Hydro-stratigraphy of the active layer in riparian valley bottoms of an arctic watershed

Abstract:

The active layer describes the ground above permafrost that seasonally thaws, allowing for groundwater flow in an otherwise frozen subsurface. The transport of carbon through groundwater flow in the active layer influences its decomposition to greenhouse gases. Thus, the groundwater flow and storage regime of soil carbon has consequences on the global climate because of the large amount of carbon stored in arctic permafrost soils. Understanding the factors that affect groundwater within the active layer is therefore important, but observations regarding the hydrology of the active layer are lacking. Previous studies have identified three main strata within the active layer, acrotelm, catotelm, and mineral soil, which have different hydrologic properties. This research characterizes active layer soils of an arctic watershed through the measurement of saturated hydraulic conductivity, porosity, and bulk density, all of which affect the flow and storage of groundwater. Soil samples were collected throughout a portion of the Imnavait Creek Watershed on the North Slope of Alaska and classified by their stratum type. The thickness of each stratum was observed directly in the field and samples were collected from each stratum. Falling-head tests were done to estimate saturated hydraulic conductivity of the samples. Porosity and bulk density were measured gravimetrically through sequentially saturating and oven-drying the samples. Statistical analysis will be employed to compare how the measured values vary between soil types and across the spatial extent of the study site. The results of this study will help bound soil parameters needed for groundwater and Earth system models to predict the fate of carbon in permafrost.