Southern Tibetan Plateau Research Articles

Aeolian activity in the Yarlung Zangbo River Basin, southern Tibetan Plateau, began at 584 ka: implications for the glaciation of the Tibetan Plateau

Aeolian activity on the Tibetan Plateau (TP) has profound effect on the Asian and global climate. In the southern TP, loess deposition widely occurred associated with the massive glaciers and large rivers, recording the interplay history among the aeolian activity, atmosphere, and cryosphere. However, the initiation age of the loess and the factor controlling the loess formation are still controversial. Here, three drilling cores were retrieved from Linzhi area, in the eastern Yarlung Zangbo River Basin of the southern TP, which reached the bedrock and documented the loess development in the southern TP. Based on the optically stimulated luminescence, electron spin resonance, paleomagnetism dating and relative paleointensity correlation, the basal age of the drilling core was constrained at 584 ka revealing the onset of significant aeolian activity on the southern TP. Synthesize this study and previous work on the loess age across the TP, three stages were identified, namely 3600, 2800–2700, and 1200–600 ka, with the age trending younger from north to south. Extensive loess development on the TP occurred between 1200 and 600 ka, which was mainly ascribed to the global cooling during the mid-Pleistocene Transition. During this time, the ampler glaciers extent significantly expanded, westerly displaced southward and the wind intensity also intensified on the TP, which resulted in the enhancement of dust generation, arid and windy condition, leading to the loess preservation and development on the TP. Moreover, numerous evidences suggested that the glaciers on the TP may significantly developed since 800 ka, then enlarged at 500–600 ka, which may lead to the massive dust/loess input to the TP, Chinese Loess Plateau and north Pacific Ocean.

The post-IR IRSL dating of an ancient dammed lake upstream of the Ganglai gorge in the upper-middle reaches of Yarlung Tsangpo

The middle reaches of Yarlung Tsangpo, situated on the southern Tibetan Plateau, have experienced extensive river damming events due to glacier advances, resulting in the formation of several ancient dammed lakes. These palaeolakes offer invaluable insights into past hydrological and geomorphological dynamics on the Tibetan Plateau. In this study, we reported a newly identified ancient dammed lake, named the Xiaru palaeolake, located upstream of the Ganglai Gorge in the uppermost segment of the middle reaches of Yarlung Tsangpo, and conducted a pioneer chronological investigation of the lake using K-feldspar post-IR IRSL (pIRIR) dating. Quartz minerals from most lacustrine and fluvial sediments can not provide reliable ages characterized with low intensity and large inter-aliquot scatter in equivalent doses (De). In contrast, the K-feldspar exhibited much greater luminescence intensity and narrower De distribution using the pIRIR225 dating protocol. Residual, dose recovery, and fading tests demonstrated that the pIRIR225 signals are well bleached with a relatively low fading rate, making it a more suitable dosimeter for dating applications in the study area. The pIRIR225 ages, derived through single aliquots, standard growth curve (SGC), and single grain measurements, reveal a major phase of the Xiaru Lake between 24.1 ± 1.0 ka and 15.8 ± 1.1 ka, that commenced aligning with the global Last Glacial Maximum. Furthermore, one lacustrine sample dated to 29.9 ± 2.2 ka suggests the possibility of multiple damming events in Ganglai Gorge during the last glacial period, although further evidence is required for a comprehensive interpretation.

Glacial lakes control ice flow: new insights from satellite SAR PO-SBAS observations in Duiya Glacier, southern Tibetan Plateau

ABSTRACT This study investigates the effects of glacial lakes on the flow velocities of Duiya Glacier, southern Tibetan Plateau, by employing satellite Synthetic Aperture Radar (SAR) Pixel-Offset-Tracking Small-Baseline-Subset (PO-SBAS) technology. Duiya Glacier, which terminates in a lake, exhibits approximately 10 m/yr higher horizontal speed and a higher melting rate with a vertical Non-Surface-Parallel-Flow (nSPF) velocity of – 7 m/yr than those of its land-terminating counterpart – West Duosangpu Glacier. Notably, Duiya Glacier experiences significant seasonal velocity fluctuations with accelerated flow between May and October. By integrating glacier geometry, changes in glacier boundaries and the extent of proglacial lakes, the distribution of supraglacial lakes, and climatic variables, we reveal that proglacial and supraglacial lakes play a crucial role in increasing the flow velocities of Duiya Glacier. Duiya Glacier flows faster because of increased subglacial water pressure resulting from water influx from these lakes. This phenomenon becomes conspicuously evident during May – October, when increased meltwater due to increased temperatures and precipitation further elevates the subglacial water pressure. Our method highlights the potential for understanding the impact of glacial lakes on glacier movements at a large scale, leveraging the capabilities of satellite SAR PO-SBAS technology for continuous, wide-scale, high temporal resolution, and 3D velocity monitoring.

The Asian rock-dwelling antlions Gatzara Navás, 1915 and Nepsalus Navás, 1914 (Neuroptera: Myrmeleontidae): new advancements in systematics, biogeography and life history.

The antlion genera Gatzara and Nepsalus (Myrmeleontidae: Dendroleontinae) inhabit mountain forests and are characterised by camouflaging larvae. Both genera remain poorly known despite recent findings on systematics and distribution. We report the discovery of new specimens and the previously unknown larvae of the rare species Gatzara jubilaea Navás, 1915, Nepsalus insolitus (Walker, 1860) and N. decorosus (Yang, 1988). These provide new evidence regarding the affinities of these species, and updated knowledge of the distribution, larval morphology and biology. Moreover, a new species of Nepsalus , N. maclachlani Badano, Zheng & Liu, sp. nov. is described from Sri Lanka based on historical museum collections. The discovery of the immature stages of Gatzara shows that the larvae of this genus share the same specialised ecological characteristics and habits as those of Nepsalus but are less morphologically derived. We also reconstruct a molecular phylogeny of this lineage, estimating the divergence time and biogeographical history by adding the new samples. The evolution of the Gatzara + Nepsalus lineage is associated with two major mountain ranges on the southern Tibetan Plateau, i.e. the Himalayas and the Hengduan Mountains. ZooBank: urn:lsid:zoobank.org:pub:68E68211-DFC1-4D98-997B-8A23BA8F9B69.

The Disparity in Normalized Difference Vegetarian Index Response to Climate Warming and Humidification in the Tibetan Plateau before and after 1998

The Tibetan Plateau (TP) serves as a crucial ecological barrier in Asia, with vegetation playing a pivotal role in the terrestrial ecosystem by facilitating energy exchange between the land and atmosphere, regulating climate, and participating in the carbon cycle. In this study, we analyze the characteristics of surface vegetation on the TP in the growing season during 1982–2018 using satellite remote sensing data obtained from the National Oceanic and Atmospheric Administration (NOAA) and China Meteorological Forcing Dataset (CMFD). We investigate how these characteristics respond to climate change under different warming and humidification conditions across the TP. The main conclusions are as follows. (1) The normalized difference vegetation index (NDVI) values on the TP exhibit a gradual decrease from southeast to northwest during the growing season. There is a significant overall increasing trend at a climate tendency rate of 0.01·decade−1 (p < 0.01) from 1982 to 2018, characterized by a notable mutation of around 1998. Over the past 37 years, a polarized trend of vegetation was observed on the TP, with notable improvement in its central and eastern regions. However, there has been noticeable degradation in northwestern TP, specifically within the Kunlun Mountains and Qaidam Basin. (2) The climate of the TP demonstrates distinct regional disparities in terms of warming and humidification characteristics before and after 1998. During the period of 1982–1998 (1998–2018), the temperature increase is primarily concentrated in the northern (southern) TP, while precipitation increase is mainly observed in the southern and northwestern (northeastern and western) regions of the TP. (3) The responses of surface vegetation to climate factors exhibit significant variations across diverse climatic backgrounds. It is noteworthy that moisture conditions have a substantial impact on the response of vegetation to air temperature on the TP. During the period of 1982–1998, under relatively insufficient moisture conditions, a positive correlation was observed between air temperature and surface vegetation in the humid and semi-humid regions of the southeastern TP, while a negative correlation was found in the semi-arid regions of northeastern TP. During 1998–2018, as moisture conditions became relatively sufficient, surface vegetation in the semi-arid regions showed positive correlations with both temperature and precipitation. However, surface vegetation in the humid and semi-humid regions exhibited a significant negative correlation with precipitation. During this period, the synergistic effects between warm and humid climates in the semi-arid regions of northeastern TP and warm and dry climates in humid and semi-humid regions of southeastern TP substantially enhanced surface vegetation on the TP. Furthermore, our results indicate that thermal factors (air temperature) primarily influence variations in surface vegetation within the high-altitude arid region of the TP. During 1998–2018, a significant cooling trend was observed in the northwestern TP, which could potentially account for the degradation of surface vegetation in the Kunlun Mountains. The findings of this study establish a scientific basis for the sustainable development of grassland ecosystems on the TP.

