Wednesday, 28 August 2013

INFOMAR reports on a successful survey season - 2013

V. Quinlan, K. Sheehan, F.Sacchetti

INFOMAR continued its survey activities in the south of the country into August. During this survey period INFOMAR completed the important South Priority Area (SPA) which stretches from near Toe Head in the southwest to Carnsore Point in the northeast.
RV Celtic Voyager operations commenced in Clonakilty Bay off the Cork coast in early July and for a period of four weeks seabed mapping continued into Glandore Bay, Baltimore Bay, Long Island and Roaring water Bay and a number of smaller bays in this region.

Figure1. Extent of Multibeam coverage during July & August 2013

The survey area included the important Special Area of Conservation (SAC) for marine mammals which encompasses Roaring water and Long Island bays. Mapping within the SAC requires a special license agreement, which was granted by National Parks and Wildlife Service (NPWS). The survey was conducted during day light hours exclusively, in compliance with the Code of Practice for the Protection of Marine Mammals during Acoustic Seafloor. Ports of significance in the area include Crookhaven, Schull, Baltimore, Cape Clear and Glandore. Water depths range from 10 to 100 meters.
Strong currents, shoals, and fishing gear made for exciting times mapping the Gascanane sound which separates Cape Clear and Sherkin Islands. This sound is regularly used by the Baltimore to Cape Clear ferry and by numerous fishing boats and pleasure crafts.
The seabed in the sound is extensively scoured by strong tidal currents, forming impressive holes of up to 50 meters depth.

Figure 2. Bathymetry image of Gascanane sound with scour holes evident.

Favorable weather periods were utilised to survey close in to the iconic feature that is the Fastnet rock. Survey data from both the Geological Survey of Ireland vessel; RV Keary and RV Celtic Voyager were required in order to map this area safely and to acquire full coverage.

Figure 3. Fastnet Rock (Photo courtesy of Nicola O'Brien)

Bad weather conditions on 31st July meant an unscheduled portcall in Castletownbere (figure 4), County Cork. Castletownbere is the biggest fishing port in the south of Ireland. Figure 4 shows the inner harbour. The weather downtime allowed the data processors to get through a backlog of processing and for the crew to do some maintenance and painting that they don’t get the opportunity to do while at sea.

Figure 4: Castletownbere Harbour.

A total of nine wrecks were mapped. Figure 4 below is an image of a wreck discovered on this survey. This wreck is previously uncharted and appears to be that of a submarine. This is currently under research, the outcome will no doubt be an interesting story. All the wrecks are initially identified from the main multibeam survey lines and are then mapped in detail using a 'box in' process of three parallel lines and one perpendicular line. Multibeam water column data is also acquired in order to maximize the mapping effort and ensure that small objects such as masts are also mapped. This effort produces the detail required both for identification and charting purposes.

Figure 4 A possible submarine.

The survey demobilised in Galway on 7th August 2013.

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