| Volumes and Issues Contents of Issue 4 |
www.biogeosciences-discuss.net/3/1313/2006/
© Author(s) 2006. This work is licensed
under a Creative Commons License.
Marine geochemical data assimilation in an efficient Earth System Model of global biogeochemical cycling
1Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC, USA
2Frontier Research Center for Global Change, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001, Japan
3Earth Sciences, The Open University, Walton Hall, Milton Keynes, UK
4School of Environmental Sciences, University of East Anglia, Norwich, UK
5National Oceanography Centre, Southampton, European Way, Southampton SO14 3ZH, UK
Abstract. We have extended the 3-D ocean based "Grid ENabled Integrated Earth system model'' (GENIE-1) to help understand the role of ocean biogeochemistry and marine sediments in the "long-term'' (~100 to 100 000 year) regulation of atmospheric CO2, and the importance of feedbacks between CO2 and climate. Here we describe the ocean carbon cycle, which is based around a simple single nutrient (phosphate) control on biological productivity. The addition of ocean-sediment interactions is presented elsewhere (Ridgwell and Hargreaves, 2006).
We have calibrated the model parameters controlling ocean carbon cycling in GENIE-1 by assimilating 3-D observational datasets of phosphate and alkalinity using an ensemble Kalman filter method. The calibrated (mean) model predicts a global export production of particulate organic carbon (POC) of 8.9 PgC yr−1, and reproduces the main features of dissolved oxygen distributions in the ocean. For estimating biogenic calcium carbonate (CaCO3 production, we have devised a parameterization in which the CaCO3:POC export ratio is related directly to ambient saturation state. Calibrated global CaCO3 export production (1.2 PgC yr−1 is close to recent marine carbonate budget estimates.
The GENIE-1 Earth system model is capable of simulating a wide variety of dissolved and isotopic species of relevance to the study of modern global biogeochemical cycles as well as past global environmental changes recorded in paleoceanographic proxies. Importantly, even with 12 active biogeochemical tracers in the ocean and including the calculation of feedbacks between atmospheric CO2 and climate, we achieve better than 1000 years per (2.4 GHz) CPU hour on a desktop PC. The GENIE-1 model thus provides a viable alternative to box and zonally-averaged models for studying global biogeochemical cycling over all but the very longest (>1 000 000 years) time-scales.
Discussion Paper (PDF, 884 KB) Interactive Discussion (Closed, 4 Comments) Final Revised Paper (BG)
Citation: Ridgwell, A., Hargreaves, J. C., Edwards, N. R., Annan, J. D., Lenton, T. M., Marsh, R., Yool, A., and Watson, A.: Marine geochemical data assimilation in an efficient Earth System Model of global biogeochemical cycling, Biogeosciences Discuss., 3, 1313-1354, 2006. Bibtex EndNote Reference Manager