Relationship between human activities and environmental changes in the southern Tibetan Plateau since the Little Ice Age

The Tibetan Plateau (TP) is one of the most challenging areas for human long-term settlement due to its extreme living environment. Understanding the relationship between human activities and environmental changes in this extreme environment is important and can provide a historical reference for adapting to future climate change. In this study, we took the Angren Basin in the southern TP as a case study to elucidate the relationship since Little Ice Age (LIA). Using fecal stanol in feces, lake and river surface sediments, surface soils, and sediment core, we found that specific indices S1 and S2 from the composition of coprostanol, epicoprostanol, 5β-ethylcoprostanol and 5β-ethylepicoprostanol can reflect changes in human population and herbivores, respectively. Through the comparison between environmental changes determined by grain size, elements, sedimentation rate, and other climate records, the relationship between human activities and environmental changes was interpreted. Our results indicate that: (i) during 1480–1820 CE, the fecal stanols in lake sediments mainly originated from livestock, and the human population was low. In contrast, during 1820–2021 CE, the proportion and flux of S1 have been continuously increasing, indicating significant population growth. (ii) During the middle LIA, the cold-dry climate inhibited the development of agriculture and farming. However, the increased precipitation during the late LIA promoted that development, resulting in an increase in human population and livestock in a short term. (iii) Since 1951, people have reclaimed wasteland and developed husbandry, leading to increased soil erosion. (iv) Over the past 40 years, with a warm-humid climate and good policy support, human activities, such as agriculture and husbandry, have rapidly increased, but soil erosion has declined in the recent 20 years due to good soil-water conservation efforts. This study sheds light on the relationship between human activities and environmental changes and provides insights into future climate change responses.

Fluid Chemical and Isotopic Signatures Insighting the Hydrothermal Control of the Wahongshan-Wenquan Fracture Zone (WWFZ), NE Tibetan Plateau

Compared to the southern Tibetan Plateau, the northern part has been regarded as relatively lacking geothermal resources. However, there is no lack of natural hot springs exposed in beads along large-scale fracture systems, and research on them is currently limited to individual hot springs or geothermal systems. This paper focuses on the Wahongshan-Wenquan Fracture Zone (WWFZ), analyzes the formation of five hydrothermal activity zones along the fracture zone in terms of differences in hot water hydrochemical and isotopic composition, and then explores the hot springs’ hydrothermal control in the fracture zone. The results show that the main fractures of the WWFZ are the regional heat control structures, and its near-north–south- and near-east–west-oriented fractures form a fracture system that provides favorable channels for deep hydrothermal convection. Ice and snow meltwater from the Elashan Mountains, with an average elevation of more than 4,500 m above sea level, infiltrates along the fractures, and is heated by deep circulation to form deep geothermal reservoirs. There is no detectable mantle contribution source heat to the hot spring gases, and the heat source is mainly natural heat conduction warming, but the “low-velocity body (LVB)” in the middle and lower crust may be the primary heat source of the high geothermal background in the area. The hot springs’ hydrochemical components show a certain regularity, and the main ionic components, TDS, and water temperature tend to increase away from the main rupture, reflecting the WWFZ controlling effect on hydrothermal transport. In the future, the geothermal research in this area should focus on the hydrothermal control properties of different levels, the nature of fractures, and the thermal contribution of the LVB in the middle and lower crust.

