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Severe flooding occurred in southern and northern China during the summer of 2016 when the 2015 super El Niño decayed to a normal condition. However, the mean precipitation during summer (June-July-August) 2016 does not show significant anomalies, suggesting that-over East Asia (EA)-seasonal mean anomalies have limited value in representing hydrological hazards. Scrutinizing season-evolving precipitation anomalies associated with 16 El Niño episodes during 1957-2016 reveals that, over EA, the spatiotemporal patterns among the four categories of El Niño events are quite variable, due to a large range of variability in the intensity and evolution of El Niño events and remarkable subseasonal migration of the rainfall anomalies. The only robust seasonal signal is the dry anomalies over central North China during the El Niño developing summer. Distinguishing strong and weak El Niño impacts is important. Only strong El Niño events can persistently enhance EA subtropical frontal precipitation from the peak season of El Niño to the ensuing summer, by stimulating intense interaction between the anomalous western Pacific anticyclone (WPAC) and underlying dipolar sea surface temperature anomalies in the Indo-Pacific warm pool, thereby maintaining the WPAC and leading to a prolonged El Niño impact on EA. A weak El Niño may also enhance the post-El Niño summer rainfall over EA, but through a different physical process: the WPAC re-emerges as a forced response to the rapid cooling in the eastern Pacific. The results suggest that the skillful prediction of rainfall over continental EA requires the accurate prediction of not only the strength and evolution of El Niño, but also the subseasonal migration of EA rainfall anomalies. [ABSTRACT FROM AUTHOR]

For the first time, palynological records of terrestrial palynomorphs and dinoflagellate cysts are investigated in a sediment core from the northern South China Sea (SCS) covering the last 12,500 years. Both terrestrial and marine palynomorph records show strong signals of the sea-level change during the studied interval. The highest herb pollen content was associated with extensive grasslands on the exposed shelf at the low sea-level stand during the Younger Dryas and early Holocene. The increase in fern spores and decrease in concentrations of dinoflagellate cysts and terrestrial palynomorphs was observed during the sea-level rise interval from 12,500 to ~ 6800 (or 6000) cal yr BP. Then, the sea level became stabilized and consistently low dinoflagellate cyst abundances and high abundances of fern spores were recorded. A high abundance of Impagidinium in the period ~ 12,000–10,400 cal yr BP possibly resulted from increased input of western Philippine Sea waters into the SCS and the branching of the Kuroshio Current. A short-term decrease of Impagidinium at ~ 11,700–11,000 cal yr BP corresponding to the MWP-1B event might be associated with input of the East China Sea waters through the Taiwan Strait. The relationship between the sedimentation rates and the concentrations of terrestrial palynomorphs indicates a water-dominant transport for pollen and spore dispersal prior to ~ 6300 cal yr BP, whereas wind transport became more prominent thereafter. The timing of this change corresponds to the highest sea-level stand at ~ 6800–6000 cal yr BP, when the present oceanographic setting was formed. The mid-Holocene Optimum can be seen by the highest abundance of subtropical-tropical broad-leaved arboreal pollen and by the highest abundances of Dapsilidinium pastielsii . Three strengthened winter monsoon intervals at ~ 5500 cal yr BP, 4000 cal yr BP, and 2500 cal yr BP are reflected by increases in Pinus pollen content after the present oceanographic condition formed. [ABSTRACT FROM AUTHOR]

Future hydroclimate projections from state-of-the-art climate models show large uncertainty and model spread, particularly in the tropics and over the monsoon regions. The precipitation and circulation responses to rising greenhouse gases involve a fast component associated with direct radiative forcing and a slow component associated with sea surface temperature (SST) warming; the relative importance of the two may contribute to model discrepancies. In this study, regional hydroclimate responses to greenhouse warming are assessed using output from coupled general circulation models in the Coupled Model Intercomparison Project-Phase 5 (CMIP5) and idealized atmospheric general circulation model experiments from the Atmosphere Model Intercomparison Project. The thermodynamic and dynamic mechanisms causing the rainfall changes are examined using moisture budget analysis. Results show that direct radiative forcing and SST change exert significantly different responses both over land and ocean. For most part of the Asian monsoon region, the summertime rainfall changes are dominated by the direct CO radiative effect through enhanced monsoon circulation. The response to SST warming shows a larger model spread compared to direct radiative forcing, possibly due to the cancellation between the thermodynamical and dynamical components. While the thermodynamical response of the Asian monsoon is robust across the models, there is a lack of consensus for the dynamical response among the models and weak multi-model mean responses in the CMIP5 ensemble, which may be related to the multiple physical processes evolving on different time scales. [ABSTRACT FROM AUTHOR]

Middle Miocene Earth had several boundary conditions similar to those predicted for future Earth including similar atmospheric p CO 2 and substantial Antarctic ice cover but no northern hemisphere ice sheets. We describe a 12 m outcrop of the terrestrial Yanwan Section in the Tianshui Basin, Gansu, China, following the Miocene Climate Transition (13.9–13.7 Ma). It consists of ∼25 cm thick CaCO 3 -cemented horizons that overprint siltstones every ∼1 m. We suggest that stacked soils developed in siltstones under a seasonal climate with a fluctuating water table, evidenced by roots, clay films, mottling, presence of CaCO 3 nodules, and stacked carbonate nodule δ 13 C and δ 18 O profiles that mimic modern soils. We suggest that the CaCO 3 -cemented horizons are capillary-fringe carbonates that formed in an arid climate with a steady water table and high potential evapotranspiration rates (PET), evidenced by sharp upper and basal contacts, micrite, sparite, and root-pore cements. The CaCO 3 of the cemented horizons and the carbonate nodules have similar mean δ 18 O and δ 13 C values but the cements have significantly smaller variance in δ 13 C and δ 18 O values and a different δ 18 O versus δ 13 C slope, supporting the conclusion that these carbonates are from different populations. The magneto-stratigraphic age model indicates obliquity pacing of the arid conditions required to form the CaCO 3 -cemented horizons suggesting an orbital control on water availability. We suggest two possible drivers for the obliquity pacing of arid conditions: 1) variability in the cross-equatorial pressure gradient that controls summer monsoon (ASM) strength and is influenced by obliquity-paced variations of Antarctic ice volume and 2) variability in Western Pacific Ocean–East Asian continent pressure gradient controlled by the 25–45°N meridional insolation gradient. We also suggest that variations in aridity were influenced by variations in PET and sensible heating of the regional land surface which are both influenced by precession-controlled 35°N summer insolation. We then use orbital configurations to predict lithology. Coincidence of obliquity minima (strong ASM) and 35°N summer insolation maxima (strong ASM) drives strong ASM and high PET, resulting in soil formation in an environment with relatively large seasonal changes in water availability. Coincidence of obliquity maxima (weak ASM) and 35°N summer insolation maxima (strong ASM) moderates the ASM, results in high PET, and thus drives overprinting of soils by capillary fringe carbonates above a deepened and relatively stable water table. Coincidence of obliquity and insolation minima also moderates the ASM but results in low PET and thus a high water table, which explains the previously documented occurrence of aquatic plants in this section. This context allows us to assign an orbital configuration to atmospheric p CO 2 determined from the paleosols. Our best estimate of p CO 2 during the times of intermediate ice volume is 475 + 650 / − 230 ppmV (median value with error reported as 84th–16th percentile values). Southern hemisphere control of ASM variability during the Middle Miocene may have resulted in larger orbital scale water availability variations compared with the Pleistocene. [ABSTRACT FROM AUTHOR]

Variations in the strength of the Asian monsoon during Holocene time are thought to have been associated with widespread changes in precipitation across much of Tibet. Local records of monsoon strength from cave deposits, ice cores, and lake sediments typically rely on proxy data that relate isotopic variations to changes in precipitation. Lake expansion and contraction in response to changing water balance are likewise inferred from sedimentologic, isotopic and paleobiologic proxies, but relatively few direct records of changes in lake volume from preserved shorelines exist. Here we utilize relict shoreline deposits and associated alluvial fan features around Siling Co, the largest lake in central Tibet, to reconstruct centennial-to-millennial-scale variations in lake area and volume over the Holocene. Mapping and surveying of lacustrine shorelines coupled with optically stimulated luminescence dating of associated deposits indicate protracted occupation of a highstand elevation from >8 ka to 4 ka, followed by rapid recession that was likely punctuated by several stillstands of centennial-scale duration. Calculation of the changes in lake surface area and past hydrologic indices of the Siling Co basin suggests the effective moisture during the early Holocene highstand was approximately three times greater than today. In contrast to other lakes in central and western Tibet, our results suggest that Siling Co did not begin to recede synchronously with decreasing solar insolation at ca. 9–8 ka. Rather, initial recession of Siling Co appears to correspond to a time period of enhanced aridity and weakened monsoon in both Africa and Asia at ca. 4.2 ka. Our results add to a growing body of literature that suggest a period of relatively severe aridity on the Tibetan Plateau at this time. We suggest that subsequent punctuated recession of Siling Co was punctuated by similar periods of abrupt climate change during the Late Holocene. [ABSTRACT FROM AUTHOR]

Stable isotopic measurements on the upper 168 cm of stalagmite DG24 from southern China, which is annually-laminated above 74.8 cm (∼11.8 ka), reconstruct a history of detailed Asian summer monsoon (ASM) variability and soil processes between 14.8 and 10.3 ka. The climate sequence of Bølling-Younger Dryas (YD)-Preboreal events is evident in δ 18 O record. In the Preboreal, four-year-resolution and annually-counted δ 18 O record reveals that the ASM strengthening can be divided into three phases, with a prominent and persistent rise initiated at about 11.2 ± 0.3 ka, likely in response to interactions between ocean, atmosphere, and ice sheets. In contrast, the long-term δ 18 O depletion is absent in the δ 13 C and annual layer records, which characterize persistent centennial oscillations and likely represent relative humidity of the soil. At multi-decadal scale, prominent ASM failures are generally consistent with periods of δ 13 C enrichment and decreased layer thickness. When compared with solar proxies, centennial-scale δ 13 C changes match well with solar activity regardless of the observed disparity between ASM and solar records, and common cycles of 130 and 300 years are identified in both the atmospheric Δ 14 C and speleothem δ 13 C records. This implicates that during the Preboreal local soil humidity budget and CO 2 production, indicated by the δ 13 C and annual layer records, is more sensitive to changes in solar output than the regional hydroclimate variability recorded by the δ 18 O signal. [ABSTRACT FROM AUTHOR]

A rock magnetic study was conducted on upper Pleistocene marine sediments from International Ocean Discovery Program Expedition 350 Site U1437 in order to highlight the paleoenvironmental changes in the NW Pacific Ocean influenced by the East Asian monsoon regime. Remanent magnetization analyses, hysteresis properties, first-order reversal curves and low temperature magnetic measurements were carried out, along with electron microscope observations. The results indicate that coarse-grained (titano)-magnetite is the dominant magnetic phase in the magnetic mineral assemblage. Time-series analysis supports that this assemblage is modulated by global climate changes over the last 1 Myr. During the interglacial stages, magnetic minerals are more abundant; and are dominated by coarse-grained (titano)-magnetite of both terrigenous (likely from mainland China) and volcanic (Izu arc front, Japan) origin. During the glacial stages, the magnetic mineral content is lower, probably reflecting partial dissolution of (Ti)-magnetite, and the magnetic assemblage is composed of terrigenous coarse-grained (titano)-magnetite and of higher coercivity, presumably finer eolian particles (likely hematite) as a result of the enhancement of the winter monsoon in continental Asia. The magnetic mineral assemblage reflects a superimposition of volcanic and global climate signals. Bulk organic-geochemical analyses for total and organic carbon as well as nitrogen and sulfur contents confirm a climatic signature in the composition of the sediments with more oxygenated water masses being present during glacial periods. Additional X-ray fluorescence measurements on bulk samples indicate various origins of the sediment particles with both proximal and distal sources. [ABSTRACT FROM AUTHOR]

Several monsoon indices have been applied to multiple models from the sub-seasonal to seasonal ( S2S) prediction project database during the period May to October 1999-2010 to assess their ability to simulate the Asian monsoon. The bivariate anomaly correlation ( BAC) of the Boreal Summer IntraSeasonal Oscillation ( BSISO) index suggests that the operational models can predict the BSISO1 and BSISO2 events up to 6-24.5 and 6.5-14 days in advance respectively, although the models tend to underestimate the amplitude of BSISO as the lead time increases. For the strong BSISO events, BSISO1 ( BSISO2) display lower skill mostly in phases 3-5 for all the models, suggesting that the BSISO1 ( BSISO2) is not easy to predict when it is located over India and the Maritime Continent (South China Sea and Bay of Bengal). On the other hand, the higher skills appear in different phases for different models. For instance, the limit of predictive skill of strong BSISO1 and BSISO2 events in phases 6-7 for the ECMWF ensemble forecast could exceed 30 and 28 days, respectively. The comparisons of the BSISO life cycle among the ECMWF, NCEP and CMA models also indicate that the ECMWF model can better predict the evolution of strong BSISO events. Predictions of additional monsoon circulation indices including the Webster-Yang index ( WY), Indian Summer Monsoon index ( ISM), South Asian Monsoon index ( SAM), and SouthEast Asian Monsoon index ( SEAM) in the S2S models have statistically significant skill over the corresponding monsoon regions up to 9-31, 3-17, 7-13 and 7-14 days, respectively. However, the significant skill of summer monsoon precipitation over the SAM and SEAM regions varies significantly among the models, with the skill ranging from 2 days to 2 weeks lead time. [ABSTRACT FROM AUTHOR]

Observation of the ambient aerosol surface area concentrations is important to understand the aerosol toxicity because an increased surface area may be able to act as an enhanced reaction interface for certain reactions between aerosol particles and biological cells, as well as an extended surface for adsorbing and carrying co-pollutants that are originally in gas phase. In this study, the concentration of aerosol surface area was measured from April 2015 to March 2016 in Fukuoka, Japan. We investigated the monthly and diurnal variations in the correlations between the aerosol surface area and black carbon (BC) and sulfate concentrations. Throughout the year, aerosol surface area concentration was strongly correlated with the concentrations of BC, which has a relatively large surface area since BC particles are usually submicron agglomerates consisting of much smaller (tens of nanometers) sized primary soot particles. The slopes of the regression between the aerosol surface area and BC concentrations was highest in August and September 2015. We presented evidence that this was caused by an increase in the proportion of airmasses that originated on the main islands of Japan. This may enhance the introduction of the BC to Fukuoka from the main islands of Japan which we hypothesize to be relatively fresh or "uncoated", thereby maintaining its larger surface area. [ABSTRACT FROM AUTHOR]

