Data for the publication "Late Quaternary East Asian summer monsoon variability deduced from lacustrine mineral magnetic records of Dahu Swamp, southern China"
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Swamp
East Asian Monsoon
Southern china
Swamp
East Asian Monsoon
Southern china
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冬季モンスーンはシベリア高気圧と周囲の低気圧との間の大気循環による現象である．東アジアではシベリア高気圧とアリューシャン低気圧や赤道・オーストラリア低気圧との間の風で特徴付けられ，日本列島周辺では北西季節風が卓越する．この低温で乾燥した北西風は，ロシア極東沿岸日本海の表層水を冷却し，沿岸付近では海氷を形成させる．冷却され，海氷形成時に排出された高塩分水が加わって重くなった表層水は沈み込んで日本海固有水と呼ばれる深層水を形成する．最近の海洋観測結果から，深層水の形成は海氷が形成される極端に寒い冬に起こっているので，海氷と深層水の形成は冬季モンスーンの指標となると考えられる．本稿では，過去16万年間の海氷の発達度合いを示す漂流岩屑の量と冷たくて酸素に富んだ深層水の指標となる放散虫Cycladophora davisianaの産出量を検討した．その結果，酸素同位体ステージ3－5においては，両者とも千年規模の変化を示し，東アジア冬季モンスーンがこの時期に千年規模で変動していたことを示唆する．両者が高い値を示す時期には冬季モンスーンが強かった可能性が高い．同時期の日本海堆積物にはやはり千年規模での変動をもつ夏季モンスーンの記録が暗色層として残されているので，これとの対応関係を見ることで，1本のコアから夏季・冬季モンスーンの強弱の歴史と両者の関係を解明できる可能性がある．
East Asian Monsoon
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Significance Desert regions were not always dry, and in the geological past, they experienced periods of wetter and drier conditions. Understanding these wet–dry cycles in arid regions is an important scientific endeavor that could provide information related to their future variations. Environmental variability of deserts in monsoonal regions are controlled by monsoon-derived precipitation. Here, we show that the Tengger Desert of northern China experienced drying every 400 thousand years, corresponding to the Earth orbital eccentricity minimum, forced by variations in the East Asian monsoon. This finding requires a revision of the traditional view of Northern Hemisphere ice sheet forcing of the East Asian monsoon based on Chinese Loess Plateau records.
East Asian Monsoon
Speleothem
Tropical monsoon climate
Forcing (mathematics)
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Polar front
East Asian Monsoon
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Studies on climate variability over the region of monsoon Asia mostly during the Quaternary, based on various sources of proxy data have been reviewed. Increasing interest to understand the processes of monsoon system over the Asian region as well as the availability of data from variety of reliable proxy sources such as, ocean sediments, ice cores and historical documents have encouraged the palaeoclimatic studies in this region. Inferences drawn from the multiproxy sources indicate good association of glacial and inter-glacial phases with over all monsoon flow. Warm and wet periods are generally characterized by strong summer monsoon, where as, weak monsoonal activities were observed during cold and dry periods. All India monsoon rainfall since early 17th century based on dendroclimatic reconstructions shows trend-less nature with large interannual variability as seen in the instrumental record of recent century. Historical evidences over this region are a potential source of information on contemporary climate change.
Proxy (statistics)
East Asian Monsoon
Ice core
Paleoclimatology
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The South Asran monsoon plays a fundamental role in determing the climatology of India and surrounding countries The Late Quaternary provides an Ideal settting on which to study the monsoon's response to the variety of forcing factors that were slowly changing throughout this time Understanding paleomonsoon varibility is a critical step towards predicting how future monsoons will respond to climate change. A sequence of atmosphere general circulation model (AGCM) simulations that spans most of the Holocene at 500-year intervals indicates a much stronger and wetter Early Holocene summer monsoon whose maxlmum jet core was dsplaced northward by nearly 3 degrees of latitude and which placed the eastern margin of the Thar Desert further west than today by nearly 5 degrees of longitude Simulated climate over India shifted towards drier and less humid conditions in the Mid-Holocene (7,000-6,000 years B P), although both the summer and winter monsoons remained stronger than today in all simulations The gradual decrease in summer monsoon strength from the Mid-Holocene to the present demonstrates the governing role of insolation during this time. A second sequence of coupled atmosphere-ocean General Circulation Model simulations is also performed to examine how the monsoon responded at the Last Glaclal Maximum (LGM) and during the Early- and Mid-Holocene (9,000 and 6,000 years B P respectively) when simulated ocean temperatures are allowed to change Changes in the coupled model are In accordance wrth those of the AGCM experiments wrth the additlon that the LGM summer monsoon was much weaker than today Simulated moisture transport in to the Himalaya results in a varying spatia1 pattern of snow accumulation that rs in accordance with reconstructions of Himalayan glacier expansion at the LGM and during the Holocene.