Changes in Late Pleistocene Dust Activity in the Southern Tibetan Plateau in Response to Orbital Precession and Mountain Glaciers

AbstractThe Tibetan Plateau (TP) serves not only as the “water tower” of Asia but also as an important source in the global atmospheric dust cycle. While our knowledge of modern dust activity and its impacts and interactions with climate change in the TP has greatly advanced in the past decades, the emission, transport, and deposition of dust on the geological time scale remains unclear. This study analyzed a 7.6‐m thick sedimentary sequence consisting of loess and sand from the Yarlung Tsangpo River (YTR) valley in the southern TP. The sequence chronology was established using nineteen K‐feldspar post‐infrared infrared stimulated luminescence (pIRIR) ages, which ranged from 47.11 ± 1.95 to 116.65 ± 5.55 ka in a general stratigraphical order. The dust sedimentation rate and sorting coefficient of grain size were used to reflect dust activity and near‐surface wind, respectively. The results indicated that dust activity in the southern TP is mainly regulated by the near‐surface wind intensity and follows the variation pattern of precession, although the waxing and waning of mountain glaciers also affect the amplitude of dust activity. This pattern is not consistent with the Greenland dust record, which follows the variation pattern of obliquity. Therefore, dust accumulation in the southern TP is concluded to be primarily controlled by the South Asian winter monsoon (SAWM) forced by precession, whereas dust accumulation in Greenland is closely related to the intensity of the high‐level westerlies forced by obliquity.

Mesoscale and Large-Eddy Simulation of the Boundary Layer Process of Cumulus Development over Naqu, Tibetan Plateau Part A: Comparison Between Simulation and Observation

Cumulus clouds are of great interest in numerical weather prediction. However, the scarcity of observed data on the Tibetan Plateau (TP) has not allowed a correct interpretation of their development. The Third TP Atmospheric Science Experiment provided experimental data to address this challenge. The objective of this study was to ascertain the effective utilization of observation-nudging techniques for the implementation of combined weather research and forecasting large-eddy simulation (WRF-LES) for further experimental designs. This study simulated cumulus clouds over southern TP on July 19, 2014, using the WRF-LES model and final reanalysis data from the Global Forecast System. We applied observation nudging and one-way nesting strategies to influence the optimality of WRF-LES runs. The study performed simulations with six different scenarios in comparison with observational data. The findings demonstrated that, despite being locally initiated and growing upscale, cumulus clouds were nonetheless subject to large-scale forcing. Simulations with observation nudging produced more accurate and trustworthy results than simulations without nudging when compared to observations. While the observed time series were misleading, LES with mesoscale forcing produced a microphysical evolution that was consistent with the observations and an accurate water vapor profile. Without mesoscale forcing, LES provided the best ABL water vapor and sensible heat flux; however, it failed to provide a good microphysics field. In this aspect, large-scale forcing played an important role in cumulus development during the model experiment. The study recommended focusing on the model's response to the boundary conditions to improve the application of one-way nesting in separate iterations and observational nudging techniques

Late quaternary lake level variations of Mabu Co-Gala Co, southern Tibetan plateau, modulated by glacial meltwater, spillover processes and the Indian summer monsoon

