Combined obliquity and precession pacing of western Pacific Intertropical Convergence Zone over the past 282,000 years

Wednesday, 16 December 2015
Poster Hall (Moscone South)
Chuan-Chou Shen1, Liu Yi1,2, Li Lo3, Zhengguo Shi4, Kuo-Yen Wei5, Chien-Ju Chou6, Yi-Chi Chen6, Chih-Kai Chuang6, Chung-Che WU5, Horng-Sheng Mii7, Hiroshi Amakawa8, George Burr9, Shih-Yu Lee10, Kristine L DeLong11 and Henry Elderfield12, (1)NTU National Taiwan University, Taipei, Taiwan, (2)USTC University of Science and Technology of China, Hefei, China, (3)National Taiwan University, Taipei, Taiwan, (4)IEE Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China, (5)Department of Geoscience, National Taiwan University, Taipei, Taiwan, (6)High-precision Mass Spectrometry and Environment Change lab (HISPEC), Department of Geosciences, National Taiwan University, Taipei, Taiwan 106, ROC, Taipei, Taiwan, (7)NTNU National Taiwan Normal University, Taipei, Taiwan, (8)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan, (9)University of Arizona, Tucson, AZ, United States, (10)Academia Sinica, Taipei, Taiwan, (11)Louisiana State University, Geography and Anthropology, Baton Rouge, LA, United States, (12)University of Cambridge, Cambridge, United Kingdom
The Intertropical convergence Zone (ITCZ) encompasses the heaviest rain belt on Earth. Few direct long-term records, especially in the Pacific, limit our understanding of long-term natural variability necessary to predict future ITCZ changes. Here we present a tropical precipitation record from the Southern Hemisphere covering the past 282,000 years, inferred from of rare earth elements (REEs) to Ca ratios in the planktonic foraminifer Globigerinoides ruber shell calcite, of a marine sedimentary core MD05-2925 (9o20.60’S, 151o27.54’E; water depth 1661 m), collected off the eastern coast of Papua New Guinea. Unlike the precession paradigm expressed in its East Asian counterpart, our record shows that the western Pacific ITCZ migration was influenced by combined precession and obliquity changes. This obliquity forcing could be primarily delivered by a cross-hemispherical thermal/pressure contrast, resulting from the asymmetric continental configuration between Asia and Australia in a coupled East Asian-Australian circulation system, supported by model simulations. Our finding suggests that the obliquity forcing may play a more important role in global hydroclimate cycles than previously thought.