The Hubbard Glacier near Yakutat has blocked the entrance to Russell Fiord with gravel, rock and other material, officials said Tuesday.
The advancing glacier gradually has been constricting the flow of water between Disenchantment Bay and Russell Fiord this summer, turning the 39-mile-long fjord into a lake. What was a gap of water between the glacier's edge and Gilbert Point, the nearest point of solid land, is now filled by the glacier's rocky moraine, U.S. Forest Service spokeswoman Faith Duncan said.
And what was a river flowing thorough the channel is now a series of water-filled pools, she said.
"The moraine has been expanding and moving in different directions," Duncan said. "It's apparent there's a lot of activity."
A U.S. Geological Survey gauge in Russell Lake shows its water level rising a little more than a half-foot a day. The latest reading shows the water level at 38 feet above mean sea level. Dennis Trabant, a U.S. Geological Survey glaciologist who is monitoring the Hubbard's movement, said the fjord has been a lake for several weeks.
"With the lake this morning a little over 38 feet above sea level, how can we claim it's not closed? It's pretty well closed," he said. "We don't like to overstate things ... but it's been essentially cut off from the ocean for a month and a half, two months."
The lake's rise is a cause for concern in Yakutat, which is about 35 miles away. Officials predict a rising Russell Lake eventually would spill over into the flat Situk River drainage to the south, which supports important subsistence, sport and commercial fisheries.
The lake could take 12 to 18 months to rise 131 feet and spill over, scientists predict.
The Hubbard Glacier blocked Russell Fiord for more than four months in 1986, until an ice dam broke in October of that year and sent a massive amount of water into Disenchantment Bay over 24 hours. The lake level rose 83 feet in 1986.
Trabant said it's impossible to predict whether the Situk River drainage would be flooded in the months ahead.
"It's something less than an even chance that it will even make that this time," he said. "The moraine that's the lowest piece of the dam is not a very stable chunk of stuff so it could let go willy-nilly any old time. In comparison, glacier ice is more stable, and that's not all that stable either."
Although the U.S. Forest Service hasn't closed the area around the Hubbard Glacier, it is urging people to be cautious and to avoid approaching the moraine, the channel or the waters around Gilbert Point.
"The area is very active and pretty hazardous," Duncan said. "To a naked eye viewing a picture it appears static, but by observing it day-to-day, you can see how the moraine has been expanding in multiple directions. ... It's hard to say what's going to happen next."
Officials also are monitoring marine life in Russell Lake. Harbor seals, porpoises and sea otters have been spotted in the lake in recent days.
Joanna Markell can be reached at firstname.lastname@example.org.