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Alpine lakes located in high-altitude mountainous regions act as vital sentinels of environmental change. Remote-sensing-based identification of these lakes is crucial for understanding their response to climate variations and for assessing associated disaster risks. However, the complex terrain and weather conditions in these areas pose significant challenges to accurate detection. This paper proposes a method that leverages the high precision of deep learning for small lake and lake boundary extraction combined with deep learning to eliminate noise and errors in the identification results. Using Sentinel-2 data, we accurately identified and delineated alpine lakes in the eastern Himalayas. A total of 2123 lakes were detected, with an average lake area of 0.035 km². Notably, 76% of these lakes had areas smaller than 0.01 km². The slope data is crucial for the lake classification model in eliminating shadow noise. The accuracy of the proposed lake classification model reached 97.7%. In the identification of small alpine lakes, the recognition rate of this method was 96.4%, significantly surpassing that of traditional deep learning approaches. Additionally, this method effectively eliminated most shadow noise present in water body detection results obtained through machine learning techniques. [ABSTRACT FROM AUTHOR]

Carbon burial patterns in lakes and their dynamic changes significantly impact terrestrial carbon sink fluxes and global carbon budgets. In this study, multi-indicator analysis of sediment core samples (P1, P2, and P3) from Pipahai Lake was conducted. Integrating the chronological sequences of 210Pb and 137Cs, we identified the historical changes and spatial characteristics of total organic carbon (TOC) and inorganic carbon (TIC) burial in Pipahai Lake since 1884. The results show that the TOC content was higher than that of the TIC. They exhibited an increasing trend with decreasing depth. Linear regression results indicated that the variation of TOC is less directly affected by precipitation (R = 0.39) and temperature (R = 0.58), while temperature may have a greater impact on TOC. From 1884 to 1995, nutrients were not the primary factor influencing changes in TOC. The synchronous variation in TIC and TOC contents reflects a higher contribution of external inputs to carbon burial in the Pipahai Lake basin. After 1996, nutrients may have begun to affect variations in TOC. The TOC primarily originates from distal aeolian transport or autochthonous sources, though human activity has played a role in its evolution. The TIC content is controlled by the TOC content and autochthonous sources. This study will contribute to the understanding of the carbon cycling dynamics and their influencing mechanisms in a high-altitude lake ecosystem. [ABSTRACT FROM AUTHOR]

Understanding the variability and related dynamic mechanisms of the Indian summer monsoon evolution over the past millenniums is crucial for disaster prevention and mitigation in the context of strengthening global warming. Here, we present a high‐resolution hydroclimate reconstruction over the past 3110 years in northwestern Yunnan Province, southwestern China, based on grain size analysis using the End‐member modeling algorithm and other environmental proxies. The results indicate that the temperature in northwestern Yunnan Province generally decreased since 3110 cal. yr BP, aligning with other temperature records on regional and global scales. Precipitation in the study area remained relatively stable before 1000 cal. yr BP, but exhibited an obvious out‐phase change compared with the temperature records over multidecadal to centennial timescale. While after 1000 cal. yr BP, the precipitation steadily increased, revealing the hydroclimate pattern of notably dry Medieval Warm Period (MWP) and relatively wet Little Ice Age (LIA) in the study area. The decoupling combination of temperature and precipitation spanning the MWP and LIA in southwestern China contrasts with that in the East Asian summer monsoon area and the Indian subcontinent which is also controlled by the Indian summer monsoon, indicating the spatial heterogeneity of precipitation in the Asian summer monsoon region. The discussion about dynamic mechanisms points out that solar activity emerges as a significant factor influencing regional temperature changes, and El Niño‐Southern Oscillation and Intertropical Convergence Zone migration jointly impact the precipitation change in the study area and the hydroclimate discrepancy in the Asian summer monsoon region. Plain Language Summary: Knowledge of the Indian summer monsoon evolution over the past millennium is vital for addressing the challenges posed by global warming. In this study, we present a high‐resolution hydroclimate reconstruction covering the last 3110 years in northwestern Yunnan Province, southwestern China. Using the End‐member Modeling Algorithm and multiple environmental proxies, we found a general temperature decrease since 3110 cal. yr BP, consistent with global and regional trends. Before 1000 cal. yr BP, precipitation in the study area remained stable but showed a distinct antiphase pattern with temperature variations over multidecadal to centennial timescales. After 1000 cal. yr BP, precipitation steadily increased, revealing a notably dry Medieval Warm Period (MWP) and a relatively wet Little Ice Age (LIA). The decoupling of temperature and precipitation during the MWP and LIA in southwestern China contrasts with the East Asian summer monsoon and the Indian subcontinent, highlighting the spatial heterogeneity of precipitation in the Asian summer monsoon (ASM) region. Our discussion on dynamic mechanisms highlights the significant role of solar activity in regional temperature changes and the joint impact of El Niño‐Southern Oscillation and Intertropical Convergence Zone migration on precipitation in the study area and the broader ASM region. Key Points: Precipitation change in the study area was indicated by the relative proportion of end membersDecoupling warming and monsoon precipitation in northwestern Yunnan Province was revealedEl Niño‐Southern Oscillation and Intertropical Convergence Zone migration jointly impact the hydroclimate discrepancy in the Asian summer monsoon region [ABSTRACT FROM AUTHOR]

