ROMS in Alaska Waters Kate Hedstrom, ARSC/UAF Enrique Curchitser, IMCS/Rutgers August, 2007

Overview GLOBEC and related modeling –NEP runs so far –Forcing –Plans –Tides CCSM connection –CORE forcing, POP global ocean for boundaries –Coupling underway at NCAR

The Model ROMS ocean –Coupled ecosystem models –Now with an adjoint and tangent linear for data assimilation Ice model from Paul Budgell –EVP dynamics (Arakawa C grid) –Mellor-Kantha thermodynamics –Oceanic molecular sublayer under the ice for improved behavior

NEP Implementation 10 km average horizontal resolution Run1: –30 vertical layers –IC’s and BC’s from NPac –Daily fluxes from NCEP hindcast (modified) – , Run2: –42 vertical layers –Six-hourly fluxes from Common Ocean-ice Reference Experiments (CORE) reanalysis –IC’s and BC’s from CCSM (POP) forced by CORE –

Evaluation of Latest Simulation We are much happier with the heat fluxes from CORE Ice area seems quite realistic Still could do better: –Not enough fresh water input at the coast –Stratification in general isn’t quite right, will perhaps be improved by tidal mixing –We want a shallower minimum depth We also need to add an ecosystem model for GLOBEC, plus need to test the new NEMURO implementation

Ice Area and Volume

Zoom In

Tides in the Bering Sea We have an effort underway to evaluate the tides in the model with Zigmunt Kowalik and Seth Danielson We started with the 4 km Bering Sea domain in 2-d with four tidal constituents We are ultimately interested in the complex 3-d structure

CCSM Coupling Thanks to the CORE group’s products, we no longer need to run the large NPAC domain (proof of one-way coupling) The CCSM model does fine for its resolution, but fails in regions needing more resolution (coastal upwelling) The idea is to couple ROMS to CCSM, where ROMS is part of a “composite ocean” providing a better sea surface temperature to the atmosphere

CCSM

CCSM Strategy The coupling interval is one day, with the atmosphere running ahead The composite ocean will receive hourly winds, etc. and interpolate to ROMS grid(s) POP runs for that day, sends “curtains” out for ROMS nests ROMS runs for that day Composite ocean merges SST from POP and ROMS for CAM

Conclusions We are excited about this opportunity to work with the CCSM group A similar effort is underway to add WRF as a regional atmospheric model One of the people we’ve been working with is on the ESMF team at NCAR and wants to make a standalone ESMF-ready version of ROMS