Satellite image analysis of recent changes in glacier extent in the northern Mackenzie Mountain range, Northwest Territories and Yukon, Canada

Abstract

The state of a small assemblage of glaciers not previously reported on in the northern Mackenzie Mountains across Yukon and Northwest Territories were investigated over the past three decades. Landsat TM and OLI satellite imagery was used from 1987 to 2013/2017, with images in the years of 1987, 1994, 1999, 2004, 2013, and 2017, to determine whether there was a trend in glacier change. A semi-automated thresholded Red/SWIR band ratio method was used to delineate the glacier boundaries. Since only ~70% of the total glaciers were visible in the 2017 image due to partial cloud cover, glacier area change was analysed from 1987-2013, and from 1987-2017 in some parts of the study area. It was hypothesised that glaciers within the study area would be affected by changes in climate by decreasing in spatial extent in accordance with other glacier studies throughout the world. Glacier area decreased from 69.9 ± 1.75 km² in 1987 to 41.0 ± 1.03 km² in 2013, a loss of 41.5 ± 2.08% or 29.0 ± 1.45 km², with an area reduction rate of 1.59% ⋅ a^-1. For the 1987-2017 period, glacier area decreased from 52.8 ± 1.32 km² in 1987 to 24.9 ± 0.62 km² in 2017, a loss of 52.9 ± 2.65% or 27.9 ± 1.40 km², with an area reduction rate of 1.76% ⋅ a^-1. The smaller size glaciers (A < 0.1 km²) were found to have the largest change in relative area. As glaciers reduced in size, there was an increase in area loss over the time period. Reduction rates are high compared to glacier area loss reported for other mountain ranges in the late twentieth century. This may be due to their small size and high perimeter-area ratio. By extrapolating the total glacier area values, it is predicted that the study area will be glacier-free by 2045 for the 1987-2013 sample and by 2044 for the 1987-2017 sample.