Search

Stable isotope paleoaltimetry has provided unprecedented insights into the topographic histories of many of the world's highest mountain ranges. However, on the Tibetan Plateau (TP), stable isotopes from paleosols generally yield much higher paleoaltitudes than those based on fossils. It is therefore essential when attempting to interpret accurately this region's paleoaltitudes that the empirical calibrations of local stable isotopes and the relations between them are established. Additionally, it is vital that careful estimations be made when estimate how different isotopes sourced from different areas may have been influenced by different controls. We present here 29 hydrogen isotopic values for leaf wax-derived n-alkanes (i.e., D values, and abundance-weighted average δD values of C and C) in surface soils, as well as the δD values of soil water ( δD) samples (totaling 22) from Mount Longmen (LM), on the eastern TP (altitude ~0.8-4.0 km above sea level (asl), a region climatically affected by the East Asian Monsoon (EAM). We compared our results with published data from Mount Gongga (GG). In addition, 47 river water samples, 55 spring water samples, and the daily and monthly summer precipitation records (from May to October, 2015) from two precipitation observation stations were collected along the GG transect for δD analysis. LM soil D values showed regional differences and responded strongly to altitude, varying from-160‰ to-219‰, with an altitudinal lapse rate (ALR) of-18‰ km ( R =0.83; p<0.0001; n=29). These D values appeared more enriched than those from the GG transect by ~40‰. We found that both the climate and moisture sources led to the differences observed in soil D values between the LM and GG transects. We found that, as a general rule, ε , ε and ε values (i.e., the isotopic fractionation of D corresponding to δD, δD and δD) increased with increasing altitude along both the LM and GG transects (up to 34‰and 50‰, respectively). Basing its research on a comparative study of D, δD, δD( δD) and δD, this paper discusses the effects of moisture recycling, glacier-fed meltwater, relative humidity ( RH), evapotranspiration ( ET), vegetation cover, latitude, topography and/or other factors on ε values. Clearly, if ε values at higher altitudes are calculated using smaller ε values from lower altitudes, the calculated paleowater δD values are going to be more depleted than the actual δD values, and any paleoaltitude would therefore be overestimated. [ABSTRACT FROM AUTHOR]

The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast, uplift of the Tibet-Himalaya orogen, and climate change in Asia. In this paper, we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates. Following a comparison of the different methods that have been used to constrain the initial timing of collision, we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event, and that paleomagnetism presents independent evidence as an alternative, reliable, and quantitative research method. In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca. 55 Ma and 50 Ma and progressively closed eastwards, more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone (YTSZ) between ca. 65 Ma and 63 Ma and then spreading both eastwards and westwards. While continental collision is a complicated process, including the processes of deformation, sedimentation, metamorphism, and magmatism, different researchers have tended to define the nature of this event based on their own understanding, an intuitive bias that has meant that its initial timing has remained controversial for decades. Here, we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods. [ABSTRACT FROM AUTHOR]

Scientific issues relevant to interactions between aerosols and the Asian monsoon climate were discussed and evaluated at the 33rd 'Forum of Science and Technology Frontiers' sponsored by the Department of Earth Sciences at the Chinese Academy of Sciences. Major results are summarized in this paper. The East Asian monsoon directly affects aerosol transport and provides a favorable background circulation for the occurrence and development of persistent fog-haze weather. Spatial features of aerosol transport and distribution are also influenced by the East Asian monsoon on seasonal, inter-annual, and decadal scales. High moisture levels in monsoon regions also affect aerosol optical and radiative properties. Observation analyses indicate that cloud physical properties and precipitation are significantly affected by aerosols in China with aerosols likely suppressing local light and moderate rainfall, and intensifying heavy rainfall in southeast coastal regions. However, the detailed mechanisms behind this pattern still need further exploration. The decadal variation in the East Asian monsoon strongly affects aerosol concentrations and their spatial patterns. The weakening monsoon circulation in recent decades has likely helped to increase regional aerosol concentrations. The substantial increase in Chinese air pollutants has likely decreased the temperature difference between land and sea, which favors intensification of the weakening monsoon circulation. Constructive suggestions regarding future studies on aerosols and monsoons were proposed in this forum and key uncertain issues were also discussed. [ABSTRACT FROM AUTHOR]

