Bermuda Rise (proposal just funded!):

        The export of many elements from the surface ocean to the deep sea is mediated by the flux of sinking particles; for example, sinking particles account for 50-80% of the vertical transport of organic carbon through the mesopelagic zone.  Heterotrophic remineralization of particulate organic carbon (POC) in the open ocean is usually very efficient, as >90% of the POC produced in surface waters is returned to inorganic form in the euphotic zone or during transit through the upper water column.  However, a small fraction of the organic matter produced in surface waters survives transit to the deep ocean or sea floor.  Similarly, the flux and composition of inorganic material also vary during transport to the sea floor.  Perhaps the most obvious example of such modification is the dissolution of carbonate and biogenic silica as they sink through the water column.  However, the flux and composition of particulate organic and inorganic matter that reaches the deep sea and sediments depend not just on their source in the surface waters, but also on alteration, supplementation, and selective removal that occurs during vertical transit.  In some regions, particularly near margins, lateral transport can also be extensive.  Exchange between sinking material and suspended particles or dissolved organic matter via aggregation/disaggregation and solution/dissolution can also influence composition. 

The goal of this work is to achieve a better mechanistic understanding of the ocean’s role in the global carbon cycle and the factors that influence the sedimentary record.  To this end we proposed five interrelated hypotheses revolving around the themes of remineralization and exchange as particles sink to the sea floor, potential horizontal influences on sinking particles, and how vertical and horizontal transport potentially influence the interpretation of the sediment record.   We will apply some of the tools developed during the recent MedFlux program to produce better quantitative models of sinking fluxes by incorporating explicit consideration of ballast minerals (including celestite and barite) and to define better the interactions among particles as they sink. We will also compare results of inorganic, organic and radiochemical analyses of particles sampled by traps and pumps with those of bottom sediments at our proposed site on the Bermuda Rise.  While this is a modern process study, it has significant paleoceanographic implications.  Quantifying the relative vertical and horizontal fluxes of key paleoceanographic proxies in combination with characterization of the seasonal fluxes will greatly enhance our understanding of the existing sediment record at the Bermuda Rise, and improve the quality of future reconstructions as well as lead to more robust interpretations from other sites with significant lateral input.  

Cariaco Basin

Santa Barbara Basin

Eastern Tropical Pacific

Caribbean Precipitation

Bermuda Rise