Erosion dynamics following localized permafrost slope disturbances

Abstract

Slope disturbances are key sources of sediment, and the impact and recovery of disturbance on downslope erosion is poorly understood. We measured the erosional response of varying extents of slope disturbance in small permafrost catchments for 5 years following disturbance by active layer detachments. Initial erosion rates increased with the size of disturbance, but subsequent fluxes depended on specific morphological evolution of disturbances. Varying degrees of (i) channel density within the disturbances, (ii) downstream channel connectivity, and (iii) geomorphic evolution of disturbances lead to significant differences in catchment response to disturbance. Our results indicate that new equilibrium states of sediment erosion are achieved within the most disturbed and channelized catchments and contribute to greater heterogeneity of erosion on the landscape.

Seasonal hydrology and permafrost disturbance impacts on dissolved organic matter composition in High Arctic headwater catchments

“…Most of precipitation falls as snow during 8-9 months (Lamoureux et al 2014). Mean monthly July and January air temperatures are 4.0 and −33.1°C, respectively.…”

“…Investigations in the ALD 05 (ALD) and Caribou (CR) catchments began in 2008 and 2009, respectively. All catchments are similar in term of size, hydrology, geology, slope, soil, and vegetation cover (Lamoureux et al 2014). Goose has never experienced any physical disturbance and represents an undisturbed control for comparison.…”

“…Streams from undisturbed and recently disturbed headwater catchments were sampled to assess the impacts of ALDs on DOM composition. Although previous research from the CBAWO reports on the impact permafrost disturbance had on sediment fluxes (Lamoureux et al 2014), total dissolved solute fluxes (Lafreniere and Lamoureux 2013), and sources of dissolved nitrogen (Louiseize et al 2014), here we characterize for the first time the optical properties of DOM in four headwater catchments during an entire hydrologic season. This study makes an important contribution to our understanding of the potential for permafrost disturbance to increase the export of fresh and low molecular weight compounds from small High Arctic streams.…”

“…Localized landscape disturbances will modify the water flow pathways, while thickening of the active layer will alter subsurface flow paths (Frey and McClelland 2009;Lamoureux et al 2014).…”

Multi-year impacts of permafrost disturbance and thermal perturbation on High Arctic stream chemistry

“…The loss of permafrost and the deep thaw of active layer soils, along with increased summer precipitation, has triggered widespread thermokarst development (Bowden et al 2008;Gooseff et al 2009) and the formation of permafrost disturbances such as active layer detachment (ALD) slides and retrogressive thaw slumps Lewkowicz 1998, 1999;Fortier et al 2007;Lamoureux and Lafrenière 2009). These physical landscape disturbances displace vegetation and thawed soils downslope along ice-rich permafrost at the base of the active layer, exposing mineral soils in the scar zone, creating incised channels and transverse ridges at the surface, and amassing soils at the base of the slope (Lewkowicz and Harris 2005a;Lewkowicz 2007;Lamoureux et al 2014). Observations indicate that when the organic soil mat is displaced during an ALD, this layer can be folded and deformed while being moved downslope and become partially incorporated into exposed, inorganic mineral soil (Lipovsky et al 2006).…”