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Characterized by elevated pCO 2 levels and global warmth, the mid-Miocene climate is a valuable analogue for investigating how the East Asian Summer Monsoon (EASM) may evolve at different time scales. In this paper, we present a quantitative EASM precipitation record with a temporal resolution of ∼14 kyr during the mid-Miocene (∼15.97 to 13.64 Ma) by applying the probabilistic CREST (Climate Reconstruction Software) method to palynological records from the northeast part of the Tibetan Plateau. Reconstructed mid-Miocene EASM precipitation (∼860 mm) was almost twice that of today (∼450 mm), indicating much stronger EASM intensity. The reconstruction shows a gradual long-term decline on which was superimposed a stronger EASM period (∼15.97–14.54 Ma) followed by a relatively stable period (∼14.54–13.84 Ma) and a short period of reduced precipitation (∼13.84–13.64 Ma). The correspondence of EASM precipitation changes with the mid-Miocene climate optimum and west-east thermal gradients in equatorial Pacific suggests these two factors were the main driving forces for EASM evolution from ∼15.97 to 14.54 Ma, whereas the combined impact of global cooling and the northward shift of the Intertropical Convergence Zone is probably responsible for the slight decline of the EASM from ∼14.54 to 13.84 Ma. The weaker EASM between ∼13.84 and 13.64 Ma was most likely a response to the global significant cooling event Mi-3. On orbital time scales, the precipitation records exhibit a dominant ∼400 kyr periodicity, indicating EASM changes were mainly paced by eccentricity via the modulation of precessional amplitude, and the East Antarctic Ice Sheet variations were probably another important driving force. • A high-resolution, quantitative mid-Miocene EASM precipitation record was obtained. • The mean mid-Miocene MAP of ∼860 mm was almost 2 times that of today in NE TP. • Global temperature played key role in long-term mid-Miocene EASM evolution. • West-east thermal gradients in EP, ITCZ are also vital drivers in some intervals. • Orbitally, mid-Miocene EASM variability was dominated by eccentricity forcing. [ABSTRACT FROM AUTHOR]

The 4.2 ka event was a period of global drought and climate cooling linked to the widespread disruption of Neolithic culture. However, the detailed climatic changes during this period are not completely understood. In this paper, we report a high-resolution pollen record for the Dayanghu wetland in the Zhejiang region of southeastern China, which we use to infer mean annual precipitation (MAP) fluctuations during the period spanning 4600–4000 calendar years before present (cal. yr BP). There was a long-term trend of decreasing MAP during this interval, consistent with weakening of the East Asian Summer Monsoon since the mid-Holocene. This trend was punctuated by episodes of relatively high MAP at 4350–4320, ca. 4260, and 4220–4200 cal. yr BP, and extreme droughts at 4200 and 4150 cal. yr BP. We propose that solar activity promoted El Niño events and contributed to dramatic MAP fluctuations in the Dayanghu wetland. La Niña events and negative-phase intervals of the Pacific Decadal Oscillation may have been responsible for the extreme drought at 4200–4150 cal. yr BP. In summary, we propose a close relationship between MAP and solar forcing, with short-term enhanced solar activity increasing the intensity of the East Asian Summer Monsoon and contributing to increasing decadal variability in the inner tropical Pacific, which ultimately leads to increased precipitation variability in southeast China. The results improve our understanding of the detailed climatic features of the 4.2 ka event. • High-resolution pollen record for ca. 4.2 ka for the Zhejiang region, China. • Pollen-based mean annual precipitation was quantitatively reconstructed. • Long-term droughts tended to occur during 4600–4000 cal. yr BP. • La Niña-dominated ENSO contributed to a catastrophic drought at 4200–4150 cal. yr BP. [ABSTRACT FROM AUTHOR]

The abrupt weakening of the East Asian summer monsoon (EASM) during Younger Dryas (YD) has been attributed to freshwater discharge into the North Atlantic ocean and resultant Northern Hemisphere cooling. Recent studies have found that sea ice variability in the Nordic Sea during the YD exerted a great influence upon the northern high-latitude climate. However, the influence of sea ice upon EASM evolution during YD event remains unclear. In this paper, we report two precisely-dated speleothem oxygen isotope records from the EASM-dominated region of central China. Our records archive abrupt changes in EASM variability during the YD event. Initially, there was a significant strengthening of the EASM during the mid-YD following the gradually increased Atlantic meridional overturning circulation (AMOC). Later this trend reversed at ∼12.15 ka due to northern high-latitude sea ice fluctuations and a consequent reduction of AMOC. At the YD termination, abrupt intensification of the EASM was synchronous with the rapid decline of sea-ice and recovery of the AMOC indicating that sea ice variability was a significant influence on high latitude climate and EASM variation during the YD. • A new speleothem δ18O record show significant EASM strengthening during mid-YD. • Mid-YD oscillation in EASM linked with NH sea ice variability. • Abrupt EASM intensification at YD termination synchronous with the rapid decline of sea ice. • Drier interval following the YD termination in central China. [ABSTRACT FROM AUTHOR]

