Pollen evidence for a wet Younger Dryas in northern NE China

The regional expression of moisture conditions during the Younger Dryas (YD) event and its forcing mechanism in northeastern (NE) China are controversial and more evidence is needed. Here, we present a reconstruction of changes in vegetation and precipitation during the YD event, based on pollen data from two well-dated, parallel sediment cores (TC2 and GQ2) from Tianchi Crater Lake in NE China. The elevated tree pollen abundance during the YD indicates an abrupt shift from steppe to forest, and therefore wetter conditions in Northeast China. Also, a pollen-based quantitative climatic reconstruction suggests that the climate was significantly colder and wetter, with a 3-5 degrees C decrease in annual temperature (Tann) and a 200 mm increase in annual precipitation (Pann) during the YD. To characterize the spatial distribution of moisture conditions in NE China during the YD, we also compiled 26 records from 14 sites in the region. Based on well-dated proxies, we conclude that the YD throughout northern NE China was characterized by wet conditions-significantly different from the consensus of a dry YD in southern NE China. We propose that the increased precipitation in northern NE China during the YD was a response to the strengthening of the Okhotsk High.