Comparing observations and parameterizations of ice-ocean drag through
an annual cycle across the Beaufort Sea
Abstract
Understanding and predicting sea ice dynamics and ice-ocean feedback
processes requires accurate descriptions of momentum fluxes across the
ice-ocean interface. In this study, we present observations from an
array of moorings in the Beaufort Sea. Using a force-balance approach,
we determine ice-ocean drag coefficient values over an annual cycle and
a range of ice conditions. Statistics from high resolution ice draft
measurements are used to calculate expected drag coefficient values from
morphology-based parameterization schemes. With both approaches, drag
coefficient values ranged from approximately 1-10×10^-3, with a
minimum in fall and a maximum at the end of spring, consistent with
previous observations. The parameterizations do a reasonable job of
predicting the observed drag values if the under ice geometry is known,
and reveal that keel drag is the primary contributor to the total
ice-ocean drag coefficient. When translations of bulk model outputs to
ice geometry are included in the parameterizations, they overpredict
drag on floe edges, leading to the inverted seasonal cycle seen in prior
models. Using these results to investigate the efficiency of total
momentum flux across the atmosphere-ice-ocean interface suggests an
inter-annual trend of increasing coupling between the atmosphere and the
ocean.