The direction and intensity of Asian Summer Monsoon (ASM) circulation in the Tibetan Plateau (TP) region strongly influence pollen dispersal patterns; however, this spatial effect has been rarely quantified. In this paper, we explore the relative importance of this directional spatial effect. Specifically, we construct a wind connectivity diagram for modern pollen sample sites according to the prevailing monsoon direction, and extract latent spatial variables representing the directional process of the ASM, using the method of asymmetric eigenvector maps. We fit redundancy analysis models using both spatial variables and local climate factors, and conduct variation partitioning to quantify the effect of directional spatial effect by the ASM. Taking into account the joint effect with local climate, the directional spatial process induced by the ASM significantly explains the variation of pollen assemblages on the TP. The effect is detected in pollen groups with contrasting functional types and dispersal modes; for example, the composition of arboreal pollen and non-arboreal pollen are both significantly affected by the ASM, yet best explained by models assuming different monsoon directions. Anemophilous pollen shows a higher percentage of variation explained by the ASM than non-anemophilous pollen. Our results indicate that directional processes induced by the monsoon is an important influence on pollen assemblages in the TP and support the idea that deposition patterns of pollen, especially arboreal pollen is a useful proxy for studying monsoon evolution. A similar approach can also be applied to paleomonsoon simulations using fossil pollen records. The role of directional dispersal in affecting fossil pollen composition and abundance by prevailing winds deserves further investigation when undertaking Quaternary paleoenvironmental reconstructions using pollen. • Asian Summer Monsoon (ASM) affects pollen assemblages on the Tibetan Plateau via directional spatial process significantly. • Arboreal pollen and non-arboreal pollen are both significantly affected by ASM. • Anemophilous pollen shows a higher percentage of variation explained by the ASM than non-anemophilous pollen. • Arboreal pollen fossil is a suitable potential proxy of studying evolution of monsoon direction and intensity. • Role of directional pollen dispersal by winds deserves more research in pollen-based paleoenvironments reconstruction. [ABSTRACT FROM AUTHOR]

The Salawusu River Valley cuts through the Mu Us Desert in north central China, and lies at the interface of the East Asian Summer and Winter Monsoonal regions. Exposed at numerous locations in the valley side are extensive late Quaternary deposits, consisting of interbedded aeolian sands, fluvio-lacustrine units and palaeosols. Due to the importance of the location in potentially elucidating both summer and winter monsoonal regimes, and the quality of the sedimentary record, the region has a rich history of study, and yet even within the Holocene sequence, many conflicting interpretations have arisen based on studies on different sections. This paper aims to synthesize and explore these differences by exploring the lateral continuity of the Holocene sequences along a ~ 45 km reach of the valley, and presenting new, detailed physical and geochemical analyses of three sections, focusing on the lacustrine Holocene Dagouwan Formation. The absence of the lacustrine unit at several locations confirms that rather than representing a single lake, the Dagouwan Formation instead represents a series of palaeolakes, probably at least partially hydrologically isolated from each other by aeolian sands. All begin with sand-dominated deposits during the early−/mid-Holocene, which is interpreted as the result of abundant sand-supply to the north and west, under the influence of an enhanced East Asian Winter Monsoon, and all switch to silt-dominated, more carbonate-rich deposits during the mid−/late-Holocene, which is attributed to an enhanced East Asian Summer Monsoon bringing loessic silts from the Chinese Loess Plateau to the east and south. The timing of this change, perhaps as late as 5.5 ka, supports the idea of a relatively enhancement late mid-Holocene of the summer monsoonal circulation in the region. However, despite the proximity of the sections and consistent analytical approaches, marked differences between the sections occur in all proxies studied. The timing and rate of the switch from sand- to silt-dominated lacustrine deposition varies between the sites by as much as 2000 years within just a few kilometres of each other, and at some sites the switch was gradual, whereas at others it was very rapid. Similar dramatic variations are also seen with organic carbon content, carbonate content, C:N ratio, and especially the δ13C isotopic ratio. These point to the lake basins behaving very differently, and emphasize that consideration must be given to the local geomorphology and palaeolimnological evolution of individual sections. • Differences in lacustrine Holocene monsoon records in northern China are explored. • The occurrence of the lakes is geomorphologically, not climatologically, controlled. • Different sections of similar units represent different lakes with varied histories. • Consistent changes in sediment suggest mid-Holocene decline of winter monsoon. • Study of individual sections or proxies cannot be used to infer regional climate. [ABSTRACT FROM AUTHOR]

