THE BC SHELF ROMS MODEL

Transcription

1 THE BC SHELF ROMS MODEL Diane Masson & Isaac Fine, Institute of Ocean Sciences The Canadian west coast perspective (filling the gap ) AVISO, Eddy Kinetic Energy (cm 2 s -2 )

2 In this talk Model set-up and forcing Model results: Mean annual cycle: - model validation of coastal sea level eddy kinetic energy coastal currents - contribution of local wind and rivers Interannual variability: - sea surface height - local response to El Nino Ongoing model developments

3 Model Setup Regional Ocean Modeling System Model domain from south of Columbia River to the Alaska panhandle 3km (236 X 410), 31 sigma (vertical) levels Forcing: tides, 3 hourly wind, daily heat flux, monthly river discharge, monthly Open Boundary Conditions Now running on new HP 256 cpu machine i.e. decadal runs feasible Depth (m)

4 Lateral boundaries Monthly results from the Simple Ocean Data Assimilation, or SODA, (Carton and Giese, 2008) are used to initialize the model and to provide open boundary conditions. Tidal forcing Tidal forcing is also applied along the open boundaries for the main 8 tidal constituents (M2, K1, O1, S2, N2, P1, K2, and Q1), with amplitude and phase from the barotropic tidal model of Foreman et al. (2000).

5 Wind forcing North American Regional Reanalysis, or NARR, (~25 km resolution) is used to provide 3-hourly wind stress and daily atmospheric parameters. The latter are used to compute atmospheric heat flux.

6 Rivers Monthly freshwater discharge from 21 watersheds (as in Morrison et al, 2011). Most of the hydrological basins affecting the coast are dominated by snow accumulation in winter, leading to maximum discharge during spring freshet.

7 Model results A 14 year ( ) hindcast was completed to examine the seasonal cycle as well as the interannual variability of the coastal ocean off BC. A series of runs were executed to better understand the ocean response to direct forcing of wind and rivers over the model domain relative to variability outside of the study area. Run Open Boundaries WIND RIVERS 1 SODA NARR yes 2 SODA NARR no 3 SODA no low frequency yes 4 SODA no low frequency no 5 SODA - climatology NARR yes

8 Mean annual cycle: CSL Coastal sea level: winter/summer difference r=0.96

9 Time averaged EKE EKE dominated by Haida eddy

10 Mean annual cycle: Haida eddy Haida eddy: annual formation of a large anticyclonic eddy off the coast of Haida Gwaii, associated with the weakening of the winter downwelling winds.

11 Mean annual cycle: alongshore current Across-shelf vertical section In summer: buoyancy-driven poleward Vancouver Island Coastal Current (VICC) found over the inner shelf, wind-driven shelf-break equatorward current subsurface poleward California undercurrent

12 Mean annual cycle: rivers Run 1 (base run) - Run 2 (no rivers)

13 Mean annual cycle: seasonality of the wind Run 1 (base run) - Run 3 (no seasonal wind reversal)

14 Inter-annual variability: de-seasonalized SSH 41% 34% 13% 16% 6% 5%

15 Inter-annual variability: 97/98 El Nino 41% 34% 13% 16% The coastal response during the El Nino is accurately captured by the model. Except for SST, strong coastal anomalies forced at lateral boundaries. 6% 5%

16 Ongoing model developments Climate impact study (Mike Foreman, IOS) Biological applications: HABs in Juan de Fuca eddy (PNWTOX, UW) fish larvae drift in Strait of Georgia (UBC) plankton bloom timing and low dissolved oxygen coastal zones (Angelica Pena, IOS) Derive OBCs from shelf model to drive local models (Salish Sea ROMS and northern Strait of Georgia FVCOM) Better define buffer zones for fishing activity around protected sponge reefs in Hecate Strait