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Abstract: Beaufort’s Dyke is a disused ordnance disposal ground within the North Channel of the Irish Sea. Over 1 million tonnes of ordnance were disposed of in the dyke over a 40year period representing a substantial volume of trace metal pollutants introduced to the seabed. Utilising particle transport modelling software we simulated the potential transport of metal particles from Beaufort’s Dyke over a 3month period. This demonstrated that Beaufort’s Dyke has the potential to act as a source for trace metal contamination to areas beyond the submarine valley. Trace metal analysis of sediments from the Dyke and surrounding National Marine Monitoring Programme areas demonstrate that the Dyke is not the most contaminated site in the region. Particle transport modelling enables the transport pathways of trace metal contaminants to be predicted. Implementation of the technique in other munitions disposal grounds will provide valuable information for the selection of monitoring stations. [Copyright &y& Elsevier]

Abstract: In recent years, efforts have increased to develop quantitative, computer-directed methods for segmentation of multibeam (MBES) backscatter data. This study utilises MBES backscatter data acquired at Stanton Banks (UK) and subsequently processed through the QTC-Multiview software environment in a bid to evaluate the program''s ability to perform unsupervised classification. Statistical comparison with ground-truth data (grab, stills and video) enabled cross validation of acoustic segmentation and biological assemblages observed at the site. 132 unspecified variables were extracted from user-specified rectangular patches of the backscatter image, reduced to three vectors by PCA, then clustered and classified by the software. Multivariate analyses of ground-truth data were conducted on 75 stills images and 51 grab samples. Video footage coincident with the stills was divided into 30s segments and coded by dominant substrate and species. Cross tabulation determined the interrelationship between software classifications, multivariate analysis of the biological assemblages and coded video segments. Multiview optimally identified 19 classes using the automated clustering engine. These were revised to 6 habitats a posteriori, using combined analysis of ground-truth data and Multiview data products. These habitats broadly correspond to major physiographic provinces within the region. Multivariate statistical analysis reveals low levels of assemblage similarity (<35%) for samples occurring within Multiview classes, irrespective of the mode of acquisition. Coded video data is more spatially appropriate than the other methods of ground-truthing investigated, although it is less well suited to the extraction of truly quantitative data. Multivariate analysis indicates assemblages within physiographically distinct Multiview classes have a low degree of biological similarity, supporting the notion that abiotic proxies may be contraindicative of benthic assemblage variations. QTC-Multiview performs well as a mechanism for computer-assisted segmentation of MBES backscatter imagery into acoustic provinces; however a degree of caution is required prior to ascribing ecological significance to these classifications. [Copyright &y& Elsevier]

Abstract: Multibeam swath bathymetry and backscatter data collected as part of the Irish National Seabed Survey and Integrated Mapping for the Sustainable Development of Ireland''s Marine Resource programmes is used to investigate the glacial geomorphology of the Malin Shelf. The data provides direct evidence that the former British Irish Ice Sheet was grounded as far out as the shelf break in this sector on more than one occasion. Drumlins on the outer shelf indicate the region was a zone of confluence where ice flowing onto the shelf from northwest Ireland converged with ice flowing across the shelf from western Scotland. Ice berg furrows located on the outer shelf record ice sheet break up by a calving event that may have been triggered by rising sea levels and northwest–southeast aligned moraines indicate the ice retreated north-eastwards across the shelf towards Scotland. The absence of direct dating control from moraines on the Malin Shelf precludes a definitive assessment of the timing of ice sheet events. However, consideration of the stratigraphic relationship of the glacial landforms on the shelf with age constrained ice sheet events in the wider region indicates that the former British Irish Ice Sheet reached the outer shelf in this region on at least two occasions during the last cold stage. Moraines that have been overprinted by drumlins may possibly belong to an early phase of glaciation that occurred c 45ka B. This was subsequently followed by another episode of shelf extensive glaciation where converging ice flow from northwest Ireland and western Scotland reached the shelf break during the LGM that subsequently retreated from the shelf edge around 23ka BP. [Copyright &y& Elsevier]