The Sea Ice Physics Group at AWI works with a dynamic-thermodynamic continuum sea ice model (SIM). A large-scale numerical model describing the mass balance of sea ice typically has four components:
- a surface energy balance which determines the surface ice temperature based on the atmospheric conditions, radiation balance and conductive heat flux through the ice
- a parameterization of the conductive heat flux through the ice based on the given surface and bottom temperature of the ice, with the latter usually assumed to equal the freezing temperature of sea water
- a momentum balance consisting of acceleration, atmospheric and oceanic drag, Coriolis force, sea surface tilt force and internal stress of the ice
- a set of evolution equations for sea ice thickness and concentration and snow thickness including advection due to ice drift and freezing/melt rates.
The sea ice cover is commonly considered to be two-dimensional in such models, i.e. only its areal extent and horizontal velocity are considered dynamically. The thermodynamics often consider only one-dimensional, vertical processes.
The SIM’s dynamics are based on the fundamental work of Hibler (1979) and include a viscous-plastic rheology, its thermodynamics mainly follow the ideas of Parkinson and Washington (1979). As we focus on sea ice process studies the SIM is run in a stand-alone mode to reduce computational cost. In this mode the SIM is forced with atmospheric reanalysis data (NCEP/NCAR, ERA-40), most important are surface air temperature and wind velocity, and climatological means, which maintain a seasonal cycle, regarding ocean heat flux. The rotated model grid covers the whole Arctic Ocean and the norhtern North Atlantic with a nearly uniform horizontal resolution of a quarter degree (~27 km); the time step is 6 h. The SIM is a well-evaluated tool for developing and testing new parameterizations. For regional Arctic climate studies the SIM is run coupled as sea ice-ocean model or additionally with an atmosphere model (see Arctic Ocean modelling and Arctic climate modelling).
In recent years the following studies of the Sea Ice Physics Group were performed based on the SIM:
Hibler, W. D., III., A dynamic-thermodynamic sea ice model, J. Phys. Oceanogr., 9 (4), 815–846, 1979.
Parkinson, C. L., and W. M. Washington, A large-scale numerical model of sea ice, J. Geophys. Res., 84(C1), 311–337, 1979.