Monday, 14 December 2009

Groundtruthing in Donegal and Sligo Bays

From the 6th to 8th of July 2009, a ground truthing or seabed sampling survey was undertaken in the region of Donegal and Sligo Bay.

A local vessel, the K-Mar-K from Killybegs, was chartered for this purpose. The vessels top speed of greater than 20 knots, high maneuverability and experienced crew proved highly successful for sample acquisition.

Local vessel, the K-Mar-K from Killybegs, provided the platform for the ground truthing leg.

90 proposed sample sites were identified in the area, based on bathymetric data previously collected by INFOMAR surveys and also on seabed classification map products by INFOMAR. Of these proposed locations, 80 were successfully sampled, despite adverse weather conditions.

Map of the sample locations in Donegal and Sligo Bays .

In all instances, the 'Day Grab' was used to ensure consistency in results and due to ease of handling of this grab design. The samples recovered were described and photographed once brought on deck but will also undergo further detailed particle size analysis and will be used to refine INFOMAR seabed classification and geology products for the region.

The Day Grab (to left) on the back deck of the K-Mar-K which was used at all sampling sites.

Example of a sediment sample collected during the ground truthing leg.

The use of a suitable, locally sourced vessel capable of high-speed transits between sample locations, maximised the cost effectiveness of this sampling campaign in Donegal and Sligo Bays.

All INFOMAR data is available for free download here.

Wednesday, 9 December 2009

CV09_05 Survey off North Dublin coast

The final INFOMAR survey of the 2009 season has just been finished off the coast of north Co. Dublin. Mobilising in Galway and making a transit through heavy sea conditions, the Celtic Voyager arrived in Howth harbour on the 25th November. Surveying was concentrated to an area north of the Ben of Howth and to Skerries. The aim of the leg was to complete remaining unsurveyed areas that will allow data from three earlier survey legs to be merged together. Following this survey leg, a large portion of the Irish Sea seabed from south of Carlingford Lough to the Kish bank has been mapped.

Overview map containing multibeam echosounder dataset of the area of seabed that was surveyed during CV09_05 off the north Co. Dublin coast.

High quality shallow seismic pinger profile which penetrates beneath the seabed (to a depth of around 24 metres in this case) shows three distinct reflectors. An undulating reflector interpreted as rock or glacial sediments (blue reflector). This depression or perhaps erosion feature (channel) is filled with sediment (red reflector). A final layer of sediment, probably recent marine sediments forms what is now the current seabed (green reflector)

High quality shallow seismic pinger profile showing a distinct porabola on a section of flat seabed indictaing the possible location of a pipeline that was later confirmed on naviagtion charts.

Over the duration of the leg, weather conditions were mixed which hampered operations as poor weather effects data quality which limited the amount of surveying that can be achieved. However, all proposed survey areas were completed and some interesting datasets acquired.

During the survey, the Marine Institute's M2 oceanographic databouy was recovered to the back deck of the Celtic Voyager for repair.

The Irish Coast Guard performs training drills with the Celtic Voyager during the CV09_05 survey leg.

All INFOMAR data is available for free download here.

Thursday, 5 November 2009

RV Keary progress in Dublin Bay

Since late July, the Geological Survey of Ireland's new survey vessel, RV Keary has been making steady progress in completing the shallow water areas of Dublin Bay on survey leg KRY09_02 that were not covered by previous surveys by the Celtic Voyager. The main areas of surveying have been concentrated close to the coastline around inner Dublin Bay and on top of the shallowest areas of the Kish Bank, surveying at high spring tides to ensure safest draught clearance.

RV Keary surveying the seabed south of Dun Laoghaire in August. (Click for larger image)

To date the vessel has been operating during daylight, in weather conditions of sea state 4 or less as data quality is reduced beyond these weather conditions. Currently the crew of 4 are sufficient to perform all operation and scientific duties onboard. Weather permitting it is hoped to complete Dublin Bay by end of 2009. The RV Keary coverage will be added to by the Celtic Voyager which will be surveying in the Dublin Bay/North of Howth area in late November/early December 2009.

Overall coverage achieved by RV Keary in Dublin Bay to date. (Click for larger image)

Multibeam echosounder shaded relief image of the shallowest ridge of the Kish Bank. (Click for larger image)

Multibeam echosounder shaded relief image of the Rossbeg Bank located south east of the Baily on Howth Head. (Click for larger image)

RV Keary returning to Dun Laoghaire marina after another day of successful surveying. (Click for larger image)

More information about the RV Keary can be found here.

All INFOMAR data is available for free download here.

Wednesday, 26 August 2009

CV09_03 Survey off Wexford coast

The Celtic Voyager returned to Howth harbour on the 18th August 2009 to demobilise following another successful geophysical survey of the seabed, this time off the Wexford coastline as part of the ongoing INFOMAR project. Having mobilised in Cork on the 28th July, the vessel transited to Rosslare to begin surveying along the eastern coastline of Wexford. The initial 2 weeks of the leg were spent mapping the seabed around the busy ferry and goods port of Rosslare Harbour. This data will be of great assistance to safe navigation in the area with a large portion of the approaches and the harbour itself successfully mapped. As well as this, some very interesting scientific data of the active, large-scale sand waves on the seabed off the southeast coast was also collected (see pinger data below).

