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

APPROACH
A baseline simulation 0-f the conditions of interest in winter, performed as
part of the OCSEAP program (Pritchard et al., 19771, shows that when sufficiently
accurate barometric pressure fields and boundary motions are available the
ice model predicts ice motions and behavior remarkably well. Deformations
and stress are also simulated with physical reality, although these have not
been as thoroughly tested for accuracy as has the motion.
The purpose of the present work is to learn how badly the accuracy of
the simulation of ice response is degraded if driving forces are not as
accurate as those available for hindcasting during the AIDJEX main experiment.
We have not made a thorough evaluation of the accuracy of weather prediction.
Walsh (1977), using a statistical evaluation of many comparisons, concludes
that weather predictions degrade seriously at 72 hours. We, on the other
hand, have taken a representative case in which accurate driving forces are
known and ice motions have been accurately predicted. Using this case and
a set of weather predictions during this time, we make a sensitivity study
which will serve as a first check on the influence on ice behavior of such
errors in the weather predictions. We have chosen the period 27 January
through 3 February 1976, because accurate winds and ice motions are available
and because the drifting buoys and NOAA-4 satellite images show interesting
ice behavior in the nearshore Beaufort Sea. In this work we show how errors
in the barometric pressure field are transmitted into errors in the ice motion,
deformation, and stress for the observed conditions.
It is necessary not only to determine barometric pressure fields accurately
so that wind stress may be found, but also to provide boundary data for accurate
forecasting of ice behavior. We have integrated the model equations in time
over a portion of the Beaufort Sea approximately 800 X 1200 km in size. On
the landward parts of the boundary of this region we set the velocity to zero
to represent the lack of motion of the land mass. Since the plasticity model
admits discontinuous velocity behavior along these boundaries, this method
provides a satisfactory approach even in cases in which the ice is moving very
near the shore.
One
late the
possible alternative for providing
ice response throughout the Arctic
boundary motion would be to simu-
Basin.
Then the former boundary
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