Global and regional perspectives of Pleistocene paleoceanography in the western Pacific warm pool based on new sites from IODP Expedition 363

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The Western-Pacific Warm Pool (WPWP) is a major source of heat and moisture to the atmosphere, being a region of deep atmospheric convection and heavy rainfall. Small perturbations in sea surface temperature of the WPWP influence the location and strength of convection in the rising limb of the Hadley and Walker circulations, perturbing planetary scale atmospheric circulation, atmospheric heating, and tropical hydrology, as well as heat and CO2 storage in the thermocline and their transport to the Indian Ocean through the Indonesian Throughflow. Models disagree how departures from modern climatology will affect the hydroclimate conditions in this area i.e., whether more intense droughts or stronger monsoonal rains should be expected. Either way, these changes can disrupt the lives of many people in regions so affected, devastating local economies of heavily populated regions through crop failure, landslides, flooding of coastal regions, and loss of human and wild lives. International Ocean Discovery Program (IODP) Expedition 363 sought to document the regional expression and driving mechanisms of climate and paleoceanographic variability throughout the Neogene (~0-20 My) in the WPWP on millennial and orbital time scales in response to changes in radiative forcing and varying background climate states, in order to improve predictions of climate change in this region. This award supports research on two of the cores collected during Expedition 363. Orbital-scale benthic isotope record will be generated at Site U1486 in the Manus Basin, ~200 km north of Papua New Guinea (PNG) spanning the late Pliocene (~2.25 Ma) to Present. The oxygen isotope stratigraphy will be key for interpreting proxy reconstructions of hydroclimate variability obtained at this site, including XRF analysis of terrigenous riverine inputs originated from PNG and planktonic foraminiferal isotope and elemental records. Benthic foraminifera carbon isotope and trace metal records will be used to assess how changes in intermediate water temperature and carbon content affected the WPWP hydrography through the mid-to-late Pleistocene and their implications to the regional and global climate. A second site (U1485) on the northern margin of PNG close the Sepik/Ramu River mouths, characterized by very high sedimentation rates, will be used to reconstruct climate conditions during previous interglacials of the past 500 My. Specifically, both planktonic and benthic isotope and elemental records will be generated for Termination I and the Holocene, and compared with Terminations II and IV and the following warmer-than-present interglacial peaks (i.e., Eemian/ MIS 5e and MIS 11) to assess how the WPWP upper ocean responded to deviations from boundary conditions similar to those predicted for the next century. Funding supports a postdoctoral scientist and research opportunities for undergraduate studentsThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.