Since the early or late arrival of monsoon rainfall can be devastating to agriculture and economy, the prediction of the onset of monsoon is a very important issue. The Asian monsoon is characterized by a strong annual cycle with rainy summer and dry winter. Nevertheless, most of monsoon studies have focused on the seasonal-mean of temperature and precipitation. The present study aims to evaluate a total of 27 coupled models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5) for projection of the time evolution and the intensity of Asian monsoon on the basis of the annual cycle of temperature and precipitation. And future changes of onset, retreat, and intensity of monsoon are analyzed. Four models for good seasonal-mean (GSM) and good harmonic (GH) groups, respectively, are selected. GSM is based on the seasonal-mean of temperature and precipitation in summer and winter, and GH is based on the annual cycle of temperature and precipitation which represents a characteristic of the monsoon. To compare how well the time evolution of the monsoon is simulated in each group, the onset, retreat, and duration of Asian monsoon are examined. The highest pattern correlation coefficient (PCC) of onset, retreat, and duration between the reanalysis data and model outputs demonstrates that GH models' MME predicts time evolution of monsoon most precisely, with PCC values of 0.80, 0.52, and 0.63, respectively. To predict future changes of the monsoon, the representative concentration pathway 4.5 (RCP 4.5) experiments for the period of 2073-2099 are compared with historical simulations for the period of 1979-2005 from CMIP5 using GH models' MME. The Asian monsoon domain is expanded by 22.6% in the future projection. The onset date in the future is advanced over most parts of Asian monsoon region. The duration of summer Asian monsoon in the future projection will be lengthened by up to 2 pentads over the Asian monsoon region, as a result of advanced onset. The Asian monsoon intensity becomes stronger with the passage of time. This study has important implication for assessment of CMIP5 models in terms of the prediction of time evolution and intensity of Asian monsoon based on the annual cycle of temperature and precipitation. [ABSTRACT FROM AUTHOR]

The characteristic location of mangroves at the interface between marine and terrestrial habitats makes them vulnerable to regional environmental change. The monsoonal climate of tropical Asia, where mangrove forests are broadly distributed along the coastal zone, differs from that of the other tropical regions. Therefore, mangrove development in tropical Asia is likely related to the evolution of the Asian monsoon and related environmental changes. As a case study, mangrove development was retrospectively studied using the contribution of mangrove-derived organic matter (CMOM), combined with the total pollen concentration of mangrove species, in bulk sediments of the Yingluo Bay, northern Beibu Gulf (SW China) over the last 2000 years. The results clearly show that mangrove development (flourishing or deteriorating) is primarily controlled by the changes in the air temperature and rainfall, which are controlled by the Asian monsoon. The three mangrove flourishing stages (~2.0-1.6 cal. ka bp, ~1.4-0.8 cal. ka bp, and from ~140 years bp to present) result from warmer and wetter climates during the intensified Asian summer monsoon. In contrast, the two deteriorating stages (~1.6-1.4 cal. ka bp and from ~0.8 cal. ka bp to 140 years bp) result from colder and dryer climates during the intensified Asian winter monsoon. Unexpectedly, the relative sea-level changes, regional seawater salinity, and tidal current, as well as human activity have not imposed notable effects on extension, flourishing/deterioration, and succession of the mangrove forest over the last 2000 years in the Yingluo Bay. [ABSTRACT FROM AUTHOR]

The first emergence and development of pottery is an important archeological research topic. Climate change and associated ecological changes likely promoted the development of pottery. However, little is known about these environmental factors at the regional scale. Sedimentary Core MD01-2409 was collected off the coast of northern Honshu, Japan, and provided an excellent opportunity to quantitatively estimate temperature using an alkenone proxy. This estimation is based upon the positive correlation between the sea surface temperature (SST) and the atmospheric temperature (AT) near the core collection site. The Jōmon began to produce the earliest pottery found in Japan during this period. This corresponds to a climatic anomaly that could be attributed to one of the global effects of the Heinrich Event I. The event's origin in the northern North Atlantic consequently weakened the Asian Monsoon because the two are linked via atmospheric circulation. Japan experienced its coldest summer (SST of 8.7 °C; AT of 5.2 °C) around 15.68 cal kyr BP; these summer temperatures were approximately 7–11 °C lower than they are currently (∼15.7 °C and ∼16.7 °C), respectively. The summer environment was a little colder than those experienced in the present-day cities of Nemuro and/or Nosappu in Hokkaido. Subsistence in a terrestrial environment would have been difficult for the Jōmon people; however, marine products such as fish and shellfish would have been plentiful. These conditions are consistent with the evidence that the earliest pottery was predominantly used for cooking marine and freshwater resources and increased diversification in the range of aquatic products used. The Bølling–Allerød and pre-Boreal warm Episodes during deglaciation warmed climatic environments and enhanced marine biogenic production. The maximum SST during this period is comparable to the modern SST despite its short duration (of approximately a century or less). Even though the relationship between climate and the appearance of pottery in Japan may not be direct, the earliest pottery and projectile points (stone arrows) in the world are associated with the coldest period that Homo sapiens experienced since arriving in the colder regions of the Japanese archipelago. [ABSTRACT FROM AUTHOR]

This work investigates the variability of extreme weather events (drought spells, DS15, and daily heavy rainfall, PR99) over East Asia. It particularly focuses on the large scale atmospheric circulation associated with high levels of the occurrence of these extreme events. Two observational datasets (APHRODITE and PERSIANN) are compared with two high-resolution global climate models (HiRAM and HadGEM3-GC2) and an ensemble of other lower resolution climate models from CMIP5. We first evaluate the performance of the high resolution models. They both exhibit good skill in reproducing extreme events, especially when compared with CMIP5 results. Significant differences exist between the two observational datasets, highlighting the difficulty of having a clear estimate of extreme events. The link between the variability of the extremes and the large scale circulation is investigated, on monthly and interannual timescales, using composite and correlation analyses. Both extreme indices DS15 and PR99 are significantly linked to the low level wind intensity over East Asia, i.e. the monsoon circulation. It is also found that DS15 events are strongly linked to the surface temperature over the Siberian region and to the land-sea pressure contrast, while PR99 events are linked to the sea surface temperature anomalies over the West North Pacific. These results illustrate the importance of the monsoon circulation on extremes over East Asia. The dependencies on of the surface temperature over the continent and the sea surface temperature raise the question as to what extent they could affect the occurrence of extremes over tropical regions in future projections. [ABSTRACT FROM AUTHOR]

The nature of multidecadal to centennial variability of the Asian monsoon is largely unknown, hindering our understanding of how the modern precipitation regime compares to preindustrial variability, as well as how the Asian monsoon may change in coming decades. Here we use the sediment record from a closed-basin lake in southern Tibet, Ngamring Tso, along with other published paleoclimatic records, to assess summer monsoon precipitation variability over the 20th century and during the late Holocene (4100 cal yr BP to present). The first principal component of the Ngamring Tso grain size record, which is highly correlated with median grain size, correlates significantly with observed summer (June–September) precipitation. From CE 1940 to 2007, grain size decreased with increasing summer precipitation and increased with decreasing summer precipitation. Satellite images of Ngamring Tso reveal larger lake area in the 1970s and 2000s and smaller lake area in the 1980s and 1990s, suggesting monsoon precipitation-induced changes in lake depth or area likely govern grain size variability. In the context of the last 4100 yr, prolonged periods of relatively weak summer monsoon precipitation occurred from 2800–2600 cal yr BP, 2500–2300 cal yr BP, and 1600–400 cal yr BP. A trend toward increased summer precipitation began around 1000 cal yr BP, with above-average summer precipitation from 400 cal yr BP to present, peaking between 200–100 cal yr BP (CE 1750–1850). Dry and wet periods are coincident with dry and wet periods in other south-central Tibetan lake sediment records that reflect precipitation or moisture balance, and with regional proxies of the ISM and EASM, indicating south-central Tibet is influenced by both monsoon subsystems. However, western Tibet lake sediment records do not covary with the Ngamring Tso record, suggesting the spatial variability in Tibet precipitation that occurs on interannual timescales today may also characterize precipitation on multidecadal and centennial timescales during the late Holocene. 20th century precipitation variability in southern Tibet falls within the range of natural variability in the last 4100 yr, and does not show a clear trend of increasing precipitation as projected by models. Instead, it appears that poorly understood multidecadal to centennial internal modes of monsoon variability remained influential throughout the last 4100 yr. Thus, substantial multidecadal to centennial-scale hydroclimatic variability will complicate our ability to project and prepare for anthropogenic changes in the region's monsoon precipitation. [ABSTRACT FROM AUTHOR]

