The main stem of the Mackenzie River flows wild and uninterrupted by dams across Canada, as it has since the recession of the Laurentide Ice Sheet. Draining the eastern end of the Great Slave Lake, the river meanders for more than 1,600 northwesterly kilometers through gnarled stands of black spruce before fanning out across the treeless arctic tundra, depositing sediment in a delta stretching from the Yukon territories in the west to the hamlet of Tuktoyaktuk on its east branch. At its terminus, the Mackenzie finally discharges more than 325 cubic kilometers of fresh water into the Arctic Ocean each year, accounting for roughly 11 percent of the world's total river flow into the Arctic Ocean.
At the mouth of the Mackenzie, some 950 residents of the hamlet of Tuk live in homes, elevated slightly above the permafrost to prevent their houses from heating the permanently frozen ground. Pastel buildings and telephone poles rise above the white expanse of sea ice and tundra. Higher still are the pingoes—ice hills, superficially covered with vegetation, pushed up for centuries by a lens of remnant ice left by a drained lake. To the south of Tuk, Ibyuk Pingo towers impressively on the horizon like a volcanic island over the halcyon sea of ice and permafrost, meandering creeks and countless lakes.
In the winter, folks in Tuk watch the sun set for the last time on November 28th and celebrate its return on January 13th. The average February temperature is –26°C. Lows regularly dip to the point of convergence between Celsius and Fahrenheit: -40°. Ski-Doos brap across the crust of snow on Tuk’s lakes and lands and ocean. The frigid Arctic breeze blows snow drifts flush with the coastline, creating a barely perceptible threshold between landfast ice and frozen soil, were it not for the orange life rings and overturned rowboats marking definitively, the edge of North America and the Arctic Ocean.
This fixed line between sea and shore is merely seasonal, however. On May 18th, the sun will rise above the horizon and circle the coastal hamlet continuously until finally setting for a brief hour on July 25th. Under the midnight sun, the sea ice will melt, and the Arctic Ocean will beat relentlessly against the permafrost bluffs along the Western Arctic coast, and the increasingly warm summer air will thaw ancient ice, causing cliffs to erode and massive swaths of land to slump into mudflows. For residents of Tuktoyaktuk, longer, warmer summers have been making life more difficult for the last 40 years.
As Richard Gruben, Vice-President of the Tuktoyaktuk Hunter and Trappers Committee puts it, Tuk is “a traditional community. Just about everybody here travels around and hunts off the land and fishes our waters.” Because of this, Gruben and other Tuk residents are especially aware of climate change and its impacts: Summer storms are more frequent and intense, animal migration habits have changed and the community must prepare earlier in the year to harvest beluga whale, which arrive three weeks earlier than they used to, says Gruben. But of all the many tangible climate change impacts, none may be bigger than coastal erosion and permafrost slump.
Though coastal erosion is a challenge for nearly every marine coastal community facing pressures of storms and sea level rise, it is particularly emergent for places like Tuk, built on permafrost. Wave action eats away at coastal bluffs, exposing ancient ice to melt in continuous daylight, threatening buildings and infrastructure, exposing artifacts and muddying the waters of the Beaufort Sea.
In 1982, the sea swallowed Tuktoyaktuk’s curling rink after a storm eroded permafrost that the seaside end of the building sat on. Ten years ago, a government building fell halfway into the ocean, and had to be moved back inland. Over the past 40 years, at least two homes have been completely swallowed by the waters. Today, the femur-shaped Tuktoyaktuk Island, which protects the harbor from the ocean, is now in danger. The guardian spit of permafrost is eroding at a rate of about 1.1 meters per year, and might cease to break waves by 2050.
Mayor Erwin Elias, a lifelong resident of Tuk, cites coastal erosion as the number one issue facing the hamlet.
“The harbor is the lifeline for the community. That’s one of the main reasons Tuk is where it is today,” said Mayor Elias. “We’re a traditional fishing village, and Tuk Island is a natural wavebreak for us. If we lose that, we will lose our harbor, and I think everything will be pretty rapid after that in terms of erosion.”
The banks of the freshwater lakes inland from the Beaufort Sea are also made of ice-rich permafrost. Permanent ice, frozen during the last ice age, gives the soil structure and keeps the water contained. But warmer summers deepen the portion of the permafrost around each lake that thaws annually, until the permafrost slumps away, creating receding bluffs that creep closer and closer to each lake’s edge. Eventually, the cliff wall meets the affected lake and water pours over the exposed black soil and ice. The rushing waterfall eats away at the bank as lake water and sediment rush downstream. The effects are immediate. A lake formed between 13,000 and 8,000 years ago transformed into a mudflat in less than a day.
Paul Voudrac, a recently retired government wildlife observer, 66, lives a two-hour drive south along the newly constructed Tuktoyaktuk-Inuvik highway in the regional hub of Inuvik.Every winter when he was a kid in the early '60s, his dad would take his whole family on a trek from their home in Tuktoyaktuk, 112 kilometers east to their cabin on Tuktoyaktuk Peninsula. After the snow and freeze-up that used to happen in October, they’d make the four-day trip by dogsled to hunt and fish and trap around the Husky Lakes, a brackish estuary emptying into Liverpool Bay. When SkiDoos became popular in the late '60s, travel time changed from days to hours. And changes to the landscape began to alter well-known trails.
Permafrost thawing and slumping suddenly met the edge of lakes with increasing frequency, eroding their banks and draining them. Instead of familiar open areas of ice and snow good for winter travel, Voudrac’s family was instead met with dense willow flats—making travel difficult, and disrupting long standing trails used by the Inuvialuit.
