Characteristics and fate of isolated permafrost patches in coastal Labrador, Canada

Abstract

Abstract. Bodies of peatland permafrost were examined at five sites along a 300 km transect spanning the isolated patches permafrost zone in the coastal barrens of southeastern Labrador. Mean annual air temperatures ranged from +1°C in the south (latitude 51.4°N) to -1.1°C in the north (53.7°N) while mean ground temperatures at the top of permafrost varied 10 respectively from -0.7°C to -2.3°C with shallow active layers (40-60 cm) throughout. Small surface offsets due to wind scouring of snow from the crests of palsas and peat plateaux, and large thermal offsets due to thick peat are critical to permafrost, which is therefore absent in wetland, forested and forest-tundra areas inland, notwithstanding average air temperatures much lower than near the coast. Most permafrost peatland bodies are less than 5 m thick with a maximum of 10 m with steep geothermal gradients. One-dimensional thermal modelling for two sites showed that they are in equilibrium 15 with the current climate, but the permafrost mounds are generally relict and could not form today without the low snow depths that result from a heaved peat surface. Despite the warm permafrost, model predictions using downscaled global warming scenarios (RCP2.6, 4.5 and 8.5) indicate that perennially frozen ground will thaw from the base up and may persist at the southern site until the middle of the 21 st Century. At the northern site, permafrost is more resilient, persisting to the 2060s under RCP8.5, the 2090s under RCP4.5, or beyond the 21 st century under RCP2.6. Despite evidence of peatland 20 permafrost degradation in the study region, the local-scale modelling suggests that the southern boundary of permafrost may not move as quickly as had previously been thought.

Stability Conditions of Peat Plateaus and Palsas in Northern Norway

“…As for other types of permafrost, the relative stability of peat plateaus is also related to their slow response time to changes on the climate forcing (Throop et al, ). On the one hand, plateaus that are high enough to both (i) have low winter snow depths and (ii) drain toward the surrounding mires benefit from favorable conditions for permafrost, even in a particularly warm year as 2015–2016, with some peat plateaus being in equilibrium with the climate of the last decades (Way et al, ). On the other hand, plateaus with higher winter snow depth are likely to subside progressively due to excess ice melt (Westermann et al, ), and eventually lose their ability to drain water to the surrounding wet mire, so that permafrost is no longer stable.…”

“…Kurylyk et al () reported that, for forested peat plateaus, thaw‐induced surface evolution modifies the surface albedo, resulting in another positive feedback on permafrost degradation. In addition, modeling experiments showed that palsas and peat plateaus could persist or quickly vanished depending on the chosen climate scenario (Way et al, ), highlighting the uncertainty of future climate projections as a decisive factor when modeling the fate of these permafrost features.…”

“…Due to the spatial distribution and geometry of elevated peat plateaus and low‐lying wet mires (Figure ), permafrost‐underlain and permafrost‐free features have extended contact margins, so that nonnegligible lateral heat fluxes can be expected. In the case of 1‐D modeling these fluxes lead some author to overparameterize the geothermal heat fluxes to reproduce observed data (Way et al, ). For shallow water bodies surrounded by permafrost, Langer et al () showed that up to 70% of the heat induced by the water body was dissipated by lateral heat fluxes in this configuration.…”

“…A wet summer can produce drastic thawing of the palsa ice core (Seppälä, ), as well as a flooding (Seppälä, ). The insulation effect of the winter snow cover plays a prominent role in ground thermal regime (Jorgenson et al, ; Romanovsky & Osterkamp, ; Way et al, ). The relative top position of the peat plateaus compared to the surrounding mires enables the snow deposited on this morphology to be blown away and maintain a shallow snow cover and thus relatively weaker insulation to winter heat losses (Payette et al, ).…”

Permafrost Terrain Dynamics and Infrastructure Impacts Revealed by UAV Photogrammetry and Thermal Imaging

“…The use of UAVs has been growing within the scientific, commercial, and government spheres as a tool to rapidly collect inexpensive 3D topographic information [22,23]. A wide range of environmental applications [23,24] extend to permafrost environments [25], where UAV optical imagery has supported vegetation classifications and disturbance assessments [26,27], visualization of moraine and arctic mine tailing dynamics [28,29], delineation of alluvial fans [30], assessment of local permafrost distribution [31], and the topography of ice-wedge polygonal networks [32]. Despite these demonstrated applications, recent advances in UAV technology have only recently been utilized to quantify permafrost dynamics and the related impacts to infrastructure.…”