Climate change inferred from aeolian sediments in a lake shore environment in the central Tibetan Plateau during recent centuries

摘要

Studies of the past climate variation on the Tibetan Plateau (TP) are currently limited in number and low in density and temporal resolution.We investigated the climate condition from about 400 years before present (B.P.) in the central TP at the shore of Co (means "lake") Nag using aeolian sediments.A 2.7-m sand profile with 57 sediment samples and six optically stimulated luminescence (OSL) samples were studied through grain-size analysis,geochemical elements and parameters,and depositional rate estimation.A previous assumption was verified that sand deposition at the shore of Lake Co Nag originated from hills to the east.Two significant wet periods between 90-140 and about 380 years B.P.were indicated by the variation of element profiles and sediment depositional rates.Aeolian activity is sensitive to variations from different seasonal changing pattems of climate factors in the study area,and aeolian sediments respond differently to climate conditions during the cold little ice age (LIA) and the warm 20th century.Present day dry seasons of winter and spring might be much warmer and drier compared to seasons of 400 years ago although summer precipitation has increased,resulting in significantly more aeolian activity and higher depositional rate (about 6 times compared to 380-240 years ago) of sandy sediments.Aeolian problems like blown-sand deposition and desertification may be worse in a projected warming future in the central TP as well as other cold and high altitude regions.Our results suggest an agreement with environmental evolution during the little ice age and the 20th century in a broader scale on the TP.