Ground lee and carbon characteristics of eroding coastal permafrost at Beaufort Lagoon, northern Alaska

Coastal erosion over a fifty-year period, and permafrost characteristics of the shoreline associated with that erosion, were assessed at Beaufort Lagoon in northeast Alaska. Soil stratigraphy was obtained from two bank exposures on abandoned floodplain deposits and one exposure on a sand sheet deposit. All exposures had a thin (10-11 cm) fibrous peat accumulation at the surface underlain by a thin (17-23 cm) aeolian silt deposit. Below these surface layers were thick buried accumulations of discontinuous, amorphous peat clumps extending as deep as 1.5 m. Moisture contents (% vol.) for soils with segregated ice ranged from 52.7% to 84.4% in frozen soils. The volume of excess ice from segregated ice in the entire profiles ranged from 12.3% to 49.7%. Volume of wedge ice ranged from 10% to 20%. Organic carbon stores were 48-79 kg C/m(2) in the top 1 m, and 54-136 kg C/m(2) for the entire portion of the banks above water level (1.7-3.3 m high). Photogrammetric analysis of aerial photography from 1948 and 1978, and IKONOS imagery from 200 1, revealed a mean erosion rate of 0.5 m/yr for the 1948-1978 period and 0.5 m/yr for the 1978-2001 period along a 10 kin stretch of coastline. Annual organic carbon input from the eroding shorelines (above water portion) ranged from 3 7,800 to 68,000 kg C/km of shoreline for the three sites.