Nonlinear dynamics of ice-wedge networks and resulting sensitivity to severe cooling events

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Abstract
Patterns of subsurface wedges of ice that form along cooling-induced tension fractures, expressed at the ground surface by ridges or troughs spaced 10–30 m apart, are ubiquitous in polar lowlands1. Fossilized ice wedges, which are widespread at lower latitudes, have been used to infer the duration2,3,4 and mean temperature5,6 of cold periods within Proterozoic2 and Quaternary climates3,4,5,6,7,8,9,10,11,12,13, and recent climate trends have been inferred from fracture frequency in active ice wedges14. Here we present simulations from a numerical model for the evolution of ice-wedge networks over a range of climate scenarios, based on the interactions between thermal tensile stress, fracture and ice wedges. We find that short-lived periods of severe cooling permanently alter the spacing between ice wedges as well as their fracture frequency. This affects the rate at which the widths of ice wedges increase as well as the network's response to subsequent climate change. We conclude that wedge spacing and width in ice-wedge networks mainly reflect infrequent episodes of rapidly falling ground temperatures rather than mean conditions.