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

We found no essential differences between the 24-, 36-, and 48-hour results.
In all simulations performed there is good qualitative agreement in the
velocity, deformation, and stress fields. Although at some times and in
specific locations the velocity could be off by nearly 10 cm sec-l (or about
30%), this was not typical of the error over a large region.
A statement of the magnitude as percent of error is not as illustrative
as a thoughtful comparison of the entire field of results. In some locations
and at some times the predicted solutions compared with observed motions even
better than the baseline calculations. From these results we conclude that
errors in the 24-, 36-, and 48-hour predicted barometric pressure fields
introduce errors in the ice response that are no larger than errors in the
model itself, and there is no difference in accuracy if 24-, 36-, or 48-hour
predictions are used. It must be made clear that this conclusion has been
reached primarily when ice stress is important.
To determine ice response, boundary motion must also serve as input to
the model. We have not yet learned how to predict these quantities, although
several options have been described. In other work, however, we have determined
how errors in boundary motion influence solutions in the interior. A
thorough parameter study using a one-dimensional numerical solution scheme
has shown that zero-mean random errors in the boundary velocity decay in
magnitude with distance from the boundary (Pritchard and Thomas, 1977). This
study is completed for the velocity and deformation field and has been begun
for the stress field. To synthesize these results we have used a nondimensional
form of the AIDJEX model that was developed in another phase of our AIDJEX
modeling effort. These results are also presented, since the nondimensionalization
synthesizes results of the parameter study.
Work has begun on learning whether or not steady-state errors in the
boundary velocity can be expected to have a dominant effect on solutions in
the interior, but results are not yet available. It can be said that there
is no decay with distance, but it is not yet known how large these errors are.
In summary, the AIDJEX model may be an accurate mathematical tool for
predicting ice behavior on time scales on the order of 1-2 days. The ice
model can provide accurate forecasts if barometric pressure fields, boundary
motion, and ocean currents are input accurately. Accuracy of the ice
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