SeaWeb - Ocean Briefing Book

Climate Change in Alaska and the Western Arctic

The Problem

According to the Alaska Climate Research Center, mean annual average temperatures in Alaska increased by 2.57°F between 1971 and 2000. Regional and seasonal increases reached as much as 7.64°F in spring at Bethel on the Bering Sea coast, and 6.97°F during springtime at Barrow in Arctic Alaska. Similar temperature increases have been recorded elsewhere in the western Arctic, including Siberia and parts of Canada.
During the same period, sea ice extent diminished by approximately 5% in the Bering Sea region. Satellite monitoring has shown a similar rate of decrease in sea ice extent throughout the Arctic; the thickness of the remaining ice, as gauged by submarine sonar, declined on average by 43% from the late 1950s to the mid-1990s.
A 2001 report by the U.S. Arctic Research Commission noted that: “Reductions in sea ice cover will affect the productivity and probably the community structure of the marine flora and fauna of the Arctic seas reaching up to the highest trophic levels such as birds, seals, sea lions, walrus, whales and polar bears.”
Researchers have posited that reduced sea ice extent would likely result in declines in the algae which grow on the bottom of ice floes and provide the basis of marine ecosystems in the Arctic. They have further predicted that it would also lead to less shelter for such species as arctic cod; less resting area for seabirds; and reduced habitat for marine mammals such as seals, walruses, and polar bears.
One long-term study has recorded significant declines in black guillemot numbers in Arctic Alaska, concomitant with changes in sea ice cover and snowfall in the region. In western Hudson Bay in Canada, warmer temperatures in the 1990s led to earlier ice break up in the spring and later formation in the fall, to the detriment of the resident polar bear population; according to one researcher, for every week that the ice broke up earlier, bears came ashore 20 lbs lighter.
Alaska Natives say that thinner and less extensive sea ice has impacted subsistence hunting in the region, making it more difficult and dangerous for them to reach seals, walruses, or whales.
Near-shore sea ice cover protects coastal villages from storm surges and erosion; in recent years, increases in the frequency and severity of storms and in resulting erosion has forced villagers to abandon the Bering Sea settlement of Shishmaref, and other villages in the region are also expressing concern about rapidly-encroaching coastlines.

The Causes

A 2002 paper in the renowned journal Science concluded that the average Arctic surface air temperature in the 20th century “was exceptionally high compared with the previous 300 years,”and that this was likely the result of the effects of higher concentrations of so-called greenhouse gases—such as carbon dioxide, methane and nitrous oxide—in the atmosphere.
It is now widely accepted that atmospheric levels of carbon dioxide have increased by about 20% since the beginning of the Industrial Revolution; that this rate of increase is unprecedented in at least the last 20 000 years; and that overall levels are now higher than at any time in at least the last 420 000 years. The primary sources behind this increase are human-related: fossil fuel combustion—primarily oil, coal and gas; and deforestation.
Atmospheric methane concentration has increased by approximately 150% since the mid-1700s, largely due to livestock production and the decomposition of refuse in landfills. Nitrous oxide concentration has increased by 16% over the same time period, primarily from nitrogen fertilizer use, industrial activities, and livestock production.
Numerous studies have indicated that mean global surface air temperatures have increased by about 1oF over the last century; global climate models have long predicted that increases should be greater in the polar regions, resulting in declines in extent and thickness of sea ice, among other changes.
Many researchers caution, however, that it is difficult to separate anthropogenic causes from cyclical climatic variations. For example, follow-up studies suggest that the thickness of Arctic sea ice may be increasing again, apparently in line with variations in the Arctic Oscillation, although underlying trends still suggest, according to one researcher, a thinning by about “10% to 15%.”

The Context

Climate-related changes in Alaska have not been confined to marine and coastal regions. Average annual temperature at several locations in the interior of the state rose by as much as 3.75°F between 1971 and 2000. Among the changes that are occurring as a result, according to a 1998 study by the Center for Global Change and Arctic System Research at the University of Alaska Fairbanks: Accelerated permafrost thawing, causing major landscape changes and costly increases in road damage and maintenance; forest problems such as increased fire frequency and insect outbreaks; and an increase an human health problems, due to new diseases moving north.
Sea ice declines have also been reported from the Antarctic, with apparent consequences for some populations of penguins, pinnipeds, and perhaps whales. Rapid warming in the Antarctic Peninsula region is widely acknowledged to be the major cause of the total or near-total collapses of the Larsen A, Larsen B, and Wilkins Ice Shelves.