Lakes on the Tibetan Plateau (TP) play a major role in the regional hydrological cycle and underpin vital ecosystem services. However, the long-term lake evolution and underlying mechanisms, especially on the exorheic southern TP, remain unclear. Here, we reconstructed the lake level variations of Mabu Co and Gala Co on the southern TP through detailed paleo-shoreline dating using post-infrared infrared stimulated luminescence (pIRIR) signals of K-feldspar single grains, and explored the driving forcings based on a comparison of paleoclimate records and geomorphological analysis. The results show that a unified paleolake at Mabu Co and Gala Co at a level ∼20 m above the modern level (a.m.l.) of Mabu Co developed during the late MIS 3 (35.9 ± 1.9–29.1 ± 1.4 ka) in response to increased glacial meltwater and Indian summer monsoon (ISM) rainfall. Under intensive glacier melting, the paleolake reached its maximum level (∼29 m a.m.l.) and area (190 km2, ∼22 times larger than the modern areas of Mabu Co and Gala Co) during the last deglacial (16.8 ± 1.0–13.6 ± 0.7 ka) and began to outflow, which triggered incision and lowering of the spill-point. The lake level showed an overall decreasing trend since the last deglacial largely influenced by the lowering of the spill-point. During the last deglacial-early Holocene (12.7 ± 0.6–9.8 ± 0.6 ka), a high-stand lower than that in the previous stage (∼24 m a.m.l.) was maintained by the strengthened ISM and glacial meltwater. In the mid-Holocene (8.7 ± 0.9–4.1 ± 0.3 ka), the paleolake experienced two rapid lake level drops in response to the weakening events of the ISM. The exposed shoreline terrace between the two lakes following the lake level drop after ∼6 ka provided an ideal living surface for the inhabitants at the Mabu Co site during 4.5–4.0 ka. We found that glacial meltwater and lake spillover processes, apart from the ISM, have exerted great impacts on the hydrological history of Mabu Co and Gala Co. The paleolakes have provided critical resources for humans at the Mabu Co site living in the alpine anoxic environment. Additionally, we suggest that lakes with low spill-points adjacent to exorheic basins on the southern TP should be given more attention regarding flooding hazard risks against increasing precipitation and glacial meltwater in the future.

Assessing magmatic contributions to rift-related geothermal systems in collisional orogens: Insights from the Sangri-Cona rift, southern Tibetan Plateau

Fault-controlled geothermal systems in the Himalayan-Tibetan orogen could receive heat and material from deep-seated magmas due to crustal anatexis in orogenic settings. The near N-S trending rifts in southern Tibetan Plateau host abundant geothermal systems but potential role of residual magmas remains less constrained. Here, we evaluate magmatic contributions to geothermal systems in Sangri-Cona rift (SCR), the youngest rift in southern Tibetan Plateau, based on chemical and isotopic compositions of thermal waters from a south-to-north sampling profile. Our results show that the thermal springs in the central SCR have significant inputs from magmatic fluids, which account for high B concentrations and positive shift in δ18OH2O, while those in the southern and northern SCR are dominated by recharge of meteoric water. Water-rock interaction constrained by 87Sr/86Sr, hydrochemistry, and geothermometry results, suggests a hotter or deeper groundwater circulation path beneath central SCR than that of the southern and northern SCR. The identified magmatic fluid inputs, higher reservoir temperature, and higher degrees of water–rock interaction in the central SCR agree well with the presence of high conductivity anomalies at crustal depths of ∼ 10–30 km revealed by magnetotelluric surveys. Our findings provide geochemical evidence for the impact of lithospheric extension and associated geological and geophysical expressions (e.g., extension-induced exhumation of genesis domes that recorded crustal anatexis and upwelling of partially molten crustal channel flows) on modern geothermal systems in collisional orogens.

A research on the relationship between landslide area changes and environmental factors in the southern Tibetan plateau

Introduction: Landslides are known to be one of the most frequent types of geological disasters. However, there is not an established method for large-scale, rapid, and high-precision landslide extraction. The quantitative impact of environmental changes on landslide development is also not well understood, which hinders accurate assessments and decision-making in environmental and disaster response. The polar regions, including the Antarctic, the Arctic, and the Tibetan plateau (TP), sensitive to global environmental changes, are significantly affected by global warming. This leads to extensive landslide development, particularly in the southern TP. This research focuses on new landslides in the southern TP, exploring extraction methods and the relationship between landslides and environmental factors.Methods: Utilizing the Google Earth Engine (GEE) and an improved Otsu threshold segmentation algorithm, we processed remote sensing images with 10 m resolution to identify landslide areas. The proposed Normalized Landslide Bare-soil Separation Index (NDLBSI) achieved an 87% pre-extraction accuracy in extracting landslides from Sentinel-2 images from 2019 to 2023. For the pre-extraction results, manual interpretation and correction were carried out, and a model correlating annual landslide changes with environmental factors was established based on least squares multivariate statistical methods.Results: Results show that a significant increase in landslide areas in the southern TP over the past 5 years, correlating with the watershed-wide increase in annual average temperature and vegetation cover, along with a decrease in snow cover area.Discussion: These changes could affect soil and rock moisture, influencing soil stability and landslide occurrence. The study provides valuable insights for large-scale landslide detection and understanding the environmental factors influencing landslides, which is of some significance for landslide hazards early warning.

