Influence of Marginal Ice Cover on Storm Surges

Abstract

Observational evidence is provided to show that positive storm surges are damped more than negative surges by ice. Data on the influence of an ice layer on tides and circulation is reviewed as supportive evidence for dissipation of long waves by ice. A mechanism is suggested as to why positive surges are more strongly damped. The crest and trough of the surge wave (which is a long gravity wave) are respectively referred to as the positive and negative surge. The observations consisted of tide gage data from 23 locations in eastern Canadian water bodies for the period 1965–1975. Classical studies, while recognizing the dissipation of long gravity waves by ice, do not account for the asymmetric dissipation of the crests and troughs. Here, we suggest a mechanism involving surface contraction and dilation as responsible for the asymmetric damping. This asymmetric damping occurs during the propagation of the surge in the shallow coastal waters and not during the generation. Open water or leads play an important role in this asymmetric dissipation process.