Alpine (high mountain) ecosystems with extreme weather conditions and complex karstic geology, hosting extensive aquifers, are the two main characteristics of Taurus Mountain ranges, also affecting the distribution of living biota. Understanding these systems are important since they are potentially diverse but poorly explored habitats and are possible water source in the region, especially considering projected further aridification trends. Here, Lake Yeşilgöl (altitude 1815 m asl), a groundwater fed karstic lake at Mount Akdağ, is described in terms of its physical limnology and benthic freshwater ostracod assemblages for the first time. Three freshwater (podocopid) ostracod species were recorded: Fabaeformiscandona brisiaca (Klie, 1938), Neglecandona neglecta (Sars, 1887) Krstić, 2006 and Ilyocypris bradyiSars, 1890 in the surface sediment. Ostracods are in high abundance. According to the population structure of those species, I. bradyiSars, 1890 and N. neglecta (Sars, 1887) Krstić, 2006 are inhabiting this lake. Although F. brisiaca (Klie, 1938) is the most abundant ostracod species, it might be distributed/transported to the lake via groundwater. F. brisiaca (Klie, 1938) is the first record form Turkey and might be part of the meio-fauna of karstic groundwater of Taurus Mountains. Trace metals (Pb, Zn, Cd, Cu, and Ni) were measured in the surface sediment of the main lake basin and in the subsamples of the littoral short core. They are detectable low concentration. Atmospheric contamination does not yet appear to be an environmental threat at this remote alpine site in Western Taurus Mountains, in the south west Anatolia. This study measures basic physical limnological parameters in the lake water column and describes freshwater ostracods and trace metal concentrations in the surface sediments and in the short cores of an alpine, karst,groundwater-fed lake located in south-west Turkey. [ABSTRACT FROM AUTHOR]

