Dynamical evaluation of the surface circulation using remote sensing of drifting ice floes

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Abstract
An analysis of ice drift from consecutive Landsat multispectral scanner images of the same area taken at 24‐h interval allowed the calculation of the surface circulation using a dynamical approach. Comparison between calculated and measured values shows that this method leads to a good approximation of the surface circulation in a region where ice floes are free drifting. On the other hand, the sole use of the floe drift over time to evaluate the currents leads to results that are far from the measured values. Tests made using various air and ice drag coefficients, and wind speeds and directions for different drift distances show that the error associated with these parameters is small. Although the values obtained using the numerical data involved considerably more effort and expense, the results were not significantly better than those found using photographic products. A good approximation of the surface circulation can thus be made using a simple digitization of the floe positions on photographic products. Application of the methodology to a set of four image pairs led to the recognition of two modes of circulation in southeastern Hudson Bay in spring 1985. This method can thus become a useful tool for rapid evaluations of surface currents in ice‐covered areas that can hardly be sampled otherwise.