China's Loess Plateau is located at the edge of the Asian summer monsoon in a transition zone of climate and ecology. In the Loess Plateau, climate and environments change along with space, which has an obvious impact on the spatial distribution of surface energy fluxes. Because of scarce land-surface observation sites and short observation time in this area, previous studies have failed to fully understand the land-surface energy balance characteristics over the entire the Loess Plateau and their effect mechanisms. In this paper, we first test the simulation ability of the Community Land Model (CLM) model by comparing its simulated data with observed data. Based on the simulation data for the Loess Plateau over the past thirty years, we then analyze the spatial distribution of surface energy fluxes and compare the pattern differences between the area averages for the driest year and wettest year. Furthermore, we analyze the relationship between the spatial distribution of the components of the surface energy balance with longitude, latitude, altitude, precipitation and temperature. The main results are as follows: the spatial distribution of surface energy fluxes are significantly different, with the surface net radiation and sensible heat flux increasing from south to north and latent heat flux and soil heat flux decreasing from southeast to northwest. The sensible heat flux at the driest point is nearly twice as high as that at the wettest point, whereas the latent heat flux and soil heat flux at the driest point are half as much as that at the wettest point. The impact of variations of annual precipitation on the components of the surface energy balance is also obvious, and the maximum magnitude of the changes to the sensible heat flux and latent heat flux is nearly 30%. To a certain extent, geographical factors (including longitude, latitude, and altitude) and climate factors (including temperature and precipitation) affect the surface energy fluxes. However, the surface net radiation is more closely related to latitude and altitude, sensible heat flux is more closely related to the monsoon rainfall and latitude, and latent heat flux and soil heat flux are more closely related to the monsoon rainfall. [ABSTRACT FROM AUTHOR]

Sandstone-type uranium deposits (STUDs) are the most important global source of uranium. However, it is unclear why STUDs have a non-random distribution in time and space. It is generally thought that STUDs are formed by the circulation of groundwater in sandstone rocks. The groundwater is typically oxidized and sourced from local precipitation, which suggests the regional climate may have a role in the formation of STUDs. The groundwater circulation is mainly affected by basin evolution, which means that regional tectonism may also control the formation of STUDs. In this study, the author examined STUDs in Asia, and compiled previously reported ages for STUDs and compared these with the uplift history of the major ore-hosting regions and the late Mesozoic–Cenozoic climatic evolution of Asia. Apart from a few uranium deposits in the Transural region, most of the STUDs in Asia were formed during the Late Cretaceous to Quaternary, and can be classified into three stages: Late Cretaceous–early Paleogene (80–50 Ma; stage I), Oligocene–mid-Miocene (25–17 Ma; stage II), and late Miocene–present (8–0 Ma; stage III). The formation of STUDs in Asia was closely related to regional uplift caused by India–Eurasia collision, subduction of oceanic plates, and increased humidity during greenhouse climate periods and intensification of the Asian Monsoon. [ABSTRACT FROM AUTHOR]

As the second largest dust source on the globe, the tectonic and climatic evolution of continental Asia has an important impact on regional and global climate change. The West Pacific is the main sediment sink for eolian dust transported eastward from the Asian interior. Clay minerals, as the major fine-grained weathering products of continental rocks, can be readily transported by wind or currents over long distances and thus have been widely used in the reconstruction of paleoclimate and weathering history. However, the overall evolutionary tendency and response mechanism of clay mineral records over large spatial and long timescales across Asia remain unclear. Here, two continuous and high-resolution clay mineral records since 30 Ma were reconstructed from sediments at Deep Sea Drilling Program (DSDP) Sites 292 and 296 in the Philippine Sea. Clay minerals and Sr-Nd isotope compositions were used to constrain provenance and reconstruct the drying history of the dust source region since the Oligocene. The results show that the clay-sized detrital sediments in the Philippine Sea are a mixture of Asian eolian dust and volcanic materials from the West Pacific arcs. Based on the clay mineral compositions and eolian flux, we reveal that the Asian interior has been continuously drying since the late Oligocene and that stepwise enhanced aridification occurred at approximately 20, 14, 7, and 3 Ma. Compared with other regions of the world, the relative contents of illite and chlorite increased more dramatically in Asia during the late Cenozoic, and the inconsistency became more obvious at approximately 20 Ma. Since 3 Ma, illite and chlorite have increased consistently across the globe. Combined with the Asian tectonic and climatic history, we suggest that the increase in illite and chlorite from Asia between 20 and 3 Ma was mainly in response to the uplift of the Himalayan-Tibetan Plateau, whereas after 3 Ma, it was primarily controlled by global cooling driven by the expansion of the Arctic ice sheet. [ABSTRACT FROM AUTHOR]

