Regional precipitation variations during Heinrich events and Dansgaard-Oeschger cycles in the northern margin of the East Asian summer monsoon region

Abstract

Due to the scarcity of long, high-resolution paleoclimate records, the effects of abrupt climatic events on regional climate variations in middle to high latitudes of East Asia are unclear. We present a detailed pollen record for the past 35,000 years, with an AMS 14C chronology, from Hulun Lake in northern China. The results reveal four episodes of regional vegetation change during the Last Glaciation, characterized by increases in cold-resistant and drought-tolerant plants and decreased regional vegetation cover. These episodes coincided with Heinrich events (H3, H2 and H1) and the Younger Dryas event (YD) that originated in the North Atlantic region. Additionally, during the warm intervals of the Dansgaard-Oeschger (D-O) cycles and the Bølling-Allerød (B/A) interstadial recorded in Greenland ice cores, patches of broadleaved deciduous forest expanded in the surrounding mountains while typical steppe vegetation expanded in the vicinity of Hulun Lake. Overall, the structure and amplitude of regional vegetation change in the Hulun Lake region during abrupt climatic events differ from the registration of these events in the oxygen isotope records from Greenland ice cores; however, they are similar to coeval stalagmite oxygen isotope records from East Asia. Thus, we suggest that the regional climate variations were characterized by increased or decreased precipitation during H events and D-O cycles in the Hulun Lake region, which was mainly controlled by changes in the intensity of the East Asian summer monsoon (EASM). Our results suggest that the variability of the EASM was physically linked to the North Atlantic climate system on centennial- to millennial-scale. In addition, the amplitude of regional precipitation variations during H events and D-O cycles was low during the interstadial of the Last Glaciation and the Last Glacial Maximum; however, the amplitude of regional precipitation variations during H1 event and B/A warming event was substantially greater during the Last Deglaciation. We suggest that differences in NHSI and land surface conditions (ice sheets and sea level) were responsible for the contrasting responses of EASM precipitation to these abrupt climatic events during different intervals.