Fairbanks, AK, USA
The second-largest city in Alaska, Fairbanks lies in an area where permafrost (permanently frozen ground) is common but not continuous. Rising temperatures linked to global warming are causing this permafrost to thaw. That increases the risk of damage to both landscapes and public infrastructure—including the Trans-Alaska Pipeline, pictured here.1
Fairbanks—Alaska's second-largest city—is in a sub-Arctic interior region. Much of the city and the surrounding area are characterized by permanently frozen ground (permafrost). Rising temperatures are already degrading this permafrost, damaging forests as well as roads, buildings, and other infrastructure.2,3,4
With a population of nearly 35,000, and some 98,000 in the metropolitan area, Fairbanks is Alaska's second-largest city. Located in the state's interior, it is a major transportation, education and communication hub.8,9 Fairbanks is home to the state's oldest college—the University of Alaska at Fairbanks—and an Alaska Railroad station, and a major pump station of the Trans-Alaska Pipeline is nearby.
Over the past 50 years, the annual temperature in Alaska increased an average of 3.4° F (1.8° C), while winters have warmed even more—by 6.3° F (3.5° C).2,10 So, like the rest of the state, the Fairbanks landscape is undergoing changes linked to global warming.
About 85 percent of Alaska, including the interior, lies in permafrost zones.11,12 Permafrost—soil or rock that remains at or below 32° F (0° C) for at least two years—is an essential foundation of many high-latitude landscapes.13 However, because permafrost does not occur everywhere in the Fairbanks area, that zone is classified as "discontinuous permafrost."
In Arctic regions, permafrost temperatures often sink to -17.6° F (-8° C) or lower. Permafrost averages 656 feet (200 meters) in thickness, but can be as much as 2,132 feet (650 meters) thick.14,15 The Fairbanks climate is classified as sub-Arctic and is therefore milder than the Arctic. As such, permafrost temperatures usually average at or below freezing temperatures, and the permafrost itself is typically about 164 feet (50 meters) thick.2,14,15
Since the late 1970s, permafrost temperatures have risen.2,7 Northern Alaska has recorded the largest increases, but interior permafrost is more vulnerable to thawing because its temperatures are precariously close to above freezing.2,16
Because only about a third of Alaska's roads are paved, much of the state is more accessible in winter after "ice roads" form.2,4 As permafrost degrades more quickly, particularly in regions with discontinuous permafrost, the ice road season is likely to shorten.2,4,15 In Fairbanks, many airstrips are also built on permafrost, and they are likely to require more maintenance—and even relocation—as they undergo more thawing.2,4
Both the Alaska Railroad and the Trans-Alaska Pipeline cross various types of permafrost.2,17,18 The 800-mile pipeline runs from Prudhoe Bay on Alaska's North Slope to Valdez on its southern coast.2 Because the pipeline crosses potentially unstable permafrost, especially in the interior, elevated stands support more than half of it.2,4 The pipeline was designed and constructed in the early 1970s based on that era's climate, so it is not equipped to withstand many of the effects of substantial thawing.2,4
By 2030, degradation of permafrost is expected to increase the costs of maintaining the pipeline by U.S. $3.6 billion to $6.1 billion. Economists project another U.S. $5.6 billion to $7.6 billion in higher costs by 2080.2,8 These figures do not include damages to private infrastructure such as houses, as such costs have yet to be calculated.2
Part of a Larger Pattern
Permafrost is particularly sensitive to changes in air temperature and snow cover, making it especially vulnerable to climate change.11,19 And permafrost degradation itself is likely to worsen climate change, as the soil releases heat-trapping gases into the atmosphere that it previously stored—in many cases for thousands of years.
Thawing permafrost can release carbon dioxide and methane, depending on moisture conditions and whether the permafrost has contact with air.11,13 Scientists think permafrost degradation causes a thickening of the active layer that thaws in the summer and freezes in the winter, spurring the release of methane and carbon dioxide.11,19
The thawing of forest permafrost could completely alter local ecosystems.11,14 And that, in turn, could leave resident trees and vegetation more vulnerable to early mortality, and further disrupt the climate.6,11,14
What the Future Holds
In Alaska, average annual temperatures are projected to rise 3.5° to 7° F (1.9° to 3.8° C) by around 2050. How much temperatures rise in the second half of the century depends on whether we continue on a high-emissions path.2 If we do, temperatures in Alaska are expected to rise by 8° to 13° F (4.4° to 7.2° C) by 2100. If instead we curb our heat-trapping emissions, we can lower the expected temperature rise to 5° to 8° F (2.7 to 4.4° C).2,20
The fate of Alaska's permafrost depends on the choices we make today. Acting quickly to make deep cuts in our global warming emissions will help safeguard permafrost against complete degradation.