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

Abstract

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 (À0.3 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 1.8·105 Mg/year. Annual mineral input from eroding shorelines ranges from À1,863 (accreting) to 15,752 Mg/ km/year, average 2,743 Mg/km/year, and totals 3.3 ·106 Mg/year.

The Arctic Coastal Dynamics Database: A New Classification Scheme and Statistics on Arctic Permafrost Coastlines

“…There exists a skew towards higher concentrations for the Beaufort Sea coast: out of the 22 segments with organic carbon contents above 10%, two only are located in the Kara Sea, four in the Canadian Beaufort Sea, and 16 on the US Beaufort Sea coast. In recent estimates of the permafrost soil organic carbon pool (Tarnocai et al 2009) that were obtained using higher resolution data, the largest values of carbon content were retrieved from stretches of coast where high resolution sampling was performed, such as along the US Beaufort Sea (Jorgenson and Brown, 2005). The extreme values just mentioned are not representative for the arctic coast since 87% of the segments classified in this study feature organic carbon contents below 5% and 57% below 2%.…”

“…The geochemical characterization of the coastal segments builds on recently developed methods to characterize coastal stretches of the Arctic in Canada and in Alaska Jorgenson and Brown 2005;Ping et al 2008). At present, it includes organic carbon content of the entire coastal exposure and soil organic carbon content, and allows for expansion to include additional geochemical characteristics.…”

“…To assess the TOC contents for the rest of the profile, an empirical formula based on existing coastal exposures from North America and Siberia was used to model the TOC contents for the lower part of the coastal exposure. Data from Jorgenson and Brown (2005), Couture et al (2004), and Schirrmeister et al (2002) formed the basis for the computation of Eq. 1, which extrapolates SOC values to the rest of the backshore profile:…”

“…In the best-case scenario, rates of erosion compiled at high resolution (less than every 500 m) were used to populate the classification. These rates were extracted from the most recently published datasets, including data from Jorgenson and Brown (2005), Lantuit and Pollard (2008), Solomon (2005), Jones et al (2008Jones et al ( , 2009aJones et al ( , 2009b and Lantuit et al (2010b). They generally use remote sensing imagery from the second half of the twentieth century and sometimes cover over 50 years of coastline evolution.…”

Observing Muostakh disappear: permafrost thaw subsidence and erosion of a ground-ice-rich island in response to arctic summer warming and sea ice reduction

“…As a consequence of coastal erosion, clastic material enters the near-shore zone Jorgenson and Brown, 2005), where it is deposited, reworked and transported (Overduin et al, 2007;Winterfeld et al, 2011). Because ground ice occupies a large proportion of the land's volume above and below sea level, a much smaller amount of material is removed by wave action after thaw than along ice-free coastlines and high rates of coastline retreat are the result (Zhigarev, 1998).…”