Forecasting Pack Ice Blockage Events at St John's Harbour, Newfoundland: An Empirical Approach and Development of Ship Alert and Advisory Tables

Supply vessels for the Grand Banks oil and gas industry have faced 25 ice blockage events entering St. John’s Harbour, Newfoundland from 1979-2005. We propose an empirical approach to forecasting the occurrence of 8-10/10ths total ice concentration at the harbour, and tables for alerting and advising ship personnel on the likelihood of such an event based on offshore winds, surface ocean currents, and ice conditions. These events are primarily controlled by the strength and character of an ocean current gyre and the ice conditions over a large area offshore St. John’s Harbour.