HR: 0800h
AN: H21B-1010    [Abstracts]
TI: Seasonal Evolution of Hyporheic Zones in Arctic Tundra Streams, North Slope, Alaska
AU: * Zarnetske, J P
EM: zarnetske@cc.usu.edu
AF: Dept. of Aquatic, Watershed, and Earth Resources, Utah State University, 5200 Old Main Hill, Logan, UT 84322
AU: Gooseff, M N
EM: michael.gooseff@usu.edu
AF: Dept. of Geology and Geologic Engineering, Colorado School of Mines, 1516 Illinois Street, Golden, CO 80401
AU: Bowden, W B
EM: breck.bowden@uvm.edu
AF: School of Natural Resources, University of Vermont, 81 Carrigan Drive, Burlington, VT 05405
AU: Bradford, J H
EM: johnb@cgiss.boisestate.edu
AF: Center for Geophysical Investigations in the Shallow Subsurface, Boise State University, 1910 University Drive, Boise, ID 83725
AU: McNamara, J P
EM: jmcnamar@boisestate.edu
AF: Dept. of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725
AU: Hill, K R
EM: kenhill@cc.usu.edu
AF: Dept. of Aquatic, Watershed, and Earth Resources, Utah State University, 5200 Old Main Hill, Logan, UT 84322
AB: The depth of the active layer in permafrost dominated areas like Arctic Alaska is greater under streams than in adjacent terrestrial areas. We proposed that as the sub-stream active layer increases throughout the summer the extent of the hyporheic zone within these streams also increases. We did conservative stream tracer experiments to examine the hydrologic characteristics of four permafrost-dominated, tundra streams in Arctic Alaska, during the summer of 2004. The streams differed in morphology (alluvial to peat) and size (2nd to 3rd order). We added Rhodamine WT in pulses to these study reaches throughout the warming season to document the dynamics of the downward thaw and its influence on hyporheic exchange. Our results indicate that the hyporheic zone increases in response to seasonal warming, as expected. Tracer breakthrough curves, normalized to advection time ({\it t$_{adv}$}) collected throughout the early portion of the warming period (May - June) suggest increased transient storage associated with the hyporheic zone, which is in agreement with advancing thaw conditions occurring below the channel. However, by late in the warming period (August), when thaw advancement rate was at a minimum, the conditions at each of these sites shifted, indicating less hyporheic influence on transient storage. We hypothesize that changes in surface and subsurface dynamics, modified by geomorphic form, can be used to explain the confounding observations found late in the thaw season and plan to explore this possibility through additional groundwater modeling.
DE: 1800 HYDROLOGY
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting