Seabed Surveys to Document Groundings from the 2000 Grand Bank Iceberg Season

The 2000 iceberg season provided the first recent opportunity to investigate and develop case histories of reported iceberg groundings on Grand Bank. In 2001, the locations for eight of nine icebergs reported as grounded were investigated with sidescan sonar, Huntec sub-bottom profiler, a towed underwater camera and a light Work Class ROV. In addition to the new scours, re- surveys in 2001 extended the time series for three groundings from the 1980s. In 2002, swath bathymetric surveys were conducted to provide detailed scour depth and shape information. The 2001 and 2002 seabed surveys documented six seabed scour features attributable to year 2000 groundings. Three icebergs produced both a furrow and a terminal pit, and three produced isolated circular pits with little evidence of significant furrows leading into or out of the pit. One of the pitting icebergs produced one pit; the other two produced two pits each. Methods applied to measure scour depths from multibeam data are described for a pit and for a furrow.