High Tibetan Plateau Research Articles

Improvement of Albedo and Snow-Cover Simulation during Snow Events over the Tibetan Plateau

Abstract The snow albedo is a vital component of land–atmosphere coupling models. It plays a critical role in regulating land surface energy exchange by controlling incoming solar radiation absorbed by the land surface and influencing the timing and rate of snowmelt. Accurate snow albedo simulation is essential to obtain surface energy balance and snow-cover estimates. Here, the simulation of albedo and snow cover using the Weather Research and Forecasting Model and an improved snow albedo scheme is verified against satellite-retrieved products during and immediately following eight snowfall events over the Tibetan Plateau. The improved model successfully characterizes the spatial pattern and inverted U-shaped temporal pattern of albedo over the entire Tibetan Plateau. This is attributed to the local optimization of snow-age parameters and explicit consideration of snow depth in the improved scheme. Compared with the previous model, the model proposed herein greatly decreases the overestimated albedo (by 0.13–0.27), yielding a bias range of ±0.08, mean relative bias decrease of 70%, and significant increase in the spatial correlation coefficient of 0.03–0.39 (mean: 0.13). The significant improvements of albedo estimates appear in deep snow-covered regions, largely attributed to parameter optimization related to snow albedo decay, while less improvements appear over the shallow snow-covered regions. Accurate reproduction of the spatiotemporal variation in albedo alleviated snow-cover overestimation by small amounts. For snow-cover estimates, the improved model consistently decreases the false-alarm rate by 0.03, and increases the overall accuracy and equitable threat score by 0.04 and 0.03, respectively. Moreover, the improved scheme shows an equivalent improvement of albedo estimates at both 1- and 5-km grid spacing over the eastern Tibetan Plateau; this is also true for snow-cover estimates. Significance Statement Snow albedo schemes in widely used numerical weather prediction models show notable shortcomings in complex mountainous regions, hindering accurate surface energy balance and snow-cover prediction. The purpose of this study is to better understand the role of snow albedo on snow-cover estimates and reveal the application potential of an improved snow albedo scheme across the Tibetan Plateau. This is important because snow albedo influences the timing and rate of snowmelt, and in turn snow-cover estimates, through regulating the surface energy budget. Our results highlight the strong application potential of our improved scheme in reducing snow simulation errors, confirm the importance of snow depth on snow albedo, and provide a new perspective for improving the accuracy of snow forecast over the topographically high Tibetan Plateau.

Can Tibetan Plateau Snow Depth Influence the Interannual Association between Tropical Indian Ocean Sea Surface Temperatures and Rapidly Intensifying Typhoons?

Abstract This study finds that the observed decrease in winter–spring Tibetan Plateau snow depth since 2000 has played an important role in weakening the correlation between rapidly intensifying tropical cyclones over the western North Pacific and tropical Indian Ocean sea surface temperatures (SSTs). Tibetan Plateau snow depth modulates convective activity through changes in the South Asian high. Increased Tibetan Plateau snow depth promotes basinwide tropical Indian Ocean cooling in spring through a Gill-type response. In the following seasons, downward latent heat flux anomalies associated with a weaker monsoon circulation contributes to warm SST anomalies over the western tropical Indian Ocean, thus favoring a positive phase of the Indian Ocean dipole. This evolution of tropical Indian Ocean SSTs associated with anomalously high Tibetan Plateau snow depth potentially weakens the relationship between rapidly intensifying tropical cyclone frequency and spring tropical Indian Ocean SSTs. When the effect of Tibetan Plateau snow depth is removed via partial correlation analysis, we find a significant relationship between spring tropical Indian Ocean SSTs and rapidly intensifying tropical cyclones as well as corresponding large-scale environmental factors. The results of this study enhance understanding of changes in tropical cyclone intensity and have implications for seasonal forecasting of tropical cyclone intensity over the western North Pacific basin. This study also emphasizes the importance of Tibetan Plateau thermal forcing in atmosphere–ocean coupling.

