of the Yangtze River headwater in interior Tibetan Plateau

Located in the interior of the Tibetan Plateau (TP) and at the headwaters of the Yangtze River, the Damqu Wetland ranks among the world's highest and is highly sensitive to global climate change. Due to its remoteness and harsh, uninhabitable conditions, the sedimentological and geomorphological studies are still absent by far. Establishing a reliable chronology for sediments is crucial for this unique geographic region. Here we initiated this effort and focused on two riverbank profiles, located in the southeastern of the alpine Damqu Wetland, DQ1 (4.8 m in depth) and DQ2 (3.3 m in depth). A combination of chronological methods, including quartz Optically Stimulated Luminescence (OSL), K-feldspar post-IR InfraRed Stimulated Luminescence (pIRIR), and radiocarbon dating methods, as well as magnetic susceptibility and particle size analysis, were conducted on these profiles to establish the depositional history and reveal the palaeoenvironmental conditions of the Damqu Wetland. The dating results indicate that profiles DQ1 and DQ2 were deposited during ∼59–0.20 ka and ∼265–1.12 ka, respectively. It is interesting to note that the D0 of quartz OSL growth curve has a value as high as 129 Gy. Both profiles exhibit depositional hiatuses, with time gaps between 37 ± 2 and 2.9 ± 0.2 ka for DQ1 and between 265 ± 16 and 4.8 ± 0.4 ka for DQ2, likely due to fluvial erosion during the period of from deglaciation to middle Holocene. The resumed sediment accumulation since the mid-late Holocene is probably mainly attributed to declined fluvial erosion in response to reduced rainfall. The darker sediment layers at depths of 0.9 m–0.7 m and 0.3 m–0.1 m in DQ2, combined with magnetic susceptibility and particle size analyses results, suggest two regional climatic optimum periods at around 4.5 ka and 1 ka. Overall, our research establishes the chronological framework of the Damqu wetland since the Late Quaternary and highlights the significant impact of climate changes on fluvial processes and wetland evolution in the remote interior TP.

Spatial patterns and variations in leaf traits of alpine plants on the interior Tibetan Plateau

Spatial patterns and environmental gradients in plant traits can elucidate the relationships between plant characteristics, environmental factors, and ecosystem functions and can be used to develop the next generation of vegetation models for predicting vegetation distribution and functions. Studies of Plant traits across spatial scales have advanced significantly worldwide, including on the Tibetan Plateau (TP), the highest and largest plateau globally. Previous research on plant traits on the TP has been limited to specific areas, leaving the overall trend across the plateau unclear. In this study, we examined seven leaf traits—leaf thickness (LT), leaf dry matter content (LDMC), leaf area (LA), specific leaf area (SLA), and leaf carbon (LCC), nitrogen (LNC), and phosphorus (LPC) contents—in 1314 individuals at 237 sites within the alpine vegetation region above 3000 m on the TP to determine their distribution patterns across three spatial dimensions and their relationships with environmental factors. Our results indicated that, compared with Chinese plants, TP plants exhibited significantly greater LT, LDMC, and LNC but lower LA, LCC, and LPC. Except for SLA and LCC, most leaf traits showed significant spatial variability. Climate and soil explained 29.23 % of the total variations in traits. Radiation had the most pronounced effect on LDMC, LA, LNC, and LPC, whereas soil pH primarily constrained LT and LCC. Precipitation influenced most traits both directly and indirectly, with substantial overall effects. Temperature and soil nutrient had minimal influence on the regulation of leaf traits across most of the TP. Our findings suggest that alpine plants typically employ a conservative strategy to cope with the harsh conditions on the TP, but this strategy varies at broader spatial scales and longer environmental gradients, particularly in extreme environments such as the highest alpine regions.

