Laboratory Measurements of Surface Wave Propagation through Ice Floes in Salt Water

Surface waves traversing polar marginal ice zones (MIZs) generate a boundary layer immediately below the ice, similar in some respects to the wave boundary layer created at the seabed in shallow water. The wave–ice boundary layer has not yet been thoroughly measured, but it can significantly affect wave attenuation rates. In December 2021, we conducted a laboratory experiment designed to measure such a boundary layer and the associated attenuation, in which monochromatic waves propagated through broken surface ice in a salt water tank. A particle imaging velocimetry (PIV) instrument array was submerged in the tank and used to visualize the fluid motion under the moving ice. The surface was tracked at multiple locations with acoustic sensors and cameras mounted over the tank. A total of 64 trials were completed, each producing 3–6 s of highly resolved velocity time series and 30–40 s of surface elevation data. Preliminary analysis of the data has provided strong evidence of a boundary layer at the water–ice interface. The wave attenuation rates compare well with existing datasets. The vertical profiles of RMS velocities and wave-induced Reynolds stress have trends similar to the theoretical predictions, while the quantitative discrepancies in terms of numerical values are discussed. This is the first of two such experiments; the second is tentatively scheduled for early 2023.