Properties of permafrost soils on the northern Seward Peninsula, NorthwestAlaska

Soil processes in permafrost regions differ markedly from those of the mid and low latitudes. Permafrost soils are cold during the short growing seaso n and frozen the rest of the year, This study was conducted to describe per mafrost soils on the tundra coastal plain of northern Seward Peninsula with emphasis on soil characteristics below the active layer and cryogenic stru ctures, both aspects which were widely neglected in previous studies of per mafrost soils. We used cryogenic structures to determine active layer depth s. In describing these soils, we applied the previous soil taxonomy and tes ted the utility of the new Gelisol order. Seven pedons were excavated and d escribed in different topographic positions. Most pedons are influenced by frost action, as evidenced by irregular and broken horizons and weakly deve loped soils. Mineral horizons have predominantly reduced colors. Organic ho rizons of 7- to 50-cm thickness occur in the study area. All soils contain segregated ice and ice wedges. Segregated ice includes ice lenses, ice nets , and ataxitic ice concentrations at the base of the active layer. With the identification of these cryogenic features, it was possible to determine a ctive layer depths independently of thaw season. For describing the propert ies of permafrost soils, the new Gelisol order is shown to be a significant improvement on the previous soil taxonomy.