The Arabian Sea and Bay of Bengal play a key role in extreme precipitation during the snow season over the Tibetan Plateau

AbstractWater vapour is a critical component of the hydrological cycle and plays a key role in climate systems and water resources on the Tibetan Plateau (TP). However, the effect of water vapour on extreme precipitation during the snow season over the TP, where snow cover is widespread, has not been determined. In this study, we investigated the water vapour contributions from extreme precipitation events during the snow season from 1980 to 2017 in four subregions of the TP using the flexible particle dispersion method. We divided the TP into four regions: the northeastern TP (NETP), northwestern TP (NWTP), southeastern TP (SETP) and southwestern TP (SWTP). The water vapour contributions from extreme precipitation among the four subregions were clearly different. The most important water vapour area that contributed the most water vapour to extreme precipitation over the NETP was from local contributions; nevertheless, Central Asia contributed the most water vapour to the NWTP. Water vapour from the Arabian Sea and Bay of Bengal (ASBB) dominantly controlled extreme precipitation in the SETP at a ratio of 45% and in the SWTP at a ratio of 72.9%. The water vapour contribution from the ASBB was significantly correlated with the extreme precipitation occurring in the TP subregions during the snow season in comparison to that of non‐extreme precipitation. These results could improve the understanding of water vapour cycle differences across the interior TP; additionally, our study provides a theoretical reference for the relationship between the snow distribution and water vapour sources in the TP.

Quantifying Mineral Dust Emissions on the Tibetan Plateau With a Modified Dust Source Map

AbstractThe region surrounding the Tibetan Plateau (TP) is widely considered a primary global dust source, with mineral dust comprising a significant proportion of aerosols over the TP. Current research on TP dust has mainly focused on transport from the surrounding deserts, with little focus on dust emissions from the TP's interior. The erodibility factor used by the WRF‐Chem (ERODDEF) is 0 for the TP, so the model cannot simulate the dust emissions inside the plateau. Thus, we constructed a high‐resolution erodibility data set (ERODSDS) based on a reliable dust source distribution and intensity map. Based on the modified EROD map, the WRF‐Chem model was used to simulate dust emissions and direct radiative forcing on the TP in 2018. With the modified EROD map, WRF‐Chem can well simulate the temporal variation and spatial pattern of mineral dust on the plateau, which greatly improves the model's dust emissions simulation accuracy on the TP.

The late Eocene rise of SE Tibet formed an Asian ‘Mediterranean’ climate

Southeastern (SE) Tibet forms the transition zone between the high interior Tibetan Plateau and the lowlands of southwest China. So understanding the elevation history of SE Tibet, a biodiversity hotspot, enlightens our understanding of the interactions between tectonics, monsoon dynamics and biodiversity. Here we reconstruct the uplift history of the Markam Basin, SE Tibet, during the middle−late Eocene based on U − Pb dating, plant fossil assemblages, and stable and clumped isotope analyses. Our results suggest that the floor of the Markam Basin was at an elevation of 2.6 ± 0.9 km between 42 Ma and 39 Ma, where the mean annual air temperature (MAAT) was 13.2 ± 2.4 °C. The basin then rose rapidly to 3.8 (+0.6/−0.8) km before 36 Ma. Integrated with existing paleoelevation data, we propose that the high plateau boundary (∼3.0 km) of SE Tibet formed during the late Eocene. Numerical climate modeling with realistic paleo-landscapes shows that with the rise of SE Tibet, a Mediterranean-like climate developed in the region characterized by bi-modal precipitation with two wet seasons in boreal spring and autumn. The high topographic relief of SE Tibet, coupled with this distinctive Mediterranean-like climate system, helped develop the high biodiversity of the Hengduan Mountains.

Large methane emission during ice-melt in spring from thermokarst lakes and ponds in the interior Tibetan Plateau

The magnitudes of annual CO2 and CH4 emissions from thermokarst lakes and ponds are uncertain due to scarce measurements on the Tibetan Plateau (TP) and limited data on emissions during ice-melt. To evaluate the importance of CO2 and CH4 emissions during late winter and spring among the whole year, surface water CO2 and CH4 concentrations were measured with the headspace method in ten thermokarst lakes and ponds in 2020–2021 on the TP. The concentrations of CH4 and CO2 under ice in winter (CH4, 1.05–127.16 μmol/L, CO2, 13.24–95.57 μmol/L) were 3–4 orders of magnitude and several times higher than those in summer (CH4, 0.02–2.34 μmol/L, CO2, 7.26–49.18 μmol/L), respectively. The CH4 concentrations and fluxes during ice-melt increased with as the depth of the thermokarst lakes and ponds increased. However, the variation in CO2 concentration was not significant in depth. Snowfall events played an important role in influencing gas exchange during ice-melt. In the ten lakes researched, 42.2% and 19.2% of the annual CH4 and CO2 fluxes occurred during ice-melt, respectively. Our results indicated that CH4 and CO2 accumulation in winter should be considered when evaluating annual carbon budgets in thermokarst lakes and ponds on the TP and similarly high fluxes during ice-melt might occur in other thermokarst lakes and ponds.

