Identifying Spatial Patterns in Greenhouse Gas Fluxes through an Arctic Tundra Snowpack

Cold season greenhouse gas (GHG) emissions have been found to make non-negligible contributions to annual carbon budgets in Arctic-boreal regions. The Arctic is warming three to four times faster than the global average, changing the magnitude and phase (snow/rain) of precipitation, and the thermal regimes of snow-covered ground.

Future projections of winter GHG emissions require accurate simulations of the insulative properties of Arctic snowpacks and improved parameterisations of soil heterotrophic respiration as a function of soil thermal and moisture regimes. To improve these parameterisations in terrestrial biospheric models, we measured carbon dioxide and methane fluxes through the late-winter snowpack of a mineral upland tundra site in the western Canadian Arctic. Fluxes were calculated using highly resolved GHG snow concentration gradients and vertical snowpack microstructure (n = 119), over a range of microtopographic and vegetation types.

GHG emission rates were statistically independent of vertical snow microstructures, suggesting high snow gas porosity relative to soil emission. Carbon dioxide emissions were measured across a wide range of tundra landscape types, and were closely linked to soil temperatures, vegetation type and snow depths. Importantly, persistent net methane sinks were also found across landcover types in warmer soils (-6 to -2 ^oC), showing active methane oxidation during winter periods. Methane emissions were not always consistent within surface cover types, suggesting available liquid soil moisture and carbon availability as important controls.