AIDJEX Bulletin #40 - Polar Science Center - University of Washington

The transformation of the system of equations into characteristic coordinates
is presented by first discussing the cases where advection may be neglected
so that the system of equations separates into two independent portions, one
for stress and the other for velocity. Characteristic equations are then
found for the general case where advection and the general flow rule are
considered.
MODEL
The mathematical model developed by the AIDJEX modeling group to
describe the response of the sea ice cover to the driving forces is presented
by Coon et al. (1974). The forces contributing to the change of momentum in
the horizontal plane of the ice cover are the air stress, water stress, internal
ice stress divergence, Coriolis force, and sea surface tilt. The time
and space scales of interest are approximately one day and tens of kilometers.
On these scales it may be assumed that the acceleration occurring in the ice
is small enough that inertia may be neglected in the momentum balance. We
shall make this assumption in the current work so that the number of independent
variables needed to define the equation may be limited to the two
spatial coordinates. Were we not to consider a quasi-steady description of
the model, we would have to include time as an independent variable, thereby
increasing the complexity of the characteristic analysis.
The horizontal momentum balance may be written as
where
v
-g
:a
2 is ice velocity,
is geostrophic ocean current,
is air stress,
zw = - ) is water stress,
g
m is areal mass density,
$ is the material rate of change of 2,
V.0 is the ice stress divergence,
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