As part of the Office of Naval Research Sea Ice Mechanics Initiative, a real-time monitoring and processing program for acoustic emission from ice fracture and ridge-building events was established. A wide-aperture, horizontal hydrophone array was used in combination with a vertical line array to record the acoustic signals, which were then passed through a focused beam former for real-time generation of ice seismicity maps. A number of rapidly deployable geophone arrays were used in active zones to measure the acoustic emissions in the near field for detailed seismic event analysis. During one such deployment, a highly regular transient arrival structure was recorded on all sensors located near a major lead, with a transient appearing every 5 s. These data have been processed using frequency-wavenumber analysis to show that the transients correspond to edge waves propagating forth and back along the edges of the lead, with the probable source being a stick-slip mechanical phenomenon toward the ends of the lead. ¿ 1998 American Geophysical Union