SONARCTC: Mission accomplished

21 August 2021
Posted in News_EN
21 August 2021 Gianluca Casagrande

Aug 16, 2021 The Polarquest2021 expedition has successfully completed its seafloor mapping programme today.

The Polarquest2021 expedition has successfully completed its seafloor mapping program today, with its last sonar scanning station in Bockfjorden at 79°5N, 13°4E. The crew, directed by sonar specialist Domink Pałgan and assisted by scientific coordinator Gianluca Casagrande, support engineer Kevin Monneron and environmental science student Elias Meier, started the activity upon leaving Ny Alesund on August 8th, when the deployed a NORBIT Subsea iWBM 200 kHz multibeam echosounder, installed on the right side of the stern platform with its GPS antennas placed on an A-frame above the navigation cockpit. The arrangement proved to be perfectly integrated with the vessel’s structure and internal systems.

The arrangement was developed by shore-team scientific advisor Dr. Aleksandra Kruss (Norbit and Gdansk University), skipper Giovanni Acquarone and technical coordinator Michael Struik.

The multibeam sensor was used to conduct two different types of expeditive surveys: a route scanning during transits along the western and north-western area of Spitsbergen and Nordaustlandet, and a systematic survey of ~25 km2 area Southwestern of Lady Franklinfjorden, Nordaustlandet, down to a distance of approximately 300 metres from glacier Søre Franklinbreen front, beyond the 80th parallel.

The activity allowed to produce new data in partially charted or completely uncharted regions of the archipelago, identifying potential corridors for navigation several points of very shallow waters: These will be reported and to update navigation charts. The scarce availability of such detailed data in the area appeared evident as single depth measurement indicated on nautical maps were often shown by the sonar to correspond to relatively wide and complex morphological structures on the seafloor (e.g. plateaus).

Observations in the Lady Franklinfjorden yielded new detailed data about the features of the sea floor in a previously virtually unknown site and will provide valuable information about the evolution of the local environment with regards to glaciers and their dynamics. Initial results show multiple rows of moraines (up to few meters high “ridges”) oriented parallel to the glacier front,  indicating the position of the glacier front in the geological past. Several lineaments engraved in the outcrops of the bedrock have also been mapped, which are probably associated with an advancing glacier,  showing how powerful ice can really be.

The mapping activity confirms the suitability of small vessels to perform seafloor mapping tasks in shallow seas and particularly in close proximity to coasts, which would prove extremely challenging for larger research vessels.

Throughout the survey process, the NORBIT equipment proved consistently reliable and flexible, with no system-related inconvenience throughout the program. Particularly during transit mapping, it often outperformed expectations in terms of scanning speed, operating at nominal survey and bottom detection capabilities up to 6.5 knots SoG in good sea/weather conditions. The sensor also turned out to show operational robustness in relatively rough sea conditions for long periods.