Identification of Holocene climate events, their temporal and spatial characteristics, and their causal mechanisms are important for understanding past climate systems with implications for interpreting ancient cultural transformations. In this paper, we analyse globally-distributed, high-resolution climate proxy records from 58 sites to develop a comprehensive understanding of climate change around 7.2 ka BP. Analysis of the data compilation, which comprises records from lake sediments, one loess section, speleothems, marine sediments, and ice cores, show that the climate event is manifested as a weakening of the Asian summer monsoon and a strengthening of the South American summer monsoon. Climate change also involves dramatic cooling and wetter conditions in north-central Europe, widespread aridity across the Africa and west-south North America, contrasting patterns of precipitation variability throughout the Mediterranean, and notable cooling over the polar regions, suggesting that this is a global climate event. A close correspondence between the 7.2 ka event and the timing of solar irradiance minima, strong volcanic eruptions, meltwater flux into the North Atlantic Ocean, and an orbitally-induced decrease in summer solar insolation suggests a possible causal link with these phenomena. We suggest that climate anomalies around 7.2 ka BP may be specifically explained as a response to southward migration of the Intertropical Convergence Zone, onset of an increasingly El Niño-like state, reinforcement of the westerlies, and slowing of the Atlantic Meridional Overturning Circulation (AMOC). • The 7.2 ka event is well represented in 58 paleoclimatic records from the global. • Varying climatic responses are evidenced in different regions during 7.6–7.0 ka BP. • The 7.2 ka event arise of the atmosphere–ocean–land feedback in response to four forcing factors. [ABSTRACT FROM AUTHOR]

The marine shelves of passive margins receive huge amount of terrestrial organic carbon (OC) exported from adjacent terrestrial ecosystems. Long-term sequestration of terrestrial OC into marine sediments plays an important role in the global carbon cycle on a range of timescales. However, our knowledge of factors affecting the fate of terrestrial OC in continental-marginal settings is incomplete, with ongoing debates regarding rates of degradation during transport and burial. In this paper, we employ analyses of total OC and its stable isotope (δ13C), terrestrial biomarkers and mineral surface area in sediment core 39-A obtained from mud-rich regions of the inner shelf of the East China Sea to investigate terrestrial OC burial history over the last 3000 years. Analysis of terrestrial lipid biomarker and terrestrial OC calculated based on a δ13C-binary mixing model shows increasing trends since ∼1400 yr BP, accompanied by a synchronous increase of terrestrial OC preservation rate. By compiling terrestrial OC records from mud-rich regions of the East China Sea inner shelf, we propose that the most reasonable explanation is the intensification of the East Asian Winter Monsoon. This resulted in a strengthening of coastal currents, which accelerated lateral transport speed (thereby shortening oxygen exposure time) of Changjiang (Yangtze River)-derived terrestrial OC towards the deposition site, resulting in greater terrestrial OC preservation. Moreover, we also found delayed responses of terrestrial OC burial to the East Asian Winter Monsoon in the middle and southern part of the Min-Zhe coastal mud region, implying that the transport of terrestrial OC towards this region took place on a centennial-time scale. Our study sheds new light on mechanisms controlling terrestrial OC transport and burial processes in a typical passive marginal sea. • Sedimentary OC in the MZCM was a mixture of Changjiang-derived OC and marine OC. • Terrestrial OC content and burial efficiency increased since ∼1400 yr BP. • The EAWM-driven coastal current determined terrestrial OC burial efficiency. • Transport of terrestrial OC along the MZCM took place on centennial-time scale. [ABSTRACT FROM AUTHOR]

The Oligocene marked the beginning of the present 'icehouse' epoch and witnessed the development and evolution of the Asian monsoon system (AMS). In this paper, the early Oligocene Ningming flora of Guangxi, southern China, is analysed to investigate the AMS based on climate proxies derived from Climate Leaf Analysis Multivariate Program (CLAMP). CLAMP results suggest that the prevailing climate experienced by the Ningming flora was humid subtropical with hot summers and warm winters. Although the record of precipitation seasonality is muted, it is about half as strong as that seen today in monsoon climates of South China, indicating a very weak monsoonal signal. Despite suggesting weak rainfall seasonality, the position of the Ningming flora in physiognomic space indicates that leaves exhibit monsoon-adapted morphologies, comparable to today's vegetation exposed to the Indonesia–Australia monsoon (I-AM) and the transitional monsoon area (influenced by the East Asia monsoon, South Asia monsoon and I-AM). Leaf architectural signatures reveal that the Ningming flora grew under a humid subtropical climate with subtle monsoon signatures. Although it is difficult to distinguish the different domains of the Asian monsoon under such a subtle monsoon influence, based on leaf signatures from southern Asia, it can be inferred that the Ningming Basin during the early Oligocene was exposed to a climate regime similar to that today influenced by the I-AM. In addition, the moist enthalpy method was applied to quantitatively reconstruct the paleoelevation of the Ningming Basin. This approach suggests a paleoelevation estimate of ~1.24–1.35 ± 0.52 km for the early Oligocene, suggesting that a drop in paleoelevation of the Ningming Basin took place after the early Oligocene (Rupelian). The CLAMP results suggest that the early Oligocene Ningming area was at a mid-altitude and experienced a humid subtropical climate with subtle monsoon signatures. • Leaves from the early Oligocene Ningming Basin were subjected to a CLAMP analysis. • The prevailing paleoclimate was humid subtropical with hot summers and warm winters. • Leaf physiognomic spectra shows an adaptation to monsoon climates. • The paleoclimate is similar to a climate regime today influenced by the I-AM. • The early Oligocene Ningming Basin was likely at a height of ~ 1.24–1.35 km. [ABSTRACT FROM AUTHOR]