This study provides an overview of the Asian monsoon and its change as simulated by atmosphere-ocean coupled general circulation models and high-resolution atmospheric general circulation models, focusing on the seasonal mean circulation and precipitation climatology. After reviewing the drivers of and the elements that affect the monsoon, the ability of those climate models to reproduce the Asian monsoon is assessed. The Asian monsoon is better reproduced in the Coupled Modeling Intercomparison Project phase 5 (CMIP5) models than in the CMIP3 models, although biases remain. Projected future changes in the Asian monsoon at the end of the 21st century are then reviewed. Overall projections are similar for both CMIP3 and CMIP5 models with increases in precipitation, albeit with weakened circulation in the South Asian summer, enhanced circulation and increased precipitation in the East Asian summer, and latitude-dependent changes in the winter monsoon circulation in East Asia. However, differences exist in the projected local changes, leading to uncertainty in projections. [ABSTRACT FROM AUTHOR]

This paper describes the operational seasonal prediction system of the Japan Meteorological Agency (JMA), the Japan Meteorological Agency/Meteorological Research Institute-Coupled Prediction System version 1 (JMA/MRI-CPS1), which was in operation at JMA during the period between February 2010 and May 2015. The predictive skill of the system was assessed with a set of retrospective seasonal predictions (reforecasts) covering 30 years (1981-2010). JMA/MRI-CPS1 showed reasonable predictive skill for the El Niño-Southern Oscillation, comparable to the skills of other state-of-the-art systems. The one-tiered approach adopted in JMA/MRI-CPS1 improved its overall predictive skills for atmospheric predictions over those of the two-tiered approach of the previous uncoupled system. For 3-month predictions with a 1-month lead, JMA/MRI-CPS1 showed statistically significant skills in predicting 500-hPa geopotential height and 2-m temperature in East Asia in most seasons; thus, it is capable of providing skillful seasonal predictions for that region. Furthermore, JMA/MRI-CPS1 was superior overall to the previous system for atmospheric predictions with longer (4-month) lead times. In particular, JMA/MRI-CPS1 was much better able to predict the Asian Summer Monsoon than the previous two-tiered system. This enhanced performance was attributed to the system's ability to represent atmosphere-ocean coupled variability over the Indian Ocean and the western North Pacific from boreal winter to summer following winter El Niño events, which in turn influences the East Asian summer climate through the Pacific-Japan teleconnection pattern. These substantial improvements obtained by using an atmosphere-ocean coupled general circulation model underpin its success in providing more skillful seasonal forecasts on an operational basis. [ABSTRACT FROM AUTHOR]

• Chemical weathering intensified during warm and/or humid climate conditions. • The moisture source was controlled by the Eastern Asian Monsoon or Westerlies. • An "unusual" cold-dry episode was found in the 4.8–3.5 cal kyr BP. The links between chemical weathering on a continental scale and climate have long been a central issue in Earth science. However, the limited knowledge of the interconnections between weathering and climate impedes our understanding of its role in the evolution of the Earth's climate. The Tibetan Plateau is the world's highest and largest plateau and the source of water resources for nearly half of the world's population, it has become a key area for paleoclimate research due to its influence on the atmospheric circulation system and sensitivity to climate change. Herein, we present a major and trace elements-based record of chemical weathering from sediments in the Hurleg Lake, northeastern Tibetan Plateau, over the past 14.1 cal kyr BP. As showed in elements deduced indexes, Hurleg Lake sediments were mainly originated from felsic rocks. Besides, the sediments source remained largely unchanged in the last 14.1 cal kyr BP and the sediments underwent only minimal recycling, and not affected by diagenesis and metasomatism, thus preserving a record of the chemical weathering intensity in the lake catchment. The chemical weathering indexes presented consistent trends and were in good agreement with the variation of δ13C carb in authigenic carbonate derived from the same sequence. Chemical weathering intensified during 14.1 ∼ 12.5, 11.1 ∼ 8.7, 7.2 ∼ 4.8 cal kyr BP, and after 3.5 cal kyr BP, when the climate was warm and/or humid, but weakened in cold-dry intervals of 12.5 ∼ 11.1, 8.7 ∼ 7.2, and 4.8 ∼ 3.5 cal kyr BP. The wet intervals correspond to periods of intensification of the East Asian Summer Monsoon (EASM) or Westerlies. Furthermore, the climate changes in the study area are also typically linked to high- and low-latitude factors that influence global climate conditions, such as insolation changes, the North Atlantic ice-rafting event, and Atlantic Intertropical Convergence Zone (ITCZ) migrations. The "unusual" cold-dry episode in the 4.8 ∼ 3.5 cal kyr BP possibly dominated by both Westerlies and EASM, the result supports the point that both high and low latitude feedbacks played an important role in modulating Hurleg Lake clod-dry climate during 4.8 to 3.5 cal kyr BP. Our records suggest that the climate evolution on the northeastern Tibetan Plateau response to global climate change sensitively, and the possibility that variabilities in the ITCZ might be instrumental in understanding high to low-latitude climate linkages on a global scale. [ABSTRACT FROM AUTHOR]

Here, we infer the historical biogeography and evolutionary diversification of the genus Lilium . For this purpose, we used the complete plastomes of 64 currently accepted species in the genus Lilium (14 plastomes were newly sequenced) to recover the phylogenetic backbone of the genus and a time-calibrated phylogenetic framework to estimate biogeographical history scenarios and evolutionary diversification rates of Lilium . Our results suggest that ancient climatic changes and geological tectonic activities jointly shaped the distribution range and drove evolutionary radiation of Lilium , including the Middle Miocene Climate Optimum (MMCO), the late Miocene global cooling, as well as the successive uplift of the Qinghai-Tibet Plateau (QTP) and the strengthening of the monsoon climate in East Asia during the late Miocene and the Pliocene. This case study suggests that the unique geological and climatic events in the Neogene of East Asia, in particular the uplift of QTP and the enhancement of monsoonal climate, may have played an essential role in formation of uneven distribution of plant diversity in the Northern Hemisphere., Competing Interests: The authors declare no conflict of interest., (© 2023 Kunming Institute of Botany, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.)

The relationship between monsoon circulation and regional hydrology in the Yangtze River Basin since the Last Glacial Maximum (LGM) remains unclear. In this study, we present speleothem (LS46) δ18O and δ13C records over the past 23.5 kyr from the Luoshui Cave in Central China. Stalagmite LS46 δ13C displayed a good similarity with variations in δD wax -derived monsoon precipitation from Lake TengchongQinghai (TCQH) and the extreme precipitation events identified by the IRM soft-flux from Heshang Cave, thus indicating that speleothem calcite δ13C reflects the changes in regional hydrology. The ensemble empirical mode decomposition (EEMD) and wavelet spectrum analyses revealed that the regional hydrology was paced by ∼2000-year periodicity during the LGM and last deglaciation and ∼ 1000-year periodicity during the Holocene, respectively. Our results further indicated that the El Niño-Southern Oscillation (ENSO) plays an important role in regulating changes in the frequency and magnitude of regional hydrology in the Yangtze River Basin under different climatic conditions. Moreover, our results demonstrated that δ18O and δ13C were coupled on multiple timescales, thus potentially indicating that local hydrological variations in the middle reaches of the Yangtze River are regulated by large-scale monsoonal circulation. However, we also found that the δ18O and δ13C profiles decoupled during the last deglaciation, likely due to a decrease in evapotranspiration in combination with a decrease in monsoon intensity and temperature during this period. Consequently, the regional hydrological conditions did not experience any dramatic changes. • The relationship between monsoon circulation and regional hydrology was explored. • We interpreted that stalagmite δ13C reflects changes in regional hydrology. • The hydrology exhibited a period of ∼2000 yr from the LGM to the deglaciation and ∼1000 yr during the Holocene. • We made calculations for the precipitation integrated during the Hs1, YD, and HCO relative to the past 2 kyr. • We found that the δ18O and δ13C coupled on multiple scales, but missing in last deglaciation. [ABSTRACT FROM AUTHOR]

Leaf wax molecular distributions and isotopic values are generally considered paleohydrologic proxies. Here we evaluate the sensitivity of alkane chain length distributions and compound-specific hydrogen isotopic compositions (δ 2 H alk ) in surface peats to environmental parameters across the monsoon region of China. The alkane average chain length (ACL), carbon predominance index (CPI) and δ 2 H alk values show relatively large variations in multiple samples from a single site, highlighting the complexity of the processes affecting these ratios at small spatial scales. Nonetheless, the site-averaged CPI values correlate significantly with the mean annual temperature ( r = − 0.57, p (α) < 0.001) and precipitation ( r = − 0.53, p (α) < 0.001), suggesting that climate is important to control CPI values, together with other influences. The large variation of δ 2 H alk values in a single peatland suggests that δ 2 H alk values may be affected by factors in addition to biosynthetic isotopic discrimination and the D/H ratio of the water available to the plants. It is interesting to note that the site-averaged δ 2 H alk values correlate poorly with the modeled yearly δ 2 H p values. In addition, the site-averaged apparent hydrogen isotope fractionation between C 31 n -alkanes and precipitation correlates with mean annual temperature. Together, our results show a relatively complex spatial pattern of δ 2 H alk values in a single peatland or along a climate transection. Thus, we caution that δ 2 H alk values would be affected by a series of factors, including the growth season length, the lipid synthesis time, the plant life forms, and/or the hydrogen isotope discrimination during lipid biosynthesis. More study is clearly required to elucidate the major controllers. [ABSTRACT FROM AUTHOR]

Previous research has shown a strong persistence for direct teleconnections between the East Asian summer monsoon (EASM) and high northern latitude climate variability during the last glacial and deglaciation, in particular between monsoon weakening and a reduced Atlantic meridional overturning circulation (AMOC). However, less attention has been paid to EASM strengthening as the AMOC was reinvigorated following peak Northern Hemisphere (NH) cooling. Moreover, climate model simulations have suggested a strong role for Antarctic meltwater discharge in modulating northward heat transport and hence NH warming, yet the degree to which Southern Hemisphere (SH) climate anomalies impacted the Asian monsoon region is still unclear. Here we present a new stalagmite oxygen-isotope record from the EASM affected region of central China, which documents two prominent stages of increased 18 O-depleted moisture delivery to the region through the transition from Heinrich Stadial 1 (HS1) to the Bølling–Allerød (B–A) interstadial; this is in general agreement with the other monsoonal records from both NH and SH mid to low latitudes. Through novel comparisons with a recent iceberg-rafted debris (IRD) record from the Southern Ocean, we propose that the two-stage EASM intensification observed in our speleothem records were linked with two massive Antarctic icesheet discharge (AID) events at ∼16.0 ka and ∼14.7 ka, immediately following the peak HS1 stadial event. Notably, the large increase in EASM intensity at the beginning of the HS1/B–A transition (∼16 ka) is relatively muted in the NH higher latitudes, and better aligns with the changes observed in the SH, indicating the Antarctic and Southern Ocean perturbations could have an active role in driving the initial EASM strengthening at this time. Indeed, Antarctic freshwater input to the Southern Ocean during these AID events would have cooled the surrounding surface waters and caused an expansion of sea ice, restricting the southern extent of the SH westerlies. Moreover, increased meltwater flux during IRD events would have freshened Antarctic Intermediate Water, leading to the increased formation of North Atlantic Deep Water and enhanced North Atlantic subsurface heat release, and causing a strengthening of the AMOC during the HS1-Bølling transition. The result of this sequence-of-events would have been warming in the North Atlantic whilst at the same time cooling in the Antarctic. The ensuing interhemispheric temperature gradient would have acted to push the ITCZ northward, weakening the Australian–Indonesian summer monsoon (AISM) whilst intensifying the EASM. [ABSTRACT FROM AUTHOR]

The oxygen, hydrogen, and carbon isotope ratios and major and trace element concentrations of surface waters are reported for the catchment of Lake Donggi Cona, Qinghai Province, China. The chemistry of the surface waters in the southeastern catchment is reflecting the dissolution of carbonate rocks, whereas thermal waters add sodium and chlorine to the waters in the northern catchment. The Dongqu River, draining the southeast catchment, contributes 87 to 94% to the water budget of the lake. Thermal waters and waters from the northern catchment add 6 to 13%. The combination of hydrogen and oxygen isotopes provides evidence that only small amounts of recycled lake water contribute to the precipitation in the catchment. Most of the moisture may be transported by the East Asian summer monsoon or an eastern branch of the South Asian monsoon into the Donggi Cona region. From oxygen isotope ratios it is calculated that about 45% of the lake water input is evaporated and 55% leaves the lake through a channeled outflow. The carbon isotope ratios identifies microbial respiration of organic matter, probably in soils and sediments of the catchment, as the major source of dissolved inorganic carbon in most surface waters and the lake. An isotope effect, from biological processes, in the lake is minor, and can be neglected in order to explain isotope ratios of inorganic carbon in lake water. The results imply that oxygen isotope ratios in the lake sediment archives mainly mirror the relation between precipitation and evaporation (P/E), which may be controlled by changes in the global water cycle like monsoon intensity or by tectonically driven local changes affecting the outflow flux. A comparison between lake archives based on ostracod shells and the modern system indicates similar δ 18 O values for the lake water since 4.3 ka but different δ 13 C DIC values. This discrepancy between carbon isotope ratios in ostracod shells and modern lake water samples may be due to thermal waters with high δ 13 C DIC emerging near the coring site. It is suggested that carbon isotopes of ostracods from a sediment drill core reflect the activity of a local thermal spring at the lake bottom, whereas oxygen isotopes provide evidence for an open lake system since about 11 ka and that the climate and environment of the Donggi Cona region changed very little over the last 4300 years. [ABSTRACT FROM AUTHOR]

ᅟ: ᅟ [ABSTRACT FROM AUTHOR]

The responses of Asian summer monsoon and associated precipitation to orbital forcing have been intensively explored during the past 30 years, but debate still exists regarding whether or not the Asian monsoon is controlled by northern or southern summer insolation on the precessional timescale. Various modeling studies have been conducted that support the potential roles played by the insolation in both hemispheres. Among these previous studies, however, the main emphasis has been on the Asian monsoon intensity, with the response of monsoon duration having received little consideration. In the present study, the response of the rainy season duration over different monsoon areas to orbital forcing and its contribution to total annual precipitation are evaluated using an atmospheric general circulation model. The results show that the durations of the rainy seasons, especially their withdrawal, in northern East Asia and the India-Bay of Bengal region, are sensitive to precession change under interglacial-like conditions. Compared to those during stronger boreal summer insolation, the Asian monsoon-associated rainy seasons at weaker insolation last longer, although the peak intensity is smaller. This longer duration of rainfall, which results from the change in land-ocean thermal contrast associated with atmospheric diabatic heating, can counterbalance the weakened intensity in certain places and induce an opposite response of total annual precipitation. However, the duration effect of Asian monsoon is limited under glacial-like conditions. Nevertheless, monsoon duration is a factor that can dominate the orbital-scale variability of Asian monsoon, alongside the intensity, and it should therefore receive greater attention when attempting to explain orbital-scale monsoon change. [ABSTRACT FROM AUTHOR]

