Regional air-sea fluxes of anthropogenic carbon inferred with an Ensemble Kaiman Filter

Abstract

Regional air-sea fluxes, ocean transport, and storage of anthropogenic carbon (Canth) are quantified. Observation-based Canth data from the ocean interior are assimilated into the Bern3D dynamic ocean model using an Ensemble Kaiman Filter. Global uptake of Canth is estimated to be 131 ± 18 GtC over the period 1770 to 2000. Uncertainties from systematic biases in the reconstruction of Canth are assessed by assimilating data from four global and six Atlantic reconstructions and found to be comparable or larger than uncertainties from ocean transport. Aggregated fluxes for the southern high-latitude, tropical and midlatitude, and northern high-latitude ocean agree within 0.11 GtC a-1 for the two reconstructions with the highest skill score, whereas regional uptake rates are up to a factor of three different. Results indicate that uptake and regional partitioning of anthropogenic carbon in the Southern Ocean remains uncertain. Copyright 2009 by the American Geophysical Union.