The rapid acceleration of polar ice sheet melting under ongoing global warming represents a critical tipping point in the Earth's climate system, with profound implications for sea level rise and large-scale atmospheric and oceanic circulation. While modern observations suggest that ice sheet retreat may significantly alter the East Asian monsoon (EAM) system, the long-term impacts and underlying mechanisms remain poorly constrained, particularly concerning the differential responses of the summer and winter monsoons. Here, we present a high-resolution, multi-proxy record from the Baxie (BX) section in the western Chinese Loess Plateau (CLP), where Rb/ Sr and magnetic susceptibility serve as proxies for the East Asian summer monsoon (EASM), Zr/Rb and grain size trace the East Asian winter monsoon (EAWM). Our results reveal a divergent evolution of the two monsoon subsystems since the onset of the Holocene: the EASM remained weak during the early Holocene and only intensified markedly after similar to 8 ka BP, while the EAWM began a sustained weakening from similar to 11.5 ka BP onward. We propose that residual Northern Hemisphere ice sheets suppressed the early Holocene EASM by maintaining high surface albedo and inhibiting northward moisture transport. Meanwhile, their progressive retreat weakened the meridional temperature gradient and the Siberian High, driving a long-term decline in EAWM strength. These findings provide new paleoclimatic constraints on the seasonal evolution of the EAM and emphasize the need to pay close attention to the impacts of ongoing high-latitude ice sheet retreat on future monsoon dynamics.

The lower reaches of the Yellow River have witnessed numerous episodes of flooding and considerable channel shifts, and reconstructing paleoflood based on fluvial deposits not only extends flood records beyond the instrumental and historical period, but also offers invaluable insights into ancient Chinese civilizations. However, the majority of studies have concentrated on the tributaries of the Yellow River, leaving research on paleoflood events along the main stream comparatively underexplored. In particular, the timing of these flood events remains poorly understood, representing a significant gap in the broader understanding of the hydrological and climatic history of the region. In this study, a detailed investigation of the Sanyangzhuang (SYZ) natural profile, within 100 m of the famous Sanyangzhuang archeological site of Han dynasty (similar to 2.0 ka), in the Northern alluvial plain of the lower Yellow River, reveals ancient flood deposits of the main stream Yellow River during the Holocene. Field observation and analytical results including grain size distribution and geochemical elements indicate that well-sorted slackwater and overbank flood deposits were mainly controlled by the hydrodynamic conditions of the old Yellow River course. Using optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS(14)C) dating techniques, we identified seven periods of extreme flooding: similar to 12 ka, similar to 6.8-6.5 ka, similar to 4.2-4.0 ka, similar to 3.1-2.6 ka, similar to 2.0 ka, similar to 1.0 ka, and the last few hundred years. Among these, the similar to 2.0 ka flood event is notably the same flood that buried the renowned Sanyangzhuang archaeological site from the Han Dynasty, increasing reliablity of our age determinations of this profile. Additionally, the flood dated to similar to 4.2-4.0 ka is likely to have a significant influence on cultural transitions in the Yellow River basin, particularly from the late Longshan Culture (4.5-4 ka) to the Erlitou Culture (3.7-3.5 ka). This finding provides crucial geological evidence supporting ancient flood legends and their profound social and cultural impacts. Furthermore, our study enhances understanding of Holocene extraordinary floods along the main stream of the Yellow River, shedding light on the interplay between prehistoric environmental changes and the evolution of human cultures.

The satellite-observed sea surface temperature (SST) provides an unprecedented opportunity to evaluate the ongoing global warming and has recently reached a milestone of 40-year temporal coverage. One of the major spatial features captured by satellites is strong subtropical (weak subpolar) ocean warming. In contrast, studies of past climate changes suggest that the greatest ocean warming should occur, however, at higher latitudes. Here, by comparing satellite observations with reconstructed mid-Pliocene SST and simulated SST evolution driven by abrupt increase in CO2, we find that the currently observed warming pattern is an expression of an early and temporary stage of planetary warming under the forcing of rapidly increasing greenhouse gas. The enhanced subtropical ocean warming, sharing similar spatial structure with the subtropical ocean gyres, is likely attributed to the background subtropical convergence of surface water. In a long-term perspective, the warming of the oceans at higher latitudes is expected to overtake the temporally strong subtropical ocean warming. This delayed but amplified subpolar ocean warming has the potential to reshape the ocean-atmosphere circulation and threaten the stability of marine-terminating ice sheets.

