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

during the AIDJEX main experiment could be simulated (Colony, 1975).
addition to simulations of observed conditions, numerous calculations have
been performed using idealized driving forces (Pritchard and Schwaegler,
1975; Pritchard and Colony, 1974; Schwaegler and Pritchard, 1977). Complete
simulations during special time periods in the 1975-76 AIDJEX main experiment
also allowed a test of the model under realistic driving forces.
last cases the model response was compared with observed response of the ice
cover. These results were reported by Coon et al. (1976, 1977) and by
Pritchard et al. (1976, 1977).
In
In these
While the aforementioned calculations have increased understanding of
how the model responds to a given set of conditions, they have also raised
some questions.
The lack of answers is often caused by the difficulty of
understanding how each physical property affects response, 'and this diffi-
culty is enhanced by nonlinearities of the model.
are requi.red, it is particularly difficult to determine accurately special
local features of the response, such as velocity discontinuities. Because
of these difficulties, the present work was undertaken.
out that the jump conditions that must be satisfied when discontinuities of
various kinds are present were discussed by Nye (1975).
Since numerical solutions
It should be pointed
That analysis, how-
ever, did not address the question of when or where discontinuites might
arise or how solutions might vary along discontinuities.
It is known that
characteristics play a dominant role in the nature of the solutions of cer-
tain systems of partial differential equations (Courant an& Hilbert, 1962).
For example, discontinuities may exist in solutions only along characteris-
tic curves. Since some partial differential equations do not admit real
characteristic curves, these systems eliminate the possibility of a discont
inuity .
Satellite images of the ice cover (both NOAA-4 and Landsat) have shown
that deformations are often concentrated in narrow bands that could be well
approximated as velocity discontinuities on time scales of a day. Between
these discontinuities, deformations of lower magnitudes also occur. It is
our feeling that these features can be represented by a plastic ice model.
Therefore, it is important to understand how, when, and where discontinui-
ties may arise. Since discontinuities may arise in modeled stress fields
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