The diel vertical migration of zooplankton includes downward migration to deep water during the day and upward migration to surface water at night. Diurnal downward migration has been well explained; zooplankton migration to surface water at night remains unclear. This study aimed to explore the reason of the nocturnal upward migration of the calanoid copepod Arctodiaptomus sp. In Lake Heihai, an alpine lake (elevation 4,090 m above sea level) without predators.Herein, we present the vertical profiles of the lake, including water temperature, chlorophyll a (Chl‐a), fatty acids, and astaxanthin synthesis precursors (ASPs) of seston in the water column. The distributions and concentrations of fatty acids and astaxanthin in Arctodiaptomus sp. were characterised through field investigations during the day and at night. Meanwhile, the effect of ultraviolet radiation (UVR) on ASPs in seston was explored through indoor experiments.Lake Heihai had the characteristics of low temperature, low food availability, high transparency, and high UVR intensity. Arctodiaptomus sp. was distributed in water layers below 6 m during the day and throughout the water column at night. Arctodiaptomus sp. accumulated large amounts of fatty acids, especially polyunsaturated fatty acids (PUFAs), and inhibitors of fatty acid oxidation–astaxanthin in the cold alpine lake. The concentrations of lutein, a kind of ASP, and PUFAs in seston were highest in surface waters. The indoor experiment verified that UVR can enhance the synthesis of ASP.The calanoids migrated to surface waters at night to obtain ASPs and PUFAs in seston, which were at high concentrations in surface waters. PUFAs and ASP may be of high food quality for zooplankton in alpine lakes. The findings indicated that the upward migration of Arctodiaptomus sp. at night was driven by the high quality of food sources (PUFAs and ASP) in surface waters. Arctodiaptomus sp. adapts behaviour and physiology to the environment of the alpine lake.We explored why zooplankton migrated to surface waters at night from the perspective of their physiological characteristics and adaptability to the environment. Our findings provide a new way to investigate the diel vertical migration of zooplankton, especially in alpine lakes. [ABSTRACT FROM AUTHOR]

Atribacteria play an important role in global carbon cycling. Little is known, however, about the Atribacteria communities found in alpine lakes. The presence and diversity of Atribacteria in the sediment core of alpine Sayram lake in China were investigated using Illumina MiSeq sequencing in this study. According to the findings, Atribacteria affiliated with JS1 were dominant in the sediment core of Sayram Lake, with a relative abundance of 0.19 to 10% (average 3.75%) of all bacterial sequences. Furthermore, the relative abundance of Atribacteria associated with JS1 increased with sediment depth. As a result, this study significantly contributes to our understanding of Atribacteria community habitat.

Fish introduction into fishless high-altitude lakes has detrimental effects on biodiversity. Removal of alien fish through intensive fishing is cost-intensive and difficult to achieve in productive lakes. Lake Sulzkarsee is the only lake in the National Park Gesäuse, Austria, and was an important breeding site for amphibians until the lake was stocked with fish in the late 1970s. Salmonids were eradicated in 2005, but the lake remained degraded by the introduced minnows (Phoxinus sp.). In 2018, the lake was drained through a siphon pipe and then by pumping out water with dirt water pumps. The deepest part was treated with slaked lime, but several hundred adult minnows survived in sediment crevices and reproduced in the following season. After drainage, the phytoplankton biomass increased. Indicator species, such as Daphnia longispina and amphibians, showed signs of recovery, but they went back to an impacted state when minnows recovered after the failed eradication attempt. Purse seines proved to be the most efficient gear to catch minnows. These results indicate that deep mountain lakes are difficult to drain efficiently. Sediment treatment is required to eliminate all fish. [ABSTRACT FROM AUTHOR]

Study region: Lake Nam-Co, a typical deep alpine lake in the central of Tibetan Plateau. Study focus: This study investigates the role of surface turbulent fluxes in simulating lake freeze-up and the role of solar radiation transfer (when lake ice exists) in simulating the lake ice break-up. New hydrological insights: In the coupled model, the realistic representation of surface turbulent heat fluxes is crucial to simulate the lake freeze-up. This is because turbulent heat fluxes, especially the latent heat, directly controlling the lake water temperature through energy exchange between water and atmosphere. Additionally, the partitioning of solar radiation transfers when lake ice exist is crucial in simulating lake ice break-up. The proportion absorbed by the ice surface will be released associated with upward longwave radiation and turbulent heat fluxes, and only a fraction is used for surface ice-water phase change. The proportion absorbed by the subsurface layer ice is directly used for ice-water phase changes. The proportion absorbed by the water, through ice penetration, is temporarily stored and used for ice melting through heat exchange between the ice and water. The offline FLake model is much less sensitive to the above two processes, implying the importance and necessity in improving the model physics in coupled model.

