CO2 and CH4 Fluxes and Profile Concentrations
in a Boreal Peatland under Varying Snowpack Conditions
during the Spring Thaw, Manitoba, Canada
Jill L. Bubier1,2, Patrick M. Crill1, and Janet P. Hardy3
Carbon dioxide (CO2) and methane (CH4) fluxes and profile concentrations were measured through
the snowpack during the spring thaw from early April until June 1996, in a diverse peatland complex
in northern Canada. The research was conducted in the Northern Study Area of the Boreal Eco-
system Atmosphere Study (BOREAS) near Thompson, Manitoba. The peatland included the full
range of hydrologic, chemical, and plant community gradients typical of northern bogs and fens.
CO2 and CH4 fluxes were extremely variable both spatially and temporally during this period. CO2
fluxes ranging from 0 to 5 g CO2C m2 d1 were observed through the snowpack and were associ-
ated with presence or absence of ice lenses. CH4 fluxes as high as 200 mg CH4 m2 d1 were mea-
sured at the snow surface at flooded sites as the basal ice was melting. In drier hummock areas, CH4
fluxes remained low throughout the melt period.
Profile concentrations of CO2 and CH4 generally increased with depth from the snow surface to the
bottom of the snowpack, with the highest basal concentrations associated with the deeper snow pack.
Mean snowpack densities ranged from 300 to 400 kg m3 in well-developed faceted particles and
cup-shaped crystals. We estimated snow permeabilities using Shimizu's (1970) empirical relation-
ship and found that permeabilities were on the order of 400 1010 m2 and generally increased with
depth. Occasionally, higher gas concentrations near the surface were found beneath less permeable
ice lenses in the snow. CO2 concentrations as high as 900 ppm were measured in the snow profile at
the rich fen sites (pH 7.0) and up to 500 ppm at the bog sites (pH 3.9), indicating differences in
substrate quality and decomposition potential.
Differential rates of snowmelt in microtopographic hummocks and hollows resulted in some areas of
the peatland becoming a net sink of CO2 as the higher peat surfaces were exposed and plants began
to photosynthesize, while lower snow and ice-covered areas remained a source of CO2 to the atmo-
sphere. These highly variable carbon fluxes suggest that the quality of the snowpack, spatially vari-
able rates of snowmelt, and timing of surface peat thaw are important to the seasonal patterns of
carbon uptake and release in northern peatlands.
Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New
Hampshire, Durham, New Hampshire 03824, USA
2 Present address: Environmental Studies Program, Mount Holyoke College, 50 College Street, South Hadley,
Massachusetts 01075-6418, USA
3 U.S. Army Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, New Hampshire,