Speleothem δ18O records from central southern China have long been regarded as a key benchmark for Asian summer monsoon intensity. However, the similar δ18O minima observed among precession minima and their link to seasonal precipitation mixing remains unclear. Here, we present a 400,000-y record of summer precipitation δ18O from loess microcodium, which captures distinct precession cycles similar to those seen in speleothem δ18O records, particularly during glacial periods. Notably, our microcodium δ18O record reveals very low-δ18O values during precession minima at peak interglacials, a feature absent in speleothem δ18O records from central southern China. This discrepancy suggests that the mixed summer and nonsummer climatic signals substantially influence the speleothem δ18O records from central southern China. Proxy-model comparisons indicate that the lack of very low-δ18O values in speleothem δ18O records is due to an attenuated summer signal contribution, resulting from a lower summer-to-annual precipitation ratio in southern China at strong monsoon intervals. Our findings offer a potential explanation for the long-standing puzzle of the absence of 100- and 41-kyr cycles in speleothem δ18O records and underscore the critical role of seasonality in interpreting paleoclimatic proxies in central southern China. These insights also have broader implications for interpreting speleothem δ18O records globally, advocating for a more multiseason interpretive framework.

Abrupt climate events in the Holocene have been recognized as critical factors influencing the evolution of human civilization. The Chinese Loess Plateau (CLP), as one of the cradles of Chinese ancient civilization, witnessed the emergence of numerous early cultures. The Dadiwan Culture (7800-4800cal yr BP), situated in the western CLP, represents one of the earliest centers for dryland agricultural domestication and cultivation systems in northern China. However, this cultural sequence exhibits a pronounced similar to 500-year hiatus between its initial (Phase I: 7800-7300cal yr BP) and subsequent (Phase II: 6500-6000cal yr BP) developmental stages, with the causal relationship between this discontinuity and coeval climate variability remaining unresolved. Through high-resolution multiproxy (organic carbon, total nitrogen, grain size) analysis of a high-sedimentation-rate fluvial terrace loess-paleosol sequence in the Dadiwan region, we identified a pronounced weakening of the East Asian summer monsoon (EASM) concurrent with abrupt cooling and aridification at similar to 7.2 ka. This climatic anomaly demonstrates temporal correspondence with two key forcing mechanisms: (1) enhanced freshwater fluxes into the North Atlantic Ocean, and (2) reduced solar irradiance during the mid-Holocene. Integrating paleoclimatic reconstructions with archaeological evidence, we infer that this abrupt climate transition likely precipitated the observed cultural discontinuity in the Dadiwan sequence. Our findings elucidate the critical role of centennial-scale climate variability in shaping Neolithic societal trajectories and agricultural adaptation strategies in semi-arid East Asia.

Although normal components along the strike-slip faults have been widely found in central Tibet, poorly constrained vertical rates impede the recognition of their formation mechanism and tectonic implications. Herein, we systematically obtained spatial distribution of well-defined vertical throw rates along the Gyaring Co fault (GCF) using high-precision unmanned aerial vehicle topographic data and optically stimulated luminescence dating on oblique faulted fans and shorelines. Our integrated data indicated a southeastward decrease in Late Quaternary vertical throw rates from similar to 0.12 to 0.05 mm/yr along the GCF. The vertical and horizontal movements of the GCF have shared similar rate gradient and have been partitioned with general steady ratios of 5-7.5 % since the Late Quaternary, which suggests that at least half of the motion on the GCF is accommodated by the southern linked Xainza rift. The vertical throws of the GCF are compatible with the conjugated Wuru Co fault, other strike-slip faults, and grabens in central Tibet but are tenfold slower than those of the southern linked rifts. Thus, our results indicate that the eastward motion of the conjugate strike-slip fault system could probably contribute to normal throws along the GCF. The disperse and slow normal faulting within the conjugate zones may initiated at the Middle Miocene as the secondary structures of the conjugate system in central Tibet, kinematically different from the considerably strong and independent southern linked rifts.

