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A comprehensive and integrative view of East Asian monsoon evolution during the Holocene is still under debate, and additional high-resolution proxy records from climatically sensitive locations are requisite to solve this complex issue. In this paper, we present three well-dated mud/peat cores from a paleo-pingo depression in the Sanjiang Plain, a climatically sensitive region to monsoon variation, to reveal the paleoenvironmental history of the wetland and discuss the regional impacts from monsoon evolution. A paleolake developed in the study area before 5.5 ka BP, and a peatland initiated thereafter consequent upon the gradual shrinking of the paleolake. This transition lasted until 4.5 ka BP, when the paleolake changed entirely to a wetland. Considering the prevalent monsoon climate in the Sanjiang Plain, we suggest that the lake-to-wetland transition from 5.5 to 4.5 ka BP indicates a rapid decline of the East Asian summer monsoon in addition to autogenic basin infilling processes. Such a remarkable monsoon weakening event has been documented across northern China, and we associate this with ocean–atmosphere interactions throughout low-latitude regions. [ABSTRACT FROM AUTHOR]

In arid regions, because of spatial variability, using single climate records is difficult to reconstruct the past climate change for the drainage basins. Holocene environmental records were collected from the upper, middle and lower regions of the Shiyang River drainage basin in the marginal area of the Asian monsoon (northwest China). The main objective of this paper was to compare the records from the terminal lake and the middle and upper reaches of the basin to study the basin-wide environmental changes. During the early Holocene the vegetation was sparse, and the effective moisture was relatively low in the basin. The Holocene Climatic Optimum started between 7.0 and 8.0 cal ka BP, during which the lake level reached the highest level in the terminal lake; the vegetation density and the effective moisture reached the highest level during the Holocene in the drainage basin. From 4.7 cal ka BP the terminal lake began to shrink, while the vegetation density decreased dramatically. In the middle and upper regions of the drainage, the effective moisture began to decrease since 3.5 cal ka BP, and the arid tendency was earlier in the terminal lake than it was in the middle and upper regions of the drainage basin. During the early Holocene the relatively arid environment was affected by the gradually intensifying East Asian monsoon and the dry westerly winds. The mid-Holocene Optimum benefited from the intensive East Asian monsoon and the humid westerly winds. Then, the East Asian monsoon retreated since the late-Holocene. In the basin the arid tendency may be related to the retracting of the East Asian monsoon. However, the intensifying acidification after 1.5 cal ka BP may be correlated to the increasing dryness of the westerly winds. [ABSTRACT FROM AUTHOR]

A precisely 230Th-dated stalagmite δ13C profile from Hulu Cave, China, is presented to characterize the frequency and pattern of millennial-scale Asian monsoon (AM) variability from 160.6 to 132.5 ka. Evidence for an antiphased relationship of the δ13C and δ18O on the millennial scale suggests that the δ13C is indicative of the local hydrological cycle associated with changes in AM strength. Owing to the δ13C responding to AM changes more sensitively than the δ18O, we could identify 15 strong AM events that correlate to cold intervals recorded in Antarctic ice cores within 230Th dating uncertainty. This result supports a dynamic link of AM strength and southern hemispheric climates via the cross-equatorial airflows. Power spectrum analysis shows a predominant periodicity of 1.5–2.5 ka for the δ13C profile, similar to the Dansgaard-Oeschger frequency during the last glacial period. Moreover, the AM events are characterized by rapid transitions at the onset, suggesting that the observed millennial-scale AM variability is likely forced by northern high-latitude climates via north–south shifts of the Intertropical Convergence Zone associated with the bipolar seesaw mechanism. As evidence for a common mechanism for ice age terminations, a strong AM event (~134 ka) surrounding Termination II is analogous to the Bølling-Allerød warming interval. [ABSTRACT FROM AUTHOR]

In this study, we compare the resolution sensitivity of the Asian Summer Monsoon (ASM) in two Atmospheric General Circulation Models (AGCMs): the MRI-AGCM and the MetUM. We analyze the MetUM at three different resolutions, N96 (approximately 200-km mesh on the equator), N216 (90-km mesh) and N512 (40-km mesh), and the MRI-AGCM at TL95 (approximately 180-km mesh on the equator), TL319 (60-km mesh), and TL959 (20-km mesh). The MRI-AGCM and the MetUM both show decreasing precipitation over the western Pacific with increasing resolution, but their precipitation responses differ over the Indian Ocean. In MRI-AGCM, a large precipitation increase appears off the equator (5-20°N). In MetUM, this off-equatorial precipitation increase is less significant and precipitation decreases over the equator. Moisture budget analysis demonstrates that a changing in moisture flux convergence at higher resolution is related to the precipitation response. Orographic effects, intra-seasonal variability and the representation of the meridional thermal gradient are explored as possible causes of the resolution sensitivity. Both high-resolution AGCMs (TL959 and N512) can represent steep topography, which anchors the rainfall pattern over south Asia and the Maritime Continent. In MRI-AGCM, representation of low pressure systems in TL959 also contributes to the rainfall pattern. Furthermore, the seasonal evolution of the meridional thermal gradient appears to be more accurate at higher resolution, particularly in the MRI-AGCM. These findings emphasize that the impact of resolution is only robust across the two AGCMs for some features of the ASM, and highlights the importance of multi-model studies of GCM resolution sensitivity. [ABSTRACT FROM AUTHOR]

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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]

