Coupling ROMS and CSIM in the Okhotsk Sea Rebecca Zanzig University of Washington November 7, 2006

Outline Motivation ROMS Configuration CSIM Model Specifications Coupling Between Models – Heat and Freshwater Fluxes – Surface stresses Preliminary Results Future Work

Motivation To couple a terrain-following regional ocean model (ROMS) with a state-of-the-art ice model (CSIM). Apply this new model configuration to the Sea of Okhotsk, which is the formation region for North Pacific Intermediate Water. Investigate the deep water formation in the region and the impact of sea ice on it. Investigate the impact of tides on sea ice.

Grid Setup Resolution: –43-63 N, E –16-23 km resolution –20 vertical levels ETOPO5 Bathymetry 3000 meter maximum depth East, South and West open boundaries* * Open boundary forcing thanks to the North Pacific model by Al Hermann and Liz Dobbins at PMEL

CPP Options LMD interior mixing KPP surface and bottom boundary layer mixing Splines Third-order upstream bias horizontal advection of tracers Surface salinity flux correction Open Boundaries (East, South and West) –Chapman free-surface condition –Flather 2D-momentum condition –Radiation condition for 3D-momentum and tracers

Forcing Data Coordinated Ocean-ice Reference Experiments (CORE) dataset –6 hourly Winds Relative Humidity Sea level pressure Sea level air temperature –Daily Incoming shortwave radiation Incoming longwave radiation –Monthly Precipitation (Rain and Snow) World Ocean Atlas

Community Climate System Sea Ice Model (CSIM) Dynamic and Thermodynamic ice model Elastic- Viscous- Plastic Dynamics Supports Multiple ice types Used in CCSM- global climate model Modified to run in regional applications Capable of computing fluxes over both ice and the open ocean

ROMS & CSIM Coupling ROMSCSIM Raw input forcing data Modified forcing Surface Stresses Freshwater Fluxes Heat Fluxes

Downward Flux = Incoming * (1 – aice)

Terrain–Following Issues: Frzmlt level at_hmin at_hmax

Terrain–Following Issues: Frzmlt Temp < -1.8 ºC Temp > -1.8 ºC

Terrain–Following Issues: Frzmlt

Results– SST & Surface Currents

Results - Ice Thickness

Results - Percent Ice Coverage 3 year mean~30 year mean

Scherbina et al (2004) Data along northwestern shelf from 2 bottom moorings and a hydrographic survey in September 1999 Factors thought to be important to dense water formation: –Location of the tidal mixing front –Baroclinic instability could stop dense water formation

Bottom Temperature

Density Section

Temperature Section

Future Work Add tides to the simulation Refine resolution Interannual variability (not just climatological forcing) Examine ventilation and deep water formation Include the Amur River in simulation