Upward looking ice profiler sonar instruments for ice thickness and topography measurements

Scientific and engineering studies in polar and marginal ice zones require detailed information on sea ice thickness and topography. Until recently, vertical ice dimension data have been largely inferred from aerial and satellite remote-sensing sensors. The capabilities of these sensors are still very limited for establishing accurate ice thicknesses and do not address details of ice topography. Alternative under-ice measurement methodologies continue to be major sources of accurate sea ice thickness and topography data for basic ice-covered ocean studies and, increasingly, for addressing important navigation, offshore structure design/safety, and climate change issues. Upward-looking sonar (ULS) methods characteristically provide under-ice topography data with high horizontal and vertical spatial resolution. Originally, the great bulk of data of this type was acquired from ULS sensors mounted on polar-traversing submarines during the cold war era. Unfortunately, much of the collected information was, and remains, hard to access. Consequently, the development of sea-floor based moored upward looking sonar (ULS) instrumentation, or ice profilers, over the past decade has begun to yield large, high quality, databases on ice undersurface topography and ice draft/thickness for scientific, engineering and operational users. Recent applications of such data include regional oceanographic studies, force-on-structure analyses, real-time ice jam detection, and tactical AUV operations. Over 100 deployments of moored and AUV-mounted ice profiler sonars, associated with an overall data recovery rate of 95%, are briefly reviewed. Prospective new applications of the technology will be presented and related to likely directions of future developments in profiler hardware and software.