Under this award the PIs will investigate how the oxygenation of South Pacific intermediate waters varied through time. Little is known about the relationship between climate change and intermediate water mass circulation. The proponents will test two alternate, but not necessarily exclusive, hypotheses (1) Changes in South Pacific intermediate water oxygenation are forced by circulation-driven changes in ventilation. (2) Changes in South Pacific intermediate water oxygenation are forced by changes in the local rain rate of organic carbon. They will generate multi-proxy records of particle flux and bottom water oxygen to address dynamic changes in the globally important Antarctic Intermediate Water system, capitalizing on a set of three sites which have high sedimentation rates (>1 m/ka) and well-constrained stratigraphy. The sites occur along a depth and latitudinal transect off central Chile. This region documents variations in Antarctic Intermediate Water where it interacts with subsurface waters of tropical-to-subtropical origin, and with underlying Pacific Deep Water. They will utilize a combination of non-traditional but well-tested tracers of carbon export (231Pa/230Th and Th-normalized biogenic fluxes) and sedimentary reducing conditions (Mo, Re, U). These tracers will be coupled to more traditional studies of nutrient-like proxies (d13C in foraminifera), radiocarbon, nitrogen isotope tracers of denitrification and/or nutrient utilization, and micropaleontology of both fauna (foraminifera and radiolarians) and flora (diatoms and nannofossils).
A Ph.D. graduate student and two undergraduate students will be involved in the research. In addition two high school scholars will be supported through the Saturday Academy's Apprenticeship in Science and Engineering program. An important part of the project is collaborating with two Chilean colleagues
