Morphology and hazards related to nearshore ice in coastal areas

Abstract

The objective of this study was to develop a general morphology of nearshore ice along the Beaufort, Chukchi and Bering coasts of Alaska, and identify those features which may represent hazards imposed by ice conditions on outer continental shelf oil and gas development. Landsat imagery has been utilized to map major winter and spring Beaufort, Chukchi, and Bering Sea nearshore ice conditions for 1973–1977 related to regional ice morphology. Following this, significant features from individual Landsat image maps have been combined to yield regional maps of major ice ridge systems for each year of study and maps of flaw lead systems for representative seasons during each year of study. These regional maps have, in turn, been used to prepare seasonal ice morphology maps. The seasonal ice morphology maps show, in terms of a zonal analysis, regions of statistically uniform ice behavior. The behavioral characteristics of each zone have been described in terms of coastal processes and bathymetric configuration. Based on the combined seasonal morphologies, a zonal analysis of potential hazards related to offshore petroleum development has been made for the study area. The general conclusion is that overall nearshore sea ice behavioral patterns are sufficiently similar from year to year, that 5 years' data can yield some predictability in terms of offshore sea ice hazards to oil and gas development. The implications are that geographical zones of different design and construction criteria can be established in the offshore areas based on the probability of damage to the structure by adverse ice conditions and the relative risk imposed to the adjacent eco-systems.