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.