Alpine lakes, which include glacial and nonglacial lakes, are widely distributed in high mountain areas and are sensitive to climate and environmental changes. Remote sensing is an effective tool for identifying alpine lakes over large regions, but in the case of small lakes, the complex terrain and extreme weather make their accurate identification extremely challenging. This paper presents an automated method for alpine lake identification developed by leveraging deep learning algorithms and multi-source high-resolution satellite data. The method is able to detect the outlines and types of alpine lakes from high-resolution optical and Synthetic Aperture Radar (SAR) satellite data. In this study, a total of 4584 alpine lakes (including 2795 glacial lakes) were identified in the Eastern Himalayas from Sentinel-1 and Sentinel-2 data acquired during 2016–2020. The average area of the lakes was 0.038 km2, and the average elevation was 4974 m. High accuracy was reported for the dataset for both segmentation (mean Intersection Over Union (MIoU) > 72%) and classification (Overall Accuracy, User's and Producer's Accuracies, and F1-Score are all higher than 85%). A higher accuracy was found for the combination of optical and SAR data than relying on single-sourced data, for which the MIoU increased by at least 12%, suggesting that the combination of optical and SAR data is critical for improving the identification of alpine lakes. The deep learning-based method demonstrated a significant improvement over traditional spectral extraction methods. [ABSTRACT FROM AUTHOR]

The Holocene temperature discrepancy between paleoclimate reconstructions and climate model simulations—known as the Holocene temperature conundrum—calls for new high‐quality Holocene temperature records at high elevations. Here, we present a quantitative Holocene mean annual air temperature record based on a site‐specific branched glycerol dialkyl glycerol tetraethers calibration from a small remote alpine lake on the southeastern Tibetan Plateau. The record reveals a temperature history comprising a relatively cool early Holocene (before 7 ka) followed by a warmer mid‐ to late‐Holocene (after 7 ka), which was likely linked to increasing local annual insolation and greenhouse gases. Three cold events punctuated the general warming trend ca. 10.4 ka, 3.7 ka, and 1.7 ka BP, and correspond closely in time to ice rafting events in the North Atlantic, and to episodes of volcanism and/or unusual solar activity. The entire Holocene temperatures are cooler than the previously identified anthropogenic warming from 1990–2015 AD. Plain Language Summary: The scarcity of high‐quality, quantitative Holocene temperature records from terrestrial archives, especially at high elevations, such as the Tibetan Plateau, limits our understanding of the temperature history of the Holocene. Here, we present a molecular fossil‐based mean annual air temperature record for the last 12,000 years from sediments preserved in a small remote alpine lake. The new record shows that the early Holocene was relatively cool and was followed by a warmer mid‐ to late‐ Holocene, which is consistent with results from climate modeling studies. This Holocene warming trend was probably due to increases in regional annual solar radiation and additional radiative forcing of greenhouse gases. The reconstruction captures the anthropogenic warming of the past 25 years (1990–2015 AD) and shows it to be unusual during the past 12,000 years. Key Points: An unreported cooler early Holocene (before 7 ka BP) temperature record was presented at high elevations on the southeastern Tibetan PlateauThe entire Holocene mean annual temperatures are cooler than the previously identified anthropogenic warming at this site from 1990 to 2015 ADThree multi‐centennial cold events centered on 10.4, 3.7, and 1.7 ka BP are observed in the record [ABSTRACT FROM AUTHOR]

