Deep-Sea Research II 52 (2005) 3541–3576 A numerical model of seasonal primary production within the Chukchi/Beaufort Seas John J. Walsh a,Ã , Dwight A. Dieterle a , Wieslaw Maslowski b , Jacqueline M. Grebmeier c , Terry E. Whitledge d , Mikhail Flint e , Irina N. Sukhanova e , Nicholas Bates f , Glenn F. Cota g,{ , Dean Stockwell d , S.B. Moran h , Dennis A. Hansell i , C. Peter McRoy d a College of Marine Science, University of South Florida, St. Petersburg, FL 33701, USA b Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943, USA c Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA d School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks, AK 99775, USA e Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia f Bermuda Biological Station for Research, St. George’s, GE 01 Bermuda, USA g Center for Coastal Physical Oceanography, Old Dominion University, Norfolk, VA 23508, USA h Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA i Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA Received 3 March 2004; accepted 21 September 2005 Abstract A coupled three-dimensional circulation and ecological model provided numerical analysis of daily carbon/nitrogen cycling by the planktonic and benthic components of western Arctic shelf/basin ecosystems during 2002, when extensive field data were obtained by American and Canadian ice-breakers. Seasonal model budgets of April–May, July–August, and September–October 2002 allowed both interpolation and extrapolation of these validation data, suggesting that the most productive shelf regime of the Chukchi/Beaufort Seas was that of summer. Yet, during this period of July–August, a combination of light-limitation and nutrient-limitation limited shelf-wide mean simulated net photosynthesis to only 709 mg C m 2 day 1 for shelf waters of o220 m depth. This modeled seasonal carbon fixation then accounted for 45% of the annual shelf primary production of 97.4 g C m 2 yr 1 Identification of the relative importance of natural control factors of light and nutrients by the coupled model provided insight into possible consequences of future global climatic changes at these high latitudes. The model’s seasonal penetration of relatively saline, nutrient-rich Anadyr Water of Pacific origin into the eastern Chukchi Sea replicated the time series of observed salinity fields. A similar fidelity of the simulated nitrate, silicate and dissolved inorganic carbon fields with the observed ones yielded an assessment of nutrient uptake and photosynthesis during a natural fertilization experiment. The simulated chlorophyll, dissolved organic carbon (DOC), and NH 4 stocks also mimicked these shipboard observations. We found that the spring 2002 stocks of new nutrients were stripped by the end of summer, with little fall nutrient resupply by physical and biotic factors, when incident light waned. However, because of extensive ice cover and nutrient-poor upper waters within the Canadian Basin, the slope regions remained ARTICLE IN PRESS www.elsevier.com/locate/dsr2 0967-0645/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr2.2005.09.009 Ã Corresponding author. Fax: +1 727 553 1189. E-mail address: jwalsh@seas.marine.usf.edu (J.J. Walsh). { Deceased.