Spatial distribution of near surface soil moisture and its relationship to microtopography in the Alaskan Arctic coastal plain

The Arctic coastal plain of Alaska is characterized by marked heterogeneity in microtopography and above ground vegetation productivity at a variety of scales. This heterogeneity may be expected to lead to large variations in near surface soil moisture and have a substantial impact on measured and modeled fluxes of carbon and water. In this study, we hypothesized that microtopography was the primary control over the spatial patterns of near surface soil moisture. Near surface soil moisture measurements were collected in the summers of 2000, 2001, 2002 and 2003 in the fetch of an eddy flux tower (0.5 km²). Results confirmed the expected relationship between intra- and inter-seasonal variations in near surface soil moisture and variations in precipitation. However, over two time periods, near surface soil moisture increased without corresponding measured precipitation inputs and this was attributed to fog and dew, which are difficult to measure, and/or the melting of the active layer. Spatial variations in near surface soil moisture are largely controlled by microtopography in areas characterized by high centered polygons and troughs. In areas without large variations in microtopography, macrotopography, in the form of drained thaw lakes, has a substantial control over near surface soil moisture.