ANCHORAGE — Alaska has been referred to as ground zero for climate change because of its proximity to a vulnerable polar region where effects are accelerated. A report by the National Climate Assessment lists concerns because of disappearing sea ice, glacier melt, permafrost thawing, changes in ocean temperature and chemistry, and strong effects on Alaska Native communities:
• Alaska has warmed more than twice as fast as the rest of the United States, with a statewide average annual air temperature increasing by 3 degrees and average winter temperature by 6 degrees. Average annual temperatures are projected to rise 2 to 4 degrees more by 2050. If global emissions continue to increase, temperatures this century are projected to increase by 10 to 12 degrees in the north, 8 to 10 degrees in interior Alaska and 6 to 8 degrees elsewhere.
• Arctic sea ice has declined, with only about half as much present in late summer as was recorded when satellite records began in 1979. Less ice means dark water absorbs more heat, leading to more warming. An open Arctic Ocean makes the region more accessible for marine traffic and oil drilling but increases risks of spills and eliminates habitat for polar bears, walrus and ice-dependent seals. Without protective ice edge along shorelines, coastal communities are vulnerable to erosion from fierce ocean storms.
• Rapid ice loss from Alaska and British Columbia glaciers, perhaps 20 to 30 percent of what is melting from the Greenland Ice Sheet, contributes to increased ocean levels. Glacier water pouring into the ocean is an important source of organic carbon and other minerals that contribute to high coastal productivity and changes could alter Alaska’s rich fisheries.
• Eighty percent of Alaska is underlain by permafrost, or frozen ground, which can sink if thawed. Sinking ground is projected to add $3.6 billion to $6.1 billion to costs of maintaining public buildings, pipelines, roads, and airports over the next 20 years. Permafrost thaw in rural Alaska will disrupt water supplies and sewage systems. Lakes in the southern two-thirds of Alaska have shrunk in the last 50 years because of permafrost thaw and evaporation from higher temperatures. Wetlands drying and warmer summers have led to more large fires in the last 10 years than in any decade since record-keeping began in the 1940s. Alaska provides breeding habitat for millions or migratory birds and continued drying of Alaska wetlands could affect waterfowl management nationally. Thawing of permafrost increases the release of carbon dioxide and methane through increased decomposition, adding to the warming problem.
• Ocean waters have become 30 percent more acidic through absorption of carbon dioxide and acidity could reduce the capacity of key plankton and shelled marine animals to form and maintain shells, altering the ocean food chain. Rising ocean temperatures and declining sea ice will affect the range and abundance of fish, including commercially important species such as pollock.
• Thinning ice, melting permafrost, shifts in species range and coastal erosion already affects Alaska’s northern indigenous people who depend on subsistence resources for survival and maintaining their culture.