Archaeological discoveries indicate that a variety of economic models have operated in the inland areas of Asia. One of these models, pastoral nomadism, differs from agriculture, agro-pastoral, and settled pastoralism in terms of cattle-breeding, cultivation and manufacture. Pastoral nomadism is a livestock-breeding management mode of production, in which the stock is fed by uninterrupted moving in a large geographical area. The Eurasian Steppe, which includes the cold forest-steppe area in the north and the semi-arid desert-steppe in the south, is the major region in which the ancient nomadic population flourished. Because of the absence of both intrinsic motivation and external pressure for the transition to pastoral nomadism, early animal husbandry economy in the forest-steppe area could not have developed into the initial pastoral nomadic economy; instead, the pastoral nomadic economy emerged from the agro-pastoral economy in the semi-arid desert-steppe. These agro-pastoral people were forced to minimize the scale of agriculture and sedentary pastoralism and to turn to a nomadic lifestyle, with the internal cause being a shortage of feed resources caused by expansion of the human population and livestock, with the added external pressure of climatic and environmental deterioration. From archaeological findings, the eastern Tianshan area in Xinjiang, China, was a major region for the emergence of the early pastoral nomadic economy. The main evidence for this conclusion is a series of pastoral nomadic settlement sites in the northern and southern piedmonts of the Tianshan Mountains, which display settlement conditions, resources and environments entirely different from those of agricultural and agro-pastoral settlements elsewhere. [ABSTRACT FROM AUTHOR]

In the context of global warming, glaciers in the Asian High Mountains (AHMs) are shrinking at an accelerating rate. Projecting their future change is helpful for understanding the hydrological and climatic effects related to glacier retreat. Here, we projected glacier change in the AHMs from 1979 to 2100 under shared socioeconomic pathway (SSP) scenarios from the perspective of temperature, equilibrium-line altitude (ELA), and accumulation area. The annual mean temperature in the AHMs increased by 1.26°C from 1979 to 2014, corresponding to an increase of 210 m in the mean ELA and a decrease of 1.7×104 km2 in the glacier accumulation area. Under the SSP2-4.5 (SSP5-8.5) scenario, the annual mean temperature in the AHMs would increase by 2.84°C (3.38°C) in 2040–2060 relative to that in 1850–1900, leading to the mean ELA reaching an elevation of 5661 m (5777 m). The accumulation area in the AHMs decreased by 46.3% from 1995 to 2014 and was projected to decrease by 60.1% in 2040–2060. Moreover, the annual mean temperature in the AHMs was projected to increase by 3.76°C (6.44°C) in 2080–2100 relative to that in 1850–1900, corresponding to the ELA reaching an elevation of 5821 m (6245 m) and the accumulation area decreasing to 1.8×104 km2 (0.5×104 km2). These data suggest that the conditions for glacier development will disappear in most of the AHMs, except for extreme high-altitude regions in the Tianshan, Pamir, and Himalaya Mountains. Under the SSP2-4.5 (SSP5-8.5) scenario, when the global mean temperature increases 1.5°C (2°C) above pre-industrial levels, the annual mean temperature will increase by 2.12°C (2.86°C) and the accumulation area will decrease by 15% (48%) in the AHMs compared with that in 1995–2015. Therefore, a 1.5°C increase in global warming would keep 40% more of the glacial accumulation area (1.5×104 km2) in the AHMs compared to a 2°C increase in global warming. [ABSTRACT FROM AUTHOR]

Quantifying the density contrasts of the Earth's inner core boundary (ICB) is crucial to understand core-mantle coupling and the generation of the geodynamo. The PKiKP/PcP amplitude ratio is commonly used to obtain the density contrast at the ICB, but its applications are limited by scattered observed data. In this study, we selected the PKiKP and PcP phases reflected at the same region of inner-core and core-mantle boundaries beneath Northeast Asia from different earthquakes for the first time, and the observations suggested that the PKiKP/PcP amplitude ratio is widely scattered. We also compared the PKiKP and PcP amplitudes, which demonstrated that the scatter cannot be attributed only to ICB anomalies but might also arise from raypath differences and heterogeneities throughout the crust and mantle. By fitting the observed PKiKP/PcP amplitude ratio, we obtained a density contrast of approximately 0.65 g cm−3 and a compressional velocity contrast of approximately 0.87 km s−1 at the ICB beneath Northeast Asia. The larger contrast values indicate the possible occurrence of local crystallization occurring at the inner core surface. [ABSTRACT FROM AUTHOR]

