Evidence of Holocene millennial-scale climatic change from Gonghe Basin peat deposit, northeastern Qinghai-Tibet Plateau

The northeastern Qinghai-Tibetan Plateau (QTP) lies at the convergence of the Asian winter and summer monsoons and westerlies, making it an ideal place for studying the effects of climatic change, owing to its fragile ecological environment and unique geographical location. This paper reports on a multi-proxy analysis consisting of magnetic susceptibility, total organic carbon content (TOC), pollen, grain size, and geochemical parameters from the peat deposit in the Gonghe Basin to reconstruct the Holocene millennial-scale climatic variation. The results indicate that the climate tended to be warm and humid since 10.0 cal ka BP, but it deteriorated obviously (cold and dry) in 8.6-7.1 cal ka BP. The regional optimal warm and humid period was from 7.1-3.8 cal ka BP, although there were frequent climatic fluctuations during that time. Thereafter, the climate became cold and dry. 10 millennial-time-scale cold events were recorded, which were coincident with climatic records from deep sediments in the North Atlantic Ocean, ice cores, lakes, peat, and aeolian deposits in the QTP. In addition, we discovered that the southwestern monsoons forced by solar insolation in the Holocene have crucial effects on regional climatic change, and the millennial-scale cold fluctuations are possibly related to the thermohaline circulation (THC).