Modelling Extreme Storm-Induced Currents over the Grand Banks

Abstract

Extreme storm-induced currents over the Grand Banks are investigated using a three-dimensional (3-D) ocean circulation model forced by 22 storms selected from the past 50 years with return intervals ranging from 1 to 34 years. Wind data for the storms are historical atmospheric data. The modelled currents are compared with current meter measurements made during a storm in March 1983. The results indicate good agreement between the model and measurements. In the surface layer of the Grand Banks, the model extreme current speeds are approximately 80 cm s−1 over a large portion of the Grand Banks, and some areas have extreme current speeds higher than 120 cm s−1. The highest extreme current speeds occur at St. Pierre Bank, where the speed reaches 140 cm s−1. In the bottom layer, the region with high extreme current speeds is mainly in the periphery of the Grand Banks, with magnitudes over 40 cm s−1. The results also show that the response of the water to storm forcing in the Grand Banks area varies from place to place because the mechanisms of current generation are different at different locations.