Regional variability in the vertical flux of particulate organic carbon in the ocean interior



[1] Carbon transport within sinking biogenic matter in the ocean contributes to the uptake of CO2 from the atmosphere. Here we assess the extent to which particulate organic carbon (POC) transport to the ocean’s interior can be predicted from primary production or export flux. Relationships between POC flux and depth are generally described by a uniform power law or rational decrease with depth, scaled to new or total primary production of POC. While these parameterizations of flux are used in most quantitative biogeochemical models, they are based on data sets from a limited geographic and depth range. We examine these relationships through a review of parameters derived from 14C uptake experiments, regional remote sensing, 234Th studies, nitrogen balances, and sediment trap records. Ocean regions considered include sites studied by the Joint Global Ocean Flux Study, Hawaii Ocean Time-series, and Bermuda Atlantic Time-series Study programs and involve observed and radiochemically corrected flux to depth. We demonstrate regional variability in the efficiency of the biological pump to transport organic carbon from surface waters to the ocean’s interior. Commonly applied flux relationships, while representative of some areas of the ocean, generally overestimate flux to depth. We estimate that the fraction of carbon transported as POC to depths greater than 1.5 km ranges between 0.10 and 8.8% (1.1% average) of primary production and between 0.28 and 30% (5.7% average) of export from the base of the euphotic zone. We develop empirical parameterizations of flux to depth using region-specific constants. Using a one-dimensional ocean model, we predict that the residence time of biogenic carbon may vary by up to 2 orders of magnitude depending on the regional efficiency of export and vertical transport.