HR: 1340h
AN: C13B-0280    [Abstracts]
TI: Active Layer Thermal Response to Stream Water Temperatures
AU: * Cozzetto, K
EM: kcozzetto@colorado.edu
AF: Institute for Arctic and Alpine Research, University of Colorado, 1560 30th St., Boulder, CO 80303 United States
AU: McKnight, D
EM: diane.mcknight@colorado.edu
AF: Institute for Arctic and Alpine Research, University of Colorado, 1560 30th St., Boulder, CO 80303 United States
AB: The hyporheic zone is comprised of sediments below and adjacent to a stream through which stream water flows in and out. In polar regions, the shape, dimensions, physical and chemical characteristics of this zone are affected by the seasonal freezing and thawing of the active layer. One factor that may influence the active layer temperature regime is stream water temperature, both its absolute value and cyclic variations in its value. Many of the glacial meltwater streams in Taylor Valley in the McMurdo Dry Valleys of Antarctica, exhibit daily temperature patterns with lows of 0 or $1\deg$C and highs of 10 or, on occasion, $15\deg$C. Because the viscosity of water decreases significantly with increasing temperature, these daily maxima may increase infiltration and the exchange of water and heat between the stream and the hyporheic zone. To investigate the influence of stream water temperature and flow paths on the active layer temperature regime and vice versa, two conservative tracer injection experiments were conducted. Both took place in the same 200-meter reach, which was instrumented with temperature and conductivity probes. Both also took place at the same time of day during which the stream reaches its temperature maximum. However, in one experiment snow from a nearby patch was added to the stream to suppress the temperature maximum by 3$\deg$C from 10 to $7\deg$C. The temperature data show that the snow addition slowed the rate of hyporheic zone warming and suppressed temperature increases in the hyporheic zone by 1-3$\deg$C when compared with the non-perturbation experiment. The electrical conductivity data indicate that during the snow addition experiment, the stream neither gained nor lost water while during the non-perturbation experiment, the stream lost water. These results suggest that the stream water cooling decreased infiltration and heat transfer into the hyporheic zone.
DE: 1655 Water cycles (1836)
DE: 1823 Frozen ground
DE: 1860 Runoff and streamflow
DE: 1878 Water/energy interactions
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting