Coastal Breakup in the Alaskan Arctic

Abstract

During observations of breakup along the Alaskan Arctic Coast, river flooding of the frozen nearshore zone, sea ice breakup, and beach thaw were examined. Spring river flooding, generated by earlier inland melt, accompanies arrival of temperatures above 0°C on the coast. The extent of flooding over the nearshore ice is related to total flood discharge and coastal morphology. Along wave-controlled barrier-island coasts, flooding and bed load are confined to lagoons, whereas on fluvial-dominated coasts, floodwater and sediment spread across lobate delta fronts and offshore shoals. During this time, marine influence is minimal as a result of protection afforded by sea ice cover. Sea ice melt continues through summer, and the final coastal sea ice breakup and ice dispersion depend on offshore Ekman transport, breakup of the offshore pack ice, and local bathymetry. The coastal ice breaks up 4 to 8 weeks after initiation of melt. Melt of ice and snow within the beach generates beach collapse and resultant unique arctic beach features, whereas flow of tundra snowmelt across the beach produces micro-fans and micro-deltas.