Ice-Type Characterization in a Marginal Ice Zone Using RADARSAT and Ice-Profiling Sonar: Tools for Structural Design and Navigation Planning in Ice Infested Waters

Advanced versions of moored sub-surface ULS (upward-looking sonar) instrumentation, originally developed (Melling et al., 1995) to provide high resolution mappings of ice draft in mobile pack ice have been a prominent component of recent hydrocarbon exploration and production activities in ice covered waters. In each case, data gathered by adjacent iceand acoustic Doppler current-profilers have provided quasi-spatial profiles (QSPs) equivalent to quasi-continuous sampling of ice-draft along linear ice tracks. These products have offered a basis for generating ice draft/thickness statistics descriptive both of the overall regional ice covers as well as of individual ice features relevant to navigation and offshore structure design and protection. The basic methodology of ice profiling is described and illustrated in terms of ASL’s IPS4 Ice Profiler instrument. After a brief description of Radarsat SAR imagery and its applications to ice cover characterization, focus is given to results obtained on the continental shelf in the Sea of Okhotsk east of Sakhalin Island which allow comparisons of such imagery with near-simultaneously obtained draft profile data. Such comparisons facilitate evaluations of the capabilities of Radarsat SAR imagery to detect topographic features of the ice cover of concern to the offshore oil industry. Operational issues such as the remote detectability of exceptionally large (and deep) ice ridges are addressed and results presented on the observability of other ice-topographic categories of significant potential interest. Statistical characterizations of the identified ice-types are compared with available remote sensing data and with the history of the observed ice cover.