Highlight image of data collected using a multibeam echosounder of the seabed around Tuscar Rock off the coast of Wexford. The image shows the shallow rock upon which Tuscar Lighthouse is built (below).

Following a change of crew and scientific staff on the 11th August, the final week of operations were concentrated along the south Wexford coast, as far west as the Saltee Islands. Mapping this area was challenging due to the combination of strong tidal currents and dangerous outcrops of rock in shallow waters.

Data from the pinger, a seismic instrument that uses sound waves to penetrate through the seabed to image the sediments beneath the seafloor in a profile view. This image captures the symmetric sand wave forms which measure over 8 metres from crest to trough and roughly 200 metres wavelength. These sand waves lie on the seabed east of the Lucifer Bank, northeast of Rosslare Harbour.

Photograph of the new INFOMAR radar tide gauge that was installed by OTT hydrometry at Rosslare Harbour to measure variations in the tide height to correct soundings taken on the vessel throughout the duration of the survey.

Photograph of a fishing vessel just offshore of Carnsore Point, on the southeast tip of Ireland taken from the Celtic Voyager.

This survey also consisted of a large portion of the South East Priority Area (off the southeast of Ireland) that will also be mapped by INFOMAR.

All INFOMAR data is available for free download here.

Sunday, 17 May 2009

CV09_02 Survey of Dingle, Tralee, St. Finan's and Ballinskelligs Bays

The second INFOMAR survey of 2009 has just been completed in Dingle, Tralee, St. Finan's and Ballinskelligs Bay in Co. Kerry using the Marine Institutes research vessel Celtic Voyager. The month long survey was divided into fortnight long legs and kicked off from Galway Docks on Friday May 15th, just days before the arrival of the Volvo Ocean Race stopover. From May 16th to 29th, the survey was focused in an area east of a line from Slea Head on the Dingle peninsula to Doulus head on the Iveragh peninsula into the 10 metre depth contour just offshore of Inch and Rossbehy strands. The second leg from May 29th to June 12th was surveyed the remaining area of seabed in outer Dingle bay, around the Blasket Islands and further south to St. Finan's and Ballinskelligs Bay.

With the proposed area to be surveyed around Dingle bay complete before the end of the survey, the Celtic Voyager relocated to Tralee bay to survey the remaining area of seabed between the coverage from a LiDAR survey of the inner bay in 2008 and the survey of Shannon estuary and approaches earlier in the year.

Images generated from MBES data showing the wreck of the Manchester Merchant which lies 11 metres below the surface in Dingle Bay. The 137 metre long merchant vessel sank in January 1903 after being towed into Dingle Bay following a fire on board. The cargo of the ship included bales of cotton from New Orleans in transit to Manchester. Bourke, Edward J. "Shipwrecks of the Irish coast"

View of sea cliffs on Dingle Peninsula from Celtic Voyager.

View of Dingle lighthouse from Celtic Voyager while entering Dingle Harbour for crew change on May 29th.

Sunset in Dingle Bay on May 25th.

All INFOMAR data is available for free download here.

Friday, 8 May 2009

CV09_23 Ground Truthing in Bantry and Dunmanus Bays

From 22nd to 28th April, INFOMAR staff were amongst a crew of scientists that were busy collecting a large number of ground truthing samples from the seabed in Bantry and Dunmanus Bays in Cork on the Celtic Voyager as part of research by Dublin City University (DCU) on pockmark features in the bays. Also included were scientists from University of Limerick (UL) and Aquafact Environmental Survey Specialists. Before the transit to west Cork, mobilisation, testing and training was done in Cork Harbour.

Day Grab recovery from Cork Harbour of coarse grained sediment and large shells.

The 290 metre long Grand Princess cruise liner in Cobh.

Gravity cores, box cores and day grabs were recovered from the seabed with video footage from selected sites. In all over 5 days of 24 hour operations, 132 sampling stations and 12 gravity core stations were covered. The physical, chemical and biological content of these samples
will be analysed to gain an insight into the nature of the seabed in the bays and also close to the pockmarks features. The leg ended in demobilisation in Castletown Bere and was deemed very successful for all parties.

Plan view of day grab recovery. Note the muddy nature of the seabed and the brittle starfish recovered in the grab.

Elevation view of box core recovery. Note the change in colour of the sediment from green/brown to grey around 5 cm from the surface. Sediments recovered were generally composed of mud and clay.

Recovery of the gravity corer with 2 metre barrel from the A-frame of the Celtic Voyager. Average recovery from the corer was around 1.20 metres of mud and clay.

View of the west Cork coastline on the Sheep's Head peninsula from inner Dunmanus Bay.

All INFOMAR data is available for free download here.