Barrier island development along the Alaskan-Yukon coastal plains

Abstract

The Arctic coast of the Alaska and Yukon Coastal Plains extends for 1,520 km, from Cape Beaufort in northwest Alaska to the McKenzie Delta (Fig. 1). Barrier island chains occupy 55% of the 1,260-km north Alaskan coast and 35% of the 160-km Yukon coast. The barriers resemble barrier chains of the middle to low latitudes; in detail, however, distinct arctic coastal features dominate their morphology. They possess regional variations in form and stability related to alongshore variations in the process, marine and terrestrial environment, particularly to variations in wave energy and angle of approach, sediment supply, geomorphic lineaments and elevation, and nature of the tundra mainland. This paper examines the morphology and regional variations of the Alaskan-Yukon barrier islands. The Coastal Plain The Alaskan Arctic and Yukon Coastal Plains occupy a triangular shaped 75,000 km 2 on the north coast of Alaska and the Yukon Territory (Fig. 1). They have generally low relief, with an inland elevation of between 80 and 180 m at the base of the Brooks Range and British Mountains extending to the coast, where the plain terminates as tundra bluffs 1 to 15 m high. The plains are composed of unconsolidated Pleistocene sediments, predominantly shallow-water marine (Black, 1964). The plains show possible evidence of uplift in the existence of three levels of river terraces; however, these have not been confirmed (Pewe, 1975). Permafrost and polygonal development affects the entire plain, and shallow lakes occupy much of the surface. The remaining surface is capped with shallow, peaty tundra soils, covered by low tundra grasses and stunted trees. Numerous rivers and, streams flow across the plain, generating a multitude of small deltas and fans at the coast. The entire plain and surrounding seas are frozen and covered by snow for eight to nine months of the year. Summer thaw and open-water processes operate during the 3- to 4-month summer period.