Collaborative Research: Coring the Line Islands Ridge for Paleoceanographic Research

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Past changes in the behavior of two key features of the global climate, the Intertropical Convergence Zone (ITCZ) and the El-Nino Southern Oscillation (ENSO), are not clearly understood at present. Continuous records from marine sediments are needed to inform paleoreconstructions of these and other climatic and oceanographic patterns during the Holocene. This project will attempt to acquire such records from the Line Islands Ridge in the Central Tropical Pacific, a key and sensitive location with little in terms of existing samples or data. The Line Islands Ridge is an ideal site to capture paleooceanographic and paleoclimatic changes recorded in sediment for a number of reasons. First, the ITCZ and ENSO are not as susceptible to seasonal or spatial variation in this region as they are elsewhere. In addition, because the Line Islands Ridge is a bathymetric high, the calcium carbonate shells that contain the paleoenvironmental proxy indicators are less likely to be affected by dissolution than in nearby deep ocean settings. Researchers at the Georgia Institute of Technology, Columbia University's Lamont-Doherty Earth Observatory, the Graduate School of Oceanography at the University of Rhode Island, Texas A&M University, Boston University, and the University of California at Santa Cruz will collaborate to conduct a reconnaissance coring survey of the Line Islands Ridge. During a research cruise aboard the R/V Langseth, the PIs will collect bathymetric and geophysical data to constrain optimal coring locations; once optimal locations are established, they will collect a suite of physical samples (an initial gravity core, a CTD/Niskin rosette cast, a piston core, and a multi-core) at each site. Analyses of the cores will include determination of sediment composition using scanning XRF, as well as development of stratigraphic and age models using oxygen isotopes from planktonic foraminifera. Cores and associated data from this reconnaissance effort will be made available to the broader community in order to facilitate future research on paleoclimatic and -oceanographic change over scales of tens to hundreds of thousands of years. Experts in the field foresee using these datasets to better understand past changes in ITCZ and ENSO behavior, sea surface temperature, ocean chemistry, productivity, nutrient and sediment cycling, and eolian dust inputs in the region. Furthermore, these datasets will provide additional opportunities to calibrate paleoclimate models, and may be used to support a geographically overlapping US State Department initiative (Law of the Sea?Extended Continental Shelf program). Additional broader impacts include enhancing scientific infrastructure and disseminating information by adding physical data (cores) to the LDEO sample repository, cataloguing samples through SESAR (System for Earth Sample Registration), and contributing the associated datasets to widely accessible databases (SedDB, NCDC). This project will also involve training for several graduate students. Finally, the multi-faceted approach of this project will provide NSF with an opportunity to evaluate the multi-purpose functionality of the R/V Langseth.