Tibetan Plateau Lakes Research Articles

Lake responses and mechanisms to El Niño on the Tibetan Plateau using deep learning-based semantic segmentation

Numerous lakes across the Tibetan Plateau (TP) serve as crucial indicators of climate change and are significantly influenced by El Niño events. Previous studies of lake response to El Niño events have focused on a limited number of lakes. Despite advances in remote sensing technology, there have been few comprehensive and large-scale studies using deep learning, and there are still gaps in understanding the response mechanisms on a larger scale. This study leverages advanced deep-learning techniques to map lake responses, offering unprecedented insights into the large-scale hydrological impacts of El Niño. Our results show that lakes shrink significantly during El Niño events on the TP. Lakes located in the central and southern parts of the TP and small lakes with areas ranging from 1 to 50 km2 (over 60 % of them) exhibited strong responses. The range of lake response to El Niño events varies with their intensity, with stronger El Niño events causing an expansion of the response range along the latitudinal direction. We propose four possible mechanisms for lake response patterns to El Niño from the perspective of lake water sources. Strong shrinkage is primarily caused by decreased precipitation and increased evaporation, with a possible contribution from reduced meltwater. Strong expansion is due to increased precipitation, more glacier and frozen soil meltwater, and reduced evaporation. For slight shrinkage and expansion patterns, the balance of meltwater may offset or even counteract the El Niño signal. The study’s results could improve predictions of extreme weather events like droughts and floods in the Third Pole region, enhance water resource management and responsiveness, and offer valuable insights for ecological monitoring and early warning systems development.

Geochemical Indicators on the Central Tibetan Plateau Lake Sediments: Historical Climate Change and Regional Sustainability

Geochemical Indicators on the Central Tibetan Plateau Lake Sediments: Historical Climate Change and Regional Sustainability

Long-term trends in water transparency of Tibetan Plateau lakes and the response to extreme climate events

Water transparency, as indicated by the Secchi disk depth (Zsd), is a key parameter for assessing the quality of aquatic environments, reflecting the ability of light to penetrate through the water column. In the Tibetan Plateau (TP), where lakes are abundant yet remote and challenging to access, remote sensing techniques offer a promising approach for monitoring Zsd over large spatial scales. In this study, we used the semianalytical -based Zsd algorithm to study the temporal and spatial dynamics of water transparency over TP during the period from 2003 to 2022. The results show that the 173 lakes have a mean value of Zsd is 3.64 ± 2.4 m for long term, and generally with the significantly increasing change trends in the past 20 years. In the central Tibetan Plateau (CTP) region, lake transparency showed a positive correlation with lake surface temperature (r = 0.73) and a negative correlation with precipitation (r = −0.54), highlighting the region’s heightened sensitivity to meteorological changes compared to other areas. The spike in water clarity observed in the CTP region may be linked to alterations in lake hydrodynamics driven by the extremely climate events (i.e., El Niño). These results indicated the importance of considering regional climatic factors when interpreting fluctuations in water transparency.

Carbon budgets of lakes on the Tibetan Plateau: Highlighting non-negligible carbon emissions from small lakes

The release of carbon dioxide (CO2) from lakes is a critical element of carbon (C) emissions from inland waters. Within the realm of climate change, the inquiries surrounding whether lakes on the Tibetan Plateau (TP) function as C sources or sinks and the magnitude of CO2 exchange flux from these lakes have garnered significant attentions. Nevertheless, accurately assessing the lakes’ contribution to the C budgets poses challenges due to data scarcity and methodological inaccuracies. By amalgamating data from literature reviews and field measurements for different sizes of lakes during the ice-free (IF) and ice-covered (IC) periods from 2016 to 2021, this study offers a refined estimate of the CO2 exchange flux and flux rate for lakes on the TP by including lakes ranging in size from 0.01 to 1 km2 (small lakes) in the C budgets. Findings revealed that the annual CO2 exchange flux of TP lakes amounted to 7.10 Tg C yr–1, with 6.56 Tg C yr–1 and 0.54 Tg C yr–1 during the IF and IC periods, respectively. Notably, small lakes contributed 0.76 Tg C yr–1, representing 10.65 % of the total lake CO2 emissions on the TP, which indicates the significant role of small lakes in estimating CO2 emissions from TP lakes. The CO2 exchange fluxes of small lakes showed significant variability during the IF period, with the origins of lake water replenishment possibly explaining this diversity, where glacial meltwater replenishment is likely a key contributing factor. In contrast, CO2 emissions from small lakes increased during the IC period. The view of this study is that the groundwater recharge with higher CO2 concentrations and the shallow nature of small lakes may be the main reasons for the increase in CO2 emissions from small lakes during this period. The study underscores that the contribution of small lakes to the CO2 budgets of TP lakes is substantial and warrants attention, particularly in elucidating the mechanisms driving CO2 emissions from small lakes.

