Abstract

An instrument (ablatometer) was developed to measure rates of ablation of exposed ground ice. When the ablatometer is mounted on a melting ice face and linked to a portable micrologger, a continuous record of short-term ablation is obtained.The ablatometer was tested on the headwall of an active ground-ice slump located in southwest Banks Island, Northwest Territories. In general, it performed satisfactorily with little or no instrument-induced melt of the ice. Data for sunny days showed a strong diurnal rhythm of ground-ice ablation and considerable microscale spatial variability. Rates of ablation and their spatial variation were lower on cloudy days, illustrating the importance of solar insolation in inducing melt. Measurements beneath a debris cover following active-layer collapse suggest that ablation soon ceases and does not recommence until after the debris is removed by mud flow.As a result of the high degree of spatial variability in energy inputs and consequently in ablation rates, results from a single ablatometer may not be representative. If two or more instruments are mounted concurrently on exposed ice, an average value of the energy used in ablation can be determined. This value can then be compared with measurements of energy fluxes such as net radiation.

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