Reconstruction of Asian Palaeomonsoon Patterns in China over the Last 40 kyrs: A Synthesis.:A Synthesis

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Lake level and pollen data were used to reconstruct palaeoclimate during the mid-Holocene, the last glacial maximum (LGM), and the later stage 3 of marine oxygen isotope (MOI) in China. Numerous lakes with freshwater and lake levels 30-200m higher than the present occurred in the Tibetan Plateau and northern China deserts during 30-40ka BP, consistent with pollen evidences that cold mixed forest in the Tibet extended ca. 400-800km beyond their present western limits. The high values of isotope δ18O variations preserved in Guliya ice cap indicated that this period was warmer than today. These records reconstructed that the climate of western China was exceptionally warm and humid and a very strong summer monsoon occurred in the later stage 3. During the LGM, there were high lake levels in Tibet and Xinjiang of western China though these lake levels were lower than 30ka BP but much higher than the present, while very low lake-level and/or dry lake basins occurred in eastern China. The lake level indicated dry conditions in the eastern China suggested less summer precipitation due to weakened summer Asian monsoon flows, while the wet conditions in western China implied decreases of the evaporation and increase of precipitation. During the mid-Holocene, the lake records indicated that conditions in most area of China including the Northeast China, the North China, Xinjiang inland and the Tibetan Plateau were wetter than present. Pollen-based reconstruction of vegetation at 6ka BP suggested that forest zones were systematically shifted northwards and the area of tundra in Tibetan Plateau was largely reduced, replaced by steppe vegetation. Lake and pollen data suggest enhanced summer monsoon but weakened winter monsoon at 6ka BP.Synthesis of lake levels and vegetation records from China provides reconstruct climate signals in response to changes in insolation, glaciation and land surface for evolution of Asian palaeomonsoons during the last 40kyrs. Discrepancies between palaeo-records and palaeoclimate simulations provided basis to improve the palaeoclimate simulations to better understand the mechanisms of the climate changes.
日本第四紀学会の論文

Reconstruction of Asian Palaeomonsoon Patterns in China over the Last 40 kyrs: A Synthesis.:A Synthesis

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