Our first challenge on this survey is to produce a more
detailed map of what the seabed looks like at Offshore Overfalls MCZ. To do
this we will be using a Multibeam Echo Sounder. Multibeam uses sonar to tell us
two things about the seabed; how deep it is, and how hard it is. This is worked
out by measuring how long it takes for sound to travel from the ship to the
seabed and back again (i.e. the longer it takes, the deeper the water is), and
by measuring how strong the returning sound signal is (i.e. harder seabed like
rock will reflect more sound energy than softer seabed like mud). Due to the
large size of the area within the MCZ that we plan to map, we estimate that
this element of the survey will require 7.5 days to complete!
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| Multibeam from Offshore Overfalls MCZ survey CEND0119 © JNCC/Cefas |
Multibeam data collected for the site will be used to update
the existing map of seabed habitats at Offshore Overfalls MCZ. This mapping
will also help the team on the ship decide where to collect grab samples and drop-frame
camera images later in the trip.
For further updates before and during the survey - watch this space; follow JNCC, Cefas and the survey hashtag #CEND0119 on Twitter, or join us on Facebook.
Survey Fun Fact
The multibeam uses sound waves to “see” through even the murkiest of waters, replacing the more traditional lead weight on a rope method to provide us with colourful bathymetric pictures of the seafloor. The term bathymetry comes from the Greek meanings “Deep”(Bathy) and “Measure”(metry) and is the measurement of the depth of water in oceans, seas, lakes, rivers, and canals.Written by Jess Taylor