Peter Hale Molnar

Peter Hale Molnar

Genetic characterization of the highlander Tibetan population from Qinghai-Tibet Plateau revealed by X chromosomal STRs.

Tibetans are considered an East Asian ethnic group and primarily live in the high Tibetan plateau, the western Sichuan and Yunnan mountains of central and southern China, and areas throughout the Himalayas and around the Tibetan plateau. These people exhibit rare molecular machinery that allows them to adapt to hypoxic environments in the Qinghai-Tibet Plateau and make them a potential candidate for providing insights related to medical genetic, molecular medicine and human population studies. In the current study, we have genotyped 549 individuals with Investigator Argus X-12 Kit. For 12 X-STRs, a total of 174 unique alleles were found, among them DXS10134 and DXS10135 were the most polymorphic loci. All of the loci were in Hardy-Weinberg Equilibrium (HWE). The numbers of observed haplotypes in Highlander Tibetans males were 161,112, 96 and 108, respectively, whereas haplotype diversities (HD) were 0.9959, 0.9880, 0.9809 and 0.9873, respectively. The combined discrimination power for males (PDm) was 0.999 999 99701 and for females (PDf) was 0.999 999 999 999 9958. This study represents an extensive report on X chromosomal STR markers variation in the Highlander Tibetans population for forensic applications and population genetic studies.

The Cenozoic Multiple-Stage Uplift of the Qiangtang Terrane, Tibetan Plateau

Cenozoic collision between the Indian and Asian continents is generally considered as the main driver forming the high Tibetan Plateau (TP). However, it remains hotly debated when and how the relatively flat and highly elevated TP was formed. Here, we present combined analyses of the apatite fission track (AFT) and apatite (U-Th)/He (AHe) of 18 granite samples along three steep topographic transects in the central part of the Qiangtang Terrane (QT), TP. The results indicate that the AFT ages of all samples are mostly between 130 Ma and 80 Ma, while the AHe ages range from 80 Ma to 40 Ma. Further thermal history modeling indicates that no significant cooling occurred after 40 Ma for most samples, except those lying close to the Reganpei Co extensional fault in the QT. The results are generally consistent with other low-temperature thermochronological data, as well as structural and sedimentologic data from the QT, suggesting that low relief and the relatively flat topography of the QT were almost completely formed before ∼40 Ma. As both megafossils and pollen had undergone a sharp change from subtropical- to psychro-species, indicating a relatively low elevation (∼2 km) at ∼40 Ma and >2 km uplift during the Oligocene. We use simple one-dimensional isostatic modeling to assess the contribution of convective removal of the lithospheric mantle to the present elevation of the QT. The results suggest that a combined effect of isostatic rebound (≥2 km) and thermal expansion related to asthenosphere upwelling and subsequent crustal base heating (∼0.4 km) led to the final uplift of the QT. Therefore, the QT experienced multiple-stage uplift processes which were controlled by crustal thickening before ∼40 Ma and lithospheric mantle delamination during the Oligocene, respectively.

Linkage of the surface air temperature over Tibetan Plateau and Northeast hemisphere in winter at interannual timescale

The interannual variability of surface air temperature (SAT) over the Tibetan Plateau (TP) and its linkage to the SAT over Northeast hemisphere in winter were investigated using monthly mean SAT data. Results show that winter SAT displays consistent interannual variability over the entire TP, with a significant positive correlation (r = 0.43) with SAT over North Africa (NA) and a negative correlation (r = −0.48) with SAT over Siberia (SB). The abnormally high NA SAT causes increased SAT over the Mediterranean, triggering a Rossby wave train propagating to the TP in the upper troposphere. Ascending 300 hPa geopotential height (HGT) anomalies occur over the TP, causing abnormally high TP SAT. The negative SB SAT anomaly is accompanied by a strong negative 300 hPa HGT anomaly with westerly wind effects in the upper troposphere over the northern TP, favoring abnormal anticyclonic circulation. The anticyclonic circulation caused by the two regions strengthens descending motion with adiabatic heating of the air. The relationship between TP and NA and SB SAT levels changed abruptly in the 1990s, with the Rossby wave propagating to the TP after 1990 and stopping near 60°E before 1990. The subtropical westerly anomaly in the southern TP weakened anticyclonic circulation after 1990, with a significant easterly effect before 1990.

