HR: 17:00h
AN: H34D-05    [Abstracts]
TI: Bulk Thermal Properties of the Active Layer in the Foothills of the Brooks Range, Alaska
AU: * Overduin, P P
EM: fsppo@uaf.edu
AF: Institute For Northern Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775-5910 United States
AU: Kane, D L
EM: ffdlk@uaf.edu
AF: Institute For Northern Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775-5910 United States
AB: In the arctic in particular, where infrastructure consists of sparsely distributed resources, we are faced with the problem of relating environmental measurements at the point scale to catchment-scale processes. We ultimately seek to use landform classifications derived from photography, NDVI and SAR imagery to distribute thermal and hydrological regime data across catchments on Alaska's North Slope. The landforms differ in the type of ground surface patterning caused by ice segregation and the heave and settling of the ground during freezing and thawing, respectively. Soil surface characteristics and bulk thermal properties affect the propagation of surface temperature changes into the subsurface system, and therefore affect the intensity, duration and distribution of these processes. Numerous studies have used models of heat transfer in the subsurface system to estimate bulk soil thermal properties from temperature records. Estimations of soil thermal properties are confounded primarily by latent heat effects during phase change, and by our inability to measure soil constituent densities (ice content, for example). Common methods for measuring thermal properties involve thermally perturbing the system, usually via a steady or transient heat source, which inherently changes the system's state. Thermal diffusivity measurements are made inherently difficult because changes in surface conductance between the thermal probe and the soil are seasonally dependent. Our goal is to estimate and measure soil thermal properties simultaneously using measured vertical temperature profiles and transient heat pulses generated in the soil. We use thermistors and thermal conductivity instruments to discuss the use of both techniques and to compare estimates. Data collected from the shallow (less than 2 m) subsurface soils at a number of patterned ground sites over a three-year period provides a range of material and surface types typical for the northern foothills of the Brooks Range. Bulk soil heat capacity is calculated from mean phase densities over a sufficiently large volume. These are estimated on the basis of soil physical properties and continuous time domain reflectometry measurements of liquid water content. Thermal conductivity is not as sensitive as diffusivity to the variations in surface conductance mentioned above, and measured conductivities are compared to those derived from temperature records.
DE: 9315 Arctic region
DE: 5134 Thermal properties
DE: 3260 Inverse theory
DE: 1694 Instruments and techniques
DE: 1823 Frozen ground
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting