and Results from the 2000-2002 surveying seasons
The following primary
datasets have been acquired over the course of the first years'
- Multibeam sonar
- Multibeam backscatter
(see active channel deposition image below)
- Single beam echo
- Sub-bottom profiler
- Sound Velocity
Profiles (SVPs - see left)
The deep water Zone 3 Survey was carried
2000 and 2002 by two
to Global Ocean Technologies (GOTECH), an Irish marine survey company
which was successful in the international tender process. Zone
3 surveying was 24hrs a day and stops were very limited. However,
random, rather than regular grid spaced stops, were made to do full
ocean depth Sound Velocity Profiles (SVP's). Survey speeds were relatively
fast, with average speeds of 8 knots. The Bligh
and the Siren were the two vessels used.
map on left shows the Zone 3 area's full coverage upon its completion
in June 2002. The 2000 surveying season was quite short stretching
only from July until November. Despite this late start to the acquisition
season and some adverse weather conditions, coverage and data quality
was very good. 2001 was a much lengthier surveying season, beginning
in March and running right through to November. The 2002 season
opened on March 28th when the Bligh departed from Waterford Harbour
to complete Zone 3. This she did in 3G and she made her final return
port call at Waterford on June 6th. On October 2 the final
report for Zone 3 was handed over to G.S.I.
The Marine Institute (MI) has
been employed in Zone 2 data collection with its vessel, the Celtic
Voyager. As a prelude to formal commencement of Zone 2 in Donegal
Bay the MI undertook
a mini Survey in Galway Bay with the
Voyager in August 2001 followed by a similar exercise in August
2002. She formally commenced Zone 2 surveying later that month.
She continued surveying Donegal Bay until
above right shows the coverage of Zone 2 that was completed during the
short August-October period of the 2002 surveying season and the limited
Zone 1 coverage. The main concentration was on Donegal Bay but some coverage
was also achieved in Galway Bay, Clew Bay and along all of the transit
lines in between. In
April 2003 the newly
commissioned Celtic Explorer
takes over the Donegal Bay surveying from her sister ship.
As noted above some surveying
has also taken place in the Zone 1 area. In 2002 a pilot
LADS Survey (Laser Airborne Depth Sounder Survey) took place off the
Mayo coast in Clew Bay to see how airborne (Lidar) surveys could be applied
in Irish waters.
from this Survey which were initially
processed in Australia by the contractors, the Tenix
LADS Corporation and then QC-checked in GSI offices were found
to be excellent. Further work will be carried out on them and they
will be formally handed over to the Westport Harbour Authority and
the British Hydrographic Office so that a more than 100 year old navigation
chart for the area can be updated.
The SVP chart here
left is taken from the Edoras Bank area of 3A. The SVP readings
are taken on a regular basis and include temperature, salinity and
depth data. In addition, a programme of disposable Sippi-Can sound
velocity measurements was initiated by Glenn
Nolan, Marine Institute, Galway in 2001 over the Rockall Trough
area. To date 30 have been taken across the Rockall Trough.
The backscatter image
below taken at a water depth of in excess of 3,000m represents a
typical geomorphologic feature - an active channel deposition complex.
The width of the thalweg indicated shows the excellent resolution
addition to the geophysical and hydrographic datasets a number of
ancillary scientific datasets have been acquired;
Éireann (Irish Weather Service) - weather reporting from
vessels 4 times a day;
(Irish Whale & Dolphin Group) - spotting forms on both vessels;
Services - daily & weekly reporting;
(Bord Iascaigh Mhara, Irish Fisheries Board) - fishing activity
logging and specific fisheries maps;
(Coastal & Marine Resources Centre, University College Cork)
- Cetacean and bird watchers on both vessels.
further information see section on Ancillary
Projects and for specific information related to a CMRC study
From the maps produced
to date it is already clear that lots of exciting and interesting results
have been produced by the National Seabed Survey.
have been indications of the existence of hydrocarbons in the form of
gas escape features and mounds (see images below).
of the backscatter maps clearly identifies both active and inactive
deep-water channel complexes.
of catastrophic slope failure have also been identified.
numbers of carbonate mounds and bioherms (reefs) of Lophelia pertusa
(a deep sea cold water coral), not previously identified, have been
observed in the multibeam and sub bottom profile records.
other low relief features such as sedimentary bedforms have also been
- There is clear potential
for studying ocean circulation patterns.
above suggest the existence of gas associated with carbonate mounds. The
deep water coral, Lophelia is also associated with these mounds.
image left is taken from the Edoras Bank-Maury Channel areas of Zone
3A. It gives a clear representation of mound features, rock outcrop,
channels and mobile sediments bedforms (this is raw unfiltered data).
is a sun illuminated image of a partial area of 3E covered again showing
channel complexes and ships tracks. The image was generated on-line.
backscatter image here shows a carbonate mound field north-west
of the Rockall Bank. The mounds are 300-500m in diameter. The image
was produced on-line in real time and is unfiltered.
four survey seasons completed it is clear that many more interesting features
and possibilities continue to unfold….