ENSO induces coherent climate anomalies over the Indo-western Pacific, but these anomalies outlast SST anomalies of the equatorial Pacific by a season, with major effects on the Asian summer monsoon. This review provides historical accounts of major milestones and synthesizes recent advances in the endeavor to understand summer variability over the Indo-Northwest Pacific region. Specifically, a large-scale anomalous anticyclone (AAC) is a recurrent pattern in post-El Ni˜no summers, spanning the tropical Northwest Pacific and North Indian oceans. Regarding the ocean memory that anchors the summer AAC, competing hypotheses emphasize either SST cooling in the easterly trade wind regime of the Northwest Pacific or SST warming in the westerly monsoon regime of the North Indian Ocean. Our synthesis reveals a coupled ocean-atmosphere mode that builds on both mechanisms in a two-stage evolution. In spring, when the northeast trades prevail, the AAC and Northwest Pacific cooling are coupled via wind-evaporation-SST feedback. The Northwest Pacific cooling persists to trigger a summer feedback that arises from the interaction of the AAC and North Indian Ocean warming, enabled by the westerly monsoon wind regime. This Indo-western Pacific ocean capacitor (IPOC) effect explains why El Ni˜no stages its last act over the monsoonal Indo-Northwest Pacific and casts the Indian Ocean warming and AAC in leading roles. The IPOC displays interdecadal modulations by the ENSO variance cycle, significantly correlated with ENSO at the turn of the 20th century and after the 1970s, but not in between. Outstanding issues, including future climate projections, are also discussed. [ABSTRACT FROM AUTHOR]

The Sikouzi Section is located towards the northern limits of the East Asian summer monsoon, providing the opportunity of placing the stratigraphic record into the context of the East Asian summer monsoon history. We present here the results of the details of the sedimentology of the Neogene succession of the section and use these to provide insights into the evolving history of the East Asian summer monsoon. The record is marked by a strongly expressed early Miocene lacustrine phase. A well-defined evaporate bed defines the top of the lacustrine succession, marking the onset of more arid conditions during the middle Miocene. The overlying succession is dominated by a series of alluvial packages, extending into the late Pleistocene with varying stratigraphic architectures and including a subordinate lacustrine component. Given the regional setting, the onset of drier conditions during the middle Miocene must relate to a downturn of summer monsoon activity. We focus on the question: what 'forced' this palaeoclimate event? Earlier biostratigraphic work places the explanation of this change into the context of the global-scale middle Miocene climate reorganisation. Here we explore this question in the context of regional-scale climate dynamics and propose that the onset of drier conditions over the study area was a response to atmospheric subsidence driven by circulation changes related to the growth of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

In the Asian monsoon margin of northwest China, millennial-scale precipitation and effective moisture changes during the Holocene differ from those observed in the primary monsoon area. Whether these differences were caused by a change in precipitation or other hydroclimate factors remains controversial. We selected Huahai Lake, located in the western portion of the Hexi Corridor, at the northwest margin of the Asian monsoon area, to address this question. Using paleoclimate proxies (mineralogical assemblages and immobile elements) and results from a previous study, we inferred hydroclimate changes in this area during the early and middle Holocene (10.5-5.5 cal ka BP). Heavy precipitation and abundant runoff occurred during the early Holocene (10.5-8.8 cal ka BP). Proxies (carbonate content, total organic carbon and C/N) for precipitation minus evaporation (P − E) in the same section, however, revealed low P − E during the early Holocene and highest P − E in the middle Holocene (8.8-5.5 cal ka BP). Therefore, on a millennial timescale, precipitation amount and effective moisture changes were asynchronous during the early and middle Holocene. The precipitation and effective moisture pattern in the study area during that time span was different from patterns in both the Asian monsoon and westerly wind-influenced areas, suggesting an interplay between the two climate features. High precipitation during the early Holocene corresponded to a strengthened Asian monsoon. Highest P − E in the study area occurred during the middle Holocene and may have been caused by low evaporation, rather than high precipitation. [ABSTRACT FROM AUTHOR]

Annual radiocarbon from a massive Porites lutea coral collected from Hon Tre Island, Vietnam, South China Sea (SCS) was analyzed over a ~100-yr-long period from AD 1900 to 1986. The pre-bomb results from 1900–1953 show a steady Δ14C value of –54.4±1.8‰ (n=60). These values are similar to coral records located in the central and southern SCS and from Indonesian waters, but are lower than those from Japan. Following the input of anthropogenic bomb 14C, our results show a sharp increase in Δ14C from 1960, reaching a peak value of 155.3‰ in 1973. The Hon Tre Island post-bomb Δ14C values are lower than those of other corals located in the SCS and Japan, but higher compared to those in the Indonesian Seas. This study infers a seasonal input of upwelled water depleted in 14C from the deeper SCS basin that originates from the tropical Pacific via the Luzon Strait. The bifurcation of the North Equatorial Current feeds the surface and intermediate currents in the SCS and Makassar Strait region. However, unlike the Makassar site, this study’s coral Δ14C does not receive lower 14C water from the South Pacific Equatorial Current. The Vietnam record therefore represents a unique oceanographic position, reflecting the seasonal influence of older, deeper SCS waters that upwell periodically in this area and have modified the surface waters locally in this region over the last 100 yr. [ABSTRACT FROM AUTHOR]

Aim The accumulation of supraspecific lineages in Asia has been linked to climatic changes and tectonic events starting in the Miocene, but few studies have extended the intraspecific history of relict plants in subtropical China back to the Early or Middle Miocene. In this study, we investigate the effects of events from the late Early Miocene onwards on the evolutionary history of a relict plant, Cyclocarya paliurus, in subtropical China. Location Subtropical China. Methods Sequence variation in two chloroplast intergenic spacers ( atpB -rbcL and psbA -trnH) and one nuclear gene ( PHYA) was investigated across 57 populations of C. paliurus. Standard population genetic analyses, estimation of the most recent common ancestor of chloroplast haplotypes and diversification rate analyses were carried out, and Bayesian skyline plots were constructed. Results The time to the most recent common ancestor of all 17 chloroplast haplotypes in C. paliurus was 16.69 Ma (95% HPD 8.42-27.86 Ma), which largely coincides with the initial intensification of the Asian monsoon and global climate cooling during the Early to Middle Miocene. Chloroplast lineage diversification started to increase in the early Late Miocene, with peaks at c. 9.6 Ma and c. 3.6 Ma, corresponding temporally to two subsequent intensification events of the Asian monsoon. Bayesian skyline plots of both markers revealed that C. paliurus could have experienced at least two waves of expansion since the middle Pleistocene. The distributions of chlorotypes and clades were both consistent with a multiple-refugia model but with strong signals of range expansion. Main conclusions This study provides a long evolutionary profile of an archaic plant species in subtropical China, dating from the late Early Miocene. Our results suggest that the occurrence of the Asian monsoon and associated tectonic events, as well as Pleistocene climate changes, had a pervasive influence on the phylogeographical structure of plants in subtropical China. [ABSTRACT FROM AUTHOR]

