HR: 0800h
AN: C31A-1115    [Abstracts]
TI: Characterizing subsurface active-layer permafrost beneath arctic streams using 3D ground-penetrating radar
AU: * Brosten, T
EM: troybrosten@mail.boisestate.edu
AF: Boise State University Dept of Geosc, 1910 University Dr., Boise, ID 83725
AU: Bradford, J
EM: johnb@cgiss.boisestate.edu
AF: Boise State University Dept of Geosc, 1910 University Dr., Boise, ID 83725
AU: McNamara, J
EM: jmcnamar@boisestate.edu
AF: Boise State University Dept of Geosc, 1910 University Dr., Boise, ID 83725
AU: Bowden, W
EM: breck.bowden@uvm.edu
AF: University of Vermont Rubenstein School of Env and Nat Res, 304 Aiken Center, Burlington, VT 05405
AU: Gooseff, M
EM: mgooseff@mines.edu
AF: Colorado School of Mines, Dept of Geol and Geo Engr, Golden, CO 80401
AU: Zarnetske, J
EM: zarnetske@cc.usu.edu
AF: Utah State University Dept of Aqu, Wat, and Earth Res, 5200 Old Main, Logan, UT 84322
AB: We are investigating the responses of arctic tundra stream geomorphology, hyporheic zone hydrology, and biogeochemical cycling to climate change. Field results from summer, 2003, demonstrate that ground-penetrating radar (GPR) is an effective tool for imaging the depth to sub-stream permafrost and results from 2004 illustrate GPR time-lapse imaging of the sub-stream thaw over the summer season. From the 2004 results we discovered problematic scattering effects from inhomogeneous materials beneath the graveled lined stream sites that, in some cases, hampered our ability to accurately locate the thaw-bulb boundary. Presented here are results from the 2005 field season where we collected 3D GPR data over selected sites with two specific objectives in mind: 1) to accurately locate and model the sub-stream thaw within a riffle-pool-riffle stream reach sequence and 2) to correctly handle 3D scattering effects within the gravel-lined stream sites. Sites chosen for the 3D surveys included stream reaches representing a low-energy water flow with organic material lining the streambeds (peat streams) and a high-energy water flow with cobble to gravel material lining the streambeds (alluvial streams). We acquired data using a pulsed radar system with high-power transmitter. Data was acquired with 200 MHz antenna placed at the bottom of a small rubber boat. Profile lines were acquired by pulling the boat across the bank and through the stream while triggering at a constant time interval. Profile lines were collected at ~30cm intervals and continued upstream until a riffle-pool-riffle sequence was covered within study sites covering up to 30x10m areas. Differential GPS data was collected simultaneously with the GPR data for -/+ 5cm spatial accuracy. In addition, we recorded temperature data using thermocouples placed at varying substream depths located within or near the study sites to help constrain and verify the GPR interpretation. Results indicate a thicker sub-stream thaw within the pools relative to the narrow connecting runs between pools in the peat-lined streams and thicker thaw within the riffle sections relative to the pools in the gravel-lined streams.
UR: http://www.mines.edu/~mgooseff/arctic_proj.html
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0702 Permafrost (0475)
DE: 0999 General or miscellaneous
DE: 1835 Hydrogeophysics
DE: 1860 Streamflow
SC: Cryosphere [C]
MN: Fall Meeting 2005