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Pushing the boundaries of acoustic observation possibilities in challenging environments – Antarctica and Southern Ocean Forum

Pushing the boundaries of acoustic observation possibilities in challenging environments

August 16, 2018
09:20  -  09:40
Acoustics is important in the ocean, and passive acoustic monitoring is a key part of large scale autonomous and remote observing missions.   As the capability of every aspect of autonomous acoustic monitoring systems grows, they are becoming a more standard inclusion into monitoring programs. These monitoring systems are therefore providing previously unknown information about oceanographic properties, marine fauna presence and diversity, and anthropogenic activity, and the amount of data collected is requiring users to deal with the challenges of ‘big data’.
Remote observation missions in extreme environments can involve autonomous, telemetered or mobile platforms that all need reliability, longevity, and precision.  The ability to store and computational power to process  significant amounts of data are crucial. The Canada Basin Ambient Noise and Propagation Experiment (CANAPE) is an ideal example of a mission to the Arctic that had to consider these factors and pushed the boundaries for what has been demonstrated to be possible.
CANAPE occurred north of Barrow, AK, between the Chukchi Sea and Beaufort Basin, and consisted of a deepwater experiment (DW CANAPE) with its site in the central Canadian Basin and a shallow-water experiment (SW CANAPE) with its site in the northeast Chukchi Shelf. Both experiments included acoustic sources and acoustic receivers. The SW CANAPE objectives were to receive and record signals to quantify shallow and deepwater propagation and its spatio-temporal variability, assess ambient noise on the shelf, investigate environmental measurements and inference, and measure mid-frequency reverberation and propagation. It was expected that the SW CANAPE acoustic receivers would record both DW CANAPE and SW CANAPE sources.
Acoustic receivers in the SW CANAPE experiment were provided by several different organizations, including Defence Research and Development Canada (DRDC). DRDC’s moorings and acoustic receivers were supplied and deployed by JASCO Applied Sciences (JASCO).
As part of the SW CANAPE experiment, the four DRDC stations each consisted of a single mooring, each of which contained an 8-channel hydrophone array and an acoustic recorder. These moorings, along with 25 others from five different institutions, were deployed in October 2016 and retrieved in October 2017. The four DRDC stations used recording units based on JASCO’s Autonomous Multichannel Acoustic Recorder (AMAR) recorded on a duty-cycle to provide recording operations for 11 months of deployment. Each AMAR had an 8-channel current-loop hydrophone array (either vertical or spatial) Additionally, each AMAR had 1.72 TB of memory installed and was equipped with a Chip Scale Atomic Clock (CSAC) for improved clock accuracy in the recordings. Several external Conductivity-Temperature-Depth (CTD) and orientation/Temperature-Depth (TD) loggers were attached to each array.
A critical aspect of the monitoring program was to use a low clock drift, so that the goal of a detailed examination of the physical and acoustic environment could be achieved. All deployed recorders performed as required, and thus the project is a great example of achieving lofty project goals in an extreme environment.
New technology is now available that will allow experiments such as this, and other remote area monitoring programs, to push the boundaries in terms of the sample rates, data storage and overall system flexibility. A summary of this technology will be presented, along with brief examples of projects that are already benefiting through their application.

Session Category :  Observation Technologies