Hydraulic conductivity of active layer soils in the McMurdo Dry Valleys, Antarctica: Geological legacy controls modern hillslope connectivity

Spatial variability in the hydraulic and physical properties of active layer soils influences shallow groundwater flow through cold-desert hydrological systems. This study measures the saturated hydraulic conductivity and grain-size distribution of 90 soil samples from the McMurdo Dry Valleys (MDV), Antarctica primarily from Taylor Valley to determine what processes affect the spatial distribution of saturated hydraulic conductivity in a simple, mineral-soil-dominated natural hillslope laboratory. We find that the saturated hydraulic conductivity and the grain-size distribution of soils are organized longitudinally within Taylor Valley. Soils sampled down-valley near the coast have a higher percentage of fine-sized sediments (fine sand, silt, clay) and lower saturated hydraulic conductivities than soils collected up-valley near Taylor Glacier (1.3 x 10(-2) vs. 1.2 x 10(-1) cm/s). Soils collected mid-valley have intermediate amounts of fines and saturated hydraulic conductivity values consistent with a hydrogeologic gradient spanning the valley from high inland to low near the coast. These results suggest the organization of modem soil properties within Taylor Valley is a relict signature from past glaciations that have deposited soils of decreasing age toward the mouth of the valley, modified by fluvial activity acting along temporal and microclimate gradients. (C) 2017 Elsevier B.V. All rights reserved.