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In Arctic Alaska, the Warming Climate Threatens an Ancient Culture
Tundra lakes on the Seward Peninsula
What is causing such disruptive climate change? The question seems simple, but there are no easy explanations. The consensus view among scientists is that, globally, human activity—especially the emission of carbon dioxide and other greenhouses gasses into the atmosphere—plays a leading role.
The U.S. National Academy of Sciences, joined by academies in other countries, has concluded that most of the warming globally can be attributed to humans. AAAS President Holdren, director of the Woods Hole Research Center and the Teresa and John Heinz Professor of Environmental Policy at Harvard University, says human interference in the Earth's climate is "already dangerous and could become catastrophic."
But sorting out the causes of specific changes in Alaska's climate remains a challenge. A few researchers question whether humans play much of a role; others conclude that natural and human effects may combine in powerful but unpredictable ways.
"In Alaska and in high latitudes generally, you have a lot of large, natural variability from year to year and decade to decade," said Arctic climate expert James E. Overland, an oceanographer with the U.S. National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory. Based on climate models, "what we're seeing is a combination of natural variations that can occur, happening on top of this long-term trend" caused by the greenhouse effect.
Because the Arctic's climate is so extreme, all life exists in a precarious balance. A small rise in the average temperature can cascade into destructive changes throughout the environment.
Typically, for example, the Arctic in fall, winter, and spring is covered in snow and ice; that white blanket reflects sunlight and heat back into the atmosphere. But when the average temperature warms, that blanket arrives later and recedes earlier. Without their reflective covering, the dark-colored seas and soil absorb still more heat.
Another example: The permafrost that covers much of the Arctic holds dead and decaying plants in frozen suspension, but when it begins to thaw, decay releases methane into the atmosphere. That contributes to the greenhouse effect, causing further warming, further thawing.
According to Overland, because Alaska today is "at the warm end of natural variability," the pace of warming may slow in years ahead. Still, he said, the climate dynamics over the next 40 years are likely to bring unprecedented warmth. "We will be in a completely different environment by then, that none of the parts of the ecosystem have seen before," he said.
A similar view was offered by permafrost hydrologist Larry D. Hinzman, deputy director of the International Arctic Research Center at the University of Alaska. In a 2005 study published in the journal Climatic Change, Hinzman and his co-authors cited a range of studies showing that profound systemic changes already are underway.
The biggest problem, Hinzman said in an interview, is the thawing of permafrost—that leads to dramatic changes in the water-cycle, which in turn affects the soil that supports all tundra life. Warming temperatures may bring more rain and snow, researchers say, but the loss of water from the soil surface to infilitration, runoff and evaporation may, in years to come, make Alaskan ecosystems drier than they are today. In a study of 24 lakes on the Seward Peninsula, Hinzman found that 22 of them shrunk—by an average of 55%—between 1951 and 2000.
When ice thaws and the land grows drier, the impact can threaten every community of plants, birds and animals that live on the tundra.
The changing climate does benefit some species. As the Bering Sea warms, Overland said, whales and fish will benefit. Salmon already are being seen further north, as are some insects. The treeline is slowly advancing up into the tundra.
But many of the animals that have made their home in arctic Alaska for thousands of years are declining, researchers and local residents say.
On land, when the climate is warmer, repeated cycles of melting and freezing in the spring create a layer of ice in the snowpack. According to research cited in Hinzman's paper, caribou weakened at winter's end may have a hard time breaking through the ice to forage on buried plants.
As the sheet of Arctic sea ice diminishes and recedes north, walruses and their pups go north, too—but their prime foraging areas are further south. "So," said Overland, "people are seeing walrus pups abandoned really far north on ice floes because their parents have to go back south for their feeding range."
Polar bears similarly require a sea-ice habitat; that's where they find seals that are essential to their diet. But as the ice breaks up, seals are more scarce and the bears may have to swim great distances to find them. Some reports conclude that bear drownings are on the rise. Among those who survive, "we're already seeing...some polar bear populations where their weights are getting perilously close to the weight at which they stop breeding," said Lara Hansen, chief climate change scientist at the World Wildlife Fund.