The alpine grasslands and meadows of the Tibetan Plateau are critical for maintaining biodiversity, carbon storage, and regional ecological balance. However, the ecological response of the Tibetan Plateau to climate change and anthropogenic activity is poorly understood. We selected two alpine lakes at different altitudes on the northeastern Tibetan Plateau and used n -alkanes from lacustrine sediments to probe the process of ecological response to climate change (temperature and precipitation) during typical climatic periods of the past millennium, as well as impacts on the ecosystem caused by anthropogenic activities. Our results showed that mid- and long-chain n -alkanes in Lake Dalzong and Lake Bihu sediments, which could be used to evaluate plant biomass variations, were mainly derived from terrestrial plants around the watershed. For both the low-altitude Lake Dalzong (3120 m above sea level (a.s.l.)) and the high-altitude Lake Bihu (4360 m a.s.l.), plant biomass of the watershed increased with enhanced temperature and precipitation during the Medieval Warm Period (MWP), whereas they decreased during the Little Ice Age (LIA), under conditions of lower temperature and precipitation. A further comparison with regional climatic records indicates that temperature and precipitation may have played a more important role in plant biomass changes in the low- and high-altitude regions in the northeastern Tibetan Plateau, respectively. In addition, during the Current Warm Period (CWP), when temperature and precipitation were higher than that in the MWP, plant biomass was lower than that in the MWP in both the Lake Dalzong and Lake Bihu watersheds. The intensification of regional grazing activities and the increase in religious rituals were the primary factors contributing to CWP vegetation degradation. This study highlights the fact that a progressively warmer and wetter climate will not offset the negative impacts of anthropogenic activities on vegetation. • Two alpine lakes on the northeastern Tibetan Plateau were investigated to evaluate elevation-dependent ecological process. • n -Alkanes from lacustrine sediments were used to study vegetation response to climate change during the last millennium. • Plant biomass in the study region was controlled by temperature and precipitation variations during the MWP and the LIA. • Anthropogenic factors caused vegetation degradation during the CWP. [ABSTRACT FROM AUTHOR]

• Lipid fingerprinting of modern biota helps reconstructing past environments. • Dry climate in YD recorded by Sphagnum retreat. • Pluvial episode suggested around 5,000 B.P. • Upper limit of Pinus mugo zone never passed over 1880 m.a.s.l. in Tatra Mts. • Lithophytic lichen biomass deposits with millenial delay. Sediments of two alpine lakes in Tatra Mts., Slovakia, record the environmental history of their catchments from deglaciation in Late Glacial warming up to the Subboreal period. We present a biomarker-based reconstruction of changes in the surrounding biota of two contrasting lakes – a relic lake in open fen Trojrohé pleso (TROJ) and a tarn lake Batizovské pleso (BAT). Taking advantage of young unaltered sediments, well-known source area, and main biomass producers, we used an actualistic approach and interpreted sedimentary lipid distributions using fingerprints of modern plant groups. Four chemostratigraphic units were defined in TROJ lake and five units in BAT lake, with boundaries and environmental changes roughly conforming to paleoclimatic intervals of the Holocene. The dry climate was recorded in the period 13,200 BP–11,500 BP, coincident with Younger Dryas stadial. In the sediment of TROJ lake at ca. 5,200 BP a sharp spike in the abundance of the aromatic terpenoid retene, decoupled from the trend of other abietane-type diterpenoids, may best be explained by episodic flooding due to the rise of the water table. Diploptene as a biomarker for bacterial activity is suggested to indicate the development of soil cover at the end of the B/A interstadial and its gradual increase in abundance in the Holocene most reflecting an extension of vegetated area and more complex development of soil cover. Based on the absence of conifer biomarkers in the sediments of BAT lake, the upper limit of the continuous Pinus mugo scrub never reached the altitude of 1880 m a.s.l. between 16,247 and 4,420 BP, whereas conifer canopy was permanently present around TROJ lake at 1611 m a.s.l. between 10,439 and 3,113 BP. [ABSTRACT FROM AUTHOR]

