The Sea-Ice Model Intercomparison Project (SIMIP) is part of the activities
of the Sea Ice-Ocean Modeling Panel (SIOM) of the Arctic Climate System
Study (WMO) (ACSYS) that aims to determine the optimal sea-ice model for
climate simulations. This investigation is focused on the dynamics of sea
ice. A hierarchy of four sea-ice rheologies is applied, including a
viscous-plastic rheology, a cavitating-fluid model, a compressible Newtonian
fluid, and a simple scheme with a step-function stoppage for ice drift.
For comparison, the same grid, land boundaries and forcing fields are
applied to all models. Atmospheric forcing for a 7 year period is obtained
from the European Centre for Medium-Range Weather Forecasts (UK) (ECMWF
analyses), while occanic forcing consists of annual mean geostrophic
currents and heal fluxes into a fixed mixed layer. Daily buoy-drift data
monitored by the International Arctic Buoy Program (IABP) and ice
thicknesses at the North Pole from submarine upward-looking sonar are
available as verification data. The daily drift statistics for separate
regions and seasons contribute to an error function showing significant
differences between the models. Additionally, Fram Strait ice exports
predicted by the different models are investigated. The ice export of the
viscous-plastic model amounts to 0.11 Sv. when it is optimized to the mean
daily buoy velocities and the observed North Pole ice thicknesses. The
cavitating-fluid model yields a very similar Fram Strait outflow, but
underestimates the North Pole ice thickness. The two other dynamic schemes
predict unrealistically large ice thicknesses in the central Arctic region,
while Fram Strait ice exports are too low.