Researchers are using remotely sensed data and satellite imagery to map glacier loss in Western Canada. Scientists use satellite images, like those produced by the long-running Landsat Earth observation satellites, to compare the size and extent of glaciers over time. By examining images from different years, they can track changes in glacier size, shape, and movement.
How is glacial ice changing in Western Canada?
In 2022, researchers from the University of Northern British Columbia, published to results of a study that mapped out 14,329 glaciers (covering 30,063 square kilometers) in British Columbia and Alberta, Canada between 1984 and 2020 using Landsat imagery. This study improves on the last previous inventory of glaciers published in 2010, also done through remote sensing of Landsat imagery, looking at the state of glaciers in Western Canada for the years 1985, 2000, and 2005.
Glaciers are striking in size
What the 2022 study found was that rate at which these glaciers are getting smaller started to speed up in 2011. By 2022, 1,141 glaciers (representing 8%) had shrunk to a size where satellite imagery could no longer distinguish their presence (0.05 km2 detection limit).
Between 1984 and 2010, the average annual clean ice glacier (glaciers without any debris in them) loss was 49 square kilometers (19 square miles). During the period 2011−2020, this increased seven-fold to an average annual glacial loss of 340 square kilometers (130 square miles). This glacial loss was even more pronounced among small glaciers on Vancouver Island with a 32-fold increase in shrinkage.
Glaciers are breaking up into smaller pieces
Glaciers in western Canada are also undergoing fragmentation and retreating to higher elevations. Glacier fragmentation refers to the process by which a glacier breaks into smaller pieces or fragments. While there are other physical processes that can lead to glacial fragmentation, climate change fuels temperature variations and seasonal changes that can cause the glacier’s surface to expand and contract.
These fluctuations can lead to the development of cracks and the eventual fragmentation of the ice. The 2022 study also found that fragmentation increased from an average of 26 pieces per year to about 88 pieces per year.
Melting glaciers are leading to more freshwater lakes
Glacial melt is contributing to an increase in proglacial lake development. In this one example, comparing satellite images shows how Klinaklini Glacier, the largest glacier in western America that isn’t in Alaska, has changed over nearly four decades. The two satellite images below of Klinaklini Glacier were taken almost 40 years apart: September 26, 1984 (left), to September 22, 2023 (right).
The comparison of the satellite images shows multiple changes. The terminus of the glacier has significantly shrunken in length, with the end point now further north by over 5 kilometers (approximately 3 miles).
The melting glacier has also contributed to the enlargement of the glacial lake found at the terminus. In 1984, the glacial lake at the end of the glacier is barely visible in the satellite image. Melting ice has increased the area and volume of the lake so that by 2023, the lake measures 5 kilometers by 2 kilometers and supports floating icebergs.
References
Bevington, A. R., & Menounosm B. (2021). Accelerated change in the glaciated environments of western Canada revealed through trend analysis of optical satellite imagery (Polygons) (Version 2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5900363
Bevington, A. R., & Menounos, B. (2022). Accelerated change in the glaciated environments of western Canada revealed through trend analysis of optical satellite imagery. Remote Sensing of Environment, 270, 112862. https://doi.org/10.1016/j.rse.2021.112862
Bolch, T., Menounos, B., & Wheate, R. (2010). Landsat-based inventory of glaciers in western Canada, 1985–2005. Remote sensing of Environment, 114(1), 127-137. https://doi.org/10.1016/j.rse.2009.08.015
Voiland, A. (2024, January 29). Retreat at Klinaklini. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/152378/retreat-at-klinaklini
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Fonte : National Geographic
