| Summary: | From 1985 to 1989 high-frequency seismic reflection profiling was carried out from a drifting ice island as part of Project I.S.I.S. (Ice island Sampling and Investigation of Sediments), run by the Atlantic Geoscience Centre, Nova Scotia, Canada. Seismic sections from this initial study were found to be virtually uninterpretable. To facilitate a greater understanding of the problem the analysis has concentrated on the single trace, rather than the complete seismic section. In September 1991 a series of experiments were conducted using a digital seismograph and sub-ice hydrophone to monitor and record the return signal from an 8.5 kJ marine Sparker. This has shown that the primary influence on the initial down-going wavelet and hence the resolution attainable, is the complex morphology and acoustic nature of the ice itself. Improvements in the signal-to-noise ratio were gained by digital filtering, stacking and by the use of a conical baffle to directionalise the received hydrophone signal from below. A series of recordings made over a two week time window have shown the influence of localised ambient noise to be minimal. To complement this study an analysis has been made of the acoustic and geotechnical properties of two gravity cores from the study area, in an attempt to understand the acoustic response of the ‘first layer’. The work has highlighted the need for greater control over the survey design and has begun to investigate the viability of high quality digital acquisition for future surveys in ice covered regions. Atlantic Geoscience Centre, Dartmouth. Nova Scotia, Canada and the Scott Polar Research Institute, University of Cambridge, England
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