Lake Water Ecological Simulation for a Typical Alpine Lake on the Tibetan Plateau

Lakes on the Tibetan Plateau (TP) serve as both indicators of and safeguards against climate change, playing a crucial role in the aquatic ecosystems of the TP. While considerable attention has been devoted to studying the thermal and dynamic processes of TP lakes, research focusing on their ecological variations has been limited. In this study, we selected Namco, a representative lake on the TP, to investigate its water ecological processes using the AQUATOX lake ecological model. Long-term ecological variations spanning from 1980 to 2020 were analyzed based on lake observations. Our results revealed a consistent increase in water nutrients, particularly total nitrogen (WTN), and total phosphorus (WTP), over the study period. Additionally, the concentrations of chlorophyll-a (Chl-a) and water gross and net primary production (WGPP and WNPP) exhibited a significant upward trend. Despite the persistent state of poor nutrition in the lake, the ecological conditions improved. Multiple linear regression analysis indicated that the concentrations of WGPP, WNPP, and Chl-a were more sensitive to the local climate and hydrology compared to WTN and WTP. A continuously warming climate would heat up the lake water body, further enhancing primary production and improving water quality in the future. This study provides insights for lake limnological and ecological research and can be used to inform water management strategies in high-altitude alpine regions.

Widespread societal and ecological impacts from projected Tibetan Plateau lake expansion

Widespread societal and ecological impacts from projected Tibetan Plateau lake expansion

Salinity decreases methane concentrations in Chinese lakes

Lakes are important sources of methane (CH4), and understanding the influence of environmental factors on CH4 concentration in lake water is crucial for accurately assessing CH4 emission from lakes. In this study, we investigated CH4 concentration in two connected Tibetan Plateau lakes, Lake Keluke (an open freshwater lake) and Lake Tuosu (a closed saline lake), through in-situ continuous measurements taken in different months from 2021 to 2023. The results show substantial spatial and seasonal variations in CH4 concentrations in the two lakes, while the CH4 concentrations in Lake Keluke are consistently higher than those in Lake Tuosu for each month. Despite sharing similar environmental conditions due to connected (e.g. pH, water temperature, dissolved oxygen content, and total organic carbon content), the critical difference between the two lakes is their salinity. This implies that salinity is the critical factor contributing to the decrease in CH4 concentrations in Lake Tuosu, possibly due to the changes in microbial species between freshwater and brackish/saline lakes. Additionally, to further validate the effect of salinity on CH4 concentrations in lake water, we compared the CH4 concentrations of 33 lakes (including 5 saline lakes and 28 freshwater lakes) from the Tibetan Plateau, Chinese Loess Plateau, and Yangtze Plain, and found that saline lakes consistently exhibit lower CH4 concentrations (avg. 0.08 μmol/L), while freshwater lakes generally display higher CH4 concentrations (avg. 1.25 μmol/L) with considerable fluctuations. Consequently, freshwater and saline lakes exhibit distinct CH4 emissions, which could be used for more accurate estimation of global CH4 emission from lakes.

