Accelerated Change in the Glaciated Environments of Western Canada
by Alexandre Bevington and Brian Menounos
Worldwide, glaciers are thinning at accelerating rates.[1] In western Canada, glaciers represent a vital natural freshwater resource that is currently threatened by climate change. The 15,000 or so glaciers of western Canada were last inventoried in 2005, rendering our maps out of date and obsolete. In this article, we summarize recently published research that updates maps of western Canadian glaciers using new automated mapping tools.[2]
Figure 1: Mineral exploration camp in northwestern British Columbia. Photo: A. Bevington
Understanding trends in glacier change is important as glaciers have widespread impacts on downstream environments. For example, glaciers impact sea level rise, they moderate stream temperatures, and they provide meltwater for hydroelectric power generation in late summer when runoff from snow is low and power demand is high.
Ongoing glacier retreat can also elevate the likelihood of landslides in some mountain catchments, as detailed in Brent Ward’s contribution to the ACC’s 2020 State of the Mountains Report.[3] Glacier retreat also exposes previously hidden geology that is of great interest to mineral exploration companies.
Figure 2: Glacier road over the Knipple Glacier in northwest British Columbia that leads to the Brucejack Mine. Photo: A. Bevington
Most glaciers in western Canada are nourished by winter snowfall and undergo melt during summer. When summed over a year, these inputs and losses determine whether a glacier is gaining or losing mass. The duration and depth of winter snow cover has decreased in the last several decades, and summers – particularly recently – have been getting longer and hotter, with clear links to human impacts on climate.
When mountain glaciers retreat, remaining ice occupies higher elevations in steep north-facing locations where local meteorological factors (shade, loading of snow by wind or avalanches) favour their presence. Deglaciation also exposes terrain susceptible to rapid change, including the growth of alpine plants and shrubs, formation of new lakes, and slope instability.
To update glacier maps, the traditional method of tracing over aerial or satellite images is out of date. These days, with tens of thousands of satellite images at our disposal, we are developing automated methods to monitor our changing glaciers. Remote sensing technologies for glacier monitoring were well summarized in the 2021 State of the Mountains Report for the curious reader.[4]
The Landsat Program, perhaps the most well-known earth observation platform, has been systematically acquiring images of our glaciers since the mid-1980s. These images provide a rich archive that allows us to detail how each glacier in western Canada changed over the last forty years. Landsat records visible and infrared wavelengths are used in automatic mapping methods. Nearly two decades ago, the United States Geological Survey made the entire archive of Landsat images freely available to all. These open datasets change the way scientists can document environmental change over time.
Figure 3: Knipple Glacier in northwest British Columbia. The glacier has a 12-kilometre road on it that allows for access to the Brucejack Mine. The dark horizontal streak through the glacier is the glacier road. Photo: A. Bevington
Google Earth Engine, a free online tool for satellite data processing, has become a household name in the scientific community.[5] The tool allows for the processing of enormous amounts of satellite data by anyone, including Landsat images. Earth Engine helped us map the glaciers of western Canada using over 12,000 Landsat images. To purchase this amount of Landsat data before the open data policy came into effect would have cost about sixty million dollars.
The last systematic inventory of glaciers in western Canada was completed in a 2010 study, led by Tobias Bolch, using Landsat images from 2005.[6] That study found that western Canada was losing about 166 square-kilometres of ice per year since 1985, and lost about 300 glaciers over that period.
Figure 4: Mt Waddington and the Tiedemann Glacier as seen from space. Notable landslides and new lakes are labelled, as is the Homathko River, which drains into Bute Inlet.
In our recently published research,[7] we remap the same glaciers as Bolch et al using a fully automated method from 1984 to 2020. Unlike the previous study, our results yield annual changes in each glacier. The technique also allows us to detail trends in glacier area change and a notable acceleration of area loss since about 2011. We have since then added the glacier outlines for 2021 to the database.[8]
Western Canada lost 340 square-kilometres of glacier ice per year since 2011, which is seven times faster than rates of area loss for the period 1984-2010. In some areas, the acceleration is much greater. The few glaciers that remain on Vancouver Island, for example, saw a 32-fold acceleration in glacier area loss in our study. We report errors of about five per cent on the automated glacier outlines.[9]
We also found that glaciers are fragmenting into smaller pieces over time, which provides more surface area for melt to occur and likely contributes to the accelerated loss. Proglacial lake area growth accelerated from ten square-kilometres per year to fifty square-kilometres per year in the region. These lakes are important to map and understand as they represent not only an important water storage factor in the water cycle, but they also represent a hazard for downstream communities.
Figure 5: Examples of our automated glacier inventory for the Knipple Glacier and Tiedemann Glacier. The landslide on Tiedemann is slowly being transported downhill as the glacier flows over time. Click to enlarge.
Any spaceborne glacier mapping program needs to identify a lower threshold for contiguous snow and ice-covered pixels to be mapped as a glacier. In our work, we set a lower limit of detectability to 0.05 km2 (or about four city blocks). We found that 1,141 glaciers fell below our detection limit and ultimately disappeared from our database, representing a loss of eight per cent.
Our study is accompanied by mixed emotions. On the one hand, we are in awe of these spectacular landscapes, and we are grateful for their presence on the landscape. While on the other hand, we are documenting their last moments. Most of our southern glaciers will be lost by the end of this century, which will fundamentally change the character of our mountains and how we travel through them. This deglaciation will also have widespread impacts on downstream communities, fish and wildlife, hydroelectric power, freshwater availability, and more. Policies are required to dramatically reduce our impact on climate to ensure that at least the larger glaciers can survive.
Alex Bevington is a PhD candidate at the University of Northern British Columbia and a Research Hydrologist with the Ministry of Forests of British Columbia. Alex has spent a lot of time on glaciers for both work and pleasure and is interested in improving our understanding of how the mountain cryosphere impacts downstream environments.
Brian Menounos is a Professor of Earth Science and the Canada Research Chair in Glacier Change at the University of Northern British Columbia. In 1987, he fell in love with mountains during an exchange year in Germany and has been studying them ever since. Brian is a Hakai Affiliate and Chief Scientist of the Airborne Coastal Observatory.
References
1 Hugonnet, R., McNabb, R., Berthier, E., Menounos, B., Nuth, C., Girod, L., Farinotti, D., Huss, M., Dussaillant, I., Brun, F., & Kääb, A. (2021). Accelerated global glacier mass loss in the early twenty-first century. Nature, 592 (7856), 726–731. https://doi.org/10.1038/s41586-021-03436-z
2 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
3 Ward, B., Williams-Jones, G., & Geertsema, M. (2020). Moving Mountains: Landslides and Volcanoes in a Warming Cryosphere. In L. Parrott, Z. Robinson, & D. Hik (Eds.), The State of the Mountains Report, 3, 4-11. The Alpine Club of Canada.
4 Menounos, B. (2021). Remote Sensing Strategies to Monitor British Columbia’s Glaciers. In L. Parrott, Z. Robinson, & D. Hik (Eds.), The State of the Mountains Report, 4, 38-40. The Alpine Club of Canada.
5 Gorelick, N., Hancher, M., Dixon, M., Ilyushchenko, S., Thau, D., & Moore, R. (2017). Google Earth Engine: Planetary-scale geospatial analysis for everyone. Remote Sensing of Environment, 202, 18–27. https://doi.org/10.1016/j.rse.2017.06.031
6 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
7 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
8 Glacier polygons available here: https://zenodo.org/record/5900363#.YpkbDqAieUk
9 For more details on the error estimates, please see Bevington & Menounos 2022.