Jiang¹, M.-S., F. Chai¹, R.T. Barber², T-H Peng³ and Y. Chao⁴

¹School of Marine Science, 5471 Libby Hall, University of Maine, Orono, ME 04469, E-mail fchai@maine.edu, ²Duke University, NSOE Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, NC 28516, ³NOAA Atlantic Oceanographic and Meteorological Laboratory, Ocean Chemistry Division, 4301 Rickenbacker Causeway, Miami, FL 33149-1026 and ⁴Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109

Modeling decadal variability of carbon cycle in the Pacific Ocean

To improve our understanding of physical variability and the carbon cycle response in the Pacific Ocean, especially on seasonal to decadal time scales, we have developed a physical-biogeochemical model for the Pacific Ocean. The lower trophic level ecosystem processes are linked with upper ocean carbon chemistry and embedded into a three-dimensional circulation model that is forced with observed the air-sea fluxes between 1950 and 2000. The improved physical-biogeochemical model produces a 50-year (1950-2000) retrospective analysis for the Pacific Ocean. The physical-biogeochemical model is capable of reproducing many observed features and their variability in the Pacific Ocean. Analyses of the modeled results are focused on the North Pacific, a sink region for both natural and anthropogenic carbon. The abrupt shift in the North Pacific climate system that occurred during the mid 1970s, the modeled air-sea flux of CO₂ and the response of the upper ocean carbon cycle to this climate shift are discussed. Using the physical-biogeochemical model, we estimate how much anthropogenic CO₂ has entered into the North Pacific Ocean during the past several decades. The model estimated anthropogenic CO₂ invasion rate for various regions compare favorably with observational (Sabine et al., 2002, GBC) and other modeling (Xu et al., 2000, Mar. Chem.) estimates.