Arctic Alaska's barrier islands: Morphological types and historical change

Barrier islands comprise approximately 50% of the open-ocean exposed Alaskan Arctic coast. They are structurally and geomorphologically distinct from barrier systems at lower latitudes as a result of cryospheric processes such as ice-bonding of sediment, thermomechanical erosion, and sea-ice entrained sediment transport. The islands provide shelter and nesting habitat to shorebirds, denning habitat for polar bears, haulout areas for walruses, and physical protection of the mainland shore from direct wave attack. They serve as sites for energy and defense-related infrastructure and are home to many native villages and subsistence hunting camps. Renewed interest in nearshore oil exploration and production in the shallow waters of Arctic Alaska, the documented reduction in barrier island area due to erosion, and the imminent threats to infrastructure in Native communities highlight the urgent need for a better understanding of the rates and patterns of barrier island change as well for improved predictive modeling of future island conditions.

Alaskan barrier islands include two major types: geologically recently constructed islands and spits dominated by littoral processes, and remnant barriers, typically with a tundra core, formed by detachment from geologically older relict coastlines. Constructed barriers are commonly attached to the ends of remnant barriers. Island morphology and migration rates are spatially and temporally variable along the coast. There are long, narrow, and relatively stable islands that have retreated less than 50 m over the past 60 years, island chains that have migrated landward and/or prograded up to 1 km over the same time period, and islands and shoals that form and disappear annually. Tundra cored barrier islands along Alaska's Beaufort Sea coast show a tendency to rotate and migrate to the southwest with prevailing winds and nearshore currents. Goals of this study include the development of a morphological classification of the barrier islands along the Alaskan Arctic coast and a preliminary investigation of the geologic and oceanographic processes that control the rates and patterns of historical change.