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Active-Layer Hydrology in Nonsorted Circle Ecosystems of the Arctic Tundra

^a Geophysical Institute, Univ. of Alaska Fairbanks, Fairbanks, AK 99775
^b Geological Engineering, Dep. of Mining and Geological Engineering, College of Engineering and Mines, Univ. of Alaska Fairbanks, Fairbanks, AK 99775
^c Dep. of Environmental Sciences, Univ. of Virginia, Charlottesville, VA

View larger version (122K): [in this window] [in a new window]   FIG. 1. Top: Individual nonsorted circles in the top part of the figure near Franklin Bluffs, AK. Bottom: An aerial view of the patterned ground on Banks Island, NT, Canada (courtesy Biocomplexity Project, UAF).

View larger version (38K): [in this window] [in a new window]   FIG. 2. Schematic of heat and mass transfer fluxes in a typical nonsorted circle ecosystem.

View larger version (16K): [in this window] [in a new window]   FIG. 3. Conceptual diagram of the hydrology and its relation to other processes in a typical nonsorted circle ecosystem.

View larger version (20K): [in this window] [in a new window]   FIG. 4. Measured soil volumetric liquid water content (v/v) versus temperature and fitted freezing characteristic curve using the combination of the van Genuchten (1980) equation and the general Clapeyron relation.

View larger version (13K): [in this window] [in a new window]   FIG. 5. Model verification with data obtained from Hansson et al. (2004). The y-axis represents the distance from the top of the column (m), and the x-axis represents the volumetric moisture content (v/v).

View larger version (13K): [in this window] [in a new window]   FIG. 6. Freezing characteristic data for the adjacent tundra. The curve used in the plot is the same as in Fig. 4, measured soil volumetric water content (v/v) versus temperature and fitted freezing characteristic curve, fitted to the nonsorted circle data. This figure expresses the difference in soil character for the nonsorted circle and adjacent tundra. The field data was obtained from the location of 1.0 x 1.0 m in our simulation grid.

View larger version (21K): [in this window] [in a new window]   FIG. 7. Air temperatures for the Franklin Bluffs site as input for the simulation model.

View larger version (54K): [in this window] [in a new window]   FIG. 8. Overview of the simulation area showing the ice content distribution at a depth of 5 cm as obtained from the numerical model WIT. The arrows represent the direction of the liquid water movement.

View larger version (27K): [in this window] [in a new window]   FIG. 9. Soil temperature comparison of measured data and simulated results (a) at 5 cm depth in a nonsorted circle, (b) at 5 cm depth in the adjacent tundra, (c) at 25 cm depth in a nonsorted circle, and (d) at 25 cm depth in the adjacent tundra.

View larger version (21K): [in this window] [in a new window]   FIG. 10. Scattergrams of the measured and the simulated soil temperature (a) for the nonsorted circle at 5 cm depth, (b) for the adjacent tundra at 5 cm depth, (c) for the nonsorted circle at 25 cm depth, and (d) for the adjacent tundra at 25 cm depth.

View larger version (17K): [in this window] [in a new window]   FIG. 11. (a) Effect of relative warming of the air temperature on the horizontal movement of liquid water during freezing. (b) Effect of increased vegetation, expressed in R-values (m2 s °C J–1), in the adjacent tundra on the horizontal movement of liquid water during freezing. (c) Effect of increased vegetation, expressed in R-values, on top of the nonsorted circle on the horizontal movement of liquid water during freezing. (d) Effect of even vegetation and snow increases, expressed in R-values, on the horizontal movement of liquid water during freezing.

View larger version (14K): [in this window] [in a new window]   FIG. 12. Water accumulation in the nonsorted circle during the freezing period, using the reference (1.0 x 10–7m s–1) and an increased horizontal conductivity of 1.0 x 10–5 m s–1.

View larger version (14K): [in this window] [in a new window]   FIG. 13. Flux rate of water into the nonsorted circle (cm d–1) for the increased horizontal conductivity case.