Monday, 14 January 2013

Manic monday

We are now sadly coming to the end of the survey. We had planned on collecting some additional video footage in the core area of the Central Fladen site, where we recorded the tall seapen Funiculina quadrangularis last week. However, we were thwarted by the Scottish weather and are now collecting further multibeam data until the swell calms down.Winds have been gusting up to 53 knots for around 24 hours and the swell is around 4 metres.

Stormy seas
Multibeam echosounders (MBES) generate information about seabed bathymetry and from this we can create a map of the seabed to reveal topographical features such as depressions, mounds and trenches. The multibeam echosounder is mounted directly beneath the Endeavour, and transmits an acoustic pulse downward from a transducer at the seafloor. The signal then reflects off the seabed and the return is received by the echosounder. From the two-way travel time, the depth of the seafloor can be estimated. This data is then stitched together by the on-board hydrographic surveyor and a topographic map of the seabed formed.
At the same time, backscatter data is collected which records the strength of the return from the echosounder and tellsus something about the nature of the seabed. Different groundtypes can be distinguised from different return signals and may be linked to certain habitat types. One of the features we identified using the bathymetry data was the trench shown in the map below:

3D map of a trench created using processed bathymetry data from MBES
The scientists have been assisting the senior surveyer with logging of bathymetry lines in the plotting room. It is possible to view the position of the boat in relation to the grid of proposed lines and watch the multibeam and backscatter data come in:

Screen displaying incoming backscatter data (top left), survey grid and vessel position (top right) and incoming bathymetry data (bottom right)

While logging bathymetry there has been some free time to complete our survey mascot Nigel the Narwool (nice work, Megan! - editor).