Characterisation of iceberg pits on the Grand Banks of Newfoundland

Summary form only, substantially as follows. Numerous studies of the eastern Canadian continental shelves have indicated the presence of seabed features formed through iceberg impact processes. These features range from long, shallow scour furrows many kilometres in length to circular or elliptical pits or craters incised into the seabed. Exploration and development of Canada´s offshore hydrocarbon resources generally requires the use of bottom-founded structures, for which iceberg scouring and pitting of the seabed must be factored into the engineering design process. Previous studies have focused on furrow-type scours rather than on iceberg pit features, although the relative depth of iceberg pits indicates that the processes leading to pit formation should also be understood in assessing the risk to seabed facilities. The study described in this paper was developed to address some of the issues related to iceberg pits on the Grand Banks of Newfoundland. The purpose of this study was to examine the characteristics of iceberg pits on the Grand Banks, and to develop an overall framework for the assessment of risk to seabed facilities from the iceberg pitting process. Information on iceberg pits, their locations and observed physical characteristics was obtained from the Grand Banks Scour Catalogue (GBSC), a digital database of seabed ice-contact features previously developed by the Geological Survey of Canada from a variety of data sources. A detailed review of the GBSC has identified significant limitations in the geophysical analysis and data compilation methods. The available iceberg pit data indicate that the majority of iceberg pits have been found in three main areas: northeastern Grand Bank, Downing Basin and the southern portion of Avalon Channel. Very few pits have been observed in the shallower water regions on the bank tops. A database of environmental parameters has been developed specifically for this project, focusing on those factors thought to potentially influence the formation, characteristics and persistence of iceberg craters on the seabed