Moho depth inversion in the Tibetan Plateau from high-precision gravity data

The Tibetan Plateau (TP) is the youngest orogenic belt formed by continental collision on the Earth. It is a natural laboratory for studying continental dynamics such as continental convergence, plate subduction, and plateau uplift. Studying its deep structure has always been a hot issue in geological research. The Moho is the interface between the crust and the mantle and is an important interface in the structure of the Earth's circle. Its depth, lateral variation, and fine structure of the crust-mantle interface are important parameters to reveal the process of lithospheric dynamics in the TP. The study of the Moho surface generally has two methods: seismic and gravity. Seismic detection has the characteristics of high precision, but they are limited along a few cross-sectional lines and have a high cost. It is not suitable and cannot be carried out in a large area of the TP; Gravity inversion can obtain large-area Moho depth, but affected by gravity data and inversion methods, the accuracy is lower than that of seismic. In this paper, a high-precision gravity field model is selected. With the constraint of seismic observation, the Parker-Oldenburg interface inversion method is used, and the Bott iteration method is introduced to improve the inversion efficiency. The high-precision Moho depth in the TP is obtained, consistent with the seismic detection results. The research results show that the shape of the Moho in the TP is complex, and the variation range is large, reaching 60-80 km. In sharp contrast with the adjacent area, there is a clear sharpness zone at the plateau's edge. In the TP's interior, the Moho's buried depth is characterized by "two depressions and two uplifts". The Moho in the south of the Yarlung Zangbo River (YZR) inclines to the north, and the Moho in the north depresses downward, interpreted as the Indian plate subducts to the north below Tibet. The Moho depression on the north side of the Qiangtang block (QTB), up to 72 km deep, may be related to the southward subduction of the lithosphere. The Moho uplift of the QTB has the same strike as the Bangong-Nujiang suture zone (BNS), which may reflect that the area is compensated by a low-density and low-velocity mantle.

Concentrations, sources, fluxes, and absorption properties of carbonaceous matter in a central Tibetan Plateau river basin

Carbonaceous matter (CM) (such as water-insoluble organic carbon (WIOC), black carbon (BC), and water-soluble organic carbon (WSOC)) has a significant impact on the carbon cycle and radiative forcing (RF) of glacier. Precipitation samples and glacier's snow/ice samples (snowpit, surface snow, and granular ice) (Xiao dongkemadi Glacier) were collected at the Dongkemadi River Basin (DRB) in the central Tibetan Plateau (TP) between May and October 2016 to investigate the characteristics and roles of CM in the TP River Basin. WIOC, BC, and WSOC concentrations in precipitation were relatively higher than that in snowpit, but lower than that in surface snow/ice, with the wet deposition fluxes of 0.10 ± 0.002, 0.04 ± 0.001, and 0.12 ± 0.002 g C m−2 yr−1 at DRB, respectively. The positive matrix factorization model identified four major sources (biomass burning source, secondary precursors, secondary aerosol, and dust source) of CM in precipitation at DRB. Two source areas (South Asia and the interior of TP) contributing to the pollution at DRB were identified using a potential source contribution function model, a concentration-weighted trajectory method, and the back-trajectory model. Moreover, the light-absorption by WSOC in the ultraviolet region was 23.0%, 12.1%, and 3.4% relative to the estimated total light-absorption in precipitation, snowpit, and surface snow/ice, respectively. Optical indices analysis revealed that WSOC in snowpit samples presented higher molecular weight, while presented higher aromatic and higher molecule sizes in surface snow/ice and precipitation samples, respectively. RF by WSOC relative to that of BC was estimated to be 17.6 ± 17.6% for precipitation, 10.9 ± 5.8% for snowpit, and 10.7 ± 11.6% for surface snow/ice, respectively, during the melt season in the central TP River Basin. These results help us understand how CM affects glaciers, and they can be utilized to create policies and recommendations that efficiently reduce emissions.