Forcing (mathematics)
Longitude
East Asian Monsoon
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Abstract Quaternary East Asian winter monsoon (EAWM) evolution has long been attributed to high‐latitude Northern Hemisphere climate change. However, it cannot explain the distinct relationships of the EAWM in the northern and southern East Asian marginal sea in paleoclimatic records. Here we present an EAWM record of the northern East China Sea over the past 300 ka and a transient climate simulation with the Kiel Climate Model through the Holocene. Both proxy record and simulation suggest anticorrelated long‐term EAWM evolution between the northern East China Sea and the South China Sea. We suggest that this spatial discrepancy of EAWM can be interpreted as El Niño–Southern Oscillation (ENSO)‐like controlling, which generates cyclonic/anticyclonic wind anomalies in the northern/southern East Asian marginal sea. This research explains much of the controversy in nonorbital scale variability of Quaternary EAWM records in the East Asian marginal sea and supports a potent role of tropical forcing in East Asian winter climate change.
East Asian Monsoon
Siberian High
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Abstract The lack of long‐term and well‐preserved terrestrial archives from southern China largely impedes our understanding of past variability in the East Asian summer monsoon (EASM). In this study, we developed rainfall/precipitation‐related records by conducting a systematic mineral‐magnetic investigation on Dahu Swamp sediments over the past ~47.0 ka. The integrated magnetic results show that the magnetic minerals in the sediments were mainly catchment derived, likely reflecting hydroclimatic changes associated with EASM strength. In combination with other climatic proxies, our magnetic records reveal a relatively wet climate during the middle‐late Marine Oxygen Isotope Stage 3 and the Holocene and a relatively dry climate during the Marine Oxygen Isotope Stage 2, which broadly follow the precession‐induced summer insolation changes in the middle‐low latitudes of the Northern Hemisphere. The regional heterogeneity of the EASM rainfall evolution might be ascribed to the changes in timing and duration of Mei‐yu Front in China, which were closely associated with the El Niño/Southern Oscillation activities through its effects on the Western Pacific Subtropical High position. Long‐term climatic patterns inferred from Dahu Swamp were broadly similar to those of the Western Pacific Warm Pool region, especially during the mid‐Holocene rainfall optimum period, further supporting that the thermal mean states of the tropical Pacific associated with El Niño/Southern Oscillation modes may influence EASM precipitation. Our results highlight the coupled influence of external insolation forcing and internal low‐latitude processes on the spatial and temporal EASM variability, and understanding these influences could be critical to the prediction of future monsoon behavior under ongoing and future global warming.
East Asian Monsoon
Swamp
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Marine sediment core MD012394 from the Vietnam coastal upwelling area in the western South China Sea was investigated in order to reconstruct the last Quaternary monsoon upwelling based on planktic foraminifer fauna assemblages and fauna-based sea surface temperature (SST) estimates.The age model of core MD012394 was constructed using oxygen isotope stratigraphy of the planktic foraminifer G. sacculifer, with 10 accelerator mass spectrometry (AMS) 14 C dating of planktic foraminifers from the sediment samples.Our studies on the relative and absolute abundances of planktic foraminifer assemblages reveal eight dominant species in core MD012394: N. dutertrei + N. pachyderma (right coiling), G. ruber, G. glutinata, G. sacculifer, P. obliquiloculata, G. menardii + G. tumida, G. calida, and G. inflata.In a Q-mode factor analysis of the fauna abundance data, the fauna factors show variations that do not parallel the glacial/interglacial changes throughout the last 135 kyr.The relative abundance patterns of G. inflata and N. dutertrei (including N. pachyderma-R) are interpreted as hydrographic proxies for East Asian summer and winter monsoon, respectively, in the current study.We calculated the fluctuations in the SST using the Revised Analog Method (RAM) in MD012394 and found that the abundance changes of the summer monsoon upwelling indicator G. inflata were similar and nearly synchronous.This suggests that the summer monsoon-driven upwelling signal was strong near the local summer insolation maximum, which induced low SSTs, particular around ~11, 33, 59, and 83 kya.Our studies support the view that the strengths of both summer insolation and the East Asian summer monsoon have determined the relative abundance of planktic foraminifers and the SSTs in the western SCS during the last 135 kyr.
Margin (machine learning)
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Abstract Foraminifera from two cores off eastern Vietnam and the northwestern Philippines, where modern summer and winter monsoon-driven upwelling occurs in the South China Sea, respectively, were analyzed to evaluate the changes in paleoproductivity and upper water structure over the last 220,000 yr. We observed enhanced organic carbon flux and a shoaled thermocline when upwelling intensified off eastern Vietnam during interglacial ages and off the northwestern Philippines during glacial ages. This indicates that the East Asian summer monsoon increased while the winter monsoon decreased during interglacial ages. Particularly, the upwelling reached a maximum off eastern Vietnam during late marine isotopic stage (MIS) 5 and off the northwestern Philippines during MIS 2, implying that the summer monsoon decreased gradually since MIS 5 while the winter monsoon displayed an opposite trend. The variations in upwelling proxies exhibit a distinct cyclicity with frequencies near 41,000 yr and 23,000 yr off eastern Vietnam, in contrast to a strong frequency peak near 100,000 yr off the northwestern Philippines. We suggest that the East Asian summer monsoon has been forced by changes in solar insolation associated with precession and obliquity, while ice-volume forcing is probably a primary factor in determining the strength and timing of the East Asian winter monsoon but with less important insolation forcing.
East Asian Monsoon
Forcing (mathematics)
Orbital forcing
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