 Climate
Impacts in Alaska
Overview
Alaska is the largest state in the United States, accounting
for about 20% of the total area of the United States and
more than twice the land area of Texas. Alaska includes
lands on both sides of the Arctic Circle, which makes the
United States an Arctic nation. The state spans a wide range
of climatic and ecological conditions that include
rainforests, glaciers, boreal forest, tundra, peatlands, and
meadows. Alaska contains 16 national wildlife refuges
spanning 76 million acres and hosts 60% of the total area
managed by the National Park Service, including the largest
U.S. National Park (Wrangell-St. Elias with 13.2 million
acres).
Over the past 60 years, the average temperature across
Alaska has increased by approximately 3°F. This increase is
more than twice the warming seen in the rest of the United
States. Warming in the winter has increased by an average of
6°F and has led to changes in ecosystems, such as earlier
breakup of river ice in the spring. As the climate continues
to warm, average annual temperatures in Alaska are projected
to increase an additional 2 to 4°F by the middle of this
century. Precipitation in Alaska is projected to increase
during all seasons by the end of this century. Despite
increased precipitation, the state is likely to become drier
due to greater evaporation caused by warming temperatures
and longer growing seasons.
Rising temperatures may provide some benefits in Alaska,
such as a longer growing season for agricultural crops,
increased tourism, and access to natural resources that are
currently inaccessible due to ice cover, like offshore oil.
However, climate change is also having adverse effects on
many ecosystems and species, and is creating new hardships
for Native Alaskans. |
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Permafrost
Permafrost is frozen ground that is typically located a few
feet below the soil surface in extremely cold regions.
Eighty percent of Alaska's surface lies above permafrost.
Permafrost typically remains frozen year-round, but as air
temperatures rise, permafrost is thawing in many areas. As
permafrost thaws, ice in the permafrost melts and can cause
the soil above to sink, resulting in ground subsidence and
damage to roads, homes, and other structures. The impacts of
melting permafrost on transportation, forests, other
ecosystems, and the economy could have widespread
implications for Alaskans.
Transportation and Infrastructure
Impacts
Climate change leads to more permafrost thaw and disruptions
to freeze-thaw cycles that can increase frost heaves and
subsidence. This can potentially cause damage to
transportation infrastructure in Alaska, including highways,
railroads, and airstrips. Uneven sinking of the ground in
response to permafrost thaw is likely to add significant
costs to the maintenance and repair of transportation
infrastructure and buildings. Many of Alaska's highways are
built in permafrost areas and are subject to damage if the
permafrost thaws. Additionally, warming leads to a shorter
period when ice roads are usable and a shorter season during
which oil and gas exploration on the tundra can occur.
For more information on climate change impacts on
transportation, please visit the Transportation Impacts
page. |
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 Ecosystems
Climate change is causing changes in lakes, ponds, wetlands,
plant composition, and wildfires that impact human health,
wildlife, and ecosystems. Lakes are changing size, with most
lakes shrinking in area in the southern portion of the
state. Surface waters and wetlands provide breeding habitat
for millions of waterfowl and shorebirds that winter in the
lower 48 states. These wetland ecosystems and wildlife
resources are also important to Alaska Natives who hunt and
fish for food.
Picture - Alaska
highways susceptible to permafrost. Source: U.S. Arctic
Research Commission (2003) |
 Lakes
get smaller through a combination of increased evaporation
caused by warmer temperatures, permafrost thaw which allows
lakes to drain more readily, and greater accumulation of
decomposing plant material on lake bottoms caused by greater
plant growth. In areas where permafrost is discontinuous or
fragmented across the landscape, lakes are expected to
continue shrinking in area. Some lakes are growing in area
because of lateral permafrost thaw, which causes the edges
of the lake to collapse inward, thereby increasing the area
of the lake. Lake growth is expected to continue in areas
underlain with continuous permafrost.
