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Climate Change


Climate Impacts in Alaska

Key Points
  • Over the past 50 years, Alaska has warmed twice as fast as the national average.
  • Warming is contributing to the thawing of Alaska's permafrost. By the end of this century, the permafrost boundary is likely to shift northward hundreds of miles, increasing the risk for infrastructure damage.
  • Warming is contributing to the loss of protective sea ice along Alaska's northwestern coast, leading to increased rates of coastal erosion.
  • Warming is altering marine and terrestrial ecosystems, causing changes in the extent and location of habitat for fish and wildlife.
  • Climate change places significant stress on the livelihoods, villages, and cultures al values of Alaska Natives.

Climate Impacts on Alaska

Alaska is a huge state with a wide range of climatic and ecological conditions. It is known for its rainforests, glaciers, boreal forest, tundra, peatlands, and meadows. Alaska contains 75% of U.S. national parks and 90% of U.S. wildlife refuges, by area.[1]

Over the past 50 years, temperatures across Alaska increased by an average of 3.4°F. Winter warming was even greater, rising by an average of 6.3°F.[2]The rate of warming in Alaska was twice the national average over that same period of time. Average annual temperatures in Alaska are projected to increase an additional 3.5 to 7°F by the middle of this century.[2]

Precipitation in Alaska has also increased slightly, but the trend is not significant. Climate projections indicate that Alaskan winters are likely to be wetter, and that summers could become drier, as rising air temperatures accelerate the rate of evaporation.[2][3]

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Permafrost Impacts

Permafrost is the frozen ground located one to two feet below the surface in cold regions. As permafrost thaws and the soil sinks, structures built on or within the soil are damaged. Although most Alaskans live in permafrost-free areas, an estimated 100,000 Alaskans (about 14% of the population) live in areas sensitive to permafrost degradation.[4]As explained below, the impacts of melting permafrost on transportation, forests, ecosystems, and the economy could have widespread implications for Alaskans.

Permafrost Impacts on Transportation

Map of Alaska that shows roads and communities that are susceptible to permafrost. A summary table states that 456 miles of road and 87 communities, with have a combined population of 40,811, have a permafrost extent of 90-100%. These roads and communities are generally located in the northern and western portion of the state, with a small pocket in the south-eastern portion of the mainland. There are 1,211 miles and 79 communities, with 47,140 people, that have discontinuous permafrost extent, which is classified as 50-90% permafrost extent. These communities are spread across the central portion of Alaska, and the roads are in the middle-eastern region. There are 189 miles of roads and 26 communities, with a combined population of 5,235 people, with sporadic (or 10-50%) permafrost extent. These communities and roads are concentrated in the southeastern portion of the mainland. In southern Alaska and on the islands and peninsulas that extend to the southeast and southwest there are 281 miles of road and 129 communities with 396,821 people that have permafrost extent that is less than 10%. Overall the permafrost-susceptible highways and communities are more concentrated in areas above the most southern region of Alaska. View enlarged image

Alaska highways susceptible to permafrost. Source: U.S. Arctic Research Commission (2003)

Permafrost thawing and cycles of freezing and thawing can cause extensive damage to highways, railroads, airstrips, and other transportation infrastructure in Alaska.

Photograph of leaning evergreen trees. Some fallen trees are visible at ground-level in the photograph.

Alaska's "drunken forests" — as permafrost thaws, trees lean into the ground. Source: USGCRP (2009) (PDF)

Many of Alaska's highways are built on permafrost. When permafrost thaws, roads buckle. Vehicles are only allowed to drive across certain roads in the tundra when the ground is frozen solid. In the past 30 years, the number of days when travel is allowed on the tundra has decreased from 200 days to 100 days per year.[2]Projected increases in temperatures and permafrost thawing would continue this trend and could further limit access to the tundra. Building infrastructure on thawing permafrost requires additional engineering, and can increase the cost of construction by 10% or more.[2]

For more information on climate change impacts on transportation, please visit the Transportation Impacts page.

Permafrost Impacts on Forests

As temperatures rise and permafrost thaws, the softening soil interferes with tree root systems. The altered soil conditions cause trees to sink into the ground. As a result, the trees in many of Alaska's forests lean, creating so-called "drunken forests."[2][3]

For more information on climate change impacts on forests, please visit the Forest Impacts page.

Two pairs of aerial photographs of ponds in Alaska. The two images on the left show the pond area in 1951 and the two corresponding images on the right show the same pond areas in 2000. The 2000 images have significantly smaller water levels. View enlarged image

Pond shrinkage in Alaska's Yukon Flats National Wildlife Refuge, 1951-2000. Source: USGCRP (2009)

Permafrost Impacts on Ecosystems

Over the past 50 years, thawing permafrost and increased evaporation have caused a substantial decline in the area of Alaska's closed-basin lakes (lakes without stream inputs and outputs). These surface waters and wetlands provide breeding habitat for millions of waterfowl and shorebirds that winter in the lower 48 states.[2]These wetland ecosystems and the wildlife resources are important to Alaska Natives who hunt and fish for food.