Diversity of culturable fungi in six Tibetan Plateau lakes, with descriptions of eight new taxa

ABSTRACT The combination of low temperatures, oligotrophic conditions, high altitude, and varying salinity in Tibetan Plateau lakes endows them with a wealth of distinctive fungal resources. This study aimed to investigate the diversity of culturable fungi in sediment and water samples collected from six lakes located on the Tibetan Plateau at elevations above 4,500 m. A total of 843 fungal strains were isolated by dilution plate method using four different media. Initial ITS analyses revealed that they belong to 156 species across 83 genera, spanning 50 families, 26 orders, 12 classes, and 6 phyla. Further morphological and multi-locus phylogenetic analyses were conducted, resulting in the formal descriptions of a new genus, Xizangia, and seven new species, including Alternaria xizangensis, Emericellopsis ovoidea, Myceliophthora xizangica, Preussia cylindricalis, Preussia sedimenticola, Pseudeurotium sedimenticola, and Xizangia sedimenticola. This research provides insights into the biodiversity of culturable fungi in the unique and extreme ecosystem, shedding light on the potential discovery of novel species and genera.

A comparative study of satellite altimetry-based and DEM-based methods for estimating lake water volume changes.

This study compared two different methods, the satellite altimetry-based and DEM (digital elevation model)-based, for estimating lake water volume changes. We focused on 34 lakes in China as the testing sites to compare the two methods for lake water volume changes from 2005 to 2020. The satellite altimetry-based method used water levels provided by the DAHITI (Database for Hydrological Time Series of Inland Waters) data and surface areas derived from Landsat imagery. The DEM-based method used the SRTM DEM data in combination with Landsat-derived lake extents. Our results showed a high degree of consistency in lake water volume changes estimated between the two methods (R2 > 0.90), but each method has its limitations. In terms of temporal coverage, the satellite altimetry-based method with the DAHITI data is limited by missing water level data in certain periods. The performance of the DEM-based method in extracting lake shore boundaries in regions with flat terrains (slope <1.5°) is not satisfactory. The DEM-based method has complete regional applicability (100%) in the Tibetan Plateau (TP) Lake Region, yet its effectiveness drops significantly in the Xinjiang and Eastern China Plain Lake Regions, with applicability rates of 50 and 40%, respectively.

ENSO-driven hydroclimate changes in central Tibetan Plateau since middle Holocene: Evidence from Zhari Namco’s lake sediments

The Tibetan Plateau, often referred to as the “Asian Water Tower”, holds immense significance as a critical water source for billions of people in surrounding regions. Its unique location and extreme environmental conditions contribute to the formation of some of the world largest lakes, crucial components of the regional water cycle. These lakes not only store vast freshwater resources but also play a vital role in regulating the flow and quality of rivers, maintaining a delicate balance in the local ecosystem. Recent decades have witnessed rapid expansion of many plateau lakes, primarily attributed to glacial melt. However, evaluating the contribution of climate forcings to these changes remains challenging. In this study, we reconstructed Zhari Namco's lake-level changes between 5.3 ka and 1.3 ka based on optically stimulated luminescence dating, a period with relatively stable glacial amount on the Tibetan Plateau. Our analysis employed sediment grain size distribution, organic matter contents and their stable carbon isotopes. In contrast to recent expansions, our findings reveal a declining trend in Zhari Namco's lake level since the middle Holocene, consistent with intermittent paleo-shoreline records from major central Tibetan Plateau lakes. This regional decline is likely the result of a weakening of the Indian Summer Monsoon. In addition to the long-term drying trend, we identified high-frequency fluctuations in Zhari Namco's lake level on centennial timescale. Further comparison with hydroclimate records from the tropics suggests that centennial high lake levels correlate with increased monsoonal precipitation during periods when ENSO activities were reduced. This study sheds lights on the historical dynamics and driving mechanisms of Zhari Namco's lake levels, providing valuable insights for predicting the impacts of future climate change on the Tibetan Plateau's water cycle.

