Dunes are widely distributed on Earth and other extraterrestrial bodies, yet relatively little is known about what controls their maximum size. Earth's megadunes (>100 m tall) have traditionally been attributed to constraints including atmospheric boundary layer depth, substrate bedrock type, and sediment supply. However, global mapping results presented here reveal that megadunes preferentially occur near mountains and within dunefield depressions. Megadune height-spacing transition from a power-law relationship to a near-normal distribution, and their aspect ratio (R-a) with height shifts from inverse to direct proportionality. To investigate their underlying formation mechanisms, we focus on how topography influences megadune development under conditions of sufficient sand supply and constant wind regime, using a dune simulation model. Simulation results indicate that both positive (mountain-like) and negative (basin-shaped) topographies generate abrupt shear stress gradients, triggering rapid localized sand accumulation. Compared to gradual evolution on flat terrains, mountain-depression settings accelerate the dune coarsening process and megadune growth through enhanced sand flux convergence and increased collision rates between migrating dunes. Critically, surrounding topography modifies wind regimes, elevating dune aspect ratios (R-a) as shear stress intensifies. Our proposed topography-aerodynamics-sediment redistribution mechanism for megadune formation on Earth and other extraterrestrial bodies demonstrates that terrain-induced wind regime heterogeneity is the fundamental control governing the formation and evolution of massive aeolian landforms.

To elucidate the relative influences of different-scale forcing factors on climate change, in particular on relative aridity, we developed a 40,000-year-long record of lake-level fluctuations using the high-resolution sedimentary archive from Huguangyan Maar Lake (HML) in the Leizhou Peninsula, southern China. Analyses on grain size and total organic matter revealed that lake levels were the lowest during the Last Glacial Maximum (LGM), while minor variations occurred during Heinrich events, and more pronounced oscillations characterized the Younger Dryas (YD). Following the YD, lake levels gradually recovered, peaking around 8000 years ago before declining to present-day levels. Our data unequivocally demonstrate that the lake-level decline during the LGM was the most extreme observed throughout the 40,000-year long record, exceeding the magnitude of other millennial-scale climate events. Crucially, despite orbital forcing imposing two distinct periods of both minimum and maximum solar insolation over the 40,000 year-long intervals, the drastic hydrological changes—total desiccation and peak water levels—each occurred only once. Total desiccation uniquely coincided with the LGM, while peak water levels were confined to the early-middle Holocene. These findings suggest that while variations in solar insolation and the Atlantic Meridional Overturning Circulation (AMOC) modulate monsoon rainfall, the extensive glacial expansion during the LGM played a significant role in southern China's extreme aridity. The LGM thus represents the driest period in southern China over the past 40,000 years, indicating that this pronounced aridity resulted from the synergistic interplay of large ice volume and low solar insolation.

Deserts' paleoenvironmental records not only reveal environmental changes during geological periods but also provide a scientific basis for addressing and predicting their response pathways to the ongoing global warming. Nevertheless, comparative studies examining the variability of dune activity in the deserts of northern China under different warming periods triggered by natural and anthropogenic factors remain scarce. Leveraging the Coupled Model Intercomparison Project Phase 6 multimodel ensemble, this study investigates the spatial patterns and underlying climatic drivers of dune activity in the deserts of northern China across distinct climatic epochs: the mid-Holocene (MH) and scenarios under three different future Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5). The results reveal different spatial heterogeneity of dune activity in the deserts of northern China during MH and future scenarios. During the MH, dune activity decreased significantly in the eastern deserts while intensifying in the west. However, under the future scenarios, this trend would be reversed, with enhanced dune activity in the east and diminished activity in the west. The spatial disparities are directly attributable to changes in surface effective moisture and near-surface wind speed induced by large-scale atmospheric circulations. In the eastern sandy lands, a stronger East Asian Summer Monsoon increased surface moisture and limited aeolian processes during MH, while higher evaporation and stronger near-surface wind in the east would intensify dune activity under future scenarios. In the western sand seas, reduced precipitation due to weaker westerlies enhanced dune activity during MH, while increased precipitation and reduced near-surface wind speeds under future scenarios would lead to decrease in dune activity.

