Environmental Health Center
What would the greenhouse effect do to Alaska, native habitat of the igloo? Would it be good news or bad news?
In a state where winter temperatures of -50ºF are common and cold snaps can go below -70ºF, weather is always big news. Adaptation to extreme climate has been the key to human survival there since the earliest humans arrived. The fisheries and forests which form much of Alaska's economic base today are shaped directly by climate.
But even though a significant part of the state lies above the Arctic Circle, stereotypes of Alaska as a frozen white expanse dotted with igloos hardly capture the state's real diversity. It also has some of the largest and lushest rain forests in the northern hemisphere. Any estimate of climate change impacts must take geographic particulars into account.
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101. Arctic Coastal Plain 102. Arctic Foothills 103. Brooks Range 104. Interior Forested Lowlands and Uplands 105. Interior Highlands 106. Interior Bottomlands 107. Yukon Flats 108. Ogilvie Mountains 109. Subarctic Coastal Plains 110. Seward Peninsula 111. Ahklun and Kilbuck Mountains 112. Bristol Bay-Nushagek Lowlands 113. Alaska Peninsula Mountains 114. Aleution Islands 115. Cook Inlet 116. Alaska Range 117. Copper Plateau 118. Wrangell Mountains 119. Pacific Coastal Mountains 120. Coastal Western Hemlock-Sitka Spruce Forest |
| Source: U.S. Geological Survey, National Mapping Information, EROS Data Center, 1997 |
Alaska is an ecologically diverse state covering 586,400 square miles. It has more than 31,000 miles of coastline on three different seas: Arctic Ocean, Pacific Ocean, and Bering Sea. It has more than three million lakes, 270,000 square miles of wetlands, and 29,000 square miles of glaciers, covering 5 percent of the state. An estimated 80 percent of Alaska's surface, including its continental shelf, is underlain by permafrost - ground that has been frozen for two or more years. Alaska also has 17 out of 20 of the highest mountains in the United States.
Because of its size, Alaska's climate is variable. The southeastern and south central coastal regions are wet and fairly mild, the interior is cool and dry, and the northern region is very cold and dry weather.
Scientists are less certain about how much the Earth will warm and how fast. Most conclude that more precipitation will fall worldwide but with significant regional and seasonal variation. The estimates come from computer models that use what is currently understood about physical climate processes to simulate how the Earth might respond to increasing greenhouse gases. The more sophisticated models are atmosphere-ocean general circulation models that take into account the large-scale climate processes involving the atmosphere, ocean, land, biosphere, and cryosphere (ice).
Even with the sophisticated models, numerous uncertainties, the complexities of the Earth's climate system, and computer limitations make the computer model projections for specific regions unreliable. In addition, U.S. Environmental Protection Agency (EPA) warns that "projections of climate change in specific areas are not forecasts but are reasonable examples of how the climate might change." The projections are often referred to more in terms of "scenarios" than "predictions."
Despite these caveats, there is some consensus on likely impacts of climate change, such as a rise in sea level. While the impacts on some species or ecosystems or economic sectors may be minimal or even beneficial, others may be much more vulnerable to even small changes in climate and weather. Understanding these potential vulnerabilities can help scientists and policy-makers mitigate, prepare for, or adapt to potential changes.
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In Anchorage, Alaska, the average temperature has increased 3.9 º F over the past century and precipitation has increased 10 percent in some areas of the state over the last 41 years, according to EPA. The reasons for such warming are not fully understood, but scientists suspect they stem from fundamental shifts in ocean currents. There is no proof that it is an early manifestation of manmade global warming - but neither is there any proof that it is not.
As manmade greenhouse warming progresses over the next century, Alaska's temperature could increase by 5 º F in the spring, summer, and fall and 10 º F in the winter, according to the Intergovernmental Panel on Climate Change (IPCC). Precipitation could increase slightly in the fall and winter and by 10 percent in the spring and summer. However, the increase in evaporation resulting from the increase in temperature will likely more than offset the increase in precipitation.
Small changes in temperature or precipitation that may have little effect in temperate regions can cause dramatic changes to permafrost regions, glaciers, or sea ice coverage. These changes could significantly impact the local economy, water resources, land resources, wildlife, and human health.
Some potential direct impacts of warming could in turn accelerate the warming trend. For example, the darker parts of the earth's surface absorb solar energy more quickly so they tend to warm more quickly than lighter parts, such as ice and snow cover, which reflect more of the sun's rays. As warmer temperatures begin to melt snow and ice, these lighter reflective surfaces would likely be replaced by the darker tundra and ocean, thus increasing the amount of sunlight absorbed by the Arctic and accelerating the warming trend. For this and other reasons, many computer climate models suggest that greenhouse warming will be greater over the Arctic than other parts of the planet.
A thawing of the permafrost could increase the load of silt in rivers making survival harder for some fish. Warming of lakes and rivers could also affect the coho, sockeye, and Chinook salmon populations. The potential loss of wetlands from sea level rise or increased erosion could decrease habitat and food supplies for some fish species.
One foundation of the Arctic marine food chain is the ice algae (phytoplankton) that cling to the bottom of sea ice all winter. When the ice breaks up, a belt of phytoplankton as wide as 50 miles reaches out from the ice edge. This ecosystem supports numerous crustaceans and other invertebrates, which are in turn consumed by Arctic cod and other fish. Warmer water temperatures could result in an increase in plankton. While some species may benefit from this increased food supply, they could be adversely affected by other climate-related changes. Many fish could be directly affected by changes in water temperature. Growth rates, sexual maturity, and distribution of some marine species are sensitive to water temperatures. Long-term temperature changes could lead to expansion or contraction of the range of some species. In addition, changes in circulation patterns could affect fish migration routes and geographic distribution.