GEA-MSNet: A Novel Model for Segmenting Remote Sensing Images of Lakes Based on the Global Efficient Attention Module and Multi-Scale Feature Extraction

The decrease in lake area has garnered significant attention within the global ecological community, prompting extensive research in remote sensing and computer vision to accurately segment lake areas from satellite images. However, existing image segmentation models suffer from poor generalization performance, the imprecise depiction of water body edges, and the inadequate inclusion of water body segmentation information. To address these limitations and improve the accuracy of water body segmentation in remote sensing images, we propose a novel GEA-MSNet segmentation model. Our model incorporates a global efficient attention module (GEA) and multi-scale feature fusion to enhance the precision of water body delineation. By emphasizing global semantic information, our GEA-MSNet effectively learns image features from remote sensing data, enabling the accurate detection and segmentation of water bodies. This study makes three key contributions: firstly, we introduce the GEA module within the encode framework to aggregate shallow feature semantics for the improved classification accuracy of lake pixels; secondly, we employ a multi-scale feature fusion structure during decoding to expand the acceptance domain for feature extraction while prioritizing water body features in images; thirdly, extensive experiments are conducted on both scene classification datasets and Tibetan Plateau lake datasets with ablation experiments validating the effectiveness of our proposed GEA module and multi-scale feature fusion structure. Ultimately, our GEA-MSNet model demonstrates exceptional performance across multiple datasets with an average intersection ratio union (mIoU) improved to 75.49%, recall enhanced to 83.79%, pixel accuracy (PA) reaching 90.21%, and the f1-score significantly elevated to 83.25%.

Interactive effects of climate-atmospheric cycling on aquatic communities and ecosystem shifts in mountain lakes of southeastern Tibetan Plateau

Recent climate warming and atmospheric reactive nitrogen (Nr) deposition are affecting a broad spectrum of physical, ecological and human systems that may be irreversible on a century time scale and have the potential to cause regime shifts in ecological systems. These changes may alter the limnological conditions with important but still unclear effects on lake ecosystems. We present changes in cladoceran with comparisons to diatom assemblages over the past ~200 years from high-resolution, well-dated sediment cores retrieved from six high mountain lakes in the southeastern (SE) margin of the Tibetan Plateau. Our findings suggest that warming and the exponential increase of atmospheric Nr deposition are the major drivers of ecological regime changes. Shifts in cladoceran and diatom communities in high alpine lakes began over a century ago and intensified since 1950 CE, indicating a regional-scale response to anthropogenic climate warming. Zooplankton in the forest lakes showed asynchronous trajectories, with increased Nr deposition as a significant explanatory factor. Forest lakes with higher dissolved organic carbon (DOC) concentrations partially buffered the impacts of Nr deposition with little structural change, while lakes with low DOC display symptoms of resilience loss related to Nr deposition. Biological community compositional turnover in subalpine lakes has shown marked shifts, equivalent to those of low-elevation lakes strongly affected by direct human impacts. This suggests that local effects override climatic forcing and that lake basin features modified by anthropogenic activity act as basin-specific filters of common forcing. Our results indicate that snow and glacial meltwaters along with nutrient enrichment related to climate warming and atmospheric Nr deposition, represent major threats for lake ecosystems, even in remote areas. We reveal that climate and atmospheric contaminants will further impact ecological conditions and alter aquatic food webs in higher altitude biomes if climate and anthropogenic forcing continue.

Impacts of human and herbivorous feces on lake surface sediments of the Tibetan Plateau based on fecal stanol proxies

Lake ecosystems on the Tibetan Plateau (TP) are highly susceptible to external input owing to their fragile environment. However, less study has been done to focus the direct influences of anthropogenic activities on the lake sediments by human activities. In this study, we performed the first large-scale investigation to use the fecal stanol proxies in lake surface sediments to assess the impact of human and herbivorous feces on TP lakes. The 75 investigated lakes were divided into three types (I, II, and III) according to cluster analysis of the fecal stanol ratios R1′ and R2′. Fecal stanols in type I lake surface sediments originate from a mixture of herbivorous and human feces; fecal stanols in type II lake surface sediments primarily originate from herbivorous feces with minimal human feces. In contrast, fecal stanols in type III lake surface sediments are mainly derived from herbivorous feces (coprostanol concentration > 100 ng/g), a mixed source of herbivorous feces and cholesterol reduction (coprostanol concentration of 10–100 ng/g), and in situ reduction of cholesterol (coprostanol concentration < 10 ng/g). Among the TP lakes investigated, 9 % had significant fecal contamination, 48 % had moderate or slight fecal contamination, and 43 % were uncontaminated. Domestic animal feces were the main source of fecal stanols in the surface sediments of moderately and slightly contaminated lakes in the central TP. There were 9 % of investigated lakes with significant fecal contamination from human and herbivorous feces; in contrast, 52 % of investigated lakes did not definitely show the presence of human fecal matter. This study has important implications for fecal contamination assessment in lake ecosystems and provides a reference for early herbivorous change and paleo-human activity research.