“On lakes we’ve traveled for years the willows rose up from the ground to about ten feet high, and we had to cut a trail through in order to get by it,” Voudrac recalls. “We were used to traveling where we went by. We had trails, one to the north, one straight to the west—always by the ice. And then we started seeing a lot of changes happening to the trails from Tuktoyaktuk. My dad passed away in 1973, and that trail west has been very little use since.”
Voudrac has noticed other changes, too—the massive, saline Husky Lake used to freeze over completely every year, forming 2.5 meters of ice in the winter months. In recent years, folks have begun to observe open water in the winter. Paul also joked that “thirty below used to be springtime weather for us. T-shirt weather. But now, you get down to about twenty below and you start feeling it. We’re spoiled, I should say. We can’t change as fast as the weather can.”
Permafrost is defined as any soil that remains continuously frozen for two or more years. If you were to dig down into permafrost on a summer day, you’d first break through an insulating dense mat of hardy tundra plants—sedges, grasses, rushes. Then, you’d reach the active layer: soil that freezes and thaws every year with the seasons. Below that is a mixture of rock, dirt and varying levels of ice that stays frozen year round. Go even deeper — anywhere between one and 1,500 meters depending on where you are, and you’d reach frost-free soil again, where geothermal heat warms the earth's crust above freezing temperature.
As far as dirt goes, permafrost is also particularly sensitive to climate change. Increases in air temperatures increase the depth of the “active layer” of the permafrost, thawing ice and destabilizing the soil's structure. Warming permafrost causes what are called retrogressive thaw slumps—landslides caused by the melting of ground ice in the permafrost. These slumps often form with a semicircular headwall, receding into the stable permafrost. Inside the half ring of exposed permafrost cliff of the headwall runs a black, boggy mudflow.
Perhaps nowhere are permafrost slumps so rapidly forming as Banks Island, a the fifth-largest island in the Canadian Arctic Archipelago. In 1984, there were 63 instances of regressive thaw slumps on Banks Island. By 2016, there were more than 4,000 observable thaw slumps.
Field Notes — Aulavik National Park
Though it is hard to get to, and Aulavik National Park in the northern end of the island receives an average of 10 annual visitors, Banks Island remains and has been inhabited by the Inuvialuit for centuries. One site in Aulavik on a bend in the Thompsen, called Head Hill, has thousands of downturned muskox skulls and dozens of rock piles used to dry meat and cache food, for many years during the 18th and 19th centuries.
Scientists can observe slumps from satellite imagery,* but studying permafrost in the field can be incredibly difficult (a trip to Aulavik National Park from Inuvik costs roughly $23,000 Canadian dollars in fuel one way). It is practical to go only during the summer months of July and August, and even with a generous weather window, it is possible to either get “weathered out” from arriving, or else stuck in place on the island. There is also the issue of polar bears — conducting research in the region requires hiring a full-time bear monitor, whose sole job is to wield a rifle and watch for bears.
Field Notes — Google Earth
Researcher Antoni G. Lewkowicz assigned senior undergraduate students at the University of Ottawa a transect of 5,000 km2 each to analyze on Google Earth. Using the Google Earth Engine Timelapse dataset, slumps in 1984 were compared to 2016. Models from Lewkowicz and Way’s study estimated that slump occurrences will rise from 4,000 in 2016 to an estimated 10,000 on Banks Island by 2075.
Even if the stars align, it’s a tough trip. Usually, a crew composed of Parks Canada researchers and local Inuvilauit hired to assist with the field work pack gear and enough food for two weeks and board a plane equipped with tundra tires. Flying from Inuvik to Sachs Harbor, the crew lands on an unimproved tundra field marked with six fuel canisters, weighed down with sand. From there, the crew stays one night at the barebones “green cabin”—the only park-managed building in all of Aulavik National Park.
Despite the challenges, researchers across North America are invested in researching the site. In 2015, Parks Canada researchers ventured on a canoe survey of the park's Thompsen river. The paddlers noticed that water coming from some of the tributaries was unusually muddy and turbid. Wondering where the cloudy water and debris was coming from, they hiked up a few of the tributaries and found dozens of slumps feeding into the Thompsen.
More recently, Colleen Arnison, Resource Conservation Manager and Hayleigh Conway, Geomatics Technician took return trips to Aulavik National park to study water quality in the Thompsen and use unmanned aerial vehicles to create three-dimensional models of the slumps, with the goal of calculating how deep and large they are, along with a study of the water quality. The team took samples above the slump, where water drained, and downstream, as well as samples from the Thompsen downstream from the tributaries.
When I sat down this spring with Arnison and Conway in the Western Arctic Field Unit in Inuvik, Conway explained to me that the scale of permafrost slumps can often be lost in the expansiveness of the Arctic landscape—seeing pictures of the slumps pales in comparison to the experience of witnessing them with boots on the ground. Though slumps are a natural phenomenon, “the rate at which they’re happening is unprecedented. And it’s such a scar on the landscape,” she said. Pointing to a picture of a particularly large semi-circular slump with a steep headwall and mud flowing to an outlet stream, she added,“this is bananas.”
Ecologist Colleen Arnision also talked about the unbelievable experience of traveling through slump areas.
“It’s unreal to see the color change. You’ll be paddling along, and though the Thompsen River is not clear, it’s cloudy, it gets black as soon as you hit the little stream coming down from the slumps. It is so difficult to even walk along the beaches because it is so mucky. You get completely stuck in the sediments deposited in the river downstream from the slumps,” said Arnison.