3D electrical structure and crustal deformation of the Lajishan Tectonic Belt, Northeastern margin of the Tibetan Plateau

• A steep high-conductivity layer exists in the middle–lower crust to the south of the belt. • The high-resistivity body on the northern side may have blocked the high-conductivity layer, which formed the positive flower structure of the Lajishan tectonic belt and resulted in intense orogenic and seismic activities. • Crustal shortening may dominate the tectonic deformation of the NE Tibetan Plateau. The Lajishan tectonic belt is the most recently active orogenic belt in the northeastern Tibetan Plateau and represents a topographical boundary between the high Tibetan Plateau and the low-lying Longzhong basin to the east. Imaging the crustal structure beneath the Lajishan tectonic belt can improve our understanding about the regional tectonic deformation pattern, mechanisms of the outward growth of the Tibetan Plateau, and seismogenic environment in this area. In this study, we conducted two magnetotelluric (MT) profile measurements across the Lajishan tectonic belt in each section. Based on our newly-collected MT data and previous dataset in this area, a three-dimensional (3D) image of the deep electrical structure of the Lajishan tectonic belt is obtained by using 3D MT inversion and imaging technologies. Furthermore, by including 3D crustal deformation field information, a tectonic deformation model of the Lajishan tectonic belt and its adjacent area was constructed. Our present results show that a steep high-conductivity layer developed beneath the Lajishan tectonic belt and the adjacent Jianzha–Xunhua Basin and West Qinling Block, which then connected with a horizontal high-conductive layer underneath the Tibetan Plateau. Findings suggest that the Lajishan tectonic belt acts as a physical property boundary zone separating a high-resistivity body to the north from a deep high-conductivity layer in the middle-lower crust to the south. The high-conductivity layer, with a shallower depth from southwest to northeast, may be related to the NE-trending compression of the northeastern Tibetan Plateau, which was blocked by the high-resistivity body underneath the Xining basin. This led to the formation of a positive flower structure in the Lajishan tectonic belt, resulting in intense orogenic and seismic activities. The south-dipping Northern Lajishan Fault is the main boundary fault of the Lajishan tectonic belt and plays an important role in the mountain formation process, as suggested by asymmetry surface topography. The absence of a large-scale NE-SW-trending continuous high-conductivity layer in middle-lower crust indicates that the tectonic deformation of the northeastern Tibetan Plateau is dominated by a continuous upper-crustal compressing and shortening, instead of the lower-crustal flow.

Earliest parietal art: hominin hand and foot traces from the middle Pleistocene of Tibet

At Quesang on the Tibetan Plateau we report a series of hand and foot impressions that appear to have been intentionally placed on the surface of a unit of soft travertine. The travertine was deposited by water from a hot spring which is now inactive and as the travertine lithified it preserved the traces. On the basis of the sizes of the hand and foot traces, we suggest that two track-makers were involved and were likely children. We interpret this event as a deliberate artistic act that created a work of parietal art. The travertine unit on which the traces were imprinted dates to between ∼169 and 226 ka BP. This would make the site the earliest currently known example of parietal art in the world and would also provide the earliest evidence discovered to date for hominins on the High Tibetan Plateau (above 4000 m a.s.l.). This remarkable discovery adds to the body of research that identifies children as some of the earliest artists within the genus Homo.

