An observation of the planetary boundary layer in the marginal ice zone

Abstract

Aircraft measurements at the marginal ice zone (MIZ) during a cold air outbreak are presented together with shipborne observations in the Fram Strait. These investigations were done during the Marginal Ice Zone Experiment in June and July 1984. The determined profiles, variances, and fluxes are discussed for different flight legs oriented parallel and normal to the ice edge. The data reveal a significant change in the turbulent momentum, heat, and moisture fluxes as the flow crosses the ice edge. The CD10 based on aircraft fluxes and surface winds were ≈2.9 × 10−3 over the MIZ and ≈2.0 × 10−3 over the nearby ocean. The variance spectra exhibit a clear shift in the peak frequency from about 1 Hz over ice to 0.4 Hz over water, which corresponds to an increase of the characteristic scale from 100 to 250 m. Secondary peaks appear in the low‐frequency range, indicating the development of secondary flows in the mixed layer over the ocean.