The dynamic process of ocean-continent subduction depends on not only the properties of the subducting oceanic plate, but also the characteristics and state of the overriding continental plate. Numerical models conducted to date have mostly focused on the oceanic lithosphere in this regard; research on the properties of overriding continental lithosphere remains relatively limited, especially the influence of its thermal state on subduction dynamics. Here we explored the performance of continental lithosphere with different thermal states during the subduction process using two-dimensional thermal-mechanical modeling and systematically investigated the effects of the thermal state of overriding continental plate, the age of subducting oceanic plate, and relative convergence rate on subduction dynamics. Modeling results show that: (1) When the geothermal gradient of continental crust is low (between 10 and 15 °C km−1), the oceanic plate first subducts at a low angle. As subduction continues, the slab dip gradually increases and the slab begins to retreat rapidly driven by its negative buoyancy, opening an ocean basin ranging from 600 to 1100 km in width. This leads to the decoupling between the overriding continental plate and oceanic plate. As the trench retreat continues, the horizontal deviatoric stress inside the overriding continental crust alternates between being positive and negative in a local area. Thinning of the overriding lithosphere mainly occurs at the region adjacent to the subduction zone, where the surface experiences significant subsidence. (2) When the geothermal gradient of continental crust is higher (greater than 15 °C km−1), oceanic plate retreat causes the overriding continental plate to be strongly stretched. In this case, the trench retreat distance decreases and the width of the ocean basin also reduces by between 100 and 1000 km. The horizontal deviatoric stress inside the whole overriding continental crust first manifests as compression and then changes into extension, which causes the surface to first uplift and then slowly subside. (3) Increasing the age of oceanic lithosphere accelerates trench retreat and promotes overriding plate thinning. (4) An advancing overriding continental plate slows down trench retreat. In cases where the geothermal gradient of continental crust is greater than 17.5 °C km−1, the hot continental crust experiences gravitational collapse and is overthrusted onto oceanic lithosphere, resulting in slow trench retreat. We analyzed the subduction process of the western Paleo-Pacific Plate in the Early Cretaceous based on our modeling results and discussed its possible control on the tectonic evolution of the rift basins in east Asia. We suggest that the development of a wide rift basin system on the Amurian Superterrane in the Early Cretaceous was likely related to slow trench retreat and the collapse of the hot crust, and the formation of a series of passive rift basins in the North China Craton was likely caused by the relatively cold thermal state of the lithosphere and the rapid retreat of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

Mammals are the most important elements in Cenozoic terrestrial ecosystem. The composition and the character of a mammalian fauna are controlled by evolution time and evolutionary rate. Here we took 50 Asian Paleogene mammalian faunas as representatives and applied Bayesian Tip-dating method to infer the relationships and divergence times among these faunas. Based on the results of Bayesian Tip-dating analyses, we discussed the correlation between the paleogeographic changes and the mammalian fauna turn-overs. Compared with the traditional fauna correlation and sorting, Bayesian Tip-dating analyses revealed more detailed similarities reflected via the divergence times among the 50 faunas. We discovered that the early Eocene mammalian fauna, which firstly appeared in India subcontinent, is similar to the faunas of the same age in other parts of Asia. It is likely that a passage for the mammalian dispersal was formed before early Eocene. Bayesian inferring suggests that the first appearance of the dispersal passage is during 64.8–61.3 Ma. This time window is close to the time estimation for the initial time of India-Asia collision. During 57.1–47.2 Ma, India subcontinent probably had a habitat different from the main part of Asia, as it was reflected from the composition of the mammalian faunas. It is probably correlated with the uplifted Gangdese Mountain and shallow seas and lowlands on both sides of the collision region. The very remote divergence time (64.8 Ma) estimated by Bayesian inferring reflects the mammalian fauna turnover during the Eocene-Oligocene transition, obviously affected by the global cooling. Till the end of Oligocene, the Arabic Peninsula and Asian mainland remained separated and the mammalian faunas did not show clear connection. [ABSTRACT FROM AUTHOR]

