HR: 16:30h
AN: OS54A-03    [Abstracts]
TI: Simulation of plankton ecosystem dynamics and upper ocean biogeochemistry in the California Current system
AU: * Frenzel, H
EM: hfrenzel@igpp.ucla.edu
AF: IGPP & Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, 5854 Slichter Hall, Los Angeles, CA 90095 United States
AU: Gruber, N
EM: ngruber@igpp.ucla.edu
AF: IGPP & Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, 5854 Slichter Hall, Los Angeles, CA 90095 United States
AU: McWilliams, J C
EM: jcm@atmos.ucla.edu
AF: IGPP & Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, 5854 Slichter Hall, Los Angeles, CA 90095 United States
AU: Plattner, G
EM: plattner@igpp.ucla.edu
AF: IGPP & Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, 5854 Slichter Hall, Los Angeles, CA 90095 United States
AB: Eastern boundary current systems are characterized by strong upwelling of nutrient-rich deep waters and high biological productivity, yet the coupling of physical processes and ecosystem response is not well understood, partly because of the importance of small-scale, short-term variability. We address this issue by investigating these processes in the California Current system with the Regional Oceanic Modeling System (ROMS). Our U.S. west coast setup of ROMS has a horizontal resolution of about 15 km with a nested model covering the central California coast with a resolution of 5 km. The biogeochemical model is an NPZD-type model with nitrogen as the limiting nutrient. The model results (e.g. Chlorophyll concentrations) agree fairly well with observations from remote sensing (SeaWiFS) and shipboard measurements (CalCOFI). However, the simulated productivity is less than estimates derived from remotely sensed or other observed data. We will discuss possible reasons for this discrepancy. We studied the fluxes of nitrogen through the system under climatological forcing. The coupling of ocean physics and biogeochemistry has a strong impact on the dynamics of the system. New production is fueled by the upwelling of nitrate along the coast. It is highest in jets and filaments originating from capes and ridges, with the f-ratio reaching values of 0.6. Further offshore, regenerated production becomes more dominant with f-ratios as low as 0.2. Both new and regenerated production undergo a distinct seasonal cycle, with production peaking between spring (Southern California Bight) and summer (central California). Zooplankton exerts a strong control on the maximum concentration of phytoplankton. Over large scales in time and space, new and export production equal each other. However, strong decoupling between the two is observed on small temporal and spatial scales as discussed in detail by Plattner et al.
DE: 4805 Biogeochemical cycles (1615)
DE: 4815 Ecosystems, structure and dynamics
DE: 4842 Modeling
DE: 4845 Nutrients and nutrient cycling
DE: 4516 Eastern boundary currents
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting