New ground ice maps for Canada using a paleogeographic modelling approach

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.