Application of a Three‐Dimensional Coupled Hydrodynamic‐Ice Model to Assess Spatiotemporal Variations in Ice Cover and Underlying Mechanisms in Lake Nam Co, Tibetan Plateau, 2007–2017

AbstractA three‐dimensional lake‐ice coupled model is used to investigate the space‐time variations of ice and underlying mechanisms in Lake Nam Co (LNC), the third largest lake over Tibetan Plateau (TP), during 2007–2017. The model reasonably reproduces the in situ measured ice thickness and water temperature profile, and satellite retrieved ice coverage and lake surface temperature. Seasonally, the lake ice first forms in the eastern basin during early January, expands from east to west during January and February, covers nearly the entire LNC in March, starts melting from west to east in April, and eventually disappears in May. The eastward drift of thin ice throughout the ice‐covered phase and the eastward water heat transport during the ice melting phase are key factors to determine the spatial variation of ice and freeze‐thaw processes. A multiple linear regression analysis confirms that the eastward drift of thin ice can be mostly attributed to the prevailing westerly. During 2007–2017, ice volume, duration, ice‐on and ice‐off dates show significant interannual variations, and they are highly correlated with the surface air temperature (T2m) averaged over January‐March, from the preceding December to May, in December and over March–May, respectively, suggesting the “cumulative effects” of T2m. Seasonal and interannual variations of ice drift are attributed to the combined effects of wind and ice volume variations. Sensitivity analysis further points out the important impacts of ice on the lake temperature and circulation structure in winter and spring, hence the necessity of hydrodynamic‐ice coupled models in large TP lakes.

Changing pattern and driving factors of ecosystem service value of the lakes in Northern China since 1990

Lakes in Northern China are widely distributed with large surface areas, and play a crucial role in maintaining ecological security in the northern regions of China. In this study, based on the relationship between ecosystem services (ES) value and lake key indicators, including lake area, potential evapotranspiration, comprehensive trophic level index (TLI), precipitation, and lake volume, the lake ecoservice production functions (LEPFs) were constructed to evaluate lake ecosystem service value (LESV) in Northern China. Subsequently, the driving factors influencing LESV were identified at the lake-basin scale. The results showed that the total LESV in Northern China increased from 5,088.7 billion yuan in 1990 to 5,112.9 billion yuan in 2020, by increasing 0.47%. The total LESV of Xinjiang (XJ) and Tibetan Plateau (TP) lake regions showed an increasing trend, with rates of 5.39% and 2.32%, respectively. However, those of Inner Mongolia Plateau (IMP), Northeast Plain and Mountains (NPM), and Eastern Plain (EP) lake regions showed a decrease, with rates of 19.83%, 6.29%, and 1.72%, respectively. The changing rate in LESV varied significantly among different lake regions. Approximately 30% and 40% of the lakes in XJ and TP lake regions had a growth rate exceeding 0.3 billion yuan, while 86% and 14% of lakes in NPM and IMP lake regions experienced a decline exceeding 0.3 billion yuan, respectively. 40% of the lakes in EP lake region had a growth rate of less than 0.05 billion yuan, and 60% of the lakes had a decline rate of less than 0.05 billion yuan. The average temperature, precipitation, impervious area, and water area within the lake-basins had a significant impact on LESV. Among them, the effect of climate change on LESV was higher than that of the anthropogenic factors. These findings can provide helpful references for the assessing methods of the LESV at a large regional scale and developing lake conservation policies.

Heavy Metals in Surface Sediment of Plateau Lakes in Tibet, China: Occurrence, Risk Assessment, and Potential Sources.