Ancient genomes revealed the complex human interactions of the ancient western Tibetans

The western Tibetan Plateau is the crossroad between the Tibetan Plateau, Central Asia, and South Asia, and it is a potential human migration pathway connecting these regions. However, the population history of the western Tibetan Plateau remains largely unexplored due to the lack of ancient genomes covering a long-time interval from this area. Here, we reported genome-wide data of 65 individuals dated to 3,500-300 years before present (BP) in the Ngari prefecture. The ancient western Tibetan Plateau populations share the majority of their genetic components with the southern Tibetan Plateau populations and have maintained genetic continuity since 3,500 BP while maintaining interactions with populations within and outside the Tibetan Plateau. Within the Tibetan Plateau, the ancient western Tibetan Plateau populations were influenced by the additional expansion from the south to the southwest plateau before 1,800 BP. Outside the Tibetan Plateau, the western Tibetan Plateau populations interacted with both South and Central Asian populations at least 2,000 years ago, and the South Asian-related genetic influence, despite being very limited, was from the Indus Valley Civilization (IVC) migrants in Central Asia instead of the IVC populations from the Indus Valley. In light of the new genetic data, our study revealed the complex population interconnections across and within the Tibetan Plateau.

Westerlies-driven transboundary transport of atmospheric mercury to the north-central Tibetan Plateau

The transboundary mercury (Hg) pollution has caused adverse effects on fragile ecosystems of the Tibetan Plateau (TP). Yet, knowledge of transport paths and source regions of atmospheric Hg on the inland TP remains poor. Continuous measurements of atmospheric total gaseous mercury (TGM) were conducted in the central TP (Tanggula station, 5100 m a.s.l., June–October). Atmospheric TGM level at Tanggula station (1.90 ± 0.30 ng m−3) was higher than the background level in the Northern Hemisphere. The identified high-potential source regions of atmospheric TGM were primarily located in the northern South Asia region. TGM concentrations were lower during the Indian summer monsoon (ISM)-dominant period (1.81 ± 0.25 ng m−3) than those of the westerly-receding period (2.18 ± 0.40 ng m−3) and westerly-intensifying period (1.91 ± 0.26 ng m−3), contrary to the seasonal pattern in southern TP. The distinct TGM minima during the ISM-dominant period indicated lesser importance of ISM-transported Hg to Tanggula station located in the northern boundary of ISM intrusion, compared to stations in proximity to South and Southeast Asia source regions. Instead, from the ISM-dominant period to the westerly-intensifying period, TGM concentrations showed an increasing trend as westerlies intensified, indicating the key role of westerlies in transboundary transport of atmospheric Hg to the inland TP.

Different Formation Modes of the North–South‐Trending Rifts in Southern Tibet: Implications From Ambient Noise Tomography

AbstractUnderstanding how the Miocene N–S‐trending rifts on the southern Tibetan Plateau formed is crucial for understanding the evolution of the plateau. Most competing models suggest that all the rifts developed uniformly, but there are differences in magmatism among them. We conducted ambient noise tomography based on a broadband seismic array deployed across the rifts. A mid‐crustal low‐Vs layer extends laterally beneath the Tangra Yum Co Rift and the Pumqu‐Xianza Rift, implying that E‒W stretching of the ductile middle crust segmented the brittle upper crust, causing rifting and subsequent magmatism. In contrast, the Yadong‐Gulu Rift, which experienced prerifting magmatism, is characterized by an isolated low‐Vs anomaly extending subvertically from the surface to the middle crust, indicating that the crust experienced magmatic intrusion and local disruption, which promoted the later formation of a large rift. The results suggest that the various rifts might have distinct formation modes.

