A 1232-YEAR TREE-RING RECORD OF CLIMATE VARIABILITY IN THE QILIAN MOUNTAINS, NORTHWESTERN CHINA

A millennium-long tree-ring width chronology for the middle Qilian Mountains in northwestern China has been developed back to A.D. 775. Correlation analysis indicates that the tree-ring width reflects growingseason moisture variability. Our chronology reveals three distinct periods based on the prevailing moisture anomalies: A.D. 775–1101 (wetness persistence), 1101–1831 (dryness persistence) and 1831–2006 (wetness persistence). A 31-year running mean through the tree-ring index series clearly shows seven obvious dry spells and eight wet spells. Compared with the proxies associated with the East Asian monsoon and the westerlies in the past millennium, our moisture-sensitive tree-ring chronology revealed that the East Asian summer monsoon had a strong influence on tree growth before A.D. 1300. From about A.D. 1450–1750, the westerlies strongly affected the Qilian Mountains. After A.D. 1750, a combined influence of both East Asian monsoon and westerlies was apparent. In the past century, the effect of westerlies has become stronger. Our results suggest that tree rings can preserve the information on the advance and retreats of the westerlies and the East Asian summer monsoon. Additionally, this research is helpful for understanding the driving mechanism of the Asian monsoon and the westerlies in northwestern China over the past thousand years.

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Three exceptionally strong East-Asian summer monsoon events during glacial conditions in the past 470 kyr

Climate of the Past Discussions ◽

10.5194/cpd-4-1289-2008 ◽

2008 ◽

Vol 4 (6) ◽

pp. 1289-1317 ◽

Cited By ~ 1

Author(s):

D.-D. Rousseau ◽

N. Wu ◽

Y. Pei ◽

F. Li

Keyword(s):

Summer Monsoon ◽

Asian Monsoon ◽

East Asian Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Precipitation Regime ◽

The Past ◽

Ecological Requirements ◽

Asian Summer ◽

The Tropics

Abstract. Chinese loess sequences are interpreted as a reliable record of the past variation of the East Asian monsoon regime through the alternation of loess and paleosols units, dominated by the winter and summer monsoon, respectively. Different proxies have been used to describe this system, mostly geophysical, geochemical or sedimentological. Terrestrial mollusks are also a reliable proxy of past environmental conditions and are often preserved in large numbers in loess deposits. The analysis of the mollusk remains in the Luochuan sequence, comprising L5 loess to S0 soil, i.e. the last 500 ka, shows that for almost all identified species, the abundance is higher at the base of the interval (L5 to L4) than in the younger deposits. Using the present ecological requirements of the identified mollusk species in the Luochuan sequence allows the definition of two main mollusk groups varying during the last 500 kyr. The cold-aridiphilous individuals indicate the so-called Asian winter monsoon regime and predominantly occur during glacials, when dust is deposited. The thermal-humidiphilous mollusks are prevalent during interglacial or interstadial conditions of the Asian summer monsoon, when soil formation takes place. In the sequence, three events with exceptionally high abundance of the Asian summer monsoon indicators are recorded during the L5, L4 and L2 glacial intervals, i.e., at about 470, 360 and 170 kyr, respectively. The L5 and L4 events appear to be the strongest (high counts). Similar variations have also been identified in the Xifeng sequence, distant enough from Luochuan, but also in Lake Baikal further North, to suggest that this phenomenon is regional rather than local. The indicators of the summer monsoon within the glacial intervals imply a strengthened East-Asian monsoon interpreted as corresponding to marine isotope stages 6, 10 and 12, respectively. The L5 and L2 summer monsoons are coeval with Mediterranean sapropels S12 and S6, which characterize a strong African summer monsoon with relatively low surface water salinity in the Indian Ocean. Changes in the precipitation regime could correspond to a response to a particular astronomical configuration (low obliquity, low precession, summer solstice at perihelion) leading to an increased summer insolation gradient between the tropics and the high latitudes and resulting in enhanced atmospheric water transport from the tropics to the African and Asian continents. However, other climate drivers such as reorganization of marine and atmospheric circulations, tectonic, and the extent of the Northern Hemisphere ice sheet are also discussed.

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Three exceptionally strong East-Asian summer monsoon events during glacial times in the past 470 kyr

Climate of the Past ◽

10.5194/cp-5-157-2009 ◽

2009 ◽

Vol 5 (2) ◽

pp. 157-169 ◽

Cited By ~ 19

Author(s):

D.-D. Rousseau ◽

N. Wu ◽

Y. Pei ◽

F. Li

Keyword(s):

Summer Monsoon ◽

Asian Monsoon ◽

East Asian Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Precipitation Regime ◽

