Quantitative reconstruction of palaeoclimate from pollen profiles in northeastern Japan and the timing of a cold reversal event during the Last Termination

We reconstructed quantified palaeoclimate changes within two Japanese pollen profiles spanning the Last Termination (LT; 18-10 cal. ka) in an attempt to better understand past monsoon activity. The reconstructed winter climate at the Tashiro mire, which is strongly influenced by the Siberian air mass, showed a weak and a short-lived cooling event at 11.8-10.6 cal. ka. This event spans part of the Younger Dryas (YD) cooling event in the North Atlantic region, suggesting the latter influenced the Siberian high-pressure system. In contrast, the summer climate at the Komado mire, which is more influenced by the Pacific air mass, experienced a strong and a prolonged cooling event at 15.5-13.0 cal. ka. The latter event is broadly synchronous with the Antarctica Cold Reversal (ACR) event, and suggests that the Pacific high-pressure system weakened during this period. The pattern of climate change across East Asia shows that the YD event did not extend beyond the East Asian monsoon front, while the ACR event strongly affected the Pacific high-pressure system during the LT. We suggest the East Asian monsoon front is an important geo-climatic boundary between YD-like and ACR-like deglacial climate changes. Copyright (C) 2009 John Wiley & Sons, Ltd.