Grassland soils in alpine regions of the Qinghai-Tibetan Plateau (QTP) constitute a crucial component of the QTP ecosystem. Understanding their formation requires accurate chronologies and insights into key pedogenic processes. This study applied multi-grain (MG) and single-grain (SG) post-infrared infrared stimulated luminescence (pIRIR) dating to alpine grassland soils around the Gonghe Basin in the northeastern (NE) QTP to gain new insights into their ages and pedogenic processes. In addition, C-14 dating was performed on soil organic matter, with the resulting C-14 ages compared with optical ages to evaluate their reliability for soil age determination. pIRIR dating showed that bioturbation-induced soil reworking is common in alpine grassland soils. SG pIRIR dating allows more accurate soil age estimation by effectively identifying grains associated with original deposition and pedoturbation, while C-14 dating yields underestimated ages due to younger carbon contamination. We proposed an SG pIRIR-based approach that can be applied to alpine grassland soils to constrain their ages and quantify bioturbation. Combined with a synthesis of regional alpine loess and palaeosol/soil chronologies and a comparison with regional climatic records, the influence of climate on alpine soil pedogenesis and bioturbation was explored. Our results showed that pedogenesis in the studied profiles started at similar to 11-5 ka, following an aeolian dust aggradation pedogenic mode. The intensity of soil mixing decreases with depth, with the most intensive mixing occurring in a near-surface zone of tens of centimetres depth. Integrating SG dating results with a new conceptual model, we for the first time estimated the recent and past downward soil mixing rates and the timing of intensified bioturbation for alpine soils on the QTP. Chronological synthesis revealed that alpine soil development on the NE-QTP was most pronounced since similar to 6 ka. Effective moisture is a key factor that affects both soil development and bioturbation intensity in alpine grassland soils.

Yardangs are streamlined ridges that form in arid environments mainly driven by the aeolian process. However, the development and evolution of yardangs could also involve feedback among other factors like the substrate, underlying topography, and rainfall. Currently, there is limited consensus on how these factors affect yardang development at the landscape scale. In this work, based on very high spatial resolution remotely sensed imagery and deep learning techniques, we conducted a comprehensive mapping of yardangs across the immense yardang fields in the Qaidam Basin, NW China. Then we used the yardang coverage that is the percentage of yardang areas per gridded zone, to estimate the yardang abundance and its spatial distribution across the study site. Then the partial least squares-structural equation modeling (PLS-SEM) was employed to quantitatively analyze the relationships among yardang coverage and wind force (Wind), substrate weakness (Substrate), underlying topography complexity (Topography), and rainfall force (Rainfall). The results indicated that Rainfall had a significant constraining effect on yardang development, accounting for 34 % of the total effect in the model. In contrast, Substrate, Wind, and Topography exhibited positive effects on yardang development, contributing 31 %, 20 %, and 15 % of the total effect, respectively. A spatial clustering of yardang fields was then carried out using the response-based unit segmentation (REBUS) algorithm, demonstrating the spatial heterogeneity of how these factors contribute to yardang development in different regions. This study improved our understanding of the mechanisms of yardang formation and evolution under the control of multiple factors.

Dunes react quickly to climatic changes, with the main drivers being the dominating wind regime (e.g. magnitude and direction), precipitation, and temperature. Further, human impact can alter dune movement by fixation of active dunes through greening projects, or reactivation of stationary ones through overgrazing by animals. The north-eastern Tibetan Plateau shows a high variability of climatic parameters like wind, temperature, and precipitation within a high elevation environment, situated between the mid-latitude westerlies and the East Asian Summer monsoon. The presented studies asses active barchan dunes in different climatic settings, from the arid southern margins of the Badain Jaran Desert, to the humid Zoige Basin.Since climate stations on the Tibetan Plateau are rare and their measurements often cover only a short time span, climatic changes were studied from ERA-5 reanalysis data, dating back to the 1950s. These metrics were processed via cloud computing, using Google Earth Engine, and were then compared to dune migration rates, which were deduced from optical satellite imagery. Here, the CORONA KH-4B images from the late 1960s, the Landsat archives, and up-to-date high resolution data (GeoEye and WorldView) were used. The Normalized Difference Vegetation Index (NDVI) was implemented to observe changes in vegetation. As a newly tested metric, dune field density changes were calculated, in order to investigate dynamics of dense dune field setting.Over 500 dunes were mapped and analyzed in total within four focus-areas for comparative purposes. The results highlight a wide range of different behavioral patterns of dunes within the environment of the north-eastern Tibetan Plateau. This showcases how dunes can be influenced by and linked to climatic changes.