Using an explicit multi-feature decision tree for wetland information extraction in Qomolangma national nature reserve

ABSTRACT The Qomolangma National Nature Reserve (QNNR) has complex geomorphological characteristics of the high altitude Tibetan Plateau and aunique plateau wetland environment. In order to extract the wetland information effectively and accurately, this research utilizes an explicit decision tree (DT) classification strategy that incorporates multiple feature nodes by using the Landsat-8 OLI imagery as the main data source to interpret the spectral signatures and spatial distribution of the wetlands, and to construct acomprehensive DT classification process for wetland information extraction in QNNR. The multiple feature nodes include snow cover, non-wetland distribution, normalized difference vegetation index (NDVI), normalized difference water index (NDWI), digital elevation model (DEM), land surface temperature (LST) and slope. This strategy produces amore accurate wetland classification in QNNR where there are various interfering factors such as snow, mountain shadows, mineralized regions, grassland and woodland. The method is straightforward and easy to implement. Its classification result has an overall accuracy of 92.75%. This method could be applied to the plateaus with vertical-step ecosystems.

Variability and environmental significance of organic carbon isotopes in Ganzi loess since the last interglacial on the eastern Tibetan Plateau

The stable carbon isotope composition of total organic matter (δ13Corg) in loess deposits has been widely used as a valuable proxy for reconstructing terrestrial paleovegetation. Aeolian loess is widely distributed on the high Tibetan Plateau (TP); however, little is known about the variability and paleoenvironmental implications of the δ13Corg of Tibetan loess. We conducted detailed δ13Corg and total organic carbon analyses of the Ganzi loess sequence on the eastern TP since the last interglacial (LIG). Our results indicate that the δ13Corg values of loess during glacial periods were lower than those during interglacial periods, with more negative values associated with the cold stages since the LIG on the eastern TP. The reconstruction of vegetation from the δ13Corg data indicated that C3/C4 mixed vegetation was dominated by C3 vegetation, and that the relative abundance of C4 vegetation during the glacial stages was much lower than that during MIS 5 and MIS 3. The high relative abundance of C4 plants during MIS 5 and MIS 3 suggested an increased proportion of C4 plants during the warm period. Since the LIG, the change in the abundance of C3/C4 vegetation in the Ganzi region has been mainly controlled by climate change at the glacial–interglacial scale. The combined effect of temperature, precipitation, and atmospheric CO2 caused changes in the paleovegetation on the eastern TP.

Sensitivity of altitudinal vegetation in southwest China to changes in the Indian summer monsoon during the past 68000 years

Reconstructing vegetation changes during a glacial-interglacial cycles in southwest (SW) China is crucial for understanding the amplitude of palaeoclimatic dynamics associated with orbital forcing and evolution of the Indian summer monsoon (ISM). However, few studies on the relationship between paleoclimate and ecosystem changes have covered all of the last glacial-interglacial cycle (or any other), which limits understanding of the ISM’s variability and its impact on mountain flora. In particular, knowledge of responses of vertical vegetation belts in margins of the high Tibetan plateau to glacial and subglacial (MIS3) climate changes is poor. To improve understanding, we have studied a continuous core extending back to MIS4 from Tengchong Qinghai volcanic lake in Yunnan Province. Identification of Quercus pollen by scanning electron microscopy showed that most of the abundant oak pollen in the core can be assigned to mountainous taxa of sclerophyllous Quercus living today on the high Tibetan plateau. Their current distribution indicates that the maximum downward shift of vertical vegetation belts during the last glacial period corresponds to a ∼5.5 °C drop in temperature, based on altitudinal lapse rates, in accordance with mean annual temperature (MAT) reconstruction from biomarkers in the same core. Our data clearly suggest that conditions were wet during MIS3, and humidity highest at 38–56 kyr. The wetting appears to have started after the Last Glacial Termination, indicating that the initial deglacial ISM intensification lagged behind rises in temperature and summer insolation. The highest charcoal concentrations and evidence of expansion of open vegetation coincide with the apparent onset of deglaciation (18-16 kyr). These observations indicate that this was the driest period, likely linked with reductions in the polar ice volume and delayed Tibetan glacier melting, which absorbed massive amounts of atmospheric heat and caused regional aridity. Our pollen data clearly correlate with rapid changes such as Younger Dryas and Heinrich Events, and marine records from the Indian Ocean, confirming climate teleconnection through ice volumes and global ocean circulation, and that the ISM is a key factor driving south-north transportation of energy and moisture. The multi-proxy data reveal with high confidence that the Holocene optimum in the region was between 9 and 4 kyr BP, and followed by weakening of the ISM accompanied by increasing anthropogenic disturbance of the vegetation.

