A pollen record of Holocene climatic changes from the Dunde ice cap, Qinghai-Tibetan Plateau

Pollen preserved in ice cores from the Dunde ice cap provides a sensitive record of Holocene climatic changes and vegetational response in the northern Qinghai-Tibetan Plateau at time scales ranging from millennia to centuries and decades. Pollen analysis of the annually resolvable ice layers for a 30 yr period (1957-1986) suggests that total pollen concentration is correlated positively,vith summer precipitation and negatively with summer temperature; thus it is a sensitive indicator of moisture availability and vegetation density in the steppe and desert regions around Dunde. High pollen concentrations between 10000 and 4800 yr B.P. suggest that the summer monsoon probably extended beyond its present limit to reach Dunde and westernmost Tibet in response to orbital forcing. The summer monsoon retreated time-transgressively across the Qinghai-Tibetan Plateau during the middle Holocene, Relatively humid periods occurred at 2700-2200, 1500-800, and 600-80 yr B.P., probably as a result of neoglacial cooling. Prominent pollen changes during the Medieval Warm Period (790-620 yr B.P.) and the Little Ice Age (330-80 yr B.P.) suggest that the vegetation in the Qinghai-Tibetan Plateau region is sensitive to abrupt, century scale climatic changes, such as those anticipated in scenarios of greenhouse warming.