ABSTRACT: Predicting active layer depht using a one dimensional heat transfer model in Salluit, Nunavik.

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Abstract

Permafrost in the village and in the surrounding area is ice-rich and occurs both in saline marine clays and in till. Observed impacts of recent climate warming include thaw settlement of buildings and roads as well as of some sections of the airport runway. The objective of this project is to predict the potential changes in active layer depth (ALD) over the target period 2010-2025 in the two major soil types currently used for residential infrastructures. Tone, a widely used, one-dimensional heat transfer numerical model was used to simulate the ALD. This model has been tested and used by many workers and is appreciated for its reliability and relative ease of use. Air temperatures and snow cover scenarios for the targeted simulation period were derived from CRCM data outputs driven by the CGCM3 with the A2 scenario for greenhouse gas increases. This data set was generated and supplied by Ouranos. Latent heat of fusion and thermal conductivity, two parameters dependant on variable water content, were also considered in the model. Measured salinity values in the interstitial water of permafrost in marine clays were applied as “modi? ed heat capacity values” (speci?c heat) in model iterations. The model was validated for a one year period (2003-2004) against temperature measurements from two boreholes instrumented with thermistor cables and dataloggers. Simulations were launched with different air temperatures and snow cover scenarios for the target period. Modeled ALD variations for the simulated period closely follow projected seasonal temperatures. Moreover, results reveal that ALD can vary widely over periods of only a few years. Also, since the salinity of marine clays affects the melting point of ice in the model, it as a major in?uence on thawing depth. For both marine clays and till deposits an increase in ALD could also have signi?cant effects on thawing rates because of ground settlement and modi?cations to water migration through the active layer. Hence in the most pessimistic cases, the model predicts that, relative to observed depths in 2004, ALD in saline marine clay could increase by a maximum of about 58 to 70 cm. In tills, ALD could increase to a maximum of about 100 cm.

Bibliography of Canadian Geomorphology