No high Tibetan Plateau until the Neogene.

The Late Paleogene surface height and paleoenvironment for the core area of the Qinghai-Tibetan Plateau (QTP) remain critically unresolved. Here, we report the discovery of the youngest well-preserved fossil palm leaves from Tibet. They were recovered from the Late Paleogene (Chattian), ca. 25.5 ± 0.5 million years, paleolake sediments within the Lunpola Basin (32.033°N, 89.767°E), central QTP at a present elevation of 4655 m. The anatomy of palms renders them intrinsically susceptible to freezing, imposing upper bounds on their latitudinal and altitudinal distribution. Combined with model-determined paleoterrestrial lapse rates, this shows that a high plateau cannot have existed in the core of Tibet in the Paleogene. Instead, a deep paleovalley, whose floor was <2.3 km above mean sea level bounded by (>4 km) high mountain systems, formed a topographically highly varied landscape. This finding challenges prevailing views on tectonic processes, monsoon dynamics, and the evolution of Asian biodiversity.

Multiple episodes of fast exhumation since Cretaceous in southeast Tibet, revealed by low-temperature thermochronology

The southeast margin of the Tibetan plateau is characterized by deeply incised river valleys separated by a perched low relief landscape that gently descends from the high Tibetan plateau towards the southeast. When and how this unique landscape formed is debated. The onset of increased river incision is often interpreted as a proxy for the timing of surface uplift. Here, apatite and zircon (U–Th)/He and apatite fission track thermochronometries are employed to map the spatial and temporal pattern of exhumation in the region. Vertical profiles of granitic rocks were collected near Deqin (∼28.5°N) and Weixi (∼27.5°N). The two transects share a similar exhumation history, with two episodes of relatively fast exhumation (∼100–300 m/Myr) in the Cenozoic: during the Paleocene to Eocene (60–40 Ma) and Miocene to present (20–0 Ma), separated by an intervening period of slow exhumation. A pulse of moderate to high exhumation (70–300 m/Myr) during the mid- to late-Cretaceous (120–80 Ma) is also present in the data. However, the rate and total amount of exhumation near Deqin is larger than at Weixi and is especially pronounced in the interval between 20 Ma to present. We interpret this difference as possibly related to differences in erosion rates between the Lancang (Deqin) and the Jinsha (Weixi) rivers. The Paleocene to Eocene episode of fast exhumation is likely in response to early Cenozoic deformation along tectonic boundary structures, related to the transpressional collision of the Indian plate with this region. Pre-Miocene episodes of fast exhumation corroborate recent paleoaltimetric studies, which show that the southeast margin of the Tibetan plateau was elevated prior to the Oligocene.

Modeled Northern Hemisphere Autumn and Winter Climate Responses to Realistic Tibetan Plateau and Mongolia Snow Anomalies

Observational studies link a persistent dipole of autumn and winter snow cover anomalies over the Tibetan Plateau (TP) and Mongolia with winter Pacific–North American (PNA)-like atmospheric variations. This study investigates atmospheric responses to such snow forcings using multiple ensemble transient integrations of the CAM4 and CLM4.0 models. Model boundary conditions are based on climatological sea ice extent and sea surface temperature, and satellite observations of snow cover extent (SCE) and snow water equivalent (SWE) over the TP and Mongolia from October to March in 1997/98 (heavy TP and light Mongolia snow) and 1984/85 (light TP and heavy Mongolia snow), with model-derived SCE and SWE elsewhere. In various forcing experiments, the ensemble-mean difference between simulations with these two extreme snow states identifies local, distant, concurrent, and delayed climatic responses. The main atmospheric responses to a dipole of high TP and low Mongolia SCE persisting from October to March (versus the opposite extreme) are strong TP surface cooling, warming in the surrounding China and Mongolia region, and a winter positive PNA-like response. The localized response is maintained by persistent diabatic cooling or heating, and the remote PNA response results mainly from the increased horizontal eastward propagation of stationary Rossby wave energy due to persistent TP snow forcing and also a winter transient eddy feedback mechanism. With a less persistent dipole anomaly in autumn or winter only, local responses are similar depending on the specific anomalies, but the winter PNA-like response is nearly absent or noticeably reduced.

