末次盛冰期以来全球湿润状况的地质证据——全球古湖泊数据库及其湖水位变化的大尺度时空分析

介绍了正在建设中的全球湖泊数据库的情况,以及该数据库的水位资料所反映的晚更新世末期以来全球湿润状况的变化。通过大尺度湖水位变化的时空分析,结果显示当今湖泊水位状态较历史时期而言,位于低纬干旱或半干旱地区的湖泊水位较低,而中纬及高纬湿润地区的湖泊水位较高。自末次冰盛期以来,北美大陆中南部地区湖泊水位自高至低,反映出该地区气候条件由湿变干,至早、中全新世达最干旱。而在非洲及南亚季风地区,冷期偏干,暖期偏湿。特别是在早、中全新世的温暖时期,为历史上最湿润时期。北半球中纬度地带的气候干湿变化与北半球冰盖的存在及其消融导致的西风带的南北摆动有关;而北半球季风区在早、中全新世出现的高潮面与北半球夏季辐射的增加有密切联系。

The geological evidence of the global moisture condition changes since the last glacial maximum:the construction of global lake status data base & the synthesis in the large spatio-temporal scale

The construction of global lake status data base has been introduced in this paper. This is a geological evidence-based semi-quantitative lake level data set. It consists of 6 regional lake vStatus data vsets, i. e. Oxford Lake Level Data Base, European Lake Status Data Bavse. Former Soviet Union and Mongolian Data Base, Updated African Lake Status Data Base and Chinese Lake Level Data BavSe. With uniform criteria, these sub-data-sets are incorporated into the Global Lake Status Data Base. The lake status record from the Global Lake Status Data Base essentially reflect the coherent patterns of changes in moisture condition in the spatio-temporal scale since the last glacial maximum. In the present, lakes from low and mid-latitudes are characterised by lower status whereas the lakevS in high latitudes register higher lake status. From the Last Glacier Maximum to the middle Holocene, the lakes from North America register high in cool period to low in Holocene, indicating the changes in moivSture condition from wetter to drier. The culminating dry period occurs in mid-Holocene. This change pattern of moisture condition is avSsociated with the shift of westerlies related to the presence and non-presence of ice sheet in the North America. In the Afro-Asia monsoon-al sector, the lake status are characterised by lower in the cool period and higher in warm pe-riod, particularly in the early Holocene. The higher lake status from monsoonal sector in early Holocene maintained until mid-Holocene is strongly linked with the increase in summer insolation in Northern Hemisphere. It, therefore, enhances the contrast of land-ocean thermal property, produces the strengthened monsoonal stream jet. The moisture condition changes in the mid-latitude in northern Hemisphere, including the midst of N. America and circum-Mediterranean, are related to the presence of ice sheet in the north and the displacement of the westerlies. But the lake status records in Central Asia show that the culmination of wetter condition appears in the middle Holocene rather than in the early Holocene, which indiactes that the enhanced summer monsoon started to prevail in the low-latitudinal areas in the early Holocence, then gradually expanded northward to experience in the mid-latitude in the middle Holocene.