2007.08.31 - Pirouette surveys of the Morris Jesup Rise
We continued moving towards the northern steep slope of the Morris Jesup Rise, where the Danish project has as a goal to map the foot of it.
When "ODEN" is breaking heavy ice using all her 25,000 hp we do not get much depth information from the multibeam, only some pings here and there pass through the noise and crushed up ice, so a new style of multibeam mapping was invented, which proved
to be very efficient in these tough ice conditions.
To get good depth data we need either to break the ice as gently as possible or break a ship's length of ice, then back up while measuring the seafloor with multibeam. This is very time consuming.
Instead we found that we could break through the ice along our intended track until we found some smaller cracks or openings in the ice where we could spin the icebreaker 360 degrees while collecting data. In this way we efficiently covered the seafloor
around us with a radius equal to the multibeam swath.
For example in 4000 m we could, during the most favourable conditions, measure with a radius of more than 10,000 m around the ship.
Our mapping soon showed that the northern slope of Morris Jesup Rise was wrongly placed on available bathymetric maps and also incredibly steep.
The Icebreaker "ODEN" is owned and managed by the Swedish Maritime Administration. It is built by Götaverken-Arendal in Gothenburg in 1987, is 107 metre long with 19 crewmembers and a top-speed of 15 knots. It is fitted with the following KONGSBERG
- EM 122 12 kHz multibeam echo sounder
- SBP 120 sub-bottom profiler