Classification of the Alaskan Beaufort Sea Coast and estimation of carbon and sediment inputs from coastal erosion

A regional classification of shoreline segments along the Alaskan Beaufort Sea Coast was developed as the basis for quantifying coastal morphology, lithology, and carbon and mineral sediment fluxes. We delineated 48 mainland segments totaling 1,957 km, as well as 1,334 km of spits and islands. Mainland coasts were grouped into five broad classes: exposed bluffs (313 km), bays and inlets (235 km), lagoons with barrier islands (546 km), tapped basins (171 km) and deltas (691 km). Sediments are mostly silts and sands, with occasional gravel, and bank heights generally are low (2-4 m), especially for deltas (< 1 m). Mean annual erosion rates (MAER) by coastline type vary from 0.7 m/year (maximum 10.4 m/year) for lagoons to 2.4 m/year for exposed bluffs (maximum 16.7 m/year). MAERs are much higher in silty soils (3.2 m/year) than in sandy (1.2 m/year) to gravelly (-0.3 m/year) soils. Soil organic carbon along eroding shorelines (deltas excluded) range from 12 to 153 kg/m(2) of bank surface down to the water line. We assume carbon flux out from depositional delta sediments is negligible. Across the entire Alaskan Beaufort Sea Coast, estimated annual carbon input from eroding shorelines ranges from -47 to 818 Mg/km/year (Metric tones/km/year) across the 48 segments, average 149 Mg/km/year (for 34 nondeltaic segments), and total 1.8x10(5) Mg/year. Annual mineral input from eroding shorelines ranges from -1,863 (accreting) to 15,752 Mg/km/year, average 2,743 Mg/km/year, and totals 3.3x10(6) Mg/year.