Interhemispheric Orbital-Scale Asymmetry of the Intertropical Convergence Zone Movement at the Asia-Pacific Realm over the Past 3 Glacial-Interglacial Cycles

The Intertropical convergence Zone (ITCZ) is the heaviest rain belt on earth and provides global water-resources for human populations around the world. Here we present a tropical precipitation record from the Southern Hemisphere covering the past 284,000 years, inferred from a marine sedimentary sequence of planktonic foraminifera collected off the eastern coast of Papua New Guinea (PNG). The foraminiferal tests of Globigerinoides ruber were sampled from a marine sediment core MD05-2925 (9^o20.60’S, 151^o27.54’E; water depth 1661 m). Using inductively coupled plasma sector field mass spectrometric (ICP-SF-MS) techniques with 2s precision of 2-6%, we measured rare earth elements (REEs) to Ca ratios in the planktonic foraminifer to reconstruct precipitation and make inferences about the orbital-timescale evolution of the Pacific ITCZ. In addition to precessional feature, which is expressed in the East Asian counterpart, our record shows that the Pacific ITCZ migration was dominantly influenced by obliquity changes. Model simulations suggest that this obliquity forcing could be primarily delivered by a meridional thermal/pressure contrast, resulting from the asymmetric continental configuration between Asia and Australia in a coupled East Asian-Australian circulation system.