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Other Impacts on Ecosystems

As the climate warms, shrubs are invading the tundra. In some areas, the shrubs are replacing lichens and other tundra vegetation. Lichens are an important winter food source for caribou, and the loss of lichens can lead to declines in the growth and abundance of these animals. Caribou in turn are a critical food source for predators such as bears and wolves, as well as for Alaska Natives.[3]

Higher temperatures and less summer moisture increase the risks of drought, wildfire, and insect infestation. Alaska's boreal spruce forest declined substantially in recent decades from both fire and insect damage. By mid-century, the average area burned by wildfire each year is likely to double.[2]

For more information on climate change impacts on ecosystems, please visit the Ecosystems Impacts page. For more information on climate change impacts on forests, please visit the Forest Impacts page.

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Graph that shows the extent of average monthly arctic sea ice by year - ranging from 1979 to 2010. The graph includes a trend line that shows the general trend starts at 8.0 million square kilometers in 1979 declines to approximately 5.5 million square kilometers in 2010. View enlarged image

Monthly September sea ice extent for 1979-2010 shows a decline of 12% per decade. Source: National Snow and Ice Data Center (2010)

Impacts on Oceans and Coasts

The extent of sea ice is declining throughout the Arctic. Sea ice is frozen seawater floating on the surface of the ocean. Some sea ice persists from year to year (known as perennial sea ice), often getting thicker as it piles up against Arctic shorelines. Other sea ice melts during the warm season and refreezes in the cold season. Over the past several decades, the perennial sea ice has declined dramatically. This decline is, in part, a result of extended periods of above-freezing air or water temperatures. Ocean currents and winds have also played an important role, pushing perennial sea ice out of the Arctic basin. The average sea ice extent in September has decreased by 11.5% per decade over the past 30 years. Climate models project that sea ice will continue to retreat during the 21st century. Late summers could be nearly ice-free as early as about the 2040s.[5]

Diminishing sea ice has opened new opportunities for shipping, oil and gas exploration, and other economic activities. However, it has also created a pathway for invasive species and caused the loss of critical habitat for a variety of ice-dependent species, including walruses and polar bears. Changes in sea ice can also affect the timing and location of plankton blooms, which can in turn affect the areas where commercial fisheries can thrive. Landfast ice (sea ice that has frozen along the shore) is important because it protects coastal shorelines and human settlements from flooding and erosion caused by storms, wind, and wave damage.[2][3][5][6]

For more information on climate change impacts on coasts, please visit the Coastal Impacts page.

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Impacts on Alaska Natives

People in Alaska are already feeling the impact of climate change. In many parts of the state, the changing climate has negatively affected the livelihood, settlements, and well-being of residents. Alaska Natives fish in ocean and inland waters. They also hunt animals such as polar bears, walruses, seals, and caribou for food. As climate change reduces these species' critical habitats, declines in their population threaten not only the livelihood of Alaska Natives, but also their cultural and social identity. As the supply of fish and game declines, hunters and fishers are forced to seek alternative sources of food.[2][3]

Photograph of seaside house that lies nearly on it's side with one end on higher sands and one side on the beach.

Ground under home in Shishmaref, Alaska collapsing from erosion. Source: Alaska Conservation Foundation (2010)

Along Alaska's northwestern coast, increased coastal erosion is causing some shorelines to retreat at rates averaging tens of feet per year.[2]Here, melting sea ice has reduced natural coastal protection. In Shishmaref, Kivalina, and other Alaska Native Villages, erosion has caused homes to collapse into the sea. Severe erosion has forced some Alaska Native Villages' populations to relocate in order to protect lives and property.[2][7]

For more information on climate change impacts on society, please visit the Society Impacts page. For information about relocation efforts in Alaska, visit the Alaska Adaptation section.

To learn more about what Alaska is doing to adapt to climate change impacts, please visit the adaptation section of the Alaska Impacts and Adaptation page.

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[1] USGCRP (2000). Climate Change Impacts in the United States: The Potential Consequences of Climate Variability and Change. United States Global Change Research Program. Cambridge University Press, Cambridge, United Kingdom.

[2] USGCRP (2009). Global Climate Change Impacts in the United States. Karl, T. R., J. M. Melillo, and T. C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.

[3] ACIA (2004). Impacts of a Warming Arctic: Arctic Climate Impact Assessment. Exit EPA Disclaimer Arctic Climate Impact Assessment. Cambridge University Press, Cambridge, United Kingdom.

[4] USARC (2003). Climate Change, Permafrost, and Impacts on Civil Infrastructure(PDF, 72 pp, 4.8MB) U.S. Arctic Research Commission, Arlington, VA, USA.

[5] NRC (2011). Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia. Exit EPA Disclaimer National Research Council. The National Academies Press, Washington, DC, USA.

[6] Anisimov, O.A., D.G. Vaughan, T.V. Callaghan, C. Furgal, H. Marchant, T.D. Prowse, H. Vilhjálmsson and J.E. Walsh (2007). Polar regions (Arctic and Antarctic). In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Exit EPA DisclaimerContribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds.). Cambridge University Press, Cambridge, United Kingdom.

[7] Alaska Climate Impact Assessment Commission (2008). Final Commission Report. Exit EPA Disclaimer Alaska State Legislature.

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