Properties of Permafrost Soils on the Northern Seward Peninsula, Northwest Alaska

Soil processes in permafrost regions differ markedly from those of the mid and low latitudes. Permafrost soils are cold during the short growing season and frozen the rest of the year. This study was conducted to describe permafrost soils on the tundra coastal plain of northern Seward Peninsula with emphasis on soil characteristics below the active layer and cryogenic structures, both aspects which were widely neglected in previous studies of permafrost soils. We used cryogenic structures to determine active layer depths. In describing these soils, we applied the previous soil taxonomy and tested the utility of the new Gelisol order. Seven pedons were excavated and described in different topographic positions. Most pedons are influenced by frost action, as evidenced by irregular and broken horizons and weakly developed soils. Mineral horizons have predominantly reduced colors. Organic horizons 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 active layer depths independently of thaw season. For describing the properties of permafrost soils, the new Gelisol order is shown to he a significant improvement on the previous soil taxonomy.