Early foraging settlement of the Tibetan Plateau highlands

We identified and dated 18 occupational events at eight sites dating to ~14.7–10.8kiloannum before present (ka BP) during a decade of archaeological survey and excavation on the northeastern high Tibetan Plateau (TP) >3200m. The ephemeral nature of the earliest sites suggests they were created by small foraging groups during very short stays. By ~12ka BP, larger foraging groups began to occupy sites >4000m leading to a more intensive occupation of the high TP after ~9.5ka BP. This archaeologically-based chronology closely matches genetically-based Tibetan population histories showing an early growth in population size and initial split with Han populations ~15–9ka BP, and a second spike in population growth during the early-mid Holocene. We found no evidence for occupation of the high TP prior to or during the Last Glacial Maximum (LGM), suggesting the initial separation of Tibetan and Han populations may have occurred at lower elevations in the TP margins or after the LGM in the high TP.

River recharge sources and the partitioning of catchment evapotranspiration fluxes as revealed by stable isotope signals in a typical high-elevation arid catchment

Catchment-scale hydrological cycles are expected to suffer more extremes under a background of climate change. Quantifying hydrological changes in high and remote areas is practically challenging. However, stable isotopes in river water can be seen to vary, dependent upon the combined influence exerted by recharge sources and local climatic conditions; the study of river water stable isotopes can therefore provide a meaningful method for delineating catchment-scale hydrological studies. In this study, we present high-resolution time series of river δ18O and d-excess values; additionally, we identify the seasonal dynamics of river recharge sources and major components of the catchment-scale water balance, together with precipitation and groundwater isotopes, and concurrent meteorological data recorded in Magazangbu catchment on the northwestern Tibetan Plateau (TP). Using isotopic analysis, and within a proportional framework, we partitioned the isotopic fractionation (E1) or non-fractionation (E2) from soil evaporation fluxes (Esoil) apparent in different processes, using NDVI (Normal Differential Vegetation Index) data collected by MODIS satellites to calculate the vegetation fractional coverage (VFC), and Global Land Data Assimilation System (GLDAS) records to determine evapotranspiration data (ET). Finally, the contributions made by each ET component (Esoil and plant transpiration) to total catchment ET were computed for the high and remote northwestern TP. Our results show that: (1) river δ18O values were high in summer and low in winter, while d-excess values displayed a contrary seasonal cycle; (2) for the monsoon period, precipitation contributed 60.6% to Magazangbu catchment runoff. Deeper groundwater was the main water source for the winter low base flow, and shallow groundwater or high elevation snowmelt was the principal component of the spring thaw and autumn freezing periods; and (3) a substantial proportion of Esoil (96.4% annually; 92.2% during monsoon) was consumed without isotopic fractionation (E2); plant transpiration (T) constituted less than half of total ET (41% annually, 29% during monsoon) in Magazangbu catchment. This calculation of river recharge sources and partitioning of catchment ET components using isotopic signals and MODIS NDVI data or GLDAS ET data provide new methods for hydrological studies in high and remote areas. These results provide important catchment-scale water-balance information which is very useful to climate models conducted in a high-elevation arid environment.