For a century, the hemispheric summer insolation is proposed as a key pacemaker of astronomical climate change. In high latitudes, these climate changes are characterized by cyclical expansion and retreat of ice sheets. While the low-latitude climate changes are featured by strong variations in the hydrological cycle, with dominant precessional variations. Existing studies argued that precession determines the inter-hemispheric summer insolation difference, thus regulating the North-South seesaw of the ITCZ. However, an increasing number of geologic records, especially those absolutely dated ones, reveal that terrestrial precipitation shows asynchronous precessional evolutions that are very often out of phase with the summer insolation. The underlying mechanism, despite being highly debated, however, remains unclear. In this study, we proposed that the astronomically driven low-latitude hydrological cycle is paced by shifting perihelion, rather than the Northern (or Southern) Hemisphere summer insolation. Precession of the Earth’s rotation axis alters the occurrence season and latitude of perihelion. When perihelion occurs, increasing insolation raises the moist static energy over land faster than over ocean due to differing thermal inertia. This thermodynamically moves the tropical convergence precipitation from the ocean to the land, contributing to enhancing the terrestrial precipitation over the latitudinal rain belt. As perihelion shifts towards different latitudes and seasons at different precessional phases, this leads to asynchronous terrestrial precipitation maxima at different latitudes. We present both model simulations and geological records to support our hypothesis. Our results suggest that the insolation in individual seasons is equally important in shaping the orbital scale climate changes at low latitudes. This offers new insight into the Milankovitch theory.

Palaeoclimate proxies reveal a significant precessional impact on the low-latitude hydrological cycle. Classical theory suggests that precession modulates the inter-hemisphere summer insolation difference and hence controls the meridional displacement of the Intertropical Convergence Zone (ITCZ). Accordingly, low-latitude precipitation variations are expected to be in phase (for the Northern Hemisphere) or anti-phase (for the Southern Hemisphere) with the Northern Hemisphere summer insolation. However, increasing numbers of proxies, particularly those that are absolutely dated, reveal that variations in terrestrial precipitation at different low latitudes follow distinct precession rhythms that are very often out of phase with hemispheric summer insolation. The mechanism underlying such spatial-temporal complexity remains elusive. In this study, we performed theoretical analysis, climate simulations, and synthesis of geological records to hypothesise that the low-latitude hydrological cycle is paced by shifting perihelion rather than by the hemispheric summer insolation. More specifically, precession of the Earth's rotation axis shifts the season and latitude of perihelion. Here, the latitude of perihelion is introduced as the latitude of Earth's subsolar point during perihelion, which is the location where the most intense solar radiation is concentrated. At the time of perihelion, intense solar radiation heats the land faster than the ocean due to differing thermal inertia. This thermodynamically moves the tropical convection from the ocean to the land, contributing to enhancing the terrestrial precipitation around the perihelion latitude. As the precessional phase changes, perihelion moves toward different latitudes, causing asynchronous maximums in terrestrial precipitation at different latitudes. Perihelion can occur in any season; therefore, the insolation in individual seasons is equally important in shaping the orbital-scale climate changes at low latitudes. This offers new insight into the Milankovitch theory, which highlights summer insolation's role in shaping orbital-scale climate change.

Observational and modeling results show that the frequency and amplitude of extreme climatic events have increased significantly in the context of global warming. However, whether abrupt climate changes intensified during past warm periods remains poorly constrained due to the lack of high-resolution geological records. Here, we report a 512-m predominantly lacustrine sedimentary record from the Weihe Basin (North China), revealing that lake levels fluctuated significantly on suborbital (half- and quarter-precession) and millennial timescales over the last 2 Ma. Grain-size results reveal that magnitudes of rapid lake level fluctuations increased dramatically during Pleistocene interglacials, differing from glacial amplification of abrupt climate events recorded in North Atlantic marine sediments. Model results indicate that summer insolation maxima in low-latitude region of both hemispheres can lead to intensified monsoon precipitation in East Asia. Our proxy-model comparison highlights the importance of low-latitude bihemispheric insolation maxima in driving millennial-scale hydroclimatic variability in a warming future.