The South Asian monsoon is one of the most significant manifestations of the seasonal cycle. It directly impacts nearly one third of the world's population and also has substantial global influence. Using 27-year integrations of a high-resolution atmospheric general circulation model (Met Office Unified Model), we study changes in South Asian monsoon precipitation and circulation when horizontal resolution is increased from approximately 200-40 km at the equator (N96-N512, 1.9°-0.35°). The high resolution, integration length and ensemble size of the dataset make this the most extensive dataset used to evaluate the resolution sensitivity of the South Asian monsoon to date. We find a consistent pattern of JJAS precipitation and circulation changes as resolution increases, which include a slight increase in precipitation over peninsular India, changes in Indian and Indochinese orographic rain bands, increasing wind speeds in the Somali Jet, increasing precipitation over the Maritime Continent islands and decreasing precipitation over the northern Maritime Continent seas. To diagnose which resolution-related processes cause these changes, we compare them to published sensitivity experiments that change regional orography and coastlines. Our analysis indicates that improved resolution of the East African Highlands results in the improved representation of the Somali Jet and further suggests that improved resolution of orography over Indochina and the Maritime Continent results in more precipitation over the Maritime Continent islands at the expense of reduced precipitation further north. We also evaluate the resolution sensitivity of monsoon depressions and lows, which contribute more precipitation over northeast India at higher resolution. We conclude that while increasing resolution at these scales does not solve the many monsoon biases that exist in GCMs, it has a number of small, beneficial impacts. [ABSTRACT FROM AUTHOR]

The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum (HCO), using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources: mangrove-derived, terrigenous, and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope ( δC) and the molar ratio of total organic carbon to total nitrogen (C/N). The percentage of mangrove-derived organic matter (MOM) contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests. [ABSTRACT FROM AUTHOR]

The degree to which warming of the planet will alter Asia's water resources is an important question for food, energy, and economic security. Here we present geological evidence, underpinned by radiometric dating and dendrochronology, and bolstered by hydrological modeling, indicating that wetter-than-present conditions characterized the core of the inner Asian desert belt during the Little Ice Age, the last major Northern Hemispheric cold spell of the Holocene. These wetter conditions accompanied northern mid-latitude cooling, glacier expansion, a strengthened/southward-shifted boreal jet, and weakened south Asian monsoons. We suggest that southward migration of grasslands in response to these wetter conditions aided the spread of Mongol Empire steppe pastoralists across Asian drylands. Conversely, net drying over the 20th century has led to drought that is unprecedented for the past ∼830 years, and that could intensify with further heating of the Asian continent. [ABSTRACT FROM AUTHOR]

In-situ observations find that offshore phytoplankton blooms occur occasionally in the north-central Taiwan Strait (TWS) in winter, but the formation mechanisms behind are not yet understood. We simulate the offshore bloom scenario in the winter of 1998 with a coupled physical–biological numerical model. Model results illustrate that when the northeasterly wind is relaxed, a cross-strait current is induced, which carries diluted Min-Zhe Coastal Water (MZCW) offshore, extending into the upper layer of the western TWS. Vertical mixing is weakened in the western TWS due to intensified stratification formed by the location of fresh MZCW over saline water. Consequently, the vertical diffusion of chlorophyll decreases, and the bloom occurs in the upper layer of the western TWS. Additionally, the cross-strait current carries the high chlorophyll concentration from near-shore to offshore regions, forming a maximal offshore chlorophyll concentration. We propose that the relaxation of the northeasterly wind acts as a trigger for the winter bloom occurrence in the TWS through complicated physical processes, i.e., the diluted MZCW extending offshore, the stratification intensifying and mixing weakening, forming distinctive characteristics of winter blooms in the TWS. [ABSTRACT FROM AUTHOR]

An empirical statistical system for quantitative forecasting of monthly precipitation in Korea has been developed using the cyclostationary empirical orthogonal function (CSEOF) and the canonical correlation analysis (CCA) with sea surface temperature (SST) data as the predictor. Monthly Korean precipitation and SST data are comprehensively analyzed using the empirical orthogonal function (EOF) technique and the CSEOF technique, respectively, and the CSEOF technique can exhibit the spatial distribution and temporal evolution characteristics of variability along with recurrent seasons of precipitation in Korea. Through a multivariate regression method, the CCA technique is used to forecast precipitation with different lead times, and the forecasting results indicate that the CSEOF-CCA forecasting model agrees well with the observation data and is particularly useful in forecasting seasonal precipitation variations in Korea. [ABSTRACT FROM AUTHOR]

Calcareous root tubes or rhizoliths have a strong potential for paleoenvironmental studies, especially in reconstructing paleoenvironmental conditions and paleovegetation. Previous studies suggested that the effectivity of the moisture level affects the formation of calcareous root tubes in the deserts of the Alashan Plateau, Northwest China. However, it remains unclear whether the temporal distribution of calcareous root tubes can be used to reconstruct paleo-effective moisture in this area. In this study, based on conventional 14 C dating results of 34 Holocene calcareous root tube samples collected from the Badain Jaran Desert, the Tengger Desert and the Ulan Buh Desert in the Alashan Plateau of northwestern China, millennial-scale changes in paleo-effective moisture during the Holocene in this area were reconstructed. The frequency of the 14 C dating results demonstrates that ~ 62% of the Holocene samples were dated to 7–5 cal kyr BP, and ~ 38% of the Holocene samples were dated to 4–2 cal kyr BP, indicating an arid period during the early Holocene (before 8.0 cal kyr BP), a humid period during the mid-Holocene (8.0–5.0 cal kyr BP) and a humid to arid period during the late Holocene (after 5.0 cal kyr BP). The reconstruction results were consistent with other previous reconstruction results from lake sediments and aeolian sand–lacustrine sequences, which indicated that temporal distribution of calcareous root tubes can reflect millennial-scale changes in paleo-effective moisture in this area. However, a single sample could indicate local environmental changes that may differ from the overall desert environmental changes. Hence, the relatively humid environmental record obtained from the presence of calcareous root tubes is a local signal or a regional signal that should be noted. [ABSTRACT FROM AUTHOR]

The 4.2 ka event was a widespread abrupt cooling event in the Northern Hemisphere. However, there was a spatially inconsistent hydroclimatic response to the 4.2 ka event in the Asian monsoon region. To further characterize and to determine the origin of this phenomenon, we present a pollen record spanning the interval from 10.7 ka to the present from a subalpine lake in the Hengduan Mountains, southwestern China, which are climatically influenced by the Indian monsoon; and we then reconstruct the spatial pattern of the hydroclimatic response to the 4.2 ka event across the Asian monsoon region, based on a synthesis of our own and previously published data. The results reveal the following. (i) During the interval of 4.5–3.9 ka (spanning the 4.2 ka event) in the subtropical mountains there were abrupt decreases in evergreen broadleaved trees, including evergreen Quercus , Castanopsis and Cyclobalanopsis. (ii) The hydroclimatic response to the 4.2 ka event across the Asian monsoon region was characterized by a tripolar precipitation pattern, with decreased rainfall over India and southwestern and northern China, and increased rainfall over central China. Therefore, we conclude that the hydroclimatic response to the 4.2 ka event in the Asian monsoon region was spatially heterogenous, which we argue was related to the slowdown of the Atlantic Meridional Overturning Circulation (AMOC). During the interval of 4.5–3.9 ka, cooling at high latitudes of the Northern Hemisphere, caused by AMOC weakening, led to the southward movement of the Intertropical Convergence Zone (ITCZ), which resulted in decreased rainfall over most of the Asian monsoon region. The wet conditions in central China may have been modulated by the southward movement of the westerlies, which was also caused by the cooling at northern high latitudes. The southward displacement of the westerlies restricted the northward penetration of the monsoonal air flow, and thus the monsoon rainbelt stagnated over central China, where there was a corresponding increase in precipitation. • Evergreen broadleaved trees decreased between 4.5 and 3.9 ka in southwestern China. • The change infers a shift to a cool and dry climate, coincident with the 4.2 ka event. • Records of the 4.2 ka event from across the Asian monsoon region were synthesized. • A tripolar Asian monsoon precipitation pattern occurred during the 4.2 ka event. • The 4.2 ka event was related to the weakened Atlantic Overturning Circulation. [ABSTRACT FROM AUTHOR]

