The effect of observed ice conditions on the drag coefficient in the summer East Greenland Sea Marginal Ice Zone

Abstract

The summer East Greenland Sea marginal ice zone is a region characterized by extreme horizontal variations of surface roughness characteristics. The surface drag coefficient is found to be correlated with these roughness characteristics, in particular, ice concentration and ice floe roughness and size. The estimates of wind stress and wind speed yield neutral drag coefficients C DN with standard deviations of 2.3 ± 0.8 × 10 −3 for areas with less than 40% ice concentration and 4.0 ± 1.1 × 10 −3 for ice concentrations greater than 70%. Much of the variation in C DN for a given ice concentration is explained by differences in ice floe size and roughness. Very small, concentrated, rough floes that have been affected by wave action produce twice as much wind stress ( C DN = 4.2 ± 0.7 × 10 −3 ) as relatively large, flat floes ( C DN = 2.1 ± 0.6 × 10 −3 ) and 4 times as much as typical open ocean for a given wind speed and stability. The drag coefficients in this region are higher than other marginal ice zones, probably a result of the presence of large amounts of multiyear ice floes that extend higher above the ocean surface and create more drag than first‐year floes.