晚第四纪中国湖泊水量变化及其古环境意义

THE LAKE STATUS CHANGE OF CHINA SINCE THE LATE QUATERNARY AND ITS SIGNIFICANCE FOR PALAEOENVIRONMENT

区域性的湖泊水位能反映有效降水及气候变化，是重建第四纪降水和地表水量平衡的重要指标之一。根据即将出版的第二版中国古湖泊数据库（ChineseLakeStatusDataBase，简称CLSDB，V．2）提供的80个湖泊水量每千年变化的空间信息，结合已有的晚第四纪古降水定量重建资料，可系统分析中国区域3万年以来地表有效湿度变化的空间格局。研究结果表明：我国西部湖泊从末次冰期间冰阶晚期以来至中全新世均为高湖面，可能对应于相对较湿润的环境状况，而晚全新世的低湖面可能表明环境趋干，推测末次间冰阶晚期的高湖面可能与西风环流和夏季风增强带来大量水汽有关，冰期内的湿润条件可能与西风带的降水以及低温低蒸发密切相关，而全新世主要为夏季风降水增加所致；我国东部地区湖泊末次冰期间冰阶晚期至晚冰期记录点较少，全新世以来湖泊记录大幅增加，湖面变化表明全新世早期区域有效降水可能较高，全新世中期达到最大值，这可能反映了早中全新世由于北半球夏季太阳辐射增强导致夏季风降水增加的效应；我国西南地区受西南季风消长控制，湿润状况的明显改善发生在晚冰期及早全新世，但该区域不同湖泊差异较大；我国东北地区湖泊记录始于晚冰期，且自晚冰期以来至全新世中期均表现为较湿润的地表湿度状况，显示该地区季风气候机制可能和东部地区有所不同。

Lake level changes respond to variations in regional water balance and are sensitive to climate changes. Thus it has been one of the most important indicators applied to reconstruct paleoprecipitation and water budget. The 80 lakes, which compiled in the Chinese Lake Status Data Base （CLSDB, Ver. 2, in press）, have provided the information of the spatial changes of lake status for each one-thousand year. Combined with the established paleoprecipitation records, the 80 lakes can be purposed for research on the land humidity changes of Chinese regions since Late Quaternary. The results have showed that, lake levels in the western part of China were relatively high from the past 30, 000 years to the Mid-Holocene, indicating a long-term trend of wet condition. However, lake levels dropped since the Mid-Holocene to the present, suggesting a more arid climate during this period. The wet condition in Western China during the Last Interglacial Period was probably related to the enhancement of westerly circulation and Asian summer monsoon, which could bring about abundant precipitation. The wet condition in the Last Glacial Maximum of Western China was likely caused by the westlies precipitation as well as the low evaporation, while in the Mid-Holocene, the wet condition could be attributed to the increasing summer monsoon precipitation. Lake records in Eastern China were relatively scarce until the Holocene, and lake level changes might demonstrate that most areas in Eastern China were wet in Early-Holocene and reached the most humid period during the Mid-Holocene. The wet condition in Eastern China might reflect the enhancement of the East Asian summer precipitation caused by the increasing summer solar radiation in northern hemisphere. The wet condition of Southwestern China occurred in Late-Glacial and Early Holocene, but differed in different lakes. The wet condition of Northeastern China began in Late-Glacial and lasted until Mid-Holocene, suggesting different monsoon system compared with the Eastern China.