Radiation budget, ground thermal regime and hydrological balance of a low arctic tundra basin, Coppermine River, Northwest Territories

The effects of slope, aspect and vegetation cover on the radiation balance and active layer thermal regime of arctic tundra were investigated during the summer of 1999 and the spring of 2000. The study site is located at Daring Lake, N.W.T (64°52\u27N, 111°35\u27W) in the Slave Geological Province of the Coppermine River Basin. A sub-basin 14 ha in area and with approximately 30 meters of relief was intensely monitored for hydrological radiation and energy balance components. Initiation of active layer development and subsequent thawing was earlier and more pronounced on predominantly west facing slopes due to increased receipt of incoming solar radiation. Late summer active layer depths were the greatest on west-facing slopes as compared to north-and east-facing slopes (\u3e170 cm. 84.0 ±21.7 cm. 49.2 ±0.8 cm respectively). Incoming shortwave radiation values were extrapolated from the met site to various basin sites taking slope and aspect into account. Spatial and diurnal variations in albedo were minimal within the Kakawi Lake Basin. As well, surface temperature measurements varied little from site to site causing the long wave radiation balance to remain relatively constant. Incoming shortwave radiation was determined to control diurnal fluctuations in the net radiation balance on a daily and seasonal basis but represented less than one half (41%) of the radiative supply to the surface. Ground heat flux increased downslope on west- and north-facing hillslopes corresponding with an increase in active layer development during the summer season. Conversely, basal flux out of the active layer to the underlying permafrost decreased downslope. The sensible heat flux varied least with depth between the study sites but accounted for a significant proportion of the ground flux at sites with deeper active layers. Active layer depths at peat dominated, east-facing hillslope sites were only 59% of the average depth on west- and north-facing slopes primarily due to the high water content and reduced thermal conductivity of peat soils. Latent heat is largest at the beginning of the thaw season when there is rapid active layer development but is later reduced as ground thaw slackens. Kakawi Lake Basin precipitation input, outflow and lake water level were recorded daily throughout the 36 day study period while evaporation was estimated based on a study conducted in a nearby basin. Lateral inflow from catchment hillslopes was determined to the dominant component of the Kakawi Lake Basin hydrological balance for the 1999 study period. Peat dominated areas were disconnected throughout much of the study period but drained as a single source during rainfall events