Differing from the classic fine silt-dominated loess on the southern and central Chinese Loess Plateau (CLP), sandy loess is extensively distributed along the southern bank of the middle Yellow River and reaches thickness of up to similar to 200 m. However, its deposition time and formation processes remain unclear. In this study, we dated three representative sandy loess sections along the middle Yellow River using single-aliquot regenerative-dose optically stimulated luminescence (OSL) and multiple-aliquot regenerative-dose recuperated OSL (ReOSL) dating protocols on fine quartz grains (4-11 mu m). The reliability of these methods was robustly verified through traditional luminescence dating checks. Our dating results showed that the sandy loess was predominantly deposited during the last glacial period and exhibited an exceptionally high dust accumulation rate surpassing that of the classic loess on the southern and central CLP. By considering atmospheric circulation, geomorphology, and proxy data from both the sandy loess and the Yellow River fluvial sediments, we propose that the sandy loess primarily originated from the proximal riverbeds and fluvial plains of the middle Yellow River, transported by northerly East Asian winter monsoon (EAWM) winds. During the last glacial period, weakened East Asian summer monsoon (EASM) in central and northern China resulted in reduced runoff and vegetation cover in the middle Yellow River region. Consequently, the riverbeds and fluvial plains served as main sources of dust material. Subsequently, the strengthened EAWM winds carried and deposited the dust along the southern bank of the middle Yellow River, culminating in the formation of the sandy loess. Our study underscores the importance of aeolian and fluvial processes interactions in contributing to the formation of the sandy loess along the middle Yellow River and suggests that the investigated sandy loess holds potential for high-resolution paleoclimate reconstruction.

The active block theory was introduced into intracontinental earthquake research that strong continental earthquakes are controlled by the movement and deformation of active block. This theory is very important for understanding strong earthquake occurrence and related mechanisms far away from the plate boundaries, and also provides conceptual framework for short- and long-term prediction of strong earthquakes on the continents. The boundary zones of active blocks composed of different types of active structures is the potential risk areas where strong earthquakes occur, which have been proved by the occurrences of modern earthquakes in recent years. With respects to this correlation between the occurrence of strong earthquake among different active tectonics, a comprehensive study is needed to focus on the faults related to strong earthquake but also the associated active block. Here we summarized long-term strong earthquake activities in the boundary zones and characteristics of the active blocks, and provides more complete estimates on future risk areas around the Ordos block. The Ordos Block, situated in the central part of the mainland of China, represents a typical active block surrounded by diverse active tectonic zones. As one of the most significant seismically active regions in the mainland of China, the Ordos Block has experienced over 50 strong earthquakes with magnitudes (M) >= 6.5 according to historical records. Notably, the vicinity of the block has experienced over 5 large earthquakes with M >= 8. Due to the dynamic effect of the Tibetan Plateau and the Pacific Plate, the Ordos block has significant strong earthquake, leading to distinct fault systems with varying characteristics of movement, zoning, and segmentation along its boundary zones. In total, we recovered 180 strong earthquake events from the main fault zones around the Ordos active block and recovered the different structural zones in the boundary zones. Based on paleoearthquake and historical earthquake records, we reconstructed time series of strong earthquake occurrence in the past 15000 years. Our time series of seismic activities extended strong earthquake research from thousand-year to ten-thousand-year scale that enabled us to obtain better spatial and temporal image of strong earthquake activities from different tectonic areas around the Ordos active block. Our results showed that there are differential active and quiet periods in each zone of the block boundary, with varying clusters of strong earthquakes in the north, northeast, east and west boundaries, quiet periods varied from similar to 200 to 500 years in the past 15000 years. In the past 5000 years, the frequency of strong earthquake has been significantly increased in each boundary zone, indicating high risk of strong earthquake in these segments. Based on historical earthquake records and our latest images, we recognized 7 high risk areas in the boundary zone, namely, Wuhai-Linhe, Tongxin-Azouqi, Tianshui-Baoji, Yuncheng basin, Taiyuan basin, northeast Shanxi basin and Hohhot-Daihai basin around the Ordos active block.

