1/12° Arctic Cap Nowcast/Forecast System (ACFNS)

This site contains real-time nowcast/forecast results from the 1/12 Arctic Cap Nowcast/Forecast System (ACNFS), including snapshots and animations of ice thickness, ice concentration, ice speed and drift, sea surface height (SSH), sea surface temperature (SST) and sea surface salinity (SSS).

ACNFS is a coupled sea ice and ocean model that nowcasts and forecasts conditions in all sea ice covered areas in the northern hemisphere (poleward of 40 N). In ACNFS, Community Ice CodE (CICE) (Hunke and Lipscomb, 2008) is used as the ice model and is coupled with HYbrid Coordinate Ocean Model (HYCOM) (Metzger et al., 2008, 2010). Ice and ocean fields are passed between the two models hourly using Earth System Modeling Framework (ESMF) (Hill et al., 2004). The ice and ocean models are set up and coupled on the same 1/12° horizontal grid. Resolution is approximately 3.5 km near the North Pole and 6.5 km near 40°N. A plot of the grid resolution can be seen here. Atmospheric forcing in ACNFS is obtained from the Fleet Numerical Meteorology and Oceanography Center 3 hrly 0.5° Naval Operational Global Atmospheric Prediction System (NOGAPS) (Hogan et al., 1991) forcing.

The data assimilation is performed using the Navy Coupled Ocean Data Assimilation (NCODA) (Cummings, 2005) system with a model forecast as the first guess. NCODA assimilates available satellite altimeter observations (along track obtained via the NAVOCEANO Altimeter Data Fusion Center), satellite ice concentration, satellite and in situ SST as well as available in situ vertical temperature and salinity profiles from XBTs, Argo floats and moored buoys using a 3-Dimensional VARiational analysis (3DVAR) scheme. For more information about the validation of the ACNFS, see (Posey, et al., 2010). For more information concerning the models see the links below:

CICE home page
HYCOM home page

Cummings, J.A., 2005: Operational multivariate ocean data assimilation. Quart. J. Royal Met. Soc., Vol. 131, pp 3583- 3604.

Hill, C., C. DeLuca, V. Balaji, M. Suarez, A. da Silva, 2004: The Architecture of the Earth System Modeling Framework. Computing in Science and Engineering, Vol. 6, pp 18-28.

Hogan, T.F., T.E. Rosmond and R. Gelaro, 1991: The description of the Navy Operational Global Atmospheric Prediction System's Forecast model (NOGAPS). NOARL Report 13, Naval Research Laboratory, Stennis Space Center, MS.

Hunke, E.C. and W. Lipscomb, 2008: CICE: The Los Alamos sea ice model, documentation and software user's manual, version 4.0. Tech. rep. LA-CC-06-012, Los Alamos National Laboratory, Los Alamos, NM. (http://climate.lanl.gov/models/cice/index.htm).

Metzger, E.J., H.E. Hurlburt, A.J. Wallcraft, J.F. Shriver, L.F. Smedstad, O.M. Smedstad, P.Thoppil, and D.S. Franklin, 2008: Validation test report for the global ocean prediction system v3.0 - 1/12 HYCOM/NCODA Phase 1. Naval Report NRL/MR/7320-08-9148, Stennis Space Center, MS.

Metzger, E.J., H.E. Hurlburt, A.J. Wallcraft, J.F. Shriver, T.L. Townsend, O.M. Smedstad, P.G. Thoppil and D.S. Franklin, 2010: Validation test report for the global ocean forecast system V3.0 - 1/12 HYCOM/NCODA: Phase 2. Naval Report NRL/MR/7320-10-9236, Stennis Space Center, MS.

Posey, P.G., E.J. Metzger, A.J. Wallcraft, O.M Smedstad and M.W. Phelps, 2010: Validation of the 1/12 Arctic Cap Nowcast/Forecast System (ACNFS). Naval Report NRL/MR/7320-10-9287, Stennis Space Center, MS.

Time line of experiment numbers



Arctic Cap Nowcast/Forecast System (ACNFS)



Experiment Number


Date of Update








01 JAN 2012


NOGAPS atmospheric forcing



Expt 03.8

08 AUG 2013


02 OCT 2013


NAVGEM 1.1 atmospheric forcing





08 APR 2014


NAVGEM 1.2 atmospheric forcing




02 FEB 2015


Includes assimilation of blended high resolution AMSR2/IMS ice concentration