Introduction
This case study shows a ROV Installation Example / CAGE mission to monitor methane seeps in the Arctic Ocean, installed with a NORBIT WBMS Bathy Sonar.
About CAGE
The Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) is a research centre located at UiT The Arctic University of Norway in Tromsø.
CAGE’s main goal is to study methane release from gas hydrates beneath the Arctic Ocean and its effect on oceans and the global climate in the future.
CAGE is an important contributor to the Arctic marine geology research.
Survey Setup
For this mission, NORBIT WBMS Bathy Sonar was installed on the SUB-fighter 30k ROV, designed by Sperre AS for NTNU/AMOS (Centre for Autonomous Marine Operations and Systems at the Norwegian University of Science and Technology in Trondheim).
WBMS Bathy is an ultra compact high-resolution multibeam sonar designed for use on all platforms. With approximately 40W power consumption, the system is suitable to operate from a battery. NORBIT wideband multibeam technology facilitates long range realtime data collection and at the same time achieves high resolution data.
Survey Location and Mission
Survey Location
The mission had two study areas at Storfjordrenna – a deep subsea channel in the Barents Sea, south of Svalbard, Norway. Water depths varied from ~380-390m at study area 1 and ~330-350mat study area 2.
The first study area featured prominent pingo-like structures (PLF) – seafloor mounds leaking plumes of gas bubbles into the water column.
The second study area was a joint PLF-crater feature with scattered gas flares and large blocks of rocks at the bottom of the crater.
Survey Mission
CAGE studies shallow geological fluid flow systems capable of transporting a significant amount of gas (mainly methane) from the subseabed up to the ocean floor and into the water column.
Normally, ship-mounted multibeam systems provide sufficient resolution (up to several meters at target water depths) allowing for fine-scale characterizing of the seafloor and mapping the gas flares in the water column. However, for detailed mapping of gas bubble streams and focused sediment sampling, high-precision multibeam systems are required.
One of the crucial objectives of the survey was to use NORBIT multibeam sonar for studying the methane seeps at the seabed.
Another important objective was mapping of the objects at the seafloor (e.g. boulders, blocks of geological rocks), which may be hazardous for CAGE’s seafloor observatories that require flat and featureless surface to be landed on. Therefore, ROV mounted multibeam is a perfect tool, providing the seafloor maps with 10th of cm resolution and neat gas flare positioning.
Conclusion
Conducting surveys in harsh and remote areas like the Arctic can be very challenging. The CAGE mission has proved the practicality of deploying the ROV equipped with the high-precision NORBIT multibeam system for conducting surveys in such areas.
The high level of detail required by the survey objectives could not have been achieved in the studied areas by conventional ship-mounted multibeam systems. Therefore, ultra-compact yet powerful NORBIT system that allows for an easy integration onto the ROV has proven to be a successful solution.