In-depth analysis of core methanogenic communities from high elevation permafrost-affected wetlands

The organic carbon of permafrost affected soils is receiving particular attention with respect to its fate and potential feedback to global warming. The structural and activity changes of methanogenic communities in the degrading permafrost-affected wetlands on the Tibetan Plateau can serve as fundamental elements for modelling feedback interaction of ecosystems to climate change. Hence, we aimed at anticipating if and how the rapid environmental changes occurring especially on the high altitude Tibetan platform will affect methanogenic communities. We identified methanogenic community composition, activity and abundance in wetland soils with different hydrological settings, permafrost extent and soil properties and pinpoint the environmental controls. We show that despite a pronounced natural gradient, the Tibetan high elevation wetland soils host a large methanogenic core microbiome. Hydrogenotrophic methanogens, in particular Methanoregula, and H2-dependent methanogenesis were overall dominant although acetoclastic methanogens in addition to hydrogenotrophs were among the dominating taxa in a minerotrophic fen. Tracing the Methanoregula community of the Tibetan Plateau using public databases revealed its global relevance in natural terrestrial habitats. Unlike the composition, the activity and abundance of methanogens varied strongly in the studied soils with higher values in alpine swamps than in alpine meadows. This study indicates that in the course of current wetland and permafrost degradation and the loss in soil moisture, a decrease in the methane production potential is expected on the high Tibetan Plateau but it will not lead to pronounced changes within the methanogenic community structure.

Permanent human occupation of the central Tibetan Plateau in the early Holocene.

Current models of the peopling of the higher-elevation zones of the Tibetan Plateau postulate that permanent occupation could only have been facilitated by an agricultural lifeway at ~3.6 thousand calibrated carbon-14 years before present. Here we report a reanalysis of the chronology of the Chusang site, located on the central Tibetan Plateau at an elevation of ~4270 meters above sea level. The minimum age of the site is fixed at ~7.4 thousand years (thorium-230/uranium dating), with a maximum age between ~8.20 and 12.67 thousand calibrated carbon-14 years before present (carbon-14 assays). Travel cost modeling and archaeological data suggest that the site was part of an annual, permanent, preagricultural occupation of the central plateau. These findings challenge current models of the occupation of the Tibetan Plateau.

Earliest record of Sinicuon in Zanda Basin, southern Tibet and implications for hypercarnivores in cold environments

The “out of Tibet” hypothesis envisions late Cenozoic Tibetan mammals acquiring adaptations to cold environments and being ancestral to several Eurasian megafaunal species in the Pleistocene. Here we report an early record of a hypercarnivorous canid, Sinicuon cf. Sinicuon dubius, from Zanda Basin in the Himalaya Range. Although the new record is recovered from reworked sediments in a Pleistocene alluvium, we can constrain the fossil to within a narrow age range of 3.8–3.4 Ma in the middle Pliocene. Presence of this hypercarnivorous canid in the Pliocene of Tibet, along with the recently described pantherine cat and arctic fox, suggests a predator guild with predominately carnivorous diet characteristic of modern arctic carnivorans such as the arctic fox and polar bear. Wintering in extremely cold climates may have been the cause of such adaptations. Sinicuon shows transitional morphology to modern hypercarnivorous hunting dogs in southern Asia (Cuon), suggesting linkage of the high Tibetan Plateau to the southern continents.

Optical turbulence profiling with single star SCIDAR technique

In order to characterize optical turbulence, we have developed a single star SCIDAR (SSS) for measurement of the distribution of C n 2 with height. The SSS consists of a 40 cm telescope and a CCD camera for fast sampling of stellar scintillation pattern. Spatiotemporal auto and cross-correlation functions of the single star images are computed, providing vertical profiles of optical turbulence intensity C n 2 (h) and wind speed V(h). Using this new SSS experiment, profiles of turbulence can be obtained from the ground to the top of atmosphere, allowing the determination of seeing, isoplanatic angle and coherence time. Detailed characteristics of atmospheric optical turbulence are important for active and passive imaging, astronomical site testing, adaptive optics, laser communications, target tracking and designation, and laser beam control. We plan to improve the robotization of the SSS to be able to use it routinely even under harsh weather and altitude conditions that we expect to encounter on the high Tibetan plateau or at Dome A in Antarctica. SSS will also be applied for the site testing campaign of the future Chinese extremely large telescope.