Collaborative Research: Particulate Organic Carbon Fluxes and Sediment Accumulation in the Cariaco Basin

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ABSTRACTOCE-0118491The Cariaco Basin is a 1,400-m deep depression on the continental shelf off Venezuela in which anoxic waters cover laminated sediments with high organic matter content (1-5 wt%). These laminae, which result from seasonal variations in primary productivity and terrigenous sediment input along the southern the Caribbean Sea, contain a high-resolution record of past climate change in the tropical Atlantic Ocean. In this collaborative effort, researchers at the University of South Florida (USF), the University of South Carolina (USC), and the State University of New York (SUNY) seek to integrate hydrographic, primary productivity, water column microbial activity, vertical particulate flux, and sediment accumulation rate measurements in the Cariaco Basin into a synthesis to understand how contemporary sedimentation patterns reflect this climatic and oceanographic variability. The central objective is to understand the factors that control the relationship between primary production and the vertical flux of particles in the Cariaco Basin. This project will continue the current time series of monthly observations at 10'30' N, 64'40' W that began in November, 1995, under the CARIACO (CArbon Retention In A Colored Ocean) Program. This includes continuing deployment of a mooring with four sediment traps (275, 350, 450, and 1,200 m) to provide bi-weekly sample collections at each depth. Complementing the traps will be a mooring with two Acoustic Doppler Current Profilers (ADCP), one looking up and the other looking down from a depth of about 250 m, to measure currents from below the sill depth to the surface for a three-year period. Each year, one transect will be conducted between the CARIACO station and 11'40' N, 64'40' W outside the basin, to help understand the characteristics of source water involved in intrusions and upwelling. Regional wind and sea level will be examined using both local and remotely-sensed data to establish whether forcing for upwelling occurs primarily through local or gyre-scale processes. Sediments from the Cariaco basin will be collected and analyzed to reconstruct the oceanographic condition in the Cariaco Basin over the past century and provide a window for longer-scale paleoceanographic studies. The program is significant because it provides groundtruthing needed for proper interpretation of past climate changes recorded in the Cariaco sediments.