摘要
通过对洱海现代沉积物的精细采样 ,将放射性核素精确计年与沉积物粒度研究相结合 ,重建了 6 0 0多年来洱海区域气候的干湿变迁 ,为恢复百年尺度的气候干湿变化提供了一条新途径。研究结果表明 ,15世纪是洱海地区最为湿润的一个世纪 ;洱海区域存在 10 0a、2 0 0a两种时间尺度的气候干湿准周期波动 ;自 19世纪末以来洱海区域气候整体上向干旱化方向发展 ,目前正处于干旱期末期 。
As a main lodging of surface substances, lake sediments continuously and sensitively record information of regional climate and environment with annual to decadal resolution. The sediment core EH911208-3-5 with a length of 83cm was taken from deepwater location in Erhai Lake in 1991, using the sediment-water interface sampler specially designed by ourselves. The sediments were cut at intervals of 0.5～1.0cm and were measured for grain sizes by the Scanning Photo Sedimentograph “Analysette 20” made in Germany. Based on accurate dating by 137 Cs and 210 Pb ex , the author reconstructs the dry-humid transformation history of the regional climate according to the vertical profile of sediment particle sizes, which provides a new effective way for recovering the century-scale climatic changes. The following conclusions are drawn: (1) General environmental significance of sediment grain size should not be applied mechanically in reconstructing palaeoclimate. Only after concretely analyzing all the factors which affect sediment grain size, can credible conclusions be obtained during discussing different time-scales climate changes. (2) During long time-scale studies, lake level is the most important factor dominating sediment grain size. Sediments are finer during the humid period of high water level because coarse particles can not be transported to the lake's deepwater part. On the contrary, during short time-scale studies within a given climate period, rainfall change in the drainage basin becomes the key factor determining sediment grain size because the lake level is basically constant. When rainfall is heavy, runoff flow is strong enough to bring coarse terrestrial particles to the sampling location, resulting in larger grain sizes. (3) The 15th century was the driest in the region of Lake Erhai during the past 640 years. There exist two time-scales(100 and 200 years) climatic quasi-periodical changes. From the end of the last century, the regional climate has been becoming drier and drier as a whole. At present, it is at the end of the dry period, so the regional climate will become humid in near future.
出处
《沉积学报》
CAS
CSCD
北大核心
2000年第3期341-345,共5页
Acta Sedimentologica Sinica
基金
国家自然科学基金!(批准号 :498941 70 )
中科院重大项目专题!(KZ951 -A1 - 4 0 2 - 0 6 - 0 4 )资助项目
关键词
沉积物粒度
准周期变化
干湿变迁
洱海
古气候
sediment grain size quasi-periodical changes dry-humid transformation Erhai Lake
