Development of underwater beacon for Arctic through-ice communication via satellite

The Arctic presents challenging circumstances that include ice floes, extreme temperatures, rough seas, geographically remote regions, and multiple international stakeholders. This paper describes the design and testing of an automatic tracking system for use in these extreme environments during an oil spill response and recovery effort. An underwater identification (UWID) tag is deployed under the ice at the site of the trapped oil which contains a pseudosonar beacon projecting upwards at a critical angle to the ice in order to preferentially generate Lamb waves in the ice that radiate outwards from the UWID location. A top-surface geo-location Lamb-wave Detector Geo-Referencing Identification GPS/satellite transponder (LD-GRIDSAT) tag is delivered by hand, or by aerial drop so that it spikes into the ice. The LD-GRIDSAT tag includes an onboard Lamb wave detector that geolocates any nearby UWID tags placed under the ice to mark the oil location. Three to five LD-GRIDSAT tags placed around a complex spill will be able to identify and triangulate a number of UWID tags, and continue to track them as the ice floe moves. We discuss the systematic acoustic simulations used to optimize the internal design of the UWID, as well as the signal processing techniques used to identify the arrival times of the Lamb wave signals during proof-of-concept testing in the Arctic.