Japan Geoscience Union Meeting 2016

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Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS17] Paleoclimatology and paleoceanography

Tue. May 24, 2016 10:45 AM - 12:15 PM A04 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Minoru Ikehara(Center for Advanced Marine Core Research, Kochi University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Ikuko Kitaba(Research Centre for Palaleoclimatology, Ritsumeikan University), Akihisa Kitamura(Institute of Geosciences, Faculty of Science, Shizuoka University), Masaki Sano(Research Institute for Humanity and Nature), Ryuji Tada(Department of Earth and Planetary Science, Graduate School of Science, The Univeristy of Tokyo), Takeshi Nakagawa(Ritsumeikan University), Akira Hayashida(Department of Environmental Systems Science, Doshisha University), Chair:Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo)

11:45 AM - 12:00 PM

[MIS17-23] Variations in East Asian summer monsoon in the last 400 ky deduced from results of Mg/Ca-sea surface temperature and oxygen isotope of IODP Site U1429

*Yoshimi Kubota1, Etsuko Wakisaka2, Steven Clemens3, Ann Holbourn4, Kyung Eun Lee6, Martin Ziegler7, Keiji Horikawa2, Katsunori Kimoto5 (1.National Museum of Nature and Science, 2.University of Toyama, 3.Brown University, 4.Christian-Albrechts-University, 5.JAMSTEC, 6.Korea Maritime University, 7.Utrecht University)

Keywords:Monsoon, East China Sea, Milankovitch cycle, Mg/Ca-temperature, Oxygen isotope

The East Asian summer monsoon (EASM) system is involved in the hydrological cycle and in latent heat and energy transport, and thus plays a crucial role in the regional and global climate system. Modern summer sea surface salinity in the northern part of the East China Sea (ECS) is mainly controlled by the discharge of the Yangtze River, which reflects East Asian summer monsoon (EASM) precipitation in the drainage area of the Yangtze River. Site U1429 was drilled by Integrated Ocean Drilling Program (IODP) Expedition 346 in the northern part of the ECS to reconstruct the Yangtze River discharge in high temporal resolution (~100 year resolution). A ~200 m long sediment succession was recovered, which covers the last 400 ky based on a benthic foraminiferal oxygen isotope. A record of oxygen isotope of seawater (δ18Ow) was reconstructed, based on high-resolution Mg/Ca and oxygen isotope measurements of the planktic foraminifera Globigerinoides ruber. The δ18Ow shows variations that have been in concert with Chinese spleothem oxygen isotope records on millennial to orbital scales. However, comparison with a global mean δ18Ow reveals that the δ18Ow of U1429 follows the global mean except from MIS 7.3 to MIS 6.4 and from MIS 5.4 to MIS 4, when the δ18Ow of U1429 was higher than the global mean during MIS 7.2, 6.4, 5.4, 5.2, 4 and lower during MIS 7.3, 7.1, 6.5, 5.3, 5.1. These intervals correspond to higher eccentricity periods during the last 400 ky. During these time periods, the amplitude variations of the regional δ18Ow increased, suggesting that the 23 ky amplitude of the EASM precipitation was also enhanced. These results suggest that the 23 ky amplitude of the EASM precipitation has been modulated by the eccentricity.