YAKUTAT, Alaska -- Hubbard Glacier, one of the world's largest, is threatening the economic life of this tiny, predominantly Tlingit fishing village on the southeast Alaskan coast.
Within days, the advancing glacier could block the outlet of Russell Fjord, a 30-mile-long habitat of porpoises, seals and salmon at the end of the Situk River.
The glacier has done this before, most recently in 1986, with an ice dam that turned the fjord into a new lake, Russell Lake, swollen with freshwater runoff. It endangered trapped wildlife for months as the level of salt in the water fell, but after several months the ice dam gave way and the glacier retreated.
The fear being voiced now was also voiced then: that if the ice blockage is severe and protracted, the lake may swell and spill its banks, flooding the Situk River and smaller streams east of Yakutat that are vital to the area's commercial and sport fishing industries.
"That would devastate the town," said Mayor Thomas Maloney, a former commercial fisherman.
Yakutat's lodges and bed-and-breakfasts cater to fishermen from around the world, and to tourists who hire local pilots to fly over the area's spectacular glaciers. But Mr. Maloney says he is more concerned about the already financially hard-hit commercial fishing boats that catch salmon in the milewide estuary at the end of the river. "If we lose the commercial fishermen," he said, "we lose the town."
Despite occasional retreats, the Hubbard Glacier has been advancing since the 1890's. Its most recent ice dam across the fjord was formed in May 1986, when the water rose a foot a day and in a matter of months produced a 100-square-mile lake.
An effort was undertaken to save the stranded animals, and various plans were proposed to blow open the passage. While volunteers tried to catch seals to carry them to safety, many skittered across the ice dam on their own. But the ice dam was structurally weak. By October, that corner of the glacier had been breached by the rising waters of the fjord, and the remaining seals and porpoises returned to the open waters of Yakutat Bay.
"This is the closest it's come since the 1986 damming," said Dennis Trabant, a glaciologist with the United States Geological Survey, who has studied the Hubbard Glacier since its previous closing. Glaciologists who flew over the site late Thursday estimated the gap at 100 feet.
In addition, this time the wall of ice poised to crunch into the far side of the fjord is wider and more likely to last. That has people worried.
"We've suffered over 9/11 like everyone else, with visitor cancellations," said Loretta Eades, the general manager of Leonard's Landing Lodge. "I just hope that this doesn't add to it."
As it happens, Yakutat is able to receive first-rate advice, and some consolation, from the world's leading experts on glaciers. The International Glaciological Society met here last week, and its scientists are of two minds about the Hubbard's assault. Though they did not wish their hosts ill, they were energized by this example of the forces they study.
"What's truly amazing is that it is happening now, while we're all here," said Ted Scambos, a glaciologist at the National Snow and Ice Data Center in Boulder, Colo. "It's like Disney World for glaciologists."
The scientists may also have good long-term news. "Initially, the fisheries in the rivers that are going to be flooded will be damaged severely," Mr. Scambos said. "But as the years go by, they'll probably come back better than ever, because Russell Lake will be a huge potential spawning area for the salmon."
It is even possible that the glacier will retreat at the last moment.
The advance of Hubbard Glacier seems to run counter to what many glaciologists see as one likely effect of global climate change: a great loss of ice by most of Alaska's glaciers. But the Hubbard, being a tidewater glacier, operates differently than valley glaciers, which do not empty into bodies of water.
At the glaciology symposium, research was presented by the Geophysical Institute at the University of Alaska, Fairbanks, showing that over the last five years, Alaskan glaciers -- even factoring in those like Hubbard that are growing -- have been melting and adding almost twice as much water to the world's oceans as the entire Greenland ice cap.
The melting is most pronounced in the region that includes Yakutat.