MacKenzie River Basin, Canada
Permafrost (permanently frozen ground) underlies most of the MacKenzie River—the longest in Canada. Rising temperatures linked to global warming are causing this permafrost to melt, contributing to disturbances in the landscape, such as the landslide near Old Fort Point in June 1997, pictured here. 1
The MacKenzie River region, which supports one of the world's last major wild rivers, has warmed by 3.1° F (1.7° C) over the past century.2,3 This warming has endangered the long-term stability of much of the permafrost—the frozen mix of rock, soil, and ice that underlies and surrounds the river basin3,3—raising the risk of erosion, flooding, landslides, and other significant changes to the landscape.2,3,4,5,6
Encompassing some 694,983 square miles (1.8 million square kilometers), the vast swath of the Mackenzie River Basin provides runoff to the Mackenzie River, gathering waters from British Columbia, Alberta, Saskatchewan, the Yukon, and the Northwest Territories.9,10,11 The basins drains 20 percent of Canada's land mass.9,10 Some 300,000 people live in or near the basin, the majority in its southern region.7,12 Because the basin includes a huge range of landscapes, it supports a wide diversity of climatic conditions, species, and ecosystems.2,7,9,10
About three-quarters of the basin sits within permafrost zones—continuous and discontinuous.7,8 Discontinuous permafrost tends to be thinner, so regions with it are particularly at risk of partial or complete thawing and permafrost breakup by the middle of this century.2,13 Most of the Yukon Territory, as well as the Northwest Territories and the MacKenzie Valley, are in zones with scattered permafrost, where it is thin.14 As the permafrost melts, the ground settles and bogs collapse as water is ejected through compaction.2,6 This causes uneven settlements and depressions in the land.2,6
Permafrost degradation in the Mackenzie Basin is a large factor in erosion, flooding, and landslides.2,3,4,5,6 Scientists have documented more than 2,000 slides in the Mackenzie Valley over the past century, as well as another 1,000 additional landslides in fine-grained sediments known as retrogressive thaw-flows in the Mackenzie Delta-Tuktoyaktuk Peninsula.2
Part of a Larger Pattern
To make matters worse, now-dark areas of open ocean—the result of retreating sea ice—are absorbing more energy from the sun. This leads to further warming, delaying the formation of sea ice in autumn.15 When this occurs, the warmer water transfers some heat to the atmosphere over adjacent shorelines—leading to further risk of permafrost degradation.15
In fact, one study showed that warming in the western Arctic owing to the rapid retreat of sea ice is 3.5 times greater than at other times and places not affected by dramatic retreat.16 This warming has been known to affect up to 932 square miles (1,500 square kilometers), with the effect peaking in autumn.16
This warming degrades permafrost—amplifying climate change through positive feedback. That is, the melting permafrost releases more heat-trapping gases formerly stored in soil, often for thousands of years, into the atmosphere.
What the Future Holds
If we continue on today's path of high rates of heat-trapping emissions, average annual temperatures in the MacKenzie Basin are projected to rise by 7.2-9° F (4-5° C) by 2050.2,3 If that occurs, permafrost in the basin's discontinuous zone is likely to become thinner and disappear altogether in some areas along the region's southern margin.2,3 Permafrost in many large areas in the basin's northern region is also projected to partially or completely disintegrate by the end of the century under this scenario.17
In Fort Simpson, in the Northwest Territories, scientists expect permafrost to gradually disappear, given an increase of 3.6° F (2° C) in average annual air temperature.2,3,18,19 In the Norman Wells region, such an increase would likely reduce permafrost coverage by about 50 percent.2,3,19
How much temperatures will rise in this century depends on whether we make significant reductions in our heat-trapping emissions. Acting quickly to make deep cuts will help safeguard the permafrost underlying the MacKenzie River Basin—and the ecosystems and species that it supports—against complete degradation.