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

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

Comparisons of topsoil geochemical elements from Northwest China and eastern Tibetan Plateau identify the plateau interior as Tibetan dust source

The high-altitude Tibetan Plateau (TP) is a potential substantial source of dust that could have major effects on the global dust cycle and lead to environmental change. Aeolian loess on the TP is a valuable archive for studying the history of dust activities. Identification of TP dust sources will deepen understanding of dust transport and atmospheric circulation patterns and their environmental impacts. However, consensus on the source of TP loess has not been reached, which hinders understanding of dust transport and paleoenvironmental explanations. In this study, topsoil and loess samples from Northwest (NW) China and eastern TP were used to systematically investigate the spatial variability in geochemical composition, and the element characteristics of the TP loess were used to identify its dust source. Compared with samples from NW China, the eastern TP topsoil and loess were relatively enriched in TiO2, MnO, Cr, Co, Y, Zr, Nb, La, Ce, and Hf, but relatively depleted in Na2O, MgO, CaO, Sr, and Pb. The geochemical composition and source analyses indicated that the dust from the Qaidam Basin, Hexi Corridor, and Tarim Basin in NW China was not the main contributing source to the TP loess. However, the elemental characteristics of the TP loess were broadly consistent, and element contents were similar to those of major and trace elements in surface sediments on the TP. Thus, the eastern TP loess was sourced primarily from the TP interior, revealing the TP as an important dust source in Asia.

Spatial distribution and potential sources of methanesulfonic acid in High Asia glaciers

As a receptor of atmospheric deposition, glaciers are considered an ideal archive in the study of climate change and geochemical cycles. The deposition of methanesulfonic acid (MSA) in the glaciers provides good opportunities to study the biogeochemical cycle of sulfur in the cryosphere. In the present work, snow samples were collected from six High Asia glaciers along a north-to-south transect to determine the spatial distribution of MSA and elucidate its potential sources. The median MSA concentration in the Urumqi Glacier No.1 of Tien Shan was 138.8 ng mL−1, which was distinctly higher than those observed in the Tibetan Plateau (TP) glaciers and polar regions. The levels of MSA in the interior TP glaciers were higher than those observed in the margins of northeastern and southeastern TP. Good correlations between MSA and K+ (r = 0.86, n = 30, α = 0.01), Mg2+ (r = 0.86), and NH4+ (r = 0.73) were observed in continental glaciers. Principal component analysis indicated that MSA may have terrigenous material inputs. At Yulong Snow Mountain, MSA was correlated with Na+ (r = 0.76, n = 8, α = 0.1), a sea-salt tracer ion, suggesting that MSA may be derived from marine environments. According to dimethyl sulfide (DMS) production and NH3 emissions in High Asia, we deduced that the high concentrations of MSA in continental glaciers are possibly related to the sources of hypersaline soil environments and animal husbandry in nomadic areas. This work is useful for further studies on regional sulfur cycling and the impacts of human activities on climate change.

Oblique fault movement during the 2016 Mw 5.9 Zaduo earthquake: insights into regional tectonics of the Qiangtang block, Tibetan Plateau

The present east–west crustal extension of the Tibetan Plateau has been demonstrated through field investigations, satellite imagery, geodetic deformation, and earthquake focal mechanisms. Normal faulting earthquakes in the interior Tibetan Plateau are almost entirely confined to regions at elevations over 4000 m. However, our knowledge of the eastward extent of normal faulting in the plateau is still uncertain due to the limited occurrence of well-documented earthquakes. Based on a retrospective analysis of the 2016 Mw 5.9 Zaduo earthquake in the Tibetan Plateau, we consider the NE trending Zaduo-Shanglaxiu fault as the most likely rupture fault through a comprehensive analysis of relocated aftershock sequences, mapped active faults, and newly acquired strain rate tensor. We further determine seismogenic fault geometry using a Bayesian approach and sample with a Markov Chain Monte Carlo method. We interpret the Zaduo earthquake to reflect the release of slowly accumulated elastic strain accumulated mainly by gravitational forces rather than a delay triggering event from the 2010 Yushu earthquake. The viscoelastic calculations to estimate Coulomb stress changes over time indicate that long-term viscous flow in a weak mid-crust can load adjacent faults far more than static stress changes alone. Our results show that the Zaduo earthquake was a Mw 5.9 oblique normal faulting event that occurred in the easternmost part of the Tibetan Plateau, suggesting that the Qiangtang block at longitude ~ 95° E accommodates east–west extensional crustal deformation by small-scale oblique normal faults, which may act as the boundary of micro-blocks. This may also mean that the normal faulting in the Qiangtang block is expanding outwards, and a new rifting system may be formed, which requires more geological evidence.

