the past 50 years, Alaska has warmed at more than twice the rate of the
rest of the United States. Its annual average temperature has increased
3.4Â°F, while winters have warmed by 6.3Â°F. The higher temperatures are
already causing earlier spring snowmelt, reduced sea ice, widespread
glacier retreat, and permafrost warming. The observed changes are
consistent with climate model projections of greater warming over
Alaska, especially in winter, as compared to the rest of the country.
Climate models also project increases in precipitation over Alaska.
Simultaneous increases in evaporation due to higher air temperatures,
however, are expected to lead to drier conditions overall, with reduced
soil moisture. Average annual temperatures are projected to rise
between 5 and 13Â°F by late this century, with lower emissions scenarios
yielding increases at the lower end of this range and higher emissions
yielding increases near the high end of the range.
Longer summers and higher temperatures are causing drier conditions, even in the absence of strong trends in precipitation.
1970 and 2000, the snow-free season increased by about 10 days across
Alaska, primarily due to earlier snowmelt in the spring. A longer
growing season has potential benefits, such as a longer season for summer
tourism and agriculture. However, the white spruce forests in Alaskaâ€™s
interior are experiencing declining growth due to drought stress and
continued warming could lead to widespread death of trees. The
decreased soil moisture also suggests that agriculture might not
benefit from the longer growing season.
Alaska Spruce Beetle Infestation
Kenai Peninsula, 1971 to 1998
Insect outbreaks and wildfires are increasing with warming.
the 1990s, south-central Alaska experienced the largest outbreak of
spruce beetles in the world as rising temperatures allowed the beetle
to survive the winter and to complete its life cycle in half the usual
time. Drought-stressed trees were unable to fight off the infestation.
Fires are also increasing. By the end of this century, the area burned
in Alaska is projected to triple under a moderate greenhouse gas
emissions scenario and to quadruple under a higher emissions scenario.
Lakes are declining in area.
the southern two-thirds of Alaska, the area of closed-basin lakes
(lakes without stream inputs or outputs) has decreased over the past 50
years. This is likely due to the greater evaporation and thawing of
permafrost that result from warming. These wetlands provide breeding
habitat for millions of waterfowl and shorebirds and are important
hunting and fishing grounds for Native People. A continued decline in
the area of surface water would present challenges for ecosystems,
natural resources, and the people who depend upon them.
Thawing permafrost damages roads, runways, water and sewer systems, and other infrastructure.
permafrost thaws, the land can sink and collapse, damaging forests,
homes, and infrastructure. Economists estimate that thawing
permafrost will add billions of dollars in repair costs to public
infrastructure (costs to private property have not yet been estimated).
Projected Coastal Erosion, 2007 to 2027
Newtok, western Alaska
Coastal storms increase risks to villages and fishing fleets.
has more coastline than the other 49 states combined. These coastlines
are increasingly threatened by a combination of losing their protective
sea ice buffer, increasing storm activity, and thawing coastal
permafrost. The ground beneath some communities is literally crumbling
into the sea. The rate of erosion along Alaskaâ€™s northeastern coastline
has doubled over the past 50 years.
Displacement of marine species will affect key fisheries.
change is altering marine ecosystems in ways that affect commercial
fisheries. The worldâ€™s largest single fishery is the Bering Sea pollock
fishery, which has undergone major declines in recent years. Air and sea temperatures have increased, and sea ice has declined in this region.