A High Resolution Record of Upwelling in the Tropical Atlantic: Atmospheric Forcings and Biogeochemical Consequences

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Abstract: Under this award the PI will investigate the importance of wind-driven coastal upwelling to the ocean margins and how this impacts primary and secondary production. Production controls/affects carbon export flux from the euphotic zone, CO2 exchange between the atmosphere and surface ocean and carbon sequestration in the ocean interior and underlying sediments. Understanding how climatic changes in the Holocene have affected the interaction among winds, upwelling and oceanic productivity and carbon export is the major scientific impetus for this proposal. This proposal seeks to analyze the biogeochemical compositions of already collected and dated sediments and use well-calibrated multiple proxies to undertake a high-resolution investigation of the climatic and ecological changes in the water column of the Cariaco Basin since the end of the Holocene Thermal Maximum. Wind-driven coastal upwelling in the Cariaco Basin is intimately tied to the seasonal position of the Intertropical Convergence Zone (ITCZ), which is to a first order controlled by solar insolation. In order to test several hypotheses regarding the forcing mechanisms and ecological responses associated with upwelling variability, sediments representing a continuous 6,000 years of anoxic deposition will be analyzed for a variety of biogeochemical variables that serve as proven paleoclimatic/paleoceanographic proxies. The planned analyses include development of a high resolution record of alkenone unsaturation (UK.37 index), determination mass accumulation rates for organic carbon, biogenic opal, calcite as well as for algal-specific biomarkers, such as sterols and alkenones, and terrigenous biomarkers, such as lignin phenols. Also included in the research plan are analyses of the stable carbon isotopic compositions of algal and terrigenous biomarkers designed to decipher the environmental conditions under which these materials were synthesized. This proposal will fund one Ph.D. student, a young research technician and two undergraduate students. As part of the educational component of this research project, data sets of Holocene climate proxies will be compiled in a website associated with a course taught by the PI entitled Earth Systems Through Time. Results will be shared with colleagues and students in Venezuela by taking advantage of the existing CARIACO program.