While a general concensus has recently been reached as to the causal relationship between the subduction of the west Pacific plate and the destruction of the North China Craton, a number of important questions remain to answer, including the initial subduction of west Pacific plate beneath the eastern Asian continent, the position of west Pacific subduction zone during the peak period of decratonization (i.e., Early Cretaceous), the formation age of the big mantle wedge under eastern Asia, and the fate of the subducted Pacific slab. Integration of available data suggests that the subduction of the western Pacific plate was initiated as early as Early Jurrasic and the subduction zone was situated to 2,200 km west of the present-day trench in the Early Creataceous, as a result of eastward migration of the Asian continent over a distance of ca. 900 km since the Early Cretaceous. The retreat of the subducting west Pacific plate started ∼145 Ma ago, corresponding to the initial formation of the big mantle wedge system in the Early Cretaceous. The subduction of the Pacific slab excerted severe influence on the North China Craton most likely through material and energy echange between the big mantle wedge and overlying cratonic lithosphere. The evolution history of the west Pacific plate was reconstructed based on tectonic events. This allows to propose that the causes of phases A and B for the Yanshanian orogeny were respectively related to rapid low-angle subduction and to lowering subduction angle of the west Pacific plate. At ca. 130–120 Ma, the subduction of the west Pacific plate was characterized by increasing subducting angle, slab rollback and rapid trench retreat, leading to the final stagnation of the subducting slab within the mantle transition zone. This process may have significantly affected the physical property and viscosity of the mantle wedge above the stagnant slab, resulting in non-steady mantle flows. The ingression of slab-released melts/fluids would significantly lower the viscosity of the mantle wedge and overlying lithosphere, inducing decratonization. This study yields important bearings on the relationship between the subduction of the west Pacific plate and the evolution of the lithospheric mantle beneath the North China Craton. [ABSTRACT FROM AUTHOR]

Monsoon and arid regions in the Asia-Africa-Australia (A-A-A) realm occupy more than 60% of the total area of these continents. Geological evidence showed that significant changes occurred to the A-A-A environments of the monsoon and arid regions, the land-ocean configuration in the Eastern Hemisphere, and the topography of the Tibetan Plateau (TP) in the Cenozoic. Motivated by this background, numerical experiments for 5 typical geological periods during the Cenozoic were conducted using a coupled ocean-atmosphere general circulation model to systemically explore the formations and evolutionary histories of the Cenozoic A-A-A monsoon and arid regions under the influences of continental drift and plateau uplift. Results of the numerical experiments indicate that the timings and causes of the formations of monsoon and arid regions in the A-A-A realm were very different. The northern and southern African monsoons existed during the mid-Paleocene, while the South Asian monsoon appeared in the Eocene after the Indian Subcontinent moved into the tropical Northern Hemisphere. In contrast, the East Asian monsoon and northern Australian monsoon were established much later in the Miocene. The establishment of the tropical monsoons in northern and southern Africa, South Asia, and Australia were determined by both the continental drift and seasonal migration of the Inter-Tropical Convergence Zone (ITCZ), while the position and height of the TP were the key factor for the establishment of the East Asian monsoon. The presence of the subtropical arid regions in northern and southern Africa, Asia, and Australia depended on the positions of the continents and the control of the planetary scale subtropical high pressure zones, while the arid regions in the Arabian Peninsula and West Asia were closely related to the retreat of the Paratethys Sea. The formation of the mid-latitude arid region in the Asian interior, on the other hand, was the consequence of the uplift of the TP. These results from this study provide insight to the important roles played by the earth's tectonic boundary conditions in the formations and evolutions of regional climates during geological times. [ABSTRACT FROM AUTHOR]

The nature and dynamics of climate change in central Asia since the late Pleistocene are controversial. Moreover, most of the published studies focus mainly on the evolution of moisture conditions, and there have been few attempts to address changes in seasonality. In this study, records of δ13Corg, TOC, TN, C/N and grain size were obtained from lacustrine sediments at Yili Basin, Xinjiang, NW China. Our aim was to reconstruct the trend in seasonality of precipitation from the last glaciation to the Holocene. The organic matter content of the sediments is derived predominantly from terrestrial plants. The δ13Corg values vary from -19.4% to -24.8%, indicating that the vegetation was dominated by C3 plants. Winter-spring precipitation is identified as the factor determining the relative proportions of C3 and C4 plants in the region. A negative trend in δ13Corg corresponding to an increase in the relative abundance of C3 plants indicate a trend of increasing winter-spring precipitation from the last glaciation to the Holocene. The increased incidence of wintertime storms in the interior of Asia is suggested to result in the increase of winterspring precipitation in the Holocene. [ABSTRACT FROM AUTHOR]

The Upper Triassic Langjiexue Group in southeastern Tibet has long been an enigmatic geological unit. It belongs tectonically to the northern Tethys Himalayan zone, but provenance signatures of the detritus it contains are significantly different from those of typical Tethys Himalayan sandstones. Because the Langjiexue Group is everywhere in fault contact with Tethys Himalayan strata, its original paleogeographic position has remained controversial for a long time. According to some researchers, the Langjiexue Group was deposited onto the northern edge of the Indian passive continental margin, whereas others interpreted it as an independent block accreted to the northern Indian margin only during final India-Asia convergence and collision in the Paleocene. This study compares the Langjiexue Group and coeval Upper Triassic strata of the southern Tethys Himalayan zone (Qulonggongba Formation). Our new provenance data indicate that Qulonggongba Formation sandstones contain common felsic volcanic rock fragments, minor plagioclase, and euhedral to subhedral zircon grains yielding Late Paleozoic to Triassic ages. These provenance features compare well with those of the Langjiexue Group. Because the Qulonggongba Formation certainly belongs to the Tethys Himalayan zone, the provenance similarity with the Langjiexue Group indicates that the latter is also an in situ Tethys Himalayan sedimentary sequence rather than part of an exotic block. Volcanic detritus including Late Paleozoic to Triassic zircon grains in both Langjiexue Group and Qulonggongba Formation are interpreted to have been derived from the distant Gondwanide orogen generated by Pan-Pacific subduction beneath the southeastern margin of Gondwana. The Qulonggongba Formation, deposited above marlstones of the lower Upper Triassic Tulong Group, is overlain by India-derived coastal quartzose sandstones of the uppermost Triassic Derirong Formation. Deposition of both the Qulonggongba Formation and the Langjiexue Group were most likely controlled by regional tectonism, possibly a rifting event along the northern margin of Gondwana. [ABSTRACT FROM AUTHOR]

A long-term perspective on the spatial variation of the northern boundary of the East Asian summer monsoon (EASM) and the related physical mechanisms is important for understanding past climate change in Asia and for predicting future changes. However, most of the meteorological definitions of the EASM northern boundary do not correspond well to the actual geographical environment, which is problematic for paleoclimatic research. Here, we use monthly CMAP and GPCP precipitation data to define a new EASM northern boundary index by using the concept of the global monsoon, which is readily applicable to paleoclimatic research. The results show that the distribution of the 2 mm day precipitation isoline (i.e., 300 mm precipitation) has a good relationship with the spatial distribution of modern land cover types, the transitional climate zone and the potential natural vegetation types, in China. The locations of the precipitation isolines also correspond well to the locations of major shifts in wind direction. These results suggest that the 2 mm day isoline has a clear physical significance since the climatic, ecological, and geographical boundary can be used as the northern boundary index of the EASM (which we call the climatological northern boundary index). The index depicts the northeast-southwest orientation of the climatological (1981−2010) EASM northern boundary, along the eastern part of the Qilian Mountains-southern foothills of the Helan Mountains-Daqing Mountains-western margin of the Greater Khingan Range, from west to east across Northwest and Northeast China. The interannual change of the EASM northern boundary from 1980 to 2015 covers the central part of Gansu, the northern part of Ningxia, the eastern part of Inner Mongolia and the northeastern region in China. It can extend northward to the border between China and Mongolia and retreat southward to Shangdong-central Henan. There is a 200−700 km fluctuation range of the interannual EASM northern boundaries around the locations of the climatological northern boundary. In addition, the spatial variation of the interannual EASM northern boundaries gradually increases from west to east, whereas the trend of north-south fluctuations maintains a roughly consistent location in different regions. [ABSTRACT FROM AUTHOR]

