Tracking solitary waves below land-fast ice

Data from two acoustic Doppler current profilers, separated by 76 m and deployed through land‐fast ice in the Canadian Arctic Archipelago in May 2002, are examined. The three velocity components were sampled intermittently at 1‐minute intervals over a 3‐week period to 19 m below the ice‐water interface. The vertical structure was resolved using empirical orthogonal functions (EOF), while the shallow water Korteweg de Vries (KdV) and deep water Benjamin‐Ono (BO) theoretical solutions were used to guide a pseudo‐wavelet analysis of the horizontal structure. Numerous instances of near‐simultaneous spikes were detected in the empirical mode 1 time series. A 3.5‐hour period on 21 May 2002 containing two disturbances was examined in detail. Wavelet scalograms suggested that there was a 20‐minute lag in the first disturbance and 16 minutes in the second. The scalogram values indicated that KdV was more consistent with the waveshapewave shapes than BO theory. The character of the two events was very different. The first had a broader spatial distribution than the second, and the measured translational speed was reasonably consistent with that of a mode 1 KdV solitary wave. The second event had a much slower propagation speed and a near surface maximum in the vertical velocity eigenvector, suggesting a mode 2 wave. It is suggested that ice keels from a nearby pressure ridge could be the source.