Prince William Sound Resurrection Bay Knight Island Passage Middleton Island The physical model is run in three dimensions and the data are used to drive a one – dimensional model at each Seward Line station location. Direct comparisons can then be made between GLOBEC field measurements and the model output. Comparisons here are done for the 2001 field season. Simulation of the Northern Gulf of Alaska Ecosystem Kenneth O. Coyle (SFOS, University of Alaska) Al Herman (NOAA, Seattle), Sarah Hinkley (NOAA Seattle) Funding Agency: North Pacific Research Board Mooring Fluorescence Data GAK5 June 2002 – July 2003 Major blooms occur in late April, May or early June with low production in March and early April Model must reproduce the timing and peaks suggested from mooring fluorescence data. Mooring data from Stabeno (PMEL) July 84 <2 µm >2-10 µm >10 µm <2 µm >2-10 µm >10 µm May Seward Line Stations Comparison of measured and simulated phytoplankton biomass at station GAK6. Simulated peak biomass occurs in mid April and May with magnitudes similar to field measurement by Lessard (University of Washington). Field measurements GAK1 GAK4 GAK9 GAK13 GAK Integrated Productivity Month gC/m2/day GAK Integrated Productivity Month gC/m2/day GAK Integrated Productivity Month gC/m2/day GAK Integrated Productivity Month gC/m2/day Simulated and measured primary production for stations GAK 1, 4, 9 and 13. Note that the magnitudes of simulated and measured production are similar but mooring data suggest that production may be more peaked than the simulation indicates. Production measurements by Whitledge and Stockwell (University of Alaska) July Hnano Hdino Ciliates August Hnano Hdino Ciliates Seward Line Stations Comparison of measured and simulated microzooplankton biomass at station GAK6. Magnitudes of simulated and measured biomass are similar. Field data from Lessard (University of Washington) Field Data Comparison of measured and simulated mesozooplankton biomass at station GAK6. Total zooplankton biomass (top panel, field data) is similar to simulation. Neocalanus biomass in simulation is high for 2001 Photosynthetically active radiation (PAR) in the model was similar to values measured at the ship’s mast head during cruises, but the range of measured values was substantially greater than simulated values. Conclusions: The model as currently parameterized was capable of reproducing broad scale patterns of nutrient concentration, primary production, and biomass of phytoplankton, microzooplankton and mesozooplankton on the northern Gulf of Alaska shelf for Remaining Tasks: 1)Get the physical model to run with tides. 2)Run the model on the 3 km Gulf of Alaska grid for 2001, 2002, 2003, 2005 and Major question: Can the model reproduce the interannual variability observed in the field data? The ecosystem model is embedded in a 3-dimensional physical circulation model (ROMS) to link climate forcing to the ecosystem response. 11 Component Model Slide by G. Gibson Iron ROMS Model and Site Description SeaWiFS Satellite Chlorophyll May Simulated primary production (g C m -2 y -1 ) Comparison of simulated primary production and satellite chlorophyll image. Note the elevated primary production and chlorophyll concentration to the west of the Seward Line (arrows) suggesting the model can reproduce physical mechanisms affecting distribution of production on the shelf. Distribution of Production Phytoplankton Biomass and Production Seasonal Zooplankton Biomass Simulated Measured July 2001 Simulated and measured nitrate and ammonium on Seward Line. The simulation can reproduce the vertical distribution and approximate magnitude of field measurement. Nutrient data from Whitledge (University of Alaska). Simulated surface nitrate (mM m -3 ), July 10 The model was capable of producing the high nitrate concentrations above the seasonal thermocline in the Alaska gyre and nitrate exhaustion typical of the shelf during summer. Seasonal and Geographic Nutrient Distribution Photosynthetically Active Radiation Conclusions and Perspectives Phytoplankton Biomass