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The influence of horizontal model grid resolution on a coupled physical-ecosystem model in the Norwegian Sea
Cecilie Hansen, Annette Samuelsen
NERSC
(Abstract received 07/13/2007 for session X)
ABSTRACT
Model studies on the importance of horizontal grid resolution and its influence on primary production has usually focused on other areas of the North Atlantic ocean, for instance the oligotrophic gyre, and little is known of the importance of resolving the mesoscale activity in northern areas. To investigate the influence of horizontal model grid resolution in a physical model on an embedded ecosystem model, HYCOM was coupled with the NORWegian ECOlogical Model system, and set up in a three model grid nested system. The ecosystem model has 10 components, including two phytoplankton classes: diatoms and flagellates. The focus area is along the Norwegian Coast, from 60N to 70N, where the warm, saline (>35) atlantic water in the North Atlantic Current meets the fresher(<35) coastal water in the Norwegian Coastal Current. The horizontal resolution in the three model grids in the focus area is 50km, 16km and 4.5km (hereafter: MODL, MODM and MODS). It was found that the differences in total annual primary production were small, roughly 17% higher in MODS compared to MODL. Annual net production for MODS, MODM and MODL was 78gC/m2, 69gC/m2 and 65gC/m2 respectively. This was an average over the whole area, and did not differenciate between coastal and open ocean areas. The timing of the start of the bloom and also the time when the different phytoplankton reached their maximum concentration in the spring was earlier in MODL and MODM compared to MODS. The composition of the phytoplankton classes in the three model grids was different, in MODS the diatom production was 60% of the total production, while in MODM and MODL it was 50% of the total production. The composition was closely connected to the representations of the mesoscale activity, and the ability of the models to reconstruct the physical processes.
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2007 LOM Workshop, Bergen, Norway, August 20-22, 2007