Knowledge of temperature and precipitation variations on the northeastern Tibetan Plateau (NETP) during the recent past can improve our understanding of late Holocene regional climate change and its response to global climate change, in the past and potentially the future. Based on records of multiple geochemical indicators and branched glycerol dialkyl glycerol tetraethers from the sediments of alpine Lake Bihu on the NETP, we reconstructed high-resolution precipitation sequences and quantified the variation of the mean air temperature of months above freezing (MAF, between May and October) over the past ∼3500 years. The MAF reconstruction shows obvious fluctuations on decadal to centennial timescales, and the absolute values of the reconstructed temperature range from 0.70 to 3.98 °C, with an average of 2.19 °C. The precipitation record reflects the high-frequency variability of the East Asian summer monsoon (EASM). The maximum precipitation and temperature on the NETP occurred during the Medieval Warm Period (MWP, ∼800–1400 CE), rather than during the Current Warm Period (CWP, the last 150 years). We also observed broadly similar patterns of warm–wet and cold–dry climatic variations over the NETP and the broader EASM region; moreover, the decadal to centennial temperature fluctuations were consistent on a large spatial scale. Our results indicate that temperature variability during the late Holocene was primarily controlled by solar radiation, interrupted by multiple decades of successive volcanic eruptions. In addition, anomalous and rapid warming during the CWP may also be related to the unprecedented increase in atmospheric greenhouse gases. Precipitation variability in this region, driven by changes in the EASM, may have been primarily a response to changes in total solar irradiance and associated changes in atmospheric–oceanic modes (e.g., the El Niño–Southern Oscillation, Intertropical Convergence Zone, and Western Pacific Subtropical High). Overall, our results provide robust evidence for global climate teleconnections between different regions, especially in high mountains, in the past, present, and potentially in the future. • Quantitative temperature reconstruction based on lacustrine sediments brGDGTs. • Geochemical indices inferred the EASM variations during the last 3500 years. • Warm-wet and cold-dry climatic patterns were observed in the studied alpine region. • Both internal and external forcings dominated the climate changes in the NETP. [ABSTRACT FROM AUTHOR]

Per-and polyfluoroalkyl substances (PFASs) are omnipresent globally and received increasing attention recently. However, there are limited data on PFASs in the Tibetan Plateau (TP), a remote high-altitude mountain region, which is regard as an important indicator region to study long-range transport behaviors of contaminants. This study investigates the occurrence, distribution, partitioning behavior, and sources of 26 PFASs in water and sediments from the four lakes of TP. The ΣPFAS concentrations ranged from 338 to 9766 pg L-1 in water, and 12.2–414 pg g-1 dry weight in sediments. Perfluorobutanonic acid (PFBA) and perfluorooctane sulfonate (PFOS) were detected in all samples. Qinghai Lake had the highest ΣPFAS concentrations in both water and sediments, while the Ranwu Lake had the lowest. The functional groups and CF 2 moiety units were investigated as essential factors influencing the partition behavior. Principal component analysis (PCA) combined back-trajectory was used to infer possible sources of PFASs. The results suggested that the main source of PFASs in Yamdrok Lake, Namco Lake, and Ranwu Lake on southern TP were mainly originated from South Asia via long-range atmospheric transport (LRAT); while for the Qinghai Lake of northern TP, LRAT, local emissions, and tourism activities were the primary sources of PFASs. [Display omitted] • 26 PFASs in different alpine lakes in the Tibetan Plateau (TP) were analyzed. • Short-chain PFCAs were dominant in water and long-chain PFSAs in sediments. • ADONA and 6:2 FTS were firstly detected in the TP. • Log K d and log K oc values of PFASs were correlated with carbon chain length. • Potential sources of PFASs in the TP lakes were identified. [ABSTRACT FROM AUTHOR]

Alpine wetland ecosystems are of importance in water conservation and animal husbandry in the arid central Asian. However, there is limited research on their formation and relationship with climate. In this study, we evaluated the long-term interactions of vegetation, hydrology, and climate based on multiple proxies (lithology, grain size, loss-on-ignition (LOI) at 550 °C, and pollen) obtained from a sediment core (BY10A) from Lake Swan, an alpine lake in the central Tianshan Mountains of northwest China (2541 m a.s.l.). Our records show that Holocene sediment facies change considerably within core BY10A, with the succession from bottom to top comprising fluvial, peat, and lake sediments. The fluvial deposits were characterized by coarser sediment, which was probably reworked from extensive sand dunes developed over the basin during the early Holocene (12.0–7.5 cal kyr BP). Regional biological productivity was low at this time as indicated by the low LOI value, and the remains of vegetation was degraded under the dry climate. A warm and wet climate prevailed from 7.5 to 2.0 cal kyr BP, resulting in the establishment of peat. The ability of the peat surface to efficiently trap fine particles was enhanced when regional sand dune bodies (coarser part) became largely stabilized by vegetation growth in response to increases in moisture availability. After 2.0 cal kyr BP, a rise in water level, leading to the formation of Lake Swan, indicated a further shift to a wetter climate. During this interval, there was an increasing influence of lacustrine settling and/or wave action on the grain size distribution and the pollen assemblage. This study indicates a stepwise wetting trend from the early to late Holocene. Findings show that changes in moisture, regulated by the prevailing westerlies, exerted a significant influence on the evolution of vegetation communities and lake level in our study area. Schematic figure showing the Holocene hydroclimate changes in an alpine lake in the central Tianshan Mountains, northwest China. During the early Holocene (12–7.5 cal kyr BP), low biological productivity and vegetation cover reflect a dry climate and correspond to a fluvial depositional environment (a). Subsequently, the development of peat sediments and increases in biological productivity and vegetation cover indicate optimum climate conditions during the mid to late Holocene (7.5–2.0 cal kyr BP) (b). After 2.0 cal kyr BP, a rise in water level, leading to the formation of Lake Swan, indicates conditions of increased moisture. During this interval, there was an increasing influence of lacustrine settling or wave action on the grain size distribution and pollen assemblage (c). [Display omitted] • Multiple proxies were used to evaluate long-term changes in vegetation, hydrology, and climate. • Variations in proxies were highly correlated with depositional processes. • A stepwise wetting trend occurred in the Tianshan Mountains from the early to late Holocene. • Changes in moisture regulated by the westerlies influenced the hydroclimate in our study area. [ABSTRACT FROM AUTHOR]

The response characteristics of East Asian summer monsoon (EASM) precipitation to abrupt climatic events during the early to middle Holocene transition may provide insights into the response of EASM precipitation to possible extreme climatic events under future global warming scenarios. We present a high-resolution (∼10 yr) pollen record from a hydrologically closed alpine lake (Yazihai Lake) in North China spanning the interval of 9000–7500 cal yr BP. The results reveal two significant weak monsoon events during 8830–8730 cal yr BP and 8100–8000 cal yr BP. Based on a comparison with the GRIP δ18O ice core record from Greenland and the stalagmite δ18O record from Dongge Cave in South China, we suggest that the second weak monsoon event (8100–8000 cal yr BP) recorded at Yazihai Lake corresponds to the 8.2 ka event that originated in the North Atlantic region, it is spatially and temporally synchronous between the northern and the southern parts of the EASM region and is characterized by a significant decrease in EASM precipitation. For the first weak monsoon event (8830–8730 cal yr BP) recorded at Yazihai Lake, it was also captured by pollen, stalagmite δ18O, and marine sedimentary records from middle to low latitudes of the Northern Hemisphere, and its nature and amplitude resemble the 8.2 ka event. We infer that the possible cause of these two significant weak monsoon events was related to the southward shift of the intertropical convergence zone (ITCZ) due to the collapse of the Atlantic Meridional Overturning Circulation (AMOC), triggered by meltwater influx to the North Atlantic Ocean, and that the abrupt climate signals were transmitted via the monsoon circulation from low latitudes to middle–high latitudes in the EASM region. • Two significant weak monsoon events occurred in North China during 9000–7500 cal yr BP. • Details are given on the effects and structure of the 8.2 ka event in North China. • Possible causes of two significant weak monsoon events are discussed. [ABSTRACT FROM AUTHOR]