Picture - Two pairs of
aerial photographs of pond areas in Alaska. The two images
on the left show the pond areas in 1951 and images on the
right show the same pond areas in 2000. The pond areas shown
on top shrunk from 180 to 10 acres, and the pond areas shown
in the bottom went from 90 to 4 acres in size. Source:
USGCRP (2009)
As the climate warms, shrubs are expanding into the tundra.
In some areas, 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 some Alaska Natives. |
 Higher
temperatures and drier conditions increase the risks of
drought, wildfire, and insect infestation. Large wildfires
have consumed more boreal forest in Alaska in the last ten
years than in any other decade recorded, and the area burned
annually is projected to double by 2050. Fires change forest
habitat, improving conditions for moose and some plant
species, but reducing the lichen that caribou rely on in
winter. Warmer temperatures are also expected to worsen
insect damage to forests across much of the state, which may
increase the area of standing dead, highly flammable trees
that are especially vulnerable to wildfire.
Picture - In recent
years, an increase in large wildfires has been seen in
Alaska. Credit: USGCRP (2014) |
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 Oceans
and Coasts
Sea ice is frozen seawater that floats 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 is seasonal,
melting during the summer and refreezing in winter.
Picture - Sea ice
extent has, on average, been declining in recent decades.
This figure shows the extent from 1979 to 2015. Source: US
EPA (2015)
Over the past several decades, perennial sea ice has
declined. This decline is, in part, a result of extended
periods of above-freezing air or water temperatures. Ocean
currents and wind patterns have also played an important
role. September 2012 had the lowest sea ice extent (or area
of ocean covered by ice) on record, 49 percent below the
1979-2000 average for that month. The September 2014 sea ice
extent was nearly 700,000 square miles less than the
historical 1979-2000 average for that month - a difference
more than twice the size of Texas. The thickness and age of
sea ice is also declining throughout the Arctic, with recent
measurements indicating a loss of 50% of sea ice since 1979.
Climate models project that sea ice will continue to
decrease and indicate that the Arctic could be nearly ice
free during the late summer by the 2030s.
Diminishing sea ice is opening new opportunities for
shipping, oil and gas exploration, tourism, and other
economic activities. However, it also creates a pathway for
invasive species and habitat loss 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. Sea ice along the shoreline
and permafrost in coastal areas help to protect human
settlements from flooding and erosion. As coast erosion
increases due to declining sea ice, residents are becoming
more vulnerable.
For more information on climate change impacts on coasts,
please visit the Coastal Impacts page. |
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 Alaska
Natives
Alaska is home to 229 federally recognized tribes that are
already experiencing the impacts of climate change in their
everyday lives. Alaska Native peoples depend economically,
nutritionally, and culturally on fishing and hunting
animals, including polar bears, walruses, seals, caribou,
and fish. As the supply of fish and game decline, they are
likely to travel onto thinning ice in search of food and are
being forced to seek alternative food sources. Arctic plants
and animals, including those harvested as subsistence food,
are also at higher risk for diseases in a warming climate,
further affecting food availability and human health.
Picture - The ground
under a home in Shishmaref, Alaska collapses from erosion. |
 The
health of native communities is also threatened by loss of
clean water, saltwater intrusion, and sewage contamination
from thawing permafrost, as well as by the northward
expansion of diseases. Warming also increases exposure to
pollutants, such mercury and organic pesticides, that have
been transported to Arctic regions and are released from
thawing soils.
Picture - Locations of
12 Native Villages considering relocation. Source: GAO
(2009)
Thawing permafrost, loss of coastal sea ice, sea level rise,
and more intense extreme weather events are also increasing
erosion and flooding along Alaska's northwestern coast. More
than 30 Native villages are either in the process of or in
need of relocating their entire village. In Shishmaref,
Kivalina, and Newtok, for example, erosion is causing
extensive damage, creating new dangers to residents, and
deepening pressure to relocate.[8] However, due to high
costs and land constraints, tribal communities in Alaska
have been experiencing difficulty relocating to safer areas.
For more information on climate change impacts on society,
please visit the Society Impacts page. |
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