The Yadong-Gulu rift (YGR) is the most prominent and seismically active of the seven main similar to NS-trending rifts in southern Tibet. Although the morphology of the southern YGR clearly indicates it has witnessed large earthquakes in the past, and despite its significant late Quaternary throw rates of similar to 1 mm/yr, no large historical or instrumental earthquakes have been reported, including in the southernmost Pagri half-graben, in contrast to the northern part of the rift which is highly seismically active. Here, geomorphic characteristics helped us constrain the timing of a paleoearthquake that produced surface ruptures along the Pagri half-graben, used to document its past activity and evaluate its seismic hazard. We demonstrate that the co-seismic surface ruptures extend for similar to 65 km along the Yadong normal fault, with a maximum vertical displacement ranging from 2 to 4.0 +/- 0.1 m. Based on empirical relationships between magnitude, surface rupture length, and fault displacement, we suggest that this event may correspond to a M(w)6.9-7.2 earthquake. Combined with previous studies, our radiocarbon (C-14) and Optically Stimulated Luminescence (OSL) ages from three pits within the earthquake wedge across the surface ruptures constrain the paleoearthquake timing at 3470-2056 years BP. We suggest that the southern YGR currently has a high regional seismic hazard for a M(w)6.8-7.1 earthquake, considering the significant throw rates and long timespan since the last strong event. Furthermore, we suggest that such different seismic activity and throw/extension rates between the southern and northern YGR may be explained by different upper crustal rheology behavior and mid-crustal structure.

Accurate reconstruction of geological dust activity is crucial for understanding past climate change and its interaction with dust cycle. Loess on the Chinese Loess Plateau (CLP) is an ideal and sensitive material for revisiting past dust activity. Previously, the changes in the dust mass accumulation rate (MAR) over various time scales were widely established on the CLP. However, few absolutely dated dust records have been obtained and synthesized for the Holocene. This study addresses this gap by compiling 23 optically stimulated luminescencedated Holocene loess sections across the CLP. We developed a high-quality chronology via Bayesian age-depth modeling and derived a MAR record for each section. Then, we obtained a mean MAR record for the CLP by stacking individual records. We propose that, in contrast to site-specific MARs, stacked MARs represent the mean dust accumulation conditions for the entire CLP and can be used to track relatively large-scale dust activity and climate change. The stacked MAR record suggests a moderate weakening trend of dust accumulation from similar to 11.5 to 7.5 thousand years ago (ka BP), followed by a pronounced strengthening trend from similar to 7.5 to 3.0 ka BP. A comparison with other regional dust records reveals a shift in dust activity at similar to 8-6 ka BP in northern China and western Mongolia. We argue that the East Asian winter and summer monsoons jointly contributed to Holocene mean dust MAR variations on the CLP by changing dust transport wind energy and dust source aridity, respectively. A comparison of Holocene dust records in Asia with those in the northwestern Pacific Ocean and Greenland suggests asynchronous variations in dust activity between proximal and distal Asia-sourced dust deposition. This is because, unlike proximal deposition, distal deposition can be controlled not only by the dust source conditions but also by the intensity and the position of the Westerlies.

