Cryostratigraphy and Soil Development in Ice Wedge Polygons on Arctic Coastal Plains, Alaska.

Title: Cryostratigraphy and soil development in ice wedge polygons on Arctic coastal plains, Alaska

C.L. Ping, J.D. Jastrow. R. Matamala, G.J. Michaelson, U. Mishra, Y. Shur

Ice wedge polygons are the predominant features of coastal plains, river deltas, broad depressions in hilly terrains in permafrost regions. Their development strongly affects soil formation and carbon storage on the coastal plains. The evolution of ice wedge polygons and soil formation on the Arctic Coastal Plain of Alaska were investigated by comparing the cryogenic features and soil morphology of flat-centered (FCP), low-centered (LCP) and high-centered (HCP) ice wedge polygons within and near the Barrow Environmental Observatory at the northern tip of Alaska. Soil parent material in this area consists of loess and glacialfluvial deposits over marine sediments. The different polygon types formed due to progressive expansion of ice wedges that increase in width from 1.5 m in FCPs to 3.5 m in HCPs. Soil horizons adjacent to the ice wedge were strongly deformed. Organic and mineral horizons were mixed due to cryoturbation in both the active layer and upper permafrost. The active layer thickness ranged from 42 to 49 cm in the polygon interiors. The intermediate layers were characterized by tonguing of organic matter and were ice-rich with ice content >70% (v/v) and thickness ranging from 40 to 60 cm attesting the fluctuation of climate over the past and ecosystem succession. The dominant cryostructures were lenticular and lenticular-reticulate. The carbon stocks increased from 60 kg C m^-2 in FCPs to 82 kg C m^-2 in HCPs measured to 2 m depth. The results of this study will be coupled with geospatial modeling and mapping to improve estimates of SOC stocks in Arctic coastal plains.