The Past ◽

Ecological Requirements ◽

Asian Summer ◽

The Tropics

Abstract. Chinese loess sequences are interpreted as a reliable record of the past variation of the East Asian monsoon regime through the alternation of loess and paleosols units, dominated by the winter and summer monsoon, respectively. Different proxies have been used to describe this system, mostly geophysical, geochemical or sedimentological. Terrestrial mollusks are also a reliable proxy of past environmental conditions and are often preserved in large numbers in loess deposits. The analysis of the mollusk remains in the Luochuan sequence, comprising L5 loess to S0 soil, i.e. the last 500 ka, shows that for almost all identified species, the abundance is higher at the base of the interval (L5 to L4) than in the younger deposits. Using the present ecological requirements of the identified mollusk species in the Luochuan sequence allows the definition of two main mollusk groups varying during the last 500 kyr. The cold-aridiphilous individuals indicate the so-called Asian winter monsoon regime and predominantly occur during glacials, when dust is deposited. The thermal-humidiphilous mollusks are prevalent during interglacial or interstadial conditions of the Asian summer monsoon, when soil formation takes place. In the sequence, three events with exceptionally high abundance of the Asian summer monsoon indicators are recorded during the L5, L4 and L2 glacial intervals, i.e., at about 470, 360 and 170 kyr, respectively. The L5 and L4 events appear to be the strongest (high counts). Similar variations have also been identified in the Xifeng sequence, distant enough from Luochuan, but also in Lake Baikal further North, to suggest that this phenomenon is regional rather than local. The indicators of the summer monsoon within the glacial intervals imply a strengthened East-Asian monsoon interpreted as corresponding to marine isotope stages 12, 10 and 6, respectively. The L5 and L2 summer monsoons are coeval with Mediterranean sapropels S12 and S6, which characterize a strong African summer monsoon with relatively low surface water salinity in the Indian Ocean. Changes in the precipitation regime could correspond to a response to a particular astronomical configuration (low obliquity, low precession, summer solstice at perihelion) leading to an increased summer insolation gradient between the tropics and the high latitudes and resulting in enhanced atmospheric water transport from the tropics to the African and Asian continents. However, other climate drivers such as reorganization of marine and atmospheric circulations, tectonic, and the extent of the Northern Hemisphere ice sheet are also discussed.

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Linking Holocene East Asian monsoon variability to solar forcing and ENSO activity: Multi-proxy evidence from a peatland in Northeastern China

The Holocene ◽

10.1177/0959683621994662 ◽

2021 ◽

pp. 095968362199466

Author(s):

Nannan Li ◽

Arash Sharifi ◽

Frank M Chambers ◽

Yong Ge ◽

Nathalie Dubois ◽

...

Keyword(s):

Asian Monsoon ◽

East Asian Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Northeastern China ◽

Solar Irradiation ◽

Enso Events ◽

Monsoon Area ◽

Wavelet Coherency ◽

Cross Wavelet

High-resolution proxy-based paleoenvironmental records derived from peatlands provide important insights into climate changes over centennial to millennial timescales. In this study, we present a composite climatic index (CCI) for the Hani peatland from northeastern China, based on an innovative combination of pollen-spore, phytolith, and grain size data. We use the CCI to reconstruct variations of the East Asian summer monsoon (EASM) intensity during the Holocene. This is accomplished with complete ensemble empirical mode decomposition (CEEMD), REDFIT, and cross-wavelet coherency analysis to reveal the periodicities (frequencies) of the multi-proxy derived CCI sequences and to assess potential external forcing of the EASM. The results showed that periodicities of ca. 300–350, 475, 600, 1075, and 1875 years were present in the Hani CCI sequence. Those periodicities are consistent with previously published periodicities in East Asia, indicating they are a product of external climate controls over an extensive region, rather than random variations caused by peatland-specific factors. Cross-wavelet coherency analysis between the decomposed CCI components and past solar activity reconstructions suggests that variations of solar irradiation are most likely responsible for the cyclic characteristics at 500-year frequency. We propose a conceptual model to interpret how the sun regulates the monsoon climate via coupling with oceanic and atmospheric circulations. It seems that slight solar irradiation changes can be amplified by coupling with ENSO events, which result in a significant impact on the regional climate in the East Asian monsoon area.

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Changes in Paleovegetation and Paleoclimate in China Since the Late Middle Pleistocene: A Case Study of the Dajiuhu Basin

Sustainability ◽

10.3390/su13094848 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4848

Author(s):

Liwei Wu ◽

Xinling Li ◽

Qinghai Xu ◽

Manyue Li ◽

Qiufeng Zheng ◽

...

Keyword(s):

Grain Size ◽

Asian Monsoon ◽

East Asian Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Central China ◽

Middle Pleistocene ◽

Pollen Record ◽

The Difference ◽

Late Middle Pleistocene

The East Asian monsoon system is an important part of global atmospheric circulation; however, records of the East Asian monsoon from different regions exhibit different evolutionary rhythms. Here, we show a high-resolution record of grain size and pollen data from a lacustrine sediment core of Dajiuhu Lake in Shennongjia, Hubei Province, China, in order to reconstruct the paleovegetation and paleoeclimate evolution of the Dajiuhu Basin since the late Middle Pleistocene (~237.9 ka to the present). The results show that grain size and pollen record of the core DJH-2 are consistent with the δ18O record of stalagmites from Sanbao Cave in the same area, which is closely related to the changes of insolation at the precessional (~20-kyr) scale in the Northern Hemisphere. This is different from the records of the Asian summer monsoon recorded in the Loess Plateau of North China, which exhibited dominant 100-kyr change cyclicities. We suggest that the difference between paleoclimatic records from North and South China is closely related to the east–west-oriented mountain ranges of the Qinling Mountains in central China that blocked weakened East Asia summer monsoons across the mountains during glacial periods.

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