Lessons in political oceanography part I: A preliminary analysis of whether an oil spill off Cape Hinchinbrook, Alaska could (or would) directly impact the Copper River Delta

Abstract

Historical data and information collected during recent and ongoing oceanographic investigations of Prince William Sound, Alaska and adjacent coastal waters, are used for a preliminary analysis of the possibility of an oil spill at the southern end of Prince William Sound directly impacting the Copper River Delta (CRD). The CRD is an economically and ecologically important region located a few kilometers to the east of Prince William Sound. The prevailing winds and ocean currents both in the coastal and offshore regions of the northern Gulf of Alaska move toward the west, indicating that a spill off of Cape Hinchinbrook would be likely to be advected westward away from the CRD, thereby having no impact on the waters of the CRD. However, eastward excursions of the Alaska Coastal Current occur, in which case there is a possibility that a spill off of Cape Hinchinbrook would be advected into the waters of the CRD region. Eastward components of the flow field within the coastal current have been frequently observed during spring, summer and fall, periods that are often characterized by westerly wind events that interrupt the prevailing easterly wind field and westward setting current. These reversals appear to be quite persistent and may have alongshore length scales from about 10 to 100 km. Although these wind and current reversals are common knowledge amonst boat captains and commercial fisherman in the region, their input to government agencies has largely been disregarded because their observations are anecdotal information. However, the combination of empirical scientific evidence (ocean current structure) and anecdotal information (which is actually also empirical) provide a powerful argument, attesting to the importance of these reversals as possible transport mechanisms for the advection of oil into the CRD region. This preliminary analysis is partly responsible for the Alaska Department of Environmental Conservation mandating a trajectory study in which the spill scenario off to Cape Hinchinbrook is analyzed in greater detail.