Sea ice cracks, sea ice movement and tide movements of Granite Harbour

Active spreading sea ice cracks were found in the sea ice of Granite Harbour over several seasons. The cracks would prove difficult for heavy surface transport required for a drill rig site establishment. Detailed measurements were made with location and orientation described. The thickness profile of the infilling ice was determined by measuring ice cores taken from the crack and the spreading rate was measured. The exact location and spreading rates of the sea ice shear cracks cannot be predicted precisely but the pattern of shearing is similar each season and the mechanism was established to enable a circuitous route to be negotiated to support a drill rig site in the future. A survey of sea ice movement in the Granite Harbour area (Cape Roberts to Dunlop Island and east of Butters Point) was completed to determine horizontal sea ice movement at potential drill sites and to measure absolute horizontal movements and to delineate the southern sea ice area influenced by the Mackey Glacier. A tide gauge recorded tidal amplitude for 11 days at both Scott Base and Cape Roberts.