WAVE ATTENUATION IN THE MARGINAL ICE-ZONE DURING LIMEX

During the Labrador Ice Margin Experiments, LIMEX '87 in March 1987 and LIMEX '89 in March and April 1989, the Canada Centre for Remote Sensing (CCRS) CV-580 aircraft collected synthetic aperture radar (SAR) image data over the marginal ice zone off the east coast of Newfoundland, Canada. One aspect of these experimental programs was the observation of ocean waves penetrating into the marginal ice zone (MIZ). Based upon directional wavenumber spectra derived from SAR image data, the wave attenuation rate is estimated using SAR image spectra and compared with predictions from a model developed by Liu and Mollo-Christensen (1988). The wave and ice conditions were considerably different in LIMEX '87 and LIMEX '89. However, the model-data comparisons are very good for all ice conditions observed. Both the model and the SAR-derived wave attenuation rates show a characteristic roll-over at high wavenumbers. A model for the eddy viscosity is proposed, using dimensional analysis, as a simple function of ice roughness and wave-induced velocity. Eddy viscosities derived from SAR and wave buoy data for the wave attenuation rate show a trend that is consistent with the proposed model.