Scientists study accelerating land subsidence affecting coastal North Slope communities
CLIMATE CHANGE
Anchorage Daily News
When a house on Qigalik Avenue in Point Lay was first built, a staircase led from an upstairs door to the ground. Thirty years later, an 8-foot ladder is now needed to get to the bottom step of the staircase.
“Every year we have to add a step or two to those staircases because of the subsidence,” said Bill Tracey, a Point Lay resident of 50 years, who lives close to the house. He said the issue is common among local homeowners. “We started noticing the ground sinking and ponds forming, roads developing sinkholes. … We are doing what we can, but doors aren’t closing, windows are cracking, walls are separating — things you’d expect when a house is moving.”
Permafrost thaw and coastal erosion are affecting Point Lay and other North Slope and Northwest Alaska communities, as well as most places across Pan-Arctic coastlines. With land subsiding, the rate of coastal erosion and the danger of inundation might increase, and all of those processes are expected to continue causing land loss, infrastructure and habitat damage and the destruction of important cultural sites.
Tracey said that a new study can help residents decide whether they can adjust to changes or need to relocate.
Louise Farquharson, a research assistant professor at the University of Alaska Fairbanks Geophysical Institute, is working on long-term projections for how coastal erosion and land subsidence in Point Lay, Wainwright and Kaktovik may lead to extensive sea water inundation.
“As permafrost thaws, the ground ice within it melts,” Farquharson explained. “This leads to the lowering of the ground surface.”
The amount of ice in permafrost varies across communities and even within one village, making up anywhere between 40% to 90% of the ground in the Arctic, explained UAF geophysicist Vladimir Romanovsky. In coastal villages like Point Lay, the ice content tends to be higher. If 10 meters of permafrost thaws in a place like that, 9 meters of ice may melt and flow away, leaving only a meter of soil in its place. Such dramatic land subsidence can bring the coastal land below sea level, allowing the ocean waves to storm in.
Predicting permafrost thaw
The researchers have developed preliminary estimates for how the permafrost will change in the upcoming years, based on a combination of ground temperature measurements from across the North Slope and numerical modeling of heat flow through the ground, Farquharson said.
Several climate change models were used to build the estimates. In a scenario where the climate warms drastically, Farquharson concluded that by the year 2100, the ground temperature in the tundra could increase by 6 to 8 degrees Celsius, or by about 11 to 14 degrees Fahrenheit. Roads and runways covered with gravel absorb warmth even faster than the untouched tundra, and the temperature can jump by 7 to 9 degrees Celsius, or by about 13 to 16 degrees Fahrenheit.
“Any kind of gravel pad on the surface will make all the surface temperature higher because it absorbs much more solar radiation during the summer,” Romanovsky said. “The tricky part is that for different landscapes, the changes in permafrost will be a bit different.”
The researchers plan to refine the study during field work over the next two years by getting ground temperature measurements and permafrost ice cores to quantify ground ice content. They plan to incorporate data from temperature sensors from a range of structures with different foundation types and a range of vegetation and soil types in the three communities involved in the study.
Scientists are currently in the process of applying for permits to install temperature sensors in Point Lay and Wainwright and hope the field work will take place this summer, Farquharson said. “When we have this projection, and there’s some knowledge of ice content, we will be able to produce maps of subsidence of the surface,” Romanovsky added. “Then the idea is to compare with sea level and see if an invasion will happen.”
Besides analyzing how permafrost changes, UAF scientists share their data with experts from the Cold Climate Housing Research Center and engineers at Penn State and Missouri University of Science and Technology, who produce engineering estimates and develop mitigation efforts based on that data.
Penn State civil engineering professor Ming Xiao and his team have been looking at the performance of infrastructure in Alaska in the face of climate change and developing computer models of how the infrastructure will be affected. He said that predicting the future soil conditions will help engineers design better foundations and infrastructure solutions.
“Before implementing solutions, I think the first step is to better understand and even predict how civil infrastructure is going to perform in the next several decades,” Xiao said. “Eventually, we want to develop a so-called infrastructure hazard map.”
Addressing land loss
Meanwhile, the landscape in the Arctic has already been changing. Riverbanks are eroding, and shrubs and other plants with deep root systems are now competing with shallow- rooted tundra plants and berries.
“The tundra used to be hard, now it is spongy just like the carpet inside your house.” Rossman Peetok of Wainwright said in an Alaska Native Tribal Health Consortium report.
A continuous increase in ground temperature lead to above-freezing conditions and to ice melting, Farquharson explained. Thawing of ice and widespread land subsidence cause development of thermokarst — irregular surfaces of marshy hollows — both within and around the communities.
To address problems caused by thawing permafrost and fix damaged infrastructure, the North Slope Borough works to apply new construction and maintenance methods, according to ANTHC.
Six years ago, the community of Point Lay lost its freshwater source when the lake eroded and drained dry, Tracey said. Now residents get water from the river and desalinate it.
Tagiugmiullu Nunamiullu Housing Authority uses different foundation styles across the North Slope to mitigate permafrost degradation, said the authority’s executive director, Griffin Hagle. For example, they previously used a foam “raft” foundation — a continuous slab made up of insulating material that distributes its weight over the entire area of the building — that can keep the heat from the house from penetrating deep into frozen soil, thawing permafrost and destabilizing the structure.
The authority also experimented with adjustable foundations using either adjustable telescoping footings or a steel “sled” frame that allows adjustment, as well as moving the entire home if needed.
“We haven’t had to do this … yet,” Hagle said.
Hagle added that though the authority is not “building homes with hot tubs, saunas, or other lavish amenities,” engineering portable, adjustable foundations add tens of thousands of dollars to the cost. The addition is necessary to protect federally funded housing projects from excessive risk. “Such engineered solutions are justified as a hedge against the far more catastrophic expense of relocating (or abandoning and replacing) conventional structures as the Arctic continues to experience disparate climate impacts,” Hagle said. “In a nutshell, they’re an insurance policy.”
Besides adjusting the infrastructure, changes happening with the land and sea also require residents to develop new knowledge to continue traditional subsistence practices, for example by extending water- based and decreasing ice-based hunting.
“You can’t use the old traditional knowledge,” Tracey said. “In the winter when rivers aren’t freezing when they used to, you have to wait and a caribou don’t wait. So if you miss a caribou season, because things haven’t frozen up and you can’t travel, you’re out of luck.”
Because of the subsidence, Point Lay residents lost all their ice cellars used for storing the harvest, whether it’s caribou, whale, walrus or seal, Tracey said. Some of them were inundated with saltwater or flooded with thaw, and some were ruined by squirrels that can dig into now-softer ground.
“Last working cellar was about 10 years ago,” Tracey said. “Every single ice cellar is gone. Nobody has space in your home for more than one freezer so food security has become an issue because of these changes.”
Residents rely more and more on the products they can purchase at their store — the fastest growing store on the North Slope, according to Tracey. But the main help comes from sharing: Other coastal villages share whale harvest after a successful catch, and hunters get seals for the elders.
“The whole North Slope is adapting by the old traditional sharing,” Tracey said.
The question remains whether these adjustments will be enough for Point Lay to sustain its lifestyle, and how quickly these changes will catch up with the most northern communities.
“Our new norm is not to expect what happened yesterday because it’s different today,” Tracey said. “If we can learn from science, maybe we could help ourselves and figure this out.”
Contact Alena Naiden at anaiden@adn.com.
