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YAKUTAT - The Hubbard Glacier is a massive, jagged sheet of ice that stretches 76 miles from Canada into Disenchantment Bay near Yakutat. It is North America's largest calving glacier, and its movement is part of a centuries-old geologic drama.
These days, a 165-foot gap between the tidewater glacier and the landform of Gilbert Point is attracting attention. If the Hubbard closes the gap, it would turn the 30-mile-long RusseIl Fiord (as fjord is spelled in its name) into a lake and possibly affect local fisheries and Yakutat, a community of 800 people 225 miles northwest of Juneau.
Officials haven't noticed much change in the opening during the past week, although the tidal flow between the bay and Russell Fiord is noticeably constricted, according to Tricia O'Connor, Yakutat District Ranger for the U.S. Forest Service. The agency has been monitoring the glacier's movement over the past several weeks from the air.
"This is a natural event. It's Mother Nature and we need to let it run its course and see what happens," she said Thursday.
Experts are not speculating on when the Hubbard might close off the fjord, but they expect it will someday. If a closure occurs, the ice dam could later break, as happened in summer and fall of 1986. Or the lake level could slowly rise and possibly spill into the Situk River, which supports valuable sport, commercial and subsistence fisheries.
Researchers studying the impact of cruise ships on the area's seal populations first noticed how close the glacier's face was to Gilbert Point in late May. Glaciologists visiting Yakutat for the International Symposium of Fast Glacier Flow in mid-June helped generate more interest, according to Wrangell-St. Elias National Park Ranger Jacqueline Lott.
"Every spring, the glacier does come fairly far forward," she said. "Through the summer and fall it starts to calve back to its, quote, normal spot. The last couple of springs, it's gotten closer and closer and last spring it got a little closer."
Records show the Hubbard Glacier has been advancing since the mid-1890s. Since 1986, the glacier has been moving at an average rate of 105 feet a year at the calving terminus into Disenchantment Bay, with tidal currents keeping a channel open toward the fjord.
Meanwhile, the glacier's average rate of advance in the narrow channel at Gilbert Point has been about 20 feet a year from 1987 to 2001, according to Dennis Trabant, a glaciologist with the U.S. Geological Survey in Fairbanks who has studied the Hubbard.
Officials have more information now about the impacts of a closure than in 1986, but unanswered questions remain.
Forest Service and National Park Service officials have been flying over the area to check on the glacier's progress, and the U.S. Geological Survey is putting in a gauge to monitor the fjord's water level. The Forest Service hopes to update maps to improve predictions of when a dammed-up lake would spill over, and will collect more fisheries data this summer, O'Connor said.
"It will close at some point in the near future, so the more prepared we are, the better," she said.
The fjord is fed, in part, by streams and rivers flowing from the mountains above. Glacial sediment from those streams, normally washed out by the tide, was collecting inside the fjord this week, O'Connor said.
During the 1986 closure, Russell Lake rose 84 feet. To flow over, the lake would need to rise about 130 feet above sea level. Studies indicate the volume of water flowing through old Situk channel could increase by 10-fold if the lake spills over, O'Connor said.
For a community that depends on the Situk's steelhead, Dolly Varden and five species of salmon to make a living, a spillover would be bad in the short term, according to Bob Johnson, the state's sport fish management biologist for the area. But in the long term, things could change for the better.
"We will end up with a lot more flow," he said. "It could lead to new spawning opportunities and will increase the habitat available for spawning and rearing fish, although it will take life cycles to establish. ... In a decade or so when it settles down, we could be looking at something altogether different."
Not everything may be affected. Productive tributaries such as the Situk's West Fork won't see an impact, studies predict. What exactly would happen depends on the time of year a spill-over occurs, Johnson said.
The Yakutat Tlingit Tribe has been involved in a multi-agency management plan for the Situk and is doing its own fisheries studies in Dry Bay, to the south of Yakutat, to see why sockeye runs have declined in the East Alsek River. Such research might be one way to counter the Hubbard's impacts, tribal president Bert Adams, Sr. said.
"People may have to look for other areas for subsistence fishing," he said.
A flight over the Russell Fiord on Thursday didn't show signs of marine life, although harbor seals, sea otters and porpoises are known to frequent the area. Their plight in 1986 drew international attention and rescue attempts by conservation groups, but many of the animals were able to cross the glacier's moraine, or gravelly endpoint, on their own.
In the past, the Forest Service and the U.S. Army Corps of Engineers have looked into the feasibility of breaking open the ice dam, but found it would be expensive and dangerous, O'Connor said. It's not something people have discussed this time around, she said.
On the less drastic side of things, a newly-formed Russell Lake could modify wildlife habitat, which might lead to changes in hunting regulations and permits for guides and outfitters, she added.
Lott emphasizes that a closure wouldn't bring immediate, catastrophic damage. Glaciologists predict it would take year to a year and a half for Russell Lake to spill into the Situk River, if an ice dam holds.
"We might have a closure and it might hold or it might not," Lott said. "We might not have a closure at all."