The early Miocene (~ 16–23 Ma) marks a critical transition in the Earth climate history from an Oligocene (~ 23–34 Ma) cooling trend towards the well-documented warm middle Miocene Climate Optimum at ~ 15 Ma. In eastern Asia, this transition links changes of key topographic features, such as the Tibetan plateau and the Mongolian plateau, and their impact on the reorganization of climate systems, such as the Eastern Asian summer monsoon. Yet the dynamics of the interplay among these factors remain poorly understood, precluding our understanding of future climate changes. Global temperatures during the early Miocene were warmer than the present day by 3–4 °C, which are seemingly incompatible with both the low (< 300 ppm) and high (> 800 ppm) ends of presently available reconstructions of atmospheric carbon dioxide (CO 2). Here we report a rare co-occurrence of two redwoods, Metasequoia and Sequoia , from sediments of the early Miocene Hannuoba Formation in Zhuozi County in China's Inner Mongolia at the southeastern margin of the current Mongolian plateau. The Zhuozi Metasequoia fossils possess uneven type cuticles, which dominate its living population but have rarely been reported throughout the abundant fossil record of this genus. By applying well-constrained Franks model parameters obtained from these redwood fossils using a cleared leaf epidermis method, we estimated the early Miocene CO 2 level at ~ 400 ppm, putting it at the lower end of the model requirement for sustaining a relatively warm global temperature during this period. Our Franks model estimates are ~ 100 ppm higher than that obtained using stomatal index method based on Metasequoia material, further confirming a systematic underestimation of ancient CO 2 using the Metasequoia stomatal index method reported in previous analyses. We recommend a re-examination of previous CO 2 reconstructions solely based upon Metasequoia 's inverse relationship between stomatal index and CO 2 concentrations. Ultimately, the occurrence of these redwood fossils in Inner Mongolia is consistent with a weak or muted Eastern Asian summer monsoon in the region with the absence of an elevated Mongolian plateau during the early Miocene. A shift of moisture sources for the region accompanying the change from a Westerlies-dominated climate to the present-day monsoon-dominated climate system occurred after the early Miocene time. • First report of co-occurring Miocene Metasequoia and Sequoia from Inner Mongolia. • Metasequoia fossils possess uneven type cuticles as in its living population. • Franks model estimates ~ 400 ppm atmospheric CO 2 for early Miocene. • Recommend a re-examination of previous CO 2 estimates based upon stomatal frequency. • Weak or muted Eastern Asian summer monsoon in the region during the early Miocene. [ABSTRACT FROM AUTHOR]

• Contributions of terrestrial and aquatic sources to stream food web were quantified. • Isotopic values of the organic matter sources showed no spatial and temporal change. • Consumer δ13C values were consistent with the instream biofilm and seston values. • Aquatic production was the primary source supporting lotic and lentic food webs. • Trophic importance of aquatic algal production counteracts terrestrial-aquatic links. Spatial and temporal variability in the trophic base of food webs is an inevitable ecological attribute in aquatic ecosystems with the role of aquatic and terrestrial sources varying from system to system. Despite high algal biomass, an apparent increase in terrestrial detritus during the East Asian summer monsoon would be expected to alter the dominant food web base from the pre- to post-monsoon period. The δ13C and δ15N values of common aquatic invertebrates and fish were compared with those of their potential sources of organic matter across the upstream channel and lacustrine habitats during the pre- and post-monsoon periods in the Se-oak Stream system of Korea. The purpose was to identify the variability in trophic structure (niche and diversity) at the community level and to quantify the contribution of terrestrial and aquatic carbon sources to the food web base. The δ13C and δ15N values of the major potential organic matter sources differentiated allochthonous leaf litter and riparian vegetation from autochthonous biofilm and seston, but with no significant spatial and temporal changes. The δ13C values of consumers fell within a narrower range than that of organic matter sources, consistent with the instream biofilm and seston values. However, the consumer δ15N values spanned a broad range, increasing from invertebrates to fish. The resultant niche overlaps of consumers in the isotopic niche space between seasons and locations, their narrower horizontal niche breadths compared to organic matter sources, and the isotope mixing-model estimates indicated that aquatic production was the primary source of organic matter supporting the aquatic food webs. Overall, the results revealed a consistent dominance of autochthonous trophic bases in both lotic and lentic food webs before and after the summer monsoon. Our findings, which highlight the trophic importance of aquatic algal production facilitated by anthropogenic nutrients in this shallow, low-turbidity, and well-illuminated stream food web, may provide insight into ecosystem processes that counteract potential terrestrial-aquatic links to influence food web dynamics based on natural nutrient sources in deep, highly turbid, or shaded stream counterparts. [ABSTRACT FROM AUTHOR]

This study investigated the future climate change impacts on water resources and delineated the highly susceptible zones in the Asian monsoon region. Three General Circulation Models (GCMs) were employed for future climate change projections. The change factor method with bilinear interpolation was used to project climate change at 0.5° horizontal gird resolution. The Variable Infiltration Capacity (VIC) macroscale hydrological model was employed to project runoff using future climate change scenarios. Average temperature, precipitation and runoff were projected to increase by all future periods i.e., 2020s, 2050s and 2080s. In particular by 2080s, they were projected to increase by 3.7 °C, 10.7 and 11.1 %, respectively. Latitudinal and longitudinal analysis was performed to investigate the features of future climate change at different latitudes and longitudes. The climate change projections revealed susceptible regions in East Asia over southern China, and in South Asia over the Tibetan plateau, India and Pakistan. Southern China was projected to be adversely affected by climate change with precipitation and runoff increase during summer and autumn seasons, and decrease during winter and spring seasons. Similarly, distinct climate change features were projected over the Tibetan plateau and north Pakistan with significant increase of average annual temperature and decrease of average annual precipitation and runoff. This change is alarming for the world's longest glaciers outside the Polar Regions. On the other hand, the precipitation and runoff were projected to significantly increase over southwest India and south Pakistan. That may have positive impact over extremely water-scarce regions i.e., the Thar Desert, the Cholistan Desert and the Kharan Desert, but also poses a serious threat to the flood prone areas of South India and Pakistan. [ABSTRACT FROM AUTHOR]

There remains substantial debate concerning the relative roles of tectonics and of global climate in pacing the evolution of aridity in Central Asia over the Cenozoic. Tibetan Plateau uplift, variable monsoonal strength, Paratethys retreat, and reduced moisture transport from the North Atlantic have all been hypothesized to drive aridity in Central Asia. Distinguishing between these mechanisms requires knowledge of moisture transport pathways to Central Asia through time. Presently, Central Asia receives recycled, high δ 18 O moisture that has been transported across Eurasia by the westerlies, while southern Tibet receives low δ 18 O moisture distilled by passage over the Himalaya. Here, we reconstruct the spatial distribution of oxygen isotopes in precipitation since the early Eocene, using a compilation of δ 18 O data from 2750 sedimentary carbonate samples. Across Asia, the spatial distribution of paleo-precipitation δ 18 O remains remarkably similar through time, with low δ 18 O values in the lee of the Himalaya in southern Tibet, constant, high δ 18 O values in Central Asia, and intermediate values on the central Plateau despite independent evidence for substantial changes in both topography and climate through time. These results suggest that a long-standing topographic feature has continuously blocked southerly moisture, and subsequent progressive uplift of the Tibetan Plateau has had little impact on Central Asian climate. In turn, southerly monsoonal moisture has never persistently extended northward of the central Plateau. As a result, the westerlies have remained the dominant moisture source in Central Asia since at least the early Eocene. Therefore, sedimentary aridity indicators in Central Asia, such as loess deposition, are controlled by the trans-Eurasian, westerly moisture flux rather than Tibetan Plateau uplift. [ABSTRACT FROM AUTHOR]