Eocene palynological samples from 37 widely distributed sites across China were analysed using co-existence approach to determine trends in space and time for seven palaeoclimate variables: Mean annual temperature, mean annual precipitation, mean temperature of the warmest month, mean temperature of the coldest month, mean annual range of temperature, mean maximum monthly precipitation and mean minimum monthly precipitation. Present day distributions and observed climates within China of the nearest living relatives of the fossil forms were used to find the range of a given variable in which a maximum number of taxa can coexist. Isotherm and isohyet maps for the early, middle and late Eocene were constructed. These illustrate regional changing patterns in thermal and precipitational gradients that may be interpreted as the beginnings of the modern Asian Monsoon system, and suggest that the uplift of parts of the Tibetan Plateau appear to have taken place by the middle to late Eocene. [ABSTRACT FROM AUTHOR]

Drought patterns across monsoon and temperate Asia over the period 1877-2005 are linked to Indo-Pacific climate variability associated with the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). Using the Monsoon Asia Drought Atlas (MADA) composed of a high-resolution network of hydroclimatically sensitive tree-ring records with a focus on the June-August months, spatial drought patterns during El Niño and IOD events are assessed as to their agreement with an instrumental drought index and consistency in the drought response amongst ENSO/IOD events. Spatial characteristics in drought patterns are related to regional climate anomalies over the Indo-Pacific basin, using reanalysis products, including changes in the Asian monsoon systems, zonal Walker circulation, moisture fluxes, and precipitation. A weakening of the monsoon circulation over the Indian subcontinent and Southeast Asia during El Niño events, along with anomalous subsidence over monsoon Asia and reduced moisture flux, is reflected in anomalous drought conditions over India, Southeast Asia and Indonesia. When an IOD event co-occurs with an El Niño, severe drought conditions identified in the MADA for Southeast Asia, Indonesia, eastern China and central Asia are associated with a weakened South Asian monsoon, reduced moisture flux over China, and anomalous divergent flow and subsidence over Indonesia. Insights into the relative influences of Pacific and Indian Ocean variability for Asian monsoon climate on interannual to decadal and longer timescales, as recorded in the MADA, provide a useful tool for assessing long-term changes in the characteristics of Asian monsoon droughts in the context of Indo-Pacific climate variability. [ABSTRACT FROM AUTHOR]

The regional monsoons of the world have long been viewed as seasonal atmospheric circulation reversal-analogous to a thermally-driven land-sea breeze on a continental scale. This conventional view of monsoons is now being integrated at a global scale and accordingly, a new paradigm has emerged which considers regional monsoons to be manifestations of global-scale seasonal changes in response to overturning of atmospheric circulation in the tropics and subtropics, and henceforth, interactive components of a singular Global Monsoon (GM) system. The paleoclimate community, however, tends to view 'paleomonsoon' (PM), largely in terms of regional circulation phenomena. In the past decade, many high-quality speleothem oxygen isotope (δO) records have been established from the Asian Monsoon and the South American Monsoon regions that primarily reflect changes in the integrated intensities of monsoons on orbital-to-decadal timescales. With the emergence of these high-resolution and absolute-dated records from both sides of the Equator, it is now possible to test a concept of the 'Global-Paleo-Monsoon' (GPM) on a wide-range of timescales. Here we present a comprehensive synthesis of globally-distributed speleothem δO records and highlight three aspects of the GPM that are comparable to the modern GM: (1) the GPM intensity swings on different timescales; (2) their global extent; and (3) an anti-phased inter-hemispheric relationship between the Asian and South American monsoon systems on a wide range of timescales. [ABSTRACT FROM AUTHOR]

In the mid-latitude regions of the Asian continent, Zhuye Lake is located in the northwest margin of the Asian monsoon, where the modern climate is affected by the Asian monsoon and Westerlies. In this study, we investigated the absolutely dated Holocene records in Zhuye Lake for detecting the Holocene climate cycles. Totally, 14 C dates and 6 optically simulated luminescence (OSL) dates are obtained from the QTH01 and QTH02 sections. The proxies of grain-size, total organic carbon content (TOC), C/N and δC are used for wavelet analysis, and the results show obvious ∼256, ∼512 and ∼1024-year climate cycles, which are consistent with the Holocene millennial and centennial scale climate cycles in the typical Asian summer monsoon domain. In different parts of the Zhuye Lake, the Holocene sediments show variable climate cycles that are affected by the lake basin topography. In the Zhuye Lake, the Holocene climate cycles are mainly correlated with the solar-related Asian summer monsoon variability and the North Atlantic ice-rafting events. [ABSTRACT FROM AUTHOR]

Limited information is available on how the Asian monsoon influences contemporary lake processes, seasonal patterns and interannual variation. Data sets from Nepal (Indian monsoon region) and South Korea (East Asian monsoon region) along with published literature show a wide range in the response of Asian lakes to the seasonal monsoon. Cross-system patterns show nutrients and algal biomass peak in most lakes in response to monsoon inflow, which suggests nonpoint sources dominate external loading. This seasonal increase may be the general phenological model for nutrients and phytoplankton in lakes in monsoon regions. Major ions show dilution by surface runoff during the monsoon and post-monsoon increases. Dilution of nutrients in fertile systems during the monsoon suggests point source inputs dominate peak loads during the non-monsoon period. Peak monsoon runoff can enter the water column of large stratified lakes as a density-dependent interflow at depth in the water column with little direct influence on the mixed layer. In these water bodies nutrients in surface water can be lower during strong monsoon seasons because of sub-surface loading. Short-interval data from individual lakes show the linkage between nutrients and phytoplankton biomass can be uncoupled by physical processes and light limitation, resulting in considerable temporal variation. Collectively these mixed responses limit our ability to generalize patterns or predict conditions in individual lakes during the monsoon. [ABSTRACT FROM AUTHOR]