Characterizing Surface Albedo of Shallow Fresh Snow and Its Importance for Snow Ablation on the Interior of the Tibetan Plateau

AbstractSnow depth on the interior of Tibetan Plateau (TP) in state-of-the-art reanalysis products is almost an order of magnitude higher than observed. This huge bias stems primarily from excessive snowfall, but inappropriate process representation of shallow snow also causes excessive snow depth and snow cover. This study investigated the issue with respect to the parameterization of fresh snow albedo. The characteristics of TP snowfall were investigated using ground truth data. Snow in the interior of the TP is usually only some centimeters in depth. The albedo of fresh snow depends on snow depth, and is frequently less than 0.4. Such low albedo values contrast with the high values (~0.8) used in the existing snow schemes of land surface models. The SNICAR radiative transfer model can reproduce the observations that fresh shallow snow has a low albedo value, based on which a fresh snow albedo scheme was derived in this study. Finally, the impact of the fresh snow albedo on snow ablation was examined at 45 meteorological stations on TP using the land surface model Noah-MP which incorporated the new scheme. Allowing albedo to change with snow depth can produce quite realistic snow depths compared with observations. In contrast, the typically assumed fresh snow albedo of 0.82 leads to too large snow depths in the snow ablation period averaged across 45 stations. The shallow snow transparency impact on snow ablation is therefore particularly important in the TP interior, where snow is rather thin and radiation is strong.

Spatially varying surface seasonal oscillations and 3-D crustal deformation of the Tibetan Plateau derived from GPS and GRACE data

Measurements of 189 continuous and 933 campaign-mode Global Positioning System (GPS) stations with 3–16 yr data spans over the Tibetan Plateau reveal contemporary three-dimensional (3-D) crustal deformation during 1999–2016. The Empirical Orthogonal Function method was used to characterize the spatial variations in the surface deformation with distinct seasonal oscillations at the GPS sites in five regions of the Tibetan Plateau. We find that these surface variations are highly correlated with the corresponding mass load signals observed by the Gravity Recovery and Climate Experiment (GRACE) mission. The improved GPS processing strategy used to determine the 3-D velocity field includes maximum likelihood estimation, removal of common mode errors from GPS time series using Principal Component Analysis (PCA), and power law plus white noise stochastic error modeling. We determined the rates of vertical crustal movement by removing GRACE-observed non-tectonic origin load deformation, 2002–2016. The corrected vertical crustal deformation shows that the Himalaya region is uplifting at an average rate of ∼1.7 mm yr−1, and that the northeastern Tibetan Plateau is uplifting at an average rate of ∼1.3 mm yr−1. In addition, the horizontal velocity relative to the stable Eurasian plate and its corresponding dilatation throughout the Tibetan Plateau suggest that tectonic shortening and crustal thickening is occurring at −90 to −80 nanostrain yr−1 in the southern Tibetan Plateau and −30 to −20 nanostrain yr−1 in the northeastern Tibetan Plateau, which could be related to the geologic shortening and elastic strain accumulation. The interior Tibetan Plateau exhibits crustal thinning and block movement along strike-slip faults. Eastward motion of the crust north of the Xianshuihe-Xiaojiang Fault system relative to crust to its south results in shear strain and reflects eastward escape of plastic crustal material in the southeastern Tibetan Plateau.

Annual Glacier-Wide Mass Balance (2000–2016) of the Interior Tibetan Plateau Reconstructed from MODIS Albedo Products

Glaciers in the Tibetan Plateau (TP) play a crucial role in regulating agriculture irrigation, river discharge and the regional/global climate system. However, mass balance records of TP glaciers have remained scarce due to challenging mountainous terrain and harsh weather conditions, which limits our understanding of the influence of melting glaciers on local water resources and responses to climate change. Here, we present and assess an albedo-based method to derive annual mass balance for three glaciers in the interior TP from Moderate Resolution Imaging Spectroradiometer (MODIS) albedo data during 2000–2016. A strong linear correlation (R2 = 0.941, P < 0.001) is found between annual minimum-averaged glacier-wide albedo (AMGA) values and annual mass balance measurements on the Xiao Dongkemadi glacier. Furthermore, the 17-year-long annual mass balance series of the Xiao Dongkemadi glacier and the Geladandong mountain region glaciers, and the Purogangri ice cap are reconstructed for the first time, with a mass loss rate of 535 ± 63 mm w.e.a−1, 243 ± 66 mm w.e.a−1 and 113 ± 68 mm w.e.a−1, respectively. The results are verified by geodetic estimates, with relative error ranging from 4.55% to 11.80%, confirming that the albedo-based method can be used to estimate specific mass budgets for interior TP glaciers. A strong correlation between the mass balance series and air temperature infers that increasing summer air temperature may be one of main reasons for glacier shrinkage of the three studied glaciers.

