This project will study the evolution of ocean circulation and biological productivity in the Northeast Pacific during the last glacial-interglacial transition. Published model results invoke the existence of a less well-ventilated, deep water mass enriched in dissolved inorganic carbon during glacial periods in order to help explain the ocean's role in influencing atmospheric pCO2 variability in the past. A clear picture of North Pacific circulation and water column structure during the last glacial period has not been produced to date. This research project seeks to answer fundamental questions about North Pacific oceanography during the glacial-interglacial transition. These include (1) did intermediate water penetrate to greater depths during glacials in the NE Pacific as they did in the NW Pacific; (2) was the age of deep waters in the NE Pacific greater during the last glacial period; and (3) did glacial/interglacial changes in iron input influence North Pacific diatom production? The PI proposes a multiproxy study of a hemipelagic sediment core raised from 2000 meters on the continental margin off the Northwestern United States. Glacial age sediment will be analyzed for its radiocarbon age (using benthic foraminifera) and authigenic trace metal content to quantify redox conditions (U, Re, Mo). Silicon isotope analyses will be conducted on diatoms from both the Cascadia Basin core and from ODP Site 882, which is situated in a demonstrated iron-limited region of the North Pacific, and will be used to shed light on the potential for the novel silicon isotope proxy in the North Pacific. The proposed research includes funds for the professional and scientific development of a postdoctoral researcher and an undergraduate student in the UW School of Oceanography.
