Abstract
Abstract. Ground ice melt caused by climate-induced permafrost degradation may trigger significant ecological change, damage infrastructure, and alter biogeochemical cycles. The fundamental ground ice mapping for Canada is now >20 years old and does not include significant new insights gained from recent field- and remote-sensing-based studies. New modelling incorporating paleogeography is presented in this paper to depict the distribution of three ground ice types (relict ice, segregated ice, and wedge ice) in northern Canada. The modelling uses an expert-system approach in a geographic information system (GIS), founded in conceptual principles gained from empirically based research, to predict ground ice abundance in near-surface permafrost. Datasets of surficial geology, deglaciation, paleovegetation, glacial lake and marine limits, and modern permafrost distribution allow representations in the models of paleoclimatic shifts, tree line migration, marine and glacial lake inundation, and terrestrial emergence, and their effect on ground ice abundance. The model outputs are generally consistent with field observations, indicating abundant relict ice in the western Arctic, where it has remained preserved since deglaciation in thick glacigenic sediments in continuous permafrost. Segregated ice is widely distributed in fine-grained deposits, occurring in the highest abundance in glacial lake and marine sediments. The modelled abundance of wedge ice largely reflects the exposure time of terrain to low air temperatures in tundra environments following deglaciation or marine/glacial lake inundation and is thus highest in the western Arctic. Holocene environmental changes result in reduced ice abundance where the tree line advanced during warmer periods. Published observations of thaw slumps and massive ice exposures, segregated ice and associated landforms, and ice wedges allow a favourable preliminary assessment of the models, and the results are generally comparable with the previous ground ice mapping for Canada. However, the model outputs are more spatially explicit and better reflect observed ground ice conditions in many regions. Synthetic modelling products that incorporated the previous ground ice information may therefore include inaccuracies. The presented modelling approach is a significant advance in permafrost mapping, but additional field observations and volumetric ice estimates from more areas in Canada are required to improve calibration and validation of small-scale ground ice modelling. The ground ice maps from this paper are available in the supplement in GeoTIFF format.
Highlights
Rather than extrapolating field observations from northwestern Canada to similar physiographic units across the Arctic (Heginbottom et al, 1995), we model ground ice abundance using an expert-system approach built on principles developed from empirical studies relating environmental conditions to ground ice formation and preservation
Modelled relict ice abundance mainly reflects the distribution of thick glacigenic sediments in regions that have remained in herb and shrub tundra environments since deglaciation and occur in the modern continuous permafrost zone (Fig. 2)
New modelling using a paleogeographic approach depicts the abundance of relict ice, segregated ice, and wedge ice in permafrost in Canada
Summary
Ground ice is a key geomorphic agent in permafrost environments, and its formation is associated with characteristic landforms including ice-wedge polygons (Fraser et al, 2018; Lachenbruch, 1962); peat plateaus, palsas, and lithalsas (Laberge and Payette, 1995; Wolfe et al, 2014; Zoltai, 1972); earth hummocks (Kokelj et al, 2007b); involuted hills (Mackay and Dallimore, 1992); and pingos (Mackay, 1973). O’Neill et al.: New ground ice maps for Canada initiates geomorphic processes including thaw subsidence, slumping, active-layer detachment sliding, thaw lake development, and thermal erosion gullying (Kokelj and Jorgenson, 2013). These processes partly drive the evolution of permafrost terrain to produce the current landscape and ecological configuration and may damage infrastructure (Jorgenson et al, 2006; Liljedahl et al, 2016; Nelson et al, 2001; Raynolds et al, 2014). The depicted ground ice contents are generally lower in regions with thin overburden (Brown et al, 1997), but the nature and origin of surficial deposits were not explicitly considered
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