Dune fields are self-organized systems shaped by nonlinear and dissipative boundary conditions. Decoding their environmental history and linking the spatial and temporal memories are challenging because the signals of environmental forcings that propagate across horizontal landscapes and get archived into vertical strata are susceptible to being shredded, reorganized, and even erased. Here we provide a real-world prototype of the coupling between spatial and temporal signals in the Wulanbuhe and Kubuqi deserts of northern China, using geospatial analysis, chrono-geographic nearest neighbor-based paleoenvironmental reconstruction, and numerical simulation. We find that the two supposedly independent deserts share similarly abrupt transitions in sand accumulation thickness near a reconstructed paleolake shoreline, suggesting their coevolution with the nearby mega paleolake. This transition in dune-field patterns manifests the history of boundary condition changes triggered by the hydrological system alterations. Our study demonstrates that a detailed investigation of spatial patterns in dune landscapes can help reconstruct the history of boundary condition changes, applicable not only on Earth but also on extraterrestrial planets.

Identifying the provenance of aeolian sand is crucial to unraveling the formation and evolution processes of dunes commonly occurring in arid and semi-arid regions. This study presents comprehensive grain size and geochemical data for the mobile dunes (n = 22), vegetated dunes, i.e., dunes stabilized or semi-stabilized by vegetation (n = 26), and fluvial sand samples (n = 10) in the Wulanbuhe (a.k.a. Ulan Buh) Desert (WD) of northwestern China. Major-elemental data and the Al2O3 - CaO*+Na2O+K2O - SiO2 (A-CNK-Si) diagram indicates that dune sands have undergone sedimentary sorting during aeolian transport, although chemical weathering was weak. Spatial variations in grain size and geochemical characteristics within the WD dune sands are not systematically observed, indicating a heterogeneous mixture of materials from diverse sources. Based on the end-members mixing model, this study found differences in the sand sources between the mobile and vegetated dunes in the WD. The bedrock detritus from the surrounding mountains is a dominant source (60 %) of the mobile dune sands in the WD, followed by the paleo-lacustrine deposits from the desert hinterlands (24 %) and the sediments of alluvial fans from the upwind areas (16 %). In contrast, the sands of vegetated dunes were derived from the bedrock detritus (48 %), alluvial fans from the upwind side (32 %), and paleo-lacustrine deposit (20 %), respectively. Our findings confirm that the presence of vegetation on the dune surface influences sediment grain-size characteristics, which in turn affects aeolian erosion and deposition processes, leading to variations in sand source materials.

Arid and semiarid regions are environmentally vulnerable to global warming. Thus, studying their environmental history during warm periods (e.g., the Last Interglacial, LIG) is crucial for understanding their future changes too. The West Gobi Desert is a transitional zone influenced by the westerlies and the East Asian monsoon system. Therefore, the variation in atmospheric circulation profoundly affects its water vapor transport and landscape evolution. Due to the scarcity of continuous records, the moisture transport process remains ambiguous, which limits further research on paleolake evolution and aeolian activity. Here, we combine paleoclimate simulations from the Coupled Model Intercomparison Project (CMIP6)-Paleoclimate Modeling Intercomparison Project 4 (PMIP4) and geological records to clarify the water vapor transport pathways and aeolian activity in the West Gobi Desert during the LIG, compared to the reference period (the piControl). Our results show that increased rainfall and meltwater were possible supplies for surface water during the LIG and were associated with enhanced East Asian summer monsoon and higher surface air temperatures. Concomitantly, weakening aeolian activity and dormant dune fields occurred in the West Gobi Desert, resulting from higher surface moisture content and weaker surface wind regimes associated with the weakening westerlies and East Asian winter monsoon. Notably, the limited weakening of aeolian activity that occurred in the LIG winter and spring was caused by weaker surface wind and deteriorating surface moisture conditions, while the significant dormancy of dune fields in the LIG summer and autumn was initiated by the combined effects of ameliorative surface moisture conditions and lower surface wind speed.

Sand dunes are a landscape feature with a quick response time to climate change and human influences (e.g. grazing, greening projects, and fixation structures). Their migration rates and their development can help to gather information about changing environmental conditions over time. The Source Area of the Yellow River (SAYR), located upon the Tibetan Plateau, is highly complex with topographical, hydrological, and climatological influences on active dunes, making it a good study area for these interactions. Based on remote sensing datasets, spanning the last 54 years, 415 dunes were mapped for migration rate calculations. Further, climate data from ERA -5 reanalysis and a local climate station was used to assess their changes within a changing climate. Generally, dune migration rates are rather slow with an average of 3.62 m y -1 . In accordance, the averaged resultant drift potential (RDP) values are lower than 10 m3/s - 3 (4-). Further, we assessed the density development of the main active barchan dune field in direct premise of the Yellow River. Throughout the past 54 years, we observed the emergence of more than 5 new barchans per square kilometer. This increase is likely attributed to higher sand flux from the Yellow River, which has resulted from increased discharge due to declining snowfall and rising precipitation levels.

The yardang-dune coexistence and the control of yardangs on dune formation reveal the joint action of wind erosion and deposition. Yardangs exhibit distinctive characteristics of streamlining and clustering, which apply unique and complicated impacts on the wind field and sand transport. However, previous studies lack systematic investigation on how yardangs exert control over dune morphology, and the intricate wind dynamics and mechanisms involved remain unclear. In this study, the "yardang-controlled dune" is systematically illustrated, supported by thorough studies of the yardang-controlled dune morphology and dynamics. Through the monitoring of the 6722 km2 dunes in the Qaidam Basin (QB), three typical yardang-dune coexistence patterns are identified and summarized: Pattern I-windward dune, crescentic dunes form on the upwind sides of the sparsely arranged yardangs; Pattern II-corridor dune, crescentic dunes form beside the narrowly arranged yardangs in the corridors and migrate; Pattern III-leeward dune, linear dune forms on the downwind side from isolated yardang tail. Computational fluid dynamics (CFD) modeling is used to analyze the dynamics and mechanisms of the three patterns and the corresponding real yardang topographies. CFD simulations show that with the control of yardangs, the winds in the locations corresponding to the dunes have significantly low velocities, leading to the wind entrainment decrease, sand accumulation and subsequent dune formation. CFD also reveals that the aspect ratios of yardangs control the formations of wind shadows and linear dunes on the yardang tails. The simulation results agree well with the actual landforms observed in the QB of the three patterns. Additionally, the dune leeward slope width and migration velocity statistics based on remote sensing provide further support for the observations and simulations. This study sheds light on the intricate influences of yardangs on wind deposition, underscoring their role in shaping the landform of dunes.

The current distribution of dune fields and sandy lands in northeastern China is closely related to the hydrological environment with fluvial processes often providing sediments for dune formation. The Keerqin Sandy Land (also known as Horqin) incised by the tributaries of the West Liao River and located at the northern boundary of East Asian summer monsoon (EAM) in northeastern China, is sensitive to monsoon system variability. As such, aeolian-fluvial-paleosol sequences in northeastern China are valuable geological archives for reconstructing river system behavior and palaeoclimate since the Late Quaternary. Here we show from analysis of these archives that fluvial systems were active at similar to 11 ka likely due to the occurrence of floods at the end of the last glaciation. This was followed by frequent channel migration within the floodplains around 7 similar to 5 ka associated with mid-Holocene monsoon precipitation fluctuation and higher humidity. Sediments from this active Holocene fluvial system along with a more humid climate produced conditions in the Keerqin Sandy Land that resulted in extensive paleosol formation. These findings are consistent with the timing and development of paleosols in other sandy lands in northeastern China. Former channels and floodplains along with a higher groundwater table aided the early development of agriculture in this region: many of the former flood plains are still intensively cultivated and highly productive.

Dunes react quickly to climatic changes, with the main drivers being the dominating wind regime (e.g. magnitude and direction), precipitation, and temperature. Further, human impact can alter dune movement by fixation of active dunes through greening projects, or reactivation of stationary ones through overgrazing by animals. The north-eastern Tibetan Plateau shows a high variability of climatic parameters like wind, temperature, and precipitation within a high elevation environment, situated between the mid-latitude westerlies and the East Asian Summer monsoon. The presented studies asses active barchan dunes in different climatic settings, from the arid southern margins of the Badain Jaran Desert, to the humid Zoige Basin. Since climate stations on the Tibetan Plateau are rare and their measurements often cover only a short time span, climatic changes were studied from ERA-5 reanalysis data, dating back to the 1950s. These metrics were processed via cloud computing, using Google Earth Engine, and were then compared to dune migration rates, which were deduced from optical satellite imagery. Here, the CORONA KH-4B images from the late 1960s, the Landsat archives, and up-to-date high resolution data (GeoEye and WorldView) were used. The Normalized Difference Vegetation Index (NDVI) was implemented to observe changes in vegetation. As a newly tested metric, dune field density changes were calculated, in order to investigate dynamics of dense dune field setting. Over 500 dunes were mapped and analyzed in total within four focus-areas for comparative purposes. The results highlight a wide range of different behavioral patterns of dunes within the environment of the north-eastern Tibetan Plateau. This showcases how dunes can be influenced by and linked to climatic changes.

Supplementary Data from Activation of YAP1 by N6-Methyladenosine–Modified circCPSF6 Drives Malignancy in Hepatocellular Carcinoma

The movement of active dunes is tightly linked to climatic conditions (e.g., wind regime, temperature and precipitation) as well as human influence (e.g., grazing, dune fixation and greening). Dune migration rates can be studied to draw conclusions of changing wind conditions over time. The Gonghe Basin (GB), located on the north-eastern Tibetan Plateau (TP), offers a good testing ground for these assumptions. The intramontane basin is highly influenced by two major wind regimes: the mid-latitude Westerlies and the East Asian summer monsoon. To investigate environmental changes, this study combines optical remote sensing techniques with climatic datasets. High-resolution satellite images of the last five decades, such as CORONA KH-4B, are used to map dunes and calculate their respective migration rates. Further, height information was extracted as well. Climatic changes from the ERA-5 reanalysis dataset and normalized difference vegetation index (NDVI) values were processed alongside. Relating the dunes' surface processes to climate model data shows an accordance between slowing migration, expanding vegetation and a decrease in sand drift potential. From 1968 to present time, an average dune migration rate of 7.3 m a(-1) was extracted from the satellite images, with an overall reduction of -1.81 m a(-1). The resultant drift potential (RDP) values for the GB are calculated to be below 10 m(3) s(-3) with a spatial decrease, following a direction from the NW to the SE, fitting well with a corresponding decrease in the migration rates. Our results indicate a good agreement between the development of aeolian landforms and the ERA-5 climate reanalysis model data, even in a high-altitude setting with complex topography, which is known to influence such datasets.

