Ice profiling sonar for an AUV: experience in the Arctic

The harsh environment and limited resources available in the Arctic region make collection of most scientifically relevant data in the area difficult and/or expensive. The Monterey Bay Aquarium Research Institute (MBARI), along with other partners, has developed an autonomous underwater vehicle (AUV) specifically designed to withstand the difficult environment in the Arctic and capable of collecting a variety of scientific data. This tool has the potential to replace capabilities previously supported by the US Navy SCICEX cruises which used submarines for measuring and monitoring Arctic oceanographic properties. Scientific access to Navy submarines has been severely restricted over the last several years, with the future prospects for continued support uncertain. Ice draft data was one important piece of data historically collected by the submarines that MBARI's AUV now has the potential to provide. This ice draft data has particular value to climatologists and Arctic scientists who are striving to evaluate the impact of global climate on the thickness and extent of the Arctic ice sheet. This paper examines the ice draft data collected by the ALTEX AUV during its engineering test cruise in the Arctic in October 2001. A description of the experiments and the general performance of the vehicle are presented along with the scientific instrumentation layout of the AUV. Further, the modifications made to the ASL Environmental Sciences Ice Profiler/spl trade/ instrument to support vehicle operations in real-time are described. The use of this real-time data to drive vehicle decision making during missions is addressed as well. The data acquisition and processing techniques used to determine ice draft are then outlined, followed by samples of the ice draft data itself and estimates of its accuracy and repeatability. The conclusion include lessons learned and future plans for the ice profiling science payload.