The advancing Hubbard Glacier near Yakutat is precariously close to blocking Russell Fjord, according to scientists who have been monitoring the area in recent days.
The news is of significant interest to residents of Yakutat, fishermen and the scientific community. If the fjord is indeed blocked and turns into a lake, rising water could flow into the valuable Situk River system, east of Yakutat. The river supports active subsistence, commercial and sport fisheries.
"If that were to happen, it would have pretty significant consequences to our community," said Yakutat District Ranger Tricia O'Connor of the U.S. Forest Service.
As of Sunday, the tidewater glacier was about 165 feet away from blocking the entrance of the fjord with an ice dam, according to Dennis Trabant, a glaciologist and hydrologist with the U.S. Geological Survey. It is impossible to predict when the glacier might close off the fjord, he said.
"Anyone who does is really going out on a limb," he said. "It's a pretty aggressively eroding system. As long as it can stay ahead of the glacier pushing the moraine up, it will stay open. And that's not a very predictable situation, frankly."
The Hubbard Glacier blocked Russell Fjord for five months in mid-1986 until the ice dam broke.
An ice dam could trap marine mammals such as harbor seals, sea otters and possibly porpoises in the fjord, said Jacqueline Lott, a park ranger in Yakutat with the Wrangell-Saint Elias National Park and Preserve. In 1986, seals were able to reach Disenchantment Bay, which the fjord feeds into, on their own, she said.
"It's really just a waiting game. We're not sure what the glacier is going to do," Lott said. "Until we have a closure, we're not going to start looking at ways to mitigate things that haven't happened yet."
Hubbard Glacier is moving forward an average of about 35 feet a day. The glacier normally is most advanced in late May and Juneau, so scientists anticipate it may begin to retreat as much as 330 feet through the summer and fall, Trabant said.
"However, this is this year," he said. "And it may not behave in the average way this particular year."
An ice dam formed by the glacier would need to be in place for a year to a year and a half before the water level is high enough to flow over natural barriers into the Situk River system, Trabant said.
"If the damming occurs late in the melt season, the stress doesn't build and it has all winter to reinforce with the flow," he said. "A lot has to do with the timing the damming actually occurs and whether there's a lot of moraine activity."
The National Park Service and the Forest Service are monitoring the glacier's movements by plane and the U.S. Geological Survey plans to set up a water level gauge in Russell Fjord. More than 100 scientists fortuitously were meeting in Yakutat last week for the International Symposium on Fast Glacier Flow and many got a look at the Hubbard Glacier.
Roman Motyka of Juneau, a research associate with the University of Alaska Fairbanks Geophysical Institute, said the event isn't unusual for the Hubbard.
"The Hubbard has been slowly advancing for many years," he said. "In the long run, it's inevitable that it will shut off Russell Fjord."
Joanna Markell can be reached at email@example.com.