The impact of experimental snow augmentation on soil thermal regimes and nutrient fluxes from High Arctic headwater catchments
Fluxes , Snow , Hydrology , Thermal regime , Biogeochemistry
Two catchments amended with snow fences were paired with unaltered controls to investigate the influences of increased snow accumulation on the hydrology, soil thermal regime, and nutrient fluxes from High Arctic headwater catchments, representative of polar desert and mid-moisture vegetative classes at the Cape Bounty Arctic Watershed Observatory (CBAWO). The impact of augmented snow accumulation on the winter soil thermal regime was highly variable during the period studied. Soil temperatures were 8-9°C warmer beneath a drift 54 cm deep compared to ambient snow (10 cm) in the winter of 2006-2007, whereas soil temperatures were not significantly warmer beneath drifts (88 and 50 cm) compared to ambient snow (18 and 35 cm) in the winter of 2007-2008. Departures between air and ground surface temperatures suggest that snow accumulation was insufficient to insulate soils before February 2007-2008 due to late snow accumulation, compared to earlier snow accumulation in September in the winter of 2006-2007. The augmented snow accumulation did not significantly impact the timing of soil thaw in spring or active layer thickness at this site. Greater snow accumulation in the amended catchments altered runoff characteristics, including an extended duration of runoff by 30-80%, a delay in peak flow of ~5 days, and increased runoff ratios. Augmented snow accumulation, resulted in greater fluxes of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved inorganic carbon (DIC), nitrate (NO3-), ammonium (NH4+) and total inorganic solutes (TIS) in amended catchments relative to control sites. The seasonality of solute fluxes were also affected, with a greater proportion of inorganic solute fluxes occurring in the later portion of the runoff season compared to the controls. Snow accumulation was strong factor in determining total specific solute fluxes, with the magnitude of DOC and DON fluxes also strongly dependent on vegetative class. An active layer detachment that occurred in one of the amended catchments may have contributed to changes in nutrient fluxes, but the precise influence of the active layer detachment could not be differentiated from the combined impact of the disturbance and increased snow accumulation.