Tibetan Plateau lakes have high ecological value and play a crucial role in maintaining ecological balance. This research aimed to study the pollution characteristics, ecological risk, and potential sources of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in the surface sediments of 12 Tibetan Plateau lakes. The results of the toxicity risk index (TRI) showed that only Gongzhu Tso (28.09) and La' ang Tso (20.25) had heavy metals that could pose a very high risk of toxicity to aquatic organisms. Hg posed the highest potential ecological risk to aquatic organisms. Based on the results of multiple analyses, we inferred that the contents of Cr, Cu, Hg, and Ni in sediments of Tibetan lakes were influenced by industrial and agricultural development; Cd, Pb, and Zn were influenced by transport and atmospheric transport; and As was derived from geothermal activity and rock weathering.

Spatial distribution of surface-sediment diatom assemblages from 45 Tibetan Plateau lakes and the development of a salinity transfer function

The Tibetan Plateau (TP) is often referred to as the “Asian Water Tower”, as it plays a crucial role in supplying water for ∼1.9 billion people. Lakes in this arid mountain region have a wide salinity gradient and are sensitive to the complex interactions between climate and the water cycle, affecting aquatic ecosystems and species distributions. Here, we analyzed relationships between measured environmental variables and the spatial distribution of surface sediment diatom assemblages from 45 lakes located throughout the TP with the intention of developing a diatom-inference model for salinity. Diatom assemblage composition and diversity differed among lakes from the western (W), southern (S), northern (N), and southeastern (E) regions of the TP. The most common taxa observed in the lake set, Pantocsekiella ocellata, Nitzschia palea, and Staurosira venter, tended to have widespread distributions across the TP. In general, diatom diversity and richness tended to be highest in lakes with salinity concentrations between 0.1 and 10 g/L and were lowest in high salinity lakes (>20 g/L) of the N region. Canonical correspondence analysis (CCA) identified lake water salinity and maximum lake depth as explaining a statistically significant portion of diatom assemblage variation. Weighted-averaging (WA) was used to develop a diatom-based salinity inference model (R2jack = 0.71, RMSEPjack = 0.28) based on diatom optima from freshwater to meso-hyposaline lakes of the TP. Diatom-salinity reconstructions and changes in diatom community composition can potentially be used to track long-term patterns in climate and environmental conditions across the highly complex mountain landscape of the TP.

Sentinel-3 OLCI observations of Chinese lake turbidity using machine learning algorithms

Turbidity has a substantial effect on light propagation in water and is an optical indicator for monitoring water quality. The Ocean and Land Colour Instrument (OLCI) installed in the Sentinel-3 satellite could help to monitor turbidity variations due to its narrow spectral bandwidth and high revisit time. This makes us develop suitable turbidity algorithms for mapping the dynamics of lake turbidity using OLCI imagery. In this study, a total of 1081 samples were collected from 73 typical lakes across China during 2017–2022. Here, we developed and proposed applicable turbidity algorithms i.e., SR (simple regression), PLSR (partial least squares regression), SVR (support vector regression), BP (backpropagation neural network), KNN (K-nearest neighbor), RF (random forest), and XGBoost (extreme gradient boosting), which integrate a broad scale dataset of turbidity ranging from 0.15 NTU to 262.57 NTU using OLCI imagery. The performance results of developed turbidity algorithms demonstrated that RF obtained performed best with good agreements of measured- and derived- fitting (validation dataset: R2 = 0.92, MAPE = 54.32%, RMSE = 12.65 NTU). This allowed us to estimate turbidity concentration in Chinese lakes with a surface area>20 km2. The averaged turbidity level of lake groups in five lake regions was investigated with a decreased tendency as Northeast Plain Lake Region (NPL, 63.31 NTU) > Eastern Plain Lake Region (EPL, 58.30 NTU) > Inner Mongolia–Xinjiang Lake Region (IMXL, 16.64 NTU) > Yunnan–Guizhou Plateau Lake Region (YGPL, 11.63 NTU) > Tibetan Plateau Lake Region (TPL, 7.05 NTU). Further, we analyze the distributions of lake turbidity considering different land use types, and the results showed a decreasing tendency as cropland (56.97 NTU) > barren land (11.22 NTU) > grassland (8.06 NTU) > forest (4.71 NTU). Our results demonstrated and highlighted the quantification of lake turbidity concentrations using OLCI imagery and the stability of the RF algorithm, which can generate turbidity data for large-scale monitoring and decision-making related to environmental protection.

Climate and vegetation codetermine the increased carbon burial rates in Tibetan Plateau lakes during the Holocene

The Tibetan Plateau (TP), also known as the “Asian Water Tower,” includes thousands of lakes containing sizable lacustrine sediments that have been proven to be important carbon pools of inland ecosystems. To develop an in-depth understanding of the status of TP lake carbon storage and its response to global changes and human activities, we accurately quantified the change trend of long-term organic carbon burial in lakes over the TP, compared levels of differentiation within the TP, and explored related driving factors of the carbon accumulation rates (CARs) by compiling 24 lake sediment cores. The results show that the lake CAR over the TP presented a rising trend during the Holocene, with an average of 6.50 g C m−2 yr−1 and levels ranging from 1.75 to 18.41 g C m−2 yr−1. The eastern TP (ETP), with warmer and wetter climate conditions and more vegetation coverage, had almost twice the CAR as that of the central and western TP (CWTP). We demonstrate that climate and vegetation could be the main drivers of the lake CAR on the TP despite environmental heterogeneity contributing to subregional discrepancies. During the early Holocene, superior summer temperatures and precipitation favored vegetation development, providing abundant material for lake carbon deposition. In the middle Holocene, together with vigorous vegetation, decreasing summer temperatures led to a decline in mineralization, which enhanced carbon storage efficiency and resulted in an increase in the CAR across the ETP. In contrast, for the CWTP, herbaceous-dominated vegetation continued to expand during the early-mid Holocene, which constrained detritus supply, thus maintaining a relatively stable CAR. However, intensive human activities could be responsible for the CAR peak in the late Holocene on the TP, especially since 2000 cal yr BP. In addition to the anthropogenic impacts, variations in CAR among lakes resulting from local factors lead to large uncertainties in future C predictions for the whole region of TP.

Seasonal ice-covered lake surface likely caused the spatial heterogeneity of aeolian sediment grain-size in the source region of Yellow River, northeastern Tibetan Plateau, China

The area of lakes in Tibetan Plateau (TP) is 36522 km2, accounting for nearly half (49.1%) of the total lake surface area in China, and the lakes in TP are seasonally ice-covered for 4–5 months per year. In such a high-cold Third Pole with extensive lakes, how does aeolian sediment transport on ice cover and to what extent can seasonal ice-covered lake cause sediment redistribution by providing pathways for sediment migration is rarely studied. The source region of Yellow River (SRYR) is located in the northeastern TP with an altitude above 4000 m, is home to large area of seasonal frozen lakes. Nine sections of aeolian sediments were collected from SRYR for grain-size study. The end-member modeling analysis (EMMA) provides a greater chance of resolving aeolian sediment sources since it can quantitatively separate the particle size components of various sedimentary dynamic processes and sources in the sediment. The result shows great spatial difference of the mean grain sizes (mainly varying between 70 and 230 μm). Parametric EMMA is applied to study the provenance tracing of aeolian sediment, combining with remote sensing images and wind data. Aeolian processes were analyzed by separating and extracting the grain size end-members of nine sections, and four statistical end-members (modal grain size is 8.9, 79.5, 141.6, and 251.8 μm, respectively) were classified from the grain size distribution. It shows that the sedimentary sequences in sections 7 and 8 have high EM2 and EM3 fractions and very low EM4 content at all depths. Based on comprehensive analysis of aeolian sediment grain-size, phenology of ice lake, wind regime and remote sensing images, it revealed that the fine aeolian sediments (sections 7 and 8) on the downwind shore of Ngoring Lake likely transported from the upwind shore, which were blown across the ice-covered lake surface by prevailing west wind in winter and spring, but the coarse sediments could be trapped by ice cracks. Therefore, it’s concluded that the aeolian sediment transport on seasonal ice-covered lakes may lead to the spatial heterogeneity of aeolian sediment grain-size in the SRYR.