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