New ground ice maps for Canada using a paleogeographic modelling approach

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 (massive ice and icy sediments, 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 massive ice and icy sediments 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 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 tree line advanced during warmer periods. Published observations of thaw slumps and 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 some 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.

Massive Ice Control on Permafrost Coast Erosion and Sensitivity

“…Massive ice collapse remains a critical but poorly quantified driver of ice rich permafrost coast erosion processes and as such is a threat to Arctic ecosystems, infrastructure, and biogeochemical cycles (O'Neill et al, 2019). Taking an ice‐rich permafrost type‐site as an example, with clear and variable exposures of massive ground ice, we set the long‐term erosion trends in context and use photogrammetric analyses of historic imagery to provide new quantitative data on decadal scale geomorphic processes.…”

Landscape matters: Predicting the biogeochemical effects of permafrost thaw on aquatic networks with a state factor approach

“…First, it requires robust spatial data to quantify state factor variation across the broad circumpolar domain (see also Vonk et al 9 for a discussion on this topic), to ensure that fine-scale patchiness does not result in biased extrapolation 120,121 . While some of these robust datasets exist (relief 122 ; soil organic carbon 123 ) or are available or under development for at least part of our domain (see the work on ice content by O'Neill et al 124 and PermafrostNet; www.permafrostnet.ca), information on the chemical composition of what we here term 'parent material' (i.e., including sulfide content 33,125 , which is virtually unknown, and carbonates 126 , which have been estimated, but with varying levels of constraint) is a clear gap, as is our understanding of permafrost extent and its vertical distribution in discontinuous terrains.…”

What and where are periglacial landscapes?

“…Excess ice in the upper meters of permafrost tends to be vulnerable to melting and landscape disturbance by thermokarst activity, producing a range of characteristic thermokarst landforms 9,67 . Excess ice is particularly common in silt‐rich sediments with an abundant moisture supply, 68–70 as silt is highly frost‐susceptible. Excess ice also occurs in frost‐susceptible bedrock such as marly limestone, arkose, 27 and shale 71 .…”