The Late Triassic I–Type Granites from the Longmu Co–Shuanghu Suture Zone in the interior of Tibetan Plateau, China: Petrogenesis and Implication for Slab Break–Off

The Jiangaidarina granitic mass (JM) is an important part of the magmatic belt in Longmu Co–Shuanghu Suture Zone (LSSZ) in the central Tibetan Plateau. An integrated research involving whole–rock geochemistry, zircon LA–ICP–MS U–Pb ages and Hf isotopic compositions was carried out to define the timing, genesis and tectonic setting of the JM. Zircon LA–ICP–MS U–Pb ages have been obtained ranging from 210 to 215 Ma, rather than the Early Jurassic as previously thought. Fifteen granite samples contain hornblendes and show a negative correlation between P2O5 and SiO2, indicating that the JM is an I –type granite. All the granites are enriched in LREE relative to HREE, with negative Eu anomalies (Eu/Eu*=0.56–0.81), and have similar trace elements patterns, with depletion of Ba, Nb, Sr and P. These suggest that the JM was fractionated, and this is also proved by the characteristic of negative correlations between oxide elements (TiO2, MgO, FeOt, MnO, CaO) and SiO2. Almost all εHf(t) values of the granites are between −10.3 and −5.8, implying that the JM has a crustal source intimately related with the South Qiangtang Block (SQB), except for one (+10.2), showing a minor contribution from mantle source. Moreover, relatively low Na2O/K2O ratios (0.42–0.93) and high A/CNK values (0.91–1.50) reflect that the JM was predominately derived from the medium–high potassium basaltic crust, interacted with greywacke. Our new geochemical data and geochronological results imply that the Late Triassic magmas were generated in a post–collisional tectonic setting, probably caused by slab break–off of the Longmu Co –Shuanghu Tethyan Ocean (LSTO). This mechanism caused the asthenosphere upwelling, formed extension setting, offered an enormous amount of heat, and provided favorable conditions for emplacement of voluminous felsic magmas. Furthermore, the LSTO could be completely closed during the Middle Triassic, succeed by continental collision and later the slab broke off in the Late Triassic.

An integrated investigation of lake storage and water level changes in the Paiku Co basin, central Himalayas

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 × 108 m3 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) × 108 m3 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.

Observational evidence of the combined influence of atmospheric circulations and local factors on near‐surface meteorology in Dagze Co basin, inner Tibetan Plateau

ABSTRACTBased on meteorological observations of three automatic weather stations (AWSs), spanning an altitudinal range of 1400 m from 4480 to 5880 m above sea level (m a.s.l.) during August 2015 to August 2016, this study presents a description of the spatio‐temporal characteristics of the near‐surface meteorology of the Dagze Co (lake) basin in the interior of the Tibetan Plateau. We also investigated the influence of synoptic atmospheric systems and local factors on the meteorological characteristics. We found that the onset and withdrawal of the South Asian summer monsoon triggered seasonal shift in meteorological variables including wind direction, precipitation, and relative humidity. In addition, the magnitude of various meteorological factors during the monsoonal period is clearly associated with the intensity of the South Asian summer monsoon, which subsequently controls the lake water budget of Dagze Co. Moreover, both the local topography and the existence of the lake contribute significantly to the altitudinal variation of several meteorological factors. For example, the orographic precipitation near the glaciated area at 5880 m a.s.l. was about three times greater than in the area adjacent to the lake. The dominating katabatic wind over these glaciated areas weakens the up‐valley wind and consequently wind speed tends to decrease with increasing elevation during the monsoonal season. In addition, different levels of cloudiness between the low‐altitude lake and the glaciated mountain area contribute to a 40–50% reduction in incoming short‐wave radiation receipt. Our observations will hopefully contribute to future glacio‐hydrological studies and will help to evaluate statistically/dynamically downscaled climate fields in the interior of Tibetan Plateau which contains numerous lakes and glaciers.