Buesseler¹, K.O., and R. Sambrotto²

¹Woods Hole Oceanographic Institution, Clark-447, MS#25, Woods Hole MA 02543, Tel: 508-289-2309, E-mail: kbuesseler@whoi.edu, ²Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10913

Resolving differences among estimates of ocean carbon export- examples from the Southern Ocean

Most of the carbon in the ocean is stored in the deep waters and sediments, thus understanding the rates and controls on ocean carbon export from the surface to deep ocean is an important JGOFS goal. Measuring export directly has been difficult however, thus a variety of direct and indirect approaches have been used during JGOFS to estimate carbon flux to the deep ocean. The Southern Ocean is one of the key regions where changes in the ocean C cycle have the potential to influence climate, however it is a sparsely sampled and poorly understood region where a wide range of C flux estimates exist. During the U.S. Antarctic Environment and Southern Ocean Process Study (AESOPS) the ocean C cycle was studied during an annual growth cycle along a transect at 170W that included the major N-S biogeochemical zonations common to the Southern Ocean. Shallow and deep POC fluxes during AESOPS and sediment data suggest enhanced POC export in the region of the Polar Front and just south thereof. A recent Southern Ocean inverse model and a global marine mixed-layer ecosystem model show a more gradual decrease in C export along a N-S gradient, while a newly developed temperature dependent food web model suggests lower fluxes under these conditions and a different N-S gradient. Comparisons of the field data to models in this region can provide insights into the processes controlling carbon export and the factors needed to adequately parameterize the Southern Ocean C sink. Also, comparisons and extrapolation of the AESOPS data to the entire Southern Ocean allows for improved quantification of strength of the Southern Ocean C sink.