[U-05] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia

[U05-P01] An 8000-year record of East Asian dust deposition in Lake Motosu

*Karin Nemoto^1,2, Yusuke Yokoyama^1,2, Stephen Obrochta³, Shinya Yamamoto⁴, Yosuke Miyairi², Atsunori Nakamura⁵, Laura Lamair⁶, Aurélia Hubert-Ferrari⁶, Vanessa Heyvaert⁷, Marc De Batist⁸, Osamu Fujiwara⁵, the QuakeRecNankai Team (1.Department of Earth and Planetary Science, The University of Tokyo, 2.Atmosphere and Ocean Research Institute, The University of Tokyo, 3.Graduate School of International Resource Sciences Faculty of International Resource Sciences, 4.Mount Fuji Research Institute, Yamanashi Prefectural Government, 5.National Institute of Advanced Industrial Science and Technology, 6.Department of Geography, University of Liège, 7.Geological Survey of Belgium, 8.Renard Centre of Marine Geology, Department of Geology, Ghent University)

Keywords:East Asia, dust, Westerly, Lake Motosu

East Asia is a major source region for dust emissions. According to the average of 15 aerosol models, dust emissions from East Asia (330 Tg yr^-1) is equivalent to approximately 20% of the global total (1800 Tg yr^-1). Clarification of past dust transport can highlight variations in Westerly wind strength and pathway, as well as in source region aridity. However, reconstructing past dust transport in East Asia is complicated by several factors. The low sedimentation rate in the Northwest Pacific (<1 cm/1000 yr) is inappropriate for millennial- to centennial-scale studies, and distinguishing aeolian and riverine sources in coastal settings is challenging. While quartz physical properties were previously used successfully to separate the two signals, the obtained record is subject to relatively high chronological uncertainty.
Here, we use quantitative X-ray diffraction to determine quartz percentage, while leveraging the favorable conditions of Lake Motosu, to present the first chronologically well-constrained, high resolution dust transport record from the Pacific sector of Japan. Because the extremely small catchment provides no local source of quartz particles to Lake Motosu sediments, the record reflects East Asian dust transport, and with a ~0.5 mm/yr sedimentation rate, the high-quality age model is capable of resolving perhaps even decadal-scale deposition variability. Despite the relatively stable Holocene climate, the Lake Motosu dust record records reveals variable transport processes during the past 8000 years that appear linked to changes in Westerlies wind strength and position, East Asia Monsoon intensity, and the broader climate variations in the Pacific Ocean