Paleoclimate proxies reveal a significant precessional impact on the low-latitude hydrological cycle. Classical theory suggests that precession modulates the inter-hemisphere summer insolation difference, and hence controls the meridional displacement of the Inter-Tropical Convergence Zone. Accordingly, the low-latitude precipitation changes are expected to be in-phase (for the Northern Hemisphere) or anti-phase (for the Southern Hemisphere) with the Northern Hemisphere summer insolation. However, increasing number of absolutely dated proxies reveal that variations in land precipitation at different low-latitudes follow distinct precession rhythms that are very often not paced by the hemispheric summer insolation. The mechanism underlying such spatial complexity remains elusive. In this study, we argued that the precession driven low-latitude land precipitation is paced by shifting perihelion, rather than the hemispheric summer insolation. More specifically, precession of the Earth’s rotation axis alters the season and latitude of perihelion. When perihelion occurs, solar radiation reaches its maximum value, thermodynamically moving the tropical convergence zone from ocean to land, contributing to enhancing the precipitation over land. As perihelion occurs towards different latitudes and seasons at different precessional phases, this leads asynchronous land precipitation maxima at different latitudes. Our hypothesis, supported by both model simulations and geologic records, suggests that the insolation in individual seasons is equally important in shaping the orbital scale climate changes at low-latitude. This provides new insight on the Milankovitch theory which highlights the role of summer isolation in driving the astronomical climate change.

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.

Parametric decomposition techniques including single-sample unmixing and parametric end-member modelling are routine mathematical methods used for interpreting grain-size distributions. In this study, transformed probability density functions for the Lognormal, Weibull, Skew Normal, and Skewed Generalized Normal distributions are derived and efficient open-source numerical programs applying these functions are presented. These new functions contain two free shape parameters characterizing the peak position and magnitude of a unimodal distribution, and they can be more easily initialized and constrained compared to their original counterparts, as the two shape parameters can be estimated directly from the grain-size distribution or its derivatives and can only vary within very narrow intervals. This enables the decomposition to converge to both reproducible/stable and structurally/genetically reasonable solutions. The transformed functions are applied to grain-size distributions of aeolian sediments collected from around the Tengger Desert, using both the single-sample unmixing and parametric end-member modelling methods, and the results of different functions are compared. The implications of the results for parametric decomposition of sediment grain-size distributions using unimodal mathematical distributions are discussed.

Intense debate persists about the timing and magnitude of the wet phases in the East Asia deserts since the late Pleistocene. Here we show reconstructions of the paleohydrology of the East Gobi Desert since the last interglacial using satellite images and digital elevation models (DEM) combined with detailed section analyses. Paleolakes with a total area of 15,500 km 2 during Marine Isotope Stage 5 (MIS 5) were identified. This expanded lake system was likely coupled to an 800–1000 km northward expansion of the humid region in East China, associated with much warmer winters. Humid climate across the Gobi Desert during MIS 5 likely resulted in a dustier MIS 4 over East Asia and the North Pacific. A second wet period characterized by an expanded, albeit smaller, lake area is dated to the mid-Holocene. Our results suggest that the East Asian Summer Monsoon (EASM) might have been much weaker during MIS 3.

第四纪碎屑沉积物是新构造运动和第四纪地质环境变化的重要信息载体.对第四纪碎屑沉积物,尤其是对距今 200ka以上不含火山灰的粗颗粒样品(如砾石堆积)进行测年,一直是第四纪年代学研究中的重点和难点问题,石英 ESR 测年法是能够直接测定这类样品的测年方法之一.但是,将石英 ESR法测年应用于早更新世沉积物(特别是粗颗粒沉积)结果的可靠性国内外至今鲜有报道,是目前亟待解决的年代学问题之一.文中基于石英 ESR法测年原理和前人的研究成果,以已知年龄的下更新统靖远砾石层为研究对象,探讨了早更新世砾石堆积石英 ESR法测年的可靠性.结果显示:1)靖远砾石层石英 Ti-Li心在 11 000Gy附加剂量范围内 ESR信号未饱和,Al心在 13 000Gy附加剂量范围内 ESR信号未饱和;2)单饱和指数函数和"指数+线性"函数可分别为 Ti-Li心和 Al心提供更优的等效剂量拟合结果,且拟合效果均优于 0.98;3)靖远砾石层石英 Ti-Li心和 Al心的平均ESR测年结果分别为(1.67±0.15)Ma和(1.65±0.69)Ma,与已知的宇生核素测年结果(约为(1.73±0.13)Ma)和岩石地层结果在误差范围内是一致的.综上所述,石英 Ti-Li 心和 Al 心 ESR法测年均可为早更新世含砂质透镜体的砾石层堆积提供可靠的年代学数据.