Changes in temperature, precipitation and sea ice.
Average temperatures in Alaska have been rising twice as fast as
temperatures in the rest of the United States. In the past fifty years,
average summer temperatures there have risen by 3.4° Fahrenheit, while
winter temperatures have risen by 6.3° Fahrenheit. These increased
temperatues are already impacting Alaskans. Snow now melts earlier in the
spring, sea ice cover is reduced, the growing season is longer, glaciers are
retreating and permafrost is warming.
Climate models project increases in precipitation for Alaska, however, the
expected increase in temperature will also cause higher evaporation rates. The
result could be drier conditions and reduced soil moisture. There will be a
longer summer growing season and an increased probability of summer drought
and wildfires.
Average annual temperatures in Alaska are projected to rise between 3.5 and
7° Fahrenheit by the middle of this century. This increase will cause the
reduction in sea ice to continue. Less sea ice will have a positive impact
upon marine shipping and resource extraction, however, it will have a
negative impact on coastal erosion and flooding associated with coastal
storms. Reduced sea ice will also change the location and timing of marine
plankton blooms which provide food for the fish harvested by commercial
fishermen.
| Coastal Villages and Fishing Fleets at Risk |
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Coastal storms increase risks to villages and fishing fleets.
Alaska 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 Alaska's northeastern coastline has doubled over the past 50 years. Photo copyright by iStockPhoto / W. Howard. |
| Thawing Permafrost Damages Infrastructure |
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Thawing permafrost damages roads, runways, water and sewer systems, and other infrastructure.
As 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). Photo copyright by iStockPhoto / R. Clark. |
| Longer, Hotter, Drier Conditions |
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Longer summers and higher temperatures are causing drier conditions, even in the absence of strong trends in precipitation.
Between 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 Alaska'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. Photo copyright by iStockPhoto / R. Van Beets. |
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Lakes are declining in area.
Across 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. Lakes along the Yukon River in western Alaska. Landsat image from NASA
GeoCover Program.
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| Climate change will have a number of severe impacts on Alaska. This page illustrates a number of the more significant impacts. Map by Geology.com and MapResources. |
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Displacement of marine species will affect key fisheries.
Climate change is altering marine ecosystems in ways that affect commercial fisheries. The world'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. Photo copyright by iStockPhoto / K. Wiedemann. |
| More Wildfires and Insect Outbreaks |
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Insect outbreaks and wildfires are increasing with warming.
During 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. Burn area near McGrath in central Alaska. Landsat image from NASA GeoCover
Program.
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