关键词: 湖泊沉积, 气候变化, 全新世, 中国内陆区

Abstract: Environmental changes recorded by lake sediments have been one of the major tools for reconstructing the palaeoenvironment and palaeoclimate in many parts of the world. Spatial and temporal patterns of humidity changes during Holocene have been reconstructed based on the compilation of recently published paleoclimate records from the inland areas of China. The climate of this region is sensitive to large-scale climate forcing. We divided China's inland areas into the arid northwestern region, the East Asian monsoon-margin region and the Qinghai-Tibet Plateau according to the amount of precipitation and natural zones. Sediment records from 30 lakes with reliable chronologies and robust proxies were selected to reconstruct dry-wet conditions based on a three-class ordinal wetness index (dry, sub-humid, humid) with assigned scores from dry to wet periods at individual sites for 500-year time slices. Then we formulated the regional dry-wet index, which may represent the average change of the regional dry-wet conditions. The proxies used in these records include pollen assemblages, oxygen isotope ratio (δ¹⁸O), organic matter and carbonate content (mainly pollen assemblages) data. The results of our synthesis show that the moisture conditions have experienced diverse changes over the Holocene in different regions of china's inland areas. Arid climate prevailed during the early Holocene, and relatively wet climate characterized the middle and late Holocene in arid northwestern China. But the climate change differed from place to place—the further into the west, the drier the climate during the early and middle Holocene and wetter in the late Holocene. In the East Asian monsoon-margin region, drier climate also prevailed during the early Holocene, and a wetter period may had occurred in the mid-Holocene, then the climate underwent another transition—it was driest in the late Holocene. In the Qinghai-Tibet Plateau, the wettest period may had occurred in the early and mid-Holocene, then the climate became dry gradually, but there was a tendency of wetness in late Holocene. The wet periods in eastern Qinghai-Tibet Plateau were longer than in the central and western regions. The comparative analysis reveals that the climate may have been mainly controlled by westerly circulation in arid northwestern China. But there were differences among the lake records in the timing of the beginning and end of the dry or humid periods as well as the intensity of the dry or wet conditions, which may be related to the strength of the Asian monsoon in the early Holocene and the influence of westerly circulation in the late Holocene. Furthermore, the insolation, global ice-sheets and topography of the Tibetan Plateau may have played important roles in controlling climate change in this area. The climate change in the East Asian monsoonmargin region is mainly influenced by the East Asian monsoon, which has also been recorded by the loess and desert deposits. The moisture conditions in the Qinghai-Tibet Plateau may have been controlled by the Indian monsoon, and the wetness in the early Holocene may be related to the strengthening of the Indian monsoon. Around 4 ka BP, a significant dry event commonly occurred in China's inland areas, which may be a global dry event that may have resulted in the decline of some ancient civilizations in the whole world.

Key words: China’s inland areas, climate change, Holocene, lake sediment