Summer thaw depths at eight monitoring sites in the Mackenzie Valley, determined from probing of grids and thaw tubes, are used to characterise the spatial and temporal variations in active-layer thickness and to investigate linkages to climatic variations. Intra-site variability in thaw depths is typically low where organic cover is thin and uniform. Higher variability occurs where moisture contents and organic cover are high and spatially variable.
Grid-mean thaw depths provide robust measures of the average site thaw depth, although they are less than annual maximum active-layer thicknesses determined by thaw tubes. Values from both measurements correlate reasonably well, permitting estimates of the variations in active-layer thickness from grid-mean thaw depths.
Active-layer response to thermal forcing in various settings is well represented by grid-mean thaw depths and the square-root of late-season thawing-degree days. However, the effect of interannual climate variability on active-layer thickness is better assessed by maximum tube thaw depths and the square-root of total thawing-degree days. Copyright © 2009 Her Majesty the Queen in right of Canada. Published by John Wiley & Sons, Ltd.