Advanced underwater ocean monitoring system deployed in the Fram Strait

In the EU-funded ACOBAR project (Acoustic technology for observing the interior of the Arctic Ocean) an ocean monitoring system for acoustic tomography and navigation is under deployment in the Fram Strait. The system will consist of three acoustic transceivers in a triangle and a receiver array in the middle (see upper part of the Figure - A-B-C are transceivers, D is the receiver). This system will provide acoustic travel times for model validation, assimilation and temperature inversions along 6 tracks in the Fram Strait.

The first two moorings (A, D) of the four acoustic moorings have been successfully deployed in the Fram Strait from RV Håkon Mosby in early August 2010. The lower part of the picture shows the 925-kilogram ACOBAR acoustic source just before deployment to the Arctic Ocean.

The two remaining moorings (B, C in the figure) will be deployed in ice from the KV Svalbard during a cruise from 3. to 19. September. Due to the infrastructure onboard KV Svalbard the sources will be deployed "anchor last". This will be the first time these type of acoustic sources are deployed and used in ice covered waters. Also, this will be the first time the sources will provide broadband signals for tomography and narrow band signals for navigation of gliders. The sources will be operational for two years, and recovery is planned during summer 2012. An under ice mission with a glider is planned by Alfred Wegners Institute in summer 2011 as part of the ACOBAR project, utilizing the acoustic sources for underwater navigation.

The Fram Strait acoustic system is implemented by the Nansen Center in collaboration with Alfred Wegener Institute, Scripps Oceanographic institution, Woods Hole Oceanographic Institution, Geophysical Institute at University of Bergen and Aker Solutions.

In the project Waves-in-Ice Forecasting for Arctic Operators (WIFAR) project, funded by the PETROMAKS program of the Research Council of Norways and Total E&P Norway, a passive acoustic listening system developed and built by NAXYS AS in Bergen will be included in mooring C. This instrument is programmed to listen to the natural ambient noise generated by sea ice dynamics caused by ocean processes such as swell and meso-scale features. The aim of WIFAR is to measure waves in ice using ambient noise in combination with satellite remote sensing. The acoustic system will record natural sound in the range is 2-6250 Hz for 6 minutes every 3 hours for a period of two years.

The first data from the experiment will be recovered and analyzed in 2011.
For further information contact prof. Stein Sandven (stein.sandven@nersc.no) og Dr. Hanne Sagen (hanne.sagen@nersc.no).

See also the ACOBAR web-site at:

http://acobar.nersc.no/

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