Taxonomy, ontogeny, and ecology of Tonnacypris stewarti (Daday 1908) comb. nov. (Ostracoda: Cyprididae) from Nam Co, Tibetan Plateau

Taxonomic clarification of Tonnacypris stewarti comb. nov. (= Herpetocypris stewarti), a non-marine ostracod first described by Daday in 1908, was required due to the existence of various synonyms without detailed morphological descriptions. Our study examined specimens from Mang-tsa, Nam Co (Tibetan Plateau) and Lake Band-e Amir (Afghanistan). We identified seven definitive synonyms (Herpetocypris stewarti Daday 1908, Ilyodromus estonicus Järvekülg 1960, Eucypris afghanistanensis Hartmann 1964, E. gyirongensis Yang 1982, E. rischtanica Schneider 1963 in Mandelstam & Schneider 1963, Tonnacypris estonica (Järvekülg 1960), and T. gyirongensis (Guo et al. 2016). After a detailed study of the morphology of valves and soft parts supplemented by a literature review, we propose combining the genus Tonnacypris with the specific epithet stewarti, resulting in the new name Tonnacypris stewarti. We documented the ontogenetic series of T. stewarti in surface sediment samples from Nam Co. Only female specimens were found, consistent with observations in Mongolia, where they were considered asexual populations. Sexual populations were reported from Afghanistan and the southern Tibetan Plateau, suggesting geographic parthenogenesis in the Palearctic region. Because of widely missing males, we explored the use of female genital lobes as a distinguishing feature for taxonomy. Considering current ecological knowledge, T. stewarti could serve as a (paleo)—bioindicator of cold, oligotrophic, and fresh to slightly brackish habitats, including rivers, lagoons, and lakes. This study emphasizes the importance of resolving taxonomic issues for future paleolimnological research. Moreover, our investigation highlights the potential use of sclerotized internal female genital lobes as distinctive characteristics for species differentiation, especially in asexual populations.

Anomalous Characteristics of Water Vapor Budget on the Tibetan Plateau under the Influence of Tropical Cyclones over the Bay of Bengal during Early Summer

Abstract Early summer is a peak time for tropical cyclone (TC) activities over the Bay of Bengal (BoB) and a period of South Asian monsoon onset, and the TCs during this time have a significant impact on the water vapor transport associated with monsoons. This study investigates the anomalous characteristics of the dynamic–thermal atmospheric circulation structure and water vapor budget over the Tibetan Plateau (TP) under the influence of BoB TCs generated in May from 1979 to 2020 with JTWC best track data and ERA5 data. Results reveal that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. A part of the water vapor is transported directly to the TP by deep southerly jet, while the other part is lifted by TCs and then climbs upward to the TP by two uplift processes occurring on the southern slope of the TP and over the TP respectively, which makes the whole troposphere over the southeastern TP warmer and wetter. It is found that anomalous southeasterly airflow in the northeast of TC circulation turns to anomalous southwesterly airflow forming an abnormal anticyclonic circulation over the southern TP in the middle and upper troposphere due to the diabatic heating effect. In this process, the TP acts as an anomalous water vapor sink with remarkable water vapor inflow through its southern boundary, with the main water vapor outflow through the eastern boundary, but a weak easterly water vapor backflow to the eastern TP in the lower troposphere. Significance Statement This study attempts to investigate the anomalous features of the water vapor budget over the Tibetan Plateau (TP) under the influence of the Bay of Bengal (BoB) tropical cyclones (TCs) during early summer. Results show that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. The TP acts as an anomalous water vapor sink with more and higher water vapor inflows through the southern boundary of the TP. A positive temperature and humidity anomaly can be found over the southeastern TP extending upward into the middle and upper troposphere. The results are helpful to understand how the BoB TCs affect the weather process over the TP.