Environmental response to the short-term warming brought on by El Niño in 1997/1998 gives some indication of sensitivities to changes in climate. The warming associated with El Niño brought a massive bloom of coccolithophores, a nontoxic, microscopic marine plant, to the Bering Sea, replacing the normal summer plankton community. Other observable changes included smaller than average fish, smaller salmon runs, and more Baleen whales on the continental shelf, all of which could harm the fishing industry.
Another factor to consider with a warming trend is that insects might migrate faster than forests, making headway into forests that had not been previously exposed to them and may be less resistant. The resulting increase in dead wood combined with a warmer temperature could make the forests more vulnerable to fires.
In a warmer climate, winter precipitation could increase in the northern latitude and Arctic regions. Even without an increase in precipitation, warmer temperatures could cause changes in the type of precipitation and timing of melting. It would likely mean more precipitation in the form of rain rather than snow, and earlier, more rapid snowmelts and ice breakups. This could increase water availability in the winter, when supplies are currently limited in some places. However, it could result in reduced flow later in the summer in some systems that depend on glacier or snowmelt.
A warmer climate could bring on an increase in rain-on-snow events or sudden winter thaws which could cause severe flooding which could increase stream bank erosion and the amount of sediment suspended in streams."
Scientists have already observed several trends consistent with observed increases in average temperatures-Northern Hemisphere snow cover and Arctic Sea ice are decreasing and alpine glaciers are continuing to melt.
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| Source: Source: U.S. Geological Survey, Programs in Alaska, http://h20usgs.gov/public/wid/html/ak.html |
As mentioned above, Alaskan forests have changed significantly in the past as a result major climate changes, such as warming that comes at the end of Ice Ages). Climate affects forest composition, geographic range, health, and productivity. Warmer temperatures allow trees to grow at higher altitudes, and the expansion of forests into higher elevations reduces the area covered by tundra.
Previous changes in climate have occurred when warming was slow, but man-made climate change is expected to happen much faster and may bring insects, disease, and wildfire that disrupt natural forest migration. Some species may be able to adapt more readily to rapid climate change, possibly affecting the composition of forest ecosystems.
Even with only small changes in sea level, waterfront areas could be flooded and shorelines and beaches eroded. Rising seas could inundate wetlands and other low-lying lands, increase flooding and susceptibility to storm surges, and increase the salinity of rivers, bays, and groundwater. Effects could be worse in areas currently protected from erosion by sea ice or areas where there is permafrost at the shoreline. According to EPA, Alaska's coastline is currently eroding at a rate of about 8 feet per year, and the rate could increase with a rising sea level rise. Severe coastal erosion in some areas has led officials to make plans to relocate some coastal villages at an estimated cost of $50 million per village.
A gradual thawing of the permafrost layer is already evident in many parts of the state and it is expected to continue. This thawing of the underlying layer can lead to sinking of the ground surface and increases in landslides and erosion. One of the direct and very costly impacts of the thawing is damage to roads and airport runways, which is very expensive to repair on the permafrost. Twenty-five percent of the paved roads in Alaska are on top of permafrost. As mentioned above, it could also damage the pipelines that are critical to Alaska's economy.
When faced with climate change, ecosystems and species can adapt, move, or disappear. Gradual changes allow time for adaptation or migration, but the rapid changes likely to result from human activity can greatly increase the chance of species disappearing.
With its wide range of ecosystems, Alaska is home to many species - some found only in the Arctic and many that are endangered. Its vast water ecosystems, its wetlands, and the tundra of the subarctic coastal plain provide summer homes for millions of migrant birds from six continents. Climate change is likely to affect Alaskan bird populations both directly and indirectly. The warmer temperature could cause them to nest earlier, which would make them older when it is time to migrate, improving their chance of survival. However, a changing climate might also affect their habitat or food supply. For example rising sea level and increased erosion could damage coastal wetland habitat.
Other types of wildlife could also be affected. A thawing of the permafrost and related landslides and erosion could disrupt the long overland migration routes of caribou and muskoxen. The retreat of sea ice would likely affect various Alaskan wildlife. Changes in the sea ice could hurt polar bears' ability to hunt for ringed seals, which they catch by waiting at holes in the pack ice or at the ice edge. Walruses use the ice to rest, molt, and bear their young. If the ice thins, it would be less able to support their weight (males up to two tons and females one ton), especially in masses. If the ice edge retreats to water deeper than the continental shelf, the walruses may not be able to dive deep enough to feed on mollusks and other invertebrates that live on the sea floor. Additionally, many species of seals depend on the sea ice for feeding, breeding, birthing, and nursing.
A changing climate could also lead to an increase in nonnative species which could adapt more easily to the new conditions.
Warmer temperatures would likely bring more and greater variety of insects and with them the potential for the spread of insect-borne diseases. For example, Lyme disease, transmitted by ticks, could travel further north. The problems could be heightened if the climate change also changes the population balance of predators such as owls, snakes, birds, and bats.
Additional responses could include:
| June 23, 2000 | | Disclaimer/Policy |