The Asian summer monsoon (ASM) anticyclone isolates upper-tropospheric air within the interior of the anticyclone from the outside. Forward trajectory simulations in previous studies have shown that much of the air within the ASM anticyclone can be trapped for up to two or three weeks, not only laterally but also vertically. Here, we investigate the locations of exit points for upper-tropospheric air trapped within the ASM anticyclone, especially the preferred tropopause-crossing locations, using a 3-dimensional trajectory model. Forward trajectory calculations show two-thirds of the air crosses the tropopause at the southern part of the anticyclone via upward diabatic transport. Furthermore, some air crosses at northern and eastern parts via isentropic shedding, but air crosses rarely through the center of the anticyclone. However, calculations also show that many stratospheric parcels within the anticyclone are traceable from the upper-tropospheric anticyclone. This implies they cannot break through the tropopause directly overhead but instead enter the stratosphere via other entry points. [ABSTRACT FROM AUTHOR]

There exist three mainstream opinions regarding the timing of the initial collision between the Indian and Eurasian continents, namely, 65±5, 45±5, and 30±5 Ma. Five criteria are proposed for determining which tectonic event was related to the initial collision between India and Asia: the rapid decrease in the rate of plate motion, the cessation of magmatic activity originating from the subduction of oceanic crust, the end of sedimentation of oceanic facies, the occurrence of intracontinental deformation, and the exchange of sediments sourced from two continents. These criteria are used to constrain the nature of these tectonic events. It is proposed that the 65±5 Ma tectonic event is consistent with some of the criteria, but the upshot of this model is that the magmatic activity originating from the Tethyan subduction since the Mesozoic restarted along the southern margin of the Asian continent in this time after a brief calm, implying that the subduction of the Neotethys slab was still taking place. The magmatic activity that occurred along the southern margin of the Asian continent had a 7-Myr break during 72-65 Ma, which in this study is interpreted as having resulted from tectonic transformation from subduction to transform faulting, indicating that the convergence between the Indian and Asian continents was once dominated by strike-slip motion. The 30±5 Ma tectonic event resulted in the uplift of the Tibetan Plateau, which was related to the late stage of the convergence between these two continents, namely, a hard collision. The 45±5 Ma tectonic event is in accordance with most of the criteria, corresponding to the initial collision between these two continents. [ABSTRACT FROM AUTHOR]

The estimation of carbon exchange between ecosystems and the atmosphere suffers unavoidable data gaps in eddy-covariance technique, especially for short-living and fast-growing croplands. In this study we developed a modified gap-filling scheme introducing a leaf area index factor as the vegetation status information based on the conventional light response function for two East-Asian cropland sites (rice and potatoes). This scheme's performance is comparable to the conventional time window scheme, but has the advantage when the gaps are large compared to the total length of the time series. To investigate how the time binning approach performs for fast-growing croplands, we tested different widths of the time window, showing that a four-day window for the potato field and an eight-day time window for the rice field perform the best. The insufficiency of the conventional temperature binning approach was explained as well as the influence of vapor pressure deficit. We found that vapor pressure deficit plays a minor role in both the potato and the rice fields under Asian monsoon weather conditions with the exception of the early pre-monsoon growing stage of the potatoes. Consequently, we recommend using the conventional time-window scheme together with our new leaf-light response function to fill data gaps of net ecosystem exchange in fast-growing croplands. [ABSTRACT FROM AUTHOR]

The term 'westerlies-dominated climatic regime' describes the pattern of precipitation/moisture variations between westerlies-dominated arid Central Asia (ACA) and mid-latitude monsoon-dominated Asia on decadal to multi-millennial time scales. However, no attempts have been made to define its core region and the possible physical mechanisms responsible during the period of instrumental observations. The present study investigates the spatiotemporal variations of summer and winter precipitation on interannual to decadal time scales over mid-latitudes of the Eurasian continent using Empirical Orthogonal Function (EOF) analysis. Our results suggest the existence of an opposing pattern of summer precipitation variations between ACA and mid-latitude monsoon-dominated Asia and Mediterranean on decadal time scales. Based on these results, the core region influenced by the westerlies is outlined, including arid central Asia and Xinjiang in China (36°-54°N, 50°-90°E). By using monthly NCEP-NCAR reanalysis, the relationship between the 'westerlies-dominated climatic regime' and atmospheric circulation were also analyzed. The combination of the zonal climatic teleconnection pattern and anomalous Indian summer monsoon precipitation (ISMP) causes the precipitation characteristics of the 'westerlies-dominated climatic regime' precipitation pattern. In addition, the Atlantic Multidecadal Oscillation (AMO) may also have an important effect on the 'westerlies-dominated climatic regime'. [ABSTRACT FROM AUTHOR]