Numerous studies have explored paleoenvironmental conditions in China's dune fields around the mid-Holocene (MH), ∼6000 calendar years ago, often based on individual paleosol-aeolian sand depositional sequences and local-scale landscape dynamics. So far, continent-scale modeling studies have only indirectly assessed dune activation and stabilization processes via changes in simulated precipitation, net precipitation (precipitation minus evaporation), and effective moisture (precipitation divided by evaporation). Here we conducted a comprehensive study using gridded data on potential evapotranspiration, precipitation, and surface wind velocity from 13 climate models participating in the Paleoclimate Modeling Intercomparison Project phases 4 (PMIP4) and compared the model results with geological records. Our evaluation of spatial patterns of dune activity in northern China around the MH reveals that the intensity of annual MH dune activity exhibited significant differences between the eastern and western parts of Chinese deserts compared to those of the preindustrial period (PI). Dune activity was significantly weaker in the eastern region, while in the western part, it was considerably stronger. The key drivers of this disparity were the distinct spatial variations in near-surface wind speed and effective moisture between the two regions. Compared with the optically stimulated luminescence ages of the paleosol-aeolian sand sedimentary sequences derived from a compilation of geological records from 88 sites across northern China, the model results suggest that the weakening of dune activity and the process of dune stabilization in eastern China around the MH were mainly attributed to a significant increase in effective moisture and a concurrent decrease in near-surface wind speed due to the intensified East Asian summer monsoon. Additionally, the weakening of westerlies in western China resulted in reduced effective moisture, contributing to increased sand availability for dune development and subsequent desert expansion.

Here we present results of The lake averaged monthly mean surface water temperature over the period from September 2013 to August 2015 from Yunlong Tianchi Lake(YL)(25°52.2′N, 99°16.8′E, altitude: 2551 m a.s.l), southwestern China. The dataset include sediment trap main diatom percentages over the period from September 2013 to August 2015 from YL. Lake water temperature profiles at different depths (1, 3, 6, 9, 11, 13, 16 m) from November 2008 to May 2009 in Huguang Maar Lake (HML)(21°9′N, 110°17′E), Southern China. AMS radiocarbon dates of plant remains and bulk sediment samples for Huguangyan Maar Lake over the last ~17 cal ka BP. The main diatom assemblage percentages (%) from 17 to 10 cal ka BP at Huguangyan Maar Lake. Diatom-based reconstruction of winter temperature (WT) from 17 to 10 cal ka BP at Huguangyan Maar Lake.

以毛乌素沙地3种沙丘(新月形沙丘、抛物线形沙丘和反向沙丘)为研究对象,对其形态、表沙粒度特征和区域风况进行了量化分析,探讨了沙丘表沙物理运动过程及其形态对外界条件(风况和地表植被)变化的反馈,揭示了沙丘表沙粒度特征对不同沙丘形态的响应机制.结果表明:新月形沙丘表沙平均粒径由迎风坡底部向顶部逐渐变小,分选呈现逐渐变好趋势,但粒径较小和分选较差的表沙样出现在沙丘迎风坡中部.随着地表植被覆盖度的增加,新月形沙丘逐渐向抛物线形沙丘转变,近地表输沙能力和沙丘上风向沙源的供应同样受到限制,致使抛物线形沙丘由迎风坡底部向顶部呈现表沙平均粒径变大,而分选逐渐变好的趋势.毛乌素沙地内季节性风况(春季盛行强劲西北风,夏季盛行较弱东南风)的变化不仅促进了反向沙丘的发育,并且重组了西北盛行风影响下的表沙粒度特征.在夏季反向风风蚀的作用下,沙丘落沙坡顶部出现反向堆积和脊线反向移动的现象,同时其顶部呈现平均粒径由小变大、分选逐渐变好的趋势.

Meltwater Pulse 1A injection into the North Atlantic coincided with the Bølling warming event, despite climate model simulations indicating that the Meltwater Pulse 1A should have inevitably lead to an extreme cooling in the northern hemisphere. However, so far no cooling event has been found in paleoclimate records responding to Meltwater Pulse 1A. Here we reconstruct winter temperature based on sedimentary diatoms from Huguangyan Maar Lake in tropical China. The results show that winter temperature dropped by at least 6°C within ∼100 years at 14.8 ± 0.02 ka BP, coeval with the onset of Meltwater Pulse 1A, within dating uncertainty. We argue that Meltwater Pulse 1A weakened the Atlantic Meridional Overturning Circulation (AMOC), resulting in abrupt severe cooling in the Northern Hemisphere that caused a severe winter temperature drop in East Asia by strengthening the winter monsoon. We propose that extreme cooling in winter temperature triggered the Bølling warming by stopping the freshwater release from the ice‐sheet, triggering the AMOC to recover quickly and causing the Bølling event as an overshoot under gradual forcing.