Magnetostratigraphy of the Late Cretaceous to Early Eocene sediments from the Tulsipur section, western Nepal: Tectonic implications for the Indian northern passive margin

The sedimentary strata from the Late Cretaceous to Early Eocene in the Himalayan foothills offer detailed insights into land collision processes. Unfortunately, a comprehensive dating study on these strata has been lacking, limiting our understanding of the collision and splicing history of the Indian and Lhasa plates. To address this question, we conducted a paleomagnetic study on the Late Cretaceous to Early Eocene succession in the Tulsipur area, western Nepal. The paleomagnetic data obtained from a 357 m thick succession were used to establish a new magnetostratigraphic framework for this region. The observed magnetic polarity sequence contains six normal and six reversed polarity zones, spanning the age range of 68–54 Ma (Maastrichtian to Early Eocene). In addition, two major and two stable sediment accumulation rates (SARs) were identified which were likely controlled by tectonics. The rifting and subsidence events caused by continuous northward movement of the Indian plate might have modulated the shifting of distal offshore to tidal flat settings in this region. We document fifteen (Unit I) and seven (Unit II) transgressive-regressive cycles, indicative of passive margin instability influenced by near-field effects of the India-Asian convergence. This new magnetostratigraphic result is expected to serve as a basic age framework in reconstructing the Late Mesozoic and Early Cenozoic tectonic evolution. Furthermore, it will also facilitate reliable cross-regional correlation between lithostratigraphic units across passive margins in the southern Himalaya and similar strata in the Tethyan Himalaya and active continental margins of the southern Tibetan Plateau.

High-resolution physicochemical dataset of atmospheric aerosols over the Tibetan Plateau and its surroundings

Abstract. Atmospheric aerosol in the Tibetan Plateau (TP) and its surroundings has attracted significant scientific interest in recent decades due to its notable impacts on regional climatic and cryospheric changes, ecological and environmental security, and the hydrological cycle. However, our understanding of the atmospheric aerosol in this remote region is highly limited by the scarcity of available datasets owing to the extremely harsh natural conditions. This challenge has been mitigated in recent decades by establishing field observatories at typical sites within the TP and its surroundings. A continuous project initiated in 2015 aims to explore the properties and sources of atmospheric aerosols, as well as their regional differences, through multiple short-term intensive observations obtained across this vast region utilizing a suite of high-time-resolution online instruments. This paper presents a systematic and hourly scale dataset of aerosol physicochemical and optical properties at eight sites across the TP and its surroundings that is derived from the project. It includes size-resolved chemical compositions of submicron aerosols, high-resolution mass spectra and sources of organic aerosols, size distributions of particle number concentrations, particle light-scattering and light-absorption coefficients, particle light absorptions attributed to different carbonaceous substances including black carbon and brown carbon, and number concentrations of cloud condensation nuclei. In brief, atmospheric aerosols in these remote sites were all well mixed and highly aged, reflecting their dominant regional transport sources. However, the southern TP region exhibited high contributions of carbonaceous organic aerosols, neutralized bulk submicron aerosols, and a relatively high light-absorption capacity, whereas in the northern TP region, secondary inorganic species were the main contributors to the overall acidic submicron aerosols. Beyond providing insights into the regional differences in aerosol sources and properties across the TP and its surroundings, the datasets will also benefit simulations of aerosol radiative forcing and evaluations of interactions among different Earth system components in numerical models for this region. The datasets are accessible through the National Cryosphere Desert Data Center, Chinese Academy of Sciences (https://doi.org/10.12072/ncdc.NIEER.db2200.2022; Xu, 2022).

Rossby Wave Amplified by Tropical Cyclones Over the Bay of Bengal and Its Downstream Impact on Precipitation in South China

AbstractTropical cyclones (TCs) over the Bay of Bengal (BOB) can interact with the South Branch Trough (SBT) as they move northward and potentially amplify Rossby waves. This study evaluates the features of Rossby waves and their downstream impact on rainfall in South China. Results indicate that TC‐SBT interactions primarily occur in May and October‐November (Oct‐Nov), with probabilities of 59% and 53% respectively. Notably, the Rossby wave train associated with BOB TCs is more pronounced during Oct‐Nov due to the stronger subtropical westerly jet, in contrast to May. The downstream atmospheric response results in positive (negative) rainfall anomalies over South China in May (Oct‐Nov), particularly on the day following the maximum interaction day. Previous researches concerning TC‐extratropical flow interaction mainly focus on other basins where TCs move to higher latitudes, this study provides fresh insights into Rossby waves related to TC‐SBT interactions over the southern Tibetan Plateau.