Resolving the Influence of Ice Wedge Polygon Formation and Geomorphology on the Carbon and Nitrogen Stocks of Arctic Coastal Lowland Soils
Julie Jastrow1* (email@example.com), Roser Matamala1, Chien-Lu Ping2, Gary Michaelson2, Timothy Vugteveen1, Jeremy Lederhouse1, Joshua Minai1
1Argonne National Laboratory, Lemont, IL; 2University of Alaska–Fairbanks, AK
Ice-wedge polygons (IWPs) are ubiquitous, patterned ground features throughout Arctic coastal plains and river deltas. At the local scale, researchers are investigating the hypothesis that progressive ice-wedge expansion creates a natural developmental evolution from flat- to low- to high-centered IWPs that influences the degree of cryoturbation and soil formation, both of which impact the distribution of soil organic carbon (OC) and total nitrogen (TN) stocks. Further, variations in OC and TN stocks at the landscape to regional scale are affected by polygon geomorphology (trough vs. center), polygon size, the spatial distribution of polygon types (i.e., flat-, low-, and high-centered IWPs), and soil parent material. To investigate these hypotheses, researchers sampled 9 to 12 IWPs (three to four of each type) formed on three contrasting parent materials typical of the Arctic Coastal Plain of Alaska: (1) glaciomarine sediments dominating the thaw-lake terrain near Utqiaġvik, (2) fluvial deposits on terraces of the Sagavanirktok River, and (3) the extensive surficial material classified as coastal plain mixed deposits near Milne Point. For each of the 30 IWPs, researchers quantified the distribution of OC and TN stocks across entire two-dimensional polygon profiles to depths up to 3 meters by extensively sampling the cross-section stratigraphy of soil horizons and ice wedges of transects spanning from trough center to trough center. Initial results indicate that OC stocks in troughs are consistently and substantially lower than those of polygon centers due to the significant subsurface volumes occupied by ice wedges. In polygon centers, OC stocks differed among parent materials. However, within parent materials, a similar pattern of increasing OC stocks from flat- to low- to high-centered IWPs lends support to the hypotheses linking OC stocks to the natural evolutionary cycle of IWP development and soil formation. Ultimately, the data generated by these studies will be used to investigate whether accounting for the fine-scale geomorphology and distribution of different polygon types can provide more accurate geospatial estimates of soil OC and N stocks for coastal landscapes dominated by IWPs. The spatially and vertically resolved data is also expected to inform and constrain the parameterization of process models being developed to simulate regional responses to future climatic conditions.