HR: 0800h
AN: H11C-0319    [Abstracts]
TI: Heat Transport in Peatlands: a bog and fen Comparison
AU: * McKenzie, J M
EM: jmmckenz@syr.edu
AF: Dept. of Earth Sciences, Syracuse University, Syracuse, NY 13244 United States
AU: Siegel, D I
EM: disiegel@syr.edu
AF: Dept. of Earth Sciences, Syracuse University, Syracuse, NY 13244 United States
AU: Glaser, P H
EM: glase001@tc.umn.edu
AF: Dept. of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455 United States
AB: Peatlands are a major terrestrial source and sink of atmospheric methane, which is transported to the land surface by diffusion, advection and ebullition. Methane production is mostly related to seasonal variations in soil temperature and fluxes of labile carbon. We report the results of a study to explore the extent to which temperature variations in the anaerobic peat in a bog-fen complex (Red Lake Peatland, MN) is controlled by conduction or fluid convection. From November 1997 to August 1998, we measured hourly temperatures at 7 depths in a fen peat profile and from January 1998 to July 2000, at 12 depths at an adjacent raised bog. At both locations, we also measured hydraulic head at sub-daily time intervals. We modeled heat transport in the profiles with SUTRA, a finite-element numerical model code that couples heat transport with advection, and specified variable pressures and temperatures at the top and bottom of the models as boundary conditions. Measured daily average temperatures were used as the boundary conditions under steady-state flow system and transient heat transport conditions. Both models calibrated well to the field temperature data; the root mean squared error was 0.6 and 0.9 $^{o}$C for the bog and fen models respectively. Calibrated bog and fen peat thermal conductivity was 0.5 and 1.0 J s$^{-1}$ m$^{-1}$ C$^{-1}$ respectively. Modeled flux of groundwater into the fen peat base was $\sim$1 L day$^{-1}$ m$^{-2}$. The largest deviations between measured and modeled results at the bog was during spring months in the near surface peat. There, modeled temperatures increased rapidly from near 0 to 15 degrees, whereas measured temperatures slowly increased. The divergence between modeled and measured temperature is probably caused by ice melting in the upper peat, and slowing the transfer of heat further into the profile. In contrast, there is minimal discrepancy between modeling and measured temperature values at the fen, although the model deviates from measured values at mid-April, possibly because of changes in the amount of groundwater flux to the peat bottom.
DE: 1823 Frozen ground
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1878 Water/energy interactions
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting