HR: 0830h
AN: OS41C-37    [PDF]
TI: A Model Study of Circulation and Biogeochemical Processes in the Ross Sea
AU: * Dinniman, M S
EM: msd@ccpo.odu.edu
AF: Center for Coastal Physical Oceanography, Old Dominion University Crittenton Hall, Norfolk, VA 23529
AU: Klinck, J M
EM: klinck@ccpo.odu.edu
AF: Center for Coastal Physical Oceanography, Old Dominion University Crittenton Hall, Norfolk, VA 23529
AU: Smith, W O
EM: wos@vims.edu
AF: Virginia Institute of Marine Science, College of William and Mary, Gloucester Pt., VA 23062
AB: Physical forcing, which includes advective circulation, vertical mixing, and vertical stratification, may be the primary factor producing the observed vertical and horizontal variability in phytoplankton distribution and primary production in the Ross Sea. Related to this, exchange of Circumpolar Deep Water (CDW) onto Antarctic Seas and continental shelves has a large influence on sea ice and biological processes. As part of the US JGOFS Synthesis and Modeling effort, we are investigating circulation and nutrient transport in the Ross Sea with an eddy permitting, regional, 3D, numerical circulation model. The present effort focuses on implementation and testing of the circulation model. Later work will consider more realistic biogeochemical processes and simulations for specific years, to compare directly to observations. We use the Rutgers/UCLA Regional Ocean Model System (ROMS) with a grid resolution of 5 km horizontally and 24 levels vertically. A gridded bathymetry is derived from ETOPO5. Initial model fields of temperature and salinity are derived from the World Ocean Atlas (WOA98). Initial values of nitrate and silicate come from a newly developed gridded nutrient and chlorophyll monthly climatology for the Ross Sea. Wind stress is from the monthly climatology of ECMWF reanalysis stress. Instead of using a fully dynamic sea-ice model, ice concentrations are specified using the SSM/I climatology and this, along with the COARE bulk flux algorithm, is used to compute the model surface heat and salt fluxes. Vertical mixing in the interior and surface boundary layer is done using the K profile parameter (KPP) vertical mixing scheme (modified for the presence of ice). A radiation boundary condition is used on all the open boundaries along with adaptive nudging (Marchesiello 2000) to monthly climatologies of temperature (WOA98), salinity (WOA98), nutrients (our database) and depth averaged circulation (OCCAM global high resolution circulation model). The effects of the Ross Ice Shelf are modeled by relaxing the temperature and salinity to climatological values along the edge of the shelf. The model circulation compares favorably to general schematics of the flow. Circumpolar Deep Water intrudes onto the shelf in the eastern Ross Sea due to wind and topographic effects. There is westward, wind driven flow along the Ross Ice Shelf and a northward boundary flow occurs along the western Ross Sea. Circulation and nutrient transport are strongly affected by bottom topography. A strong northwestward current, with an associated V-front, flows along the shelf break. Onshore flow occurs at the shelf break over shallower banks while offshore flow occurs in the troughs. Without uptake, the advection and diffusion of nutrients as passive tracers leads to them being retained in the surface layer near Ross Island.
DE: 4845 Nutrients and nutrient cycling
DE: 4207 Arctic and Antarctic oceanography
DE: 4219 Continental shelf processes
DE: 4255 Numerical modeling
SC: OS
MN: 2002 Ocean Sciences Meeting