Impacts of variations in snow cover on permafrost stability, including simulated snow management, Dempster Highway, Peel Plateau, Northwest Territories

H Brendan O’Neill,Chris R Burn

doi:10.1139/as-2016-0036

Abstract

Permafrost conditions were examined near the Dempster Highway embankment on Peel Plateau, Northwest Territories. Ground temperatures were recorded in 2013–2015 at five sites at the embankment toe and at two sites in undisturbed (control) tundra. Annual mean ground temperatures at approximately 5 m depth ranged from −2.2 to 0.0 °C at the embankment toe and were −1.8 and −2.6 °C at control sites. Permafrost is degrading beside the road at four of five sites. Thaw depths are greater at the embankment toe, where deep snow accumulates, than in undisturbed tundra. A numerical model was used to examine the influence of varying snow cover properties on the ground thermal regime. Simulations indicated that delaying the onset of deep (1 m) snow accumulation and (or) prolonging the duration of the same total accumulation accelerates removal of latent heat from the active layer, increases sensible ground cooling, and results in reduced thaw depth. Furthermore, reducing snow depth and increasing snow density may rapidly raise the permafrost table, lower ground temperatures at the embankment toe, and cool permafrost at depth over several years. In consequence, mechanical snow removal and (or) compaction should be investigated as an active management strategy for mitigating permafrost degradation in ice-rich settings.

Highlights

The western Arctic of North America has been one of the most rapidly warming environments on Earth over the past few decades (Burn and Kokelj 2009)
Curvatures of the annual mean ground temperature envelopes indicate that permafrost is presently degrading at all road sites except DST2 (Figure 4)
The measurement and modeling of permafrost conditions near the Dempster Highway road embankment on Peel Plateau has led to the following conclusions: (1) Permafrost is degrading at four of five study sites near the toe of the embankment

Summary

Introduction

The western Arctic of North America has been one of the most rapidly warming environments on Earth over the past few decades (Burn and Kokelj 2009). Infrastructure embankments may disrupt natural drainage networks, causing water to accumulate and increasing the amount of latent heat that must dissipate during freeze back of the active layer before further ground cooling may occur (Andersland and Ladanyi 2004; de Grandpré et al 2012) These problems may be pronounced along northern highways, because the road embankment acts as a windbreak and promotes snow accumulation (Auerbach et al 1997), while the elevated permafrost table in the embankment may inhibit drainage, causing ponding at the embankment toe and increasing the potential for thaw subsidence there. The technique has potential because it requires no construction of stationary infrastructure as with many passive https://mc06.manuscriptcentral.com/asopen-pubs

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