Alaska's Popular Portage Glacier Retreats, Entering New Era -- Withdrawal From Lake Earlier Than Expected

PORTAGE, Alaska - Portage Glacier, Alaska's most visited tourist attraction, has retreated past the lake in front of it about a quarter-century earlier than scientists had expected.

It marks a new era for the glacier and probably will mean fewer deep-blue chunks of ice in front of the Begich Boggs Visitors Center, said Kristine Crossen, a University of Alaska-Anchorage geologist.

After a careful survey in the early 1970s, the U.S. Geological Survey estimated that the retreating glacier would remain in Portage Lake at least until 2020.

But the glacier, about 40 miles southeast of Anchorage, this month began climbing out of the water 26 years early. As office-building-size chunks of ice from the glacier crashed into Portage Lake recently, an expanse of black bedrock was revealed. The dark cliff is the lake's long-lost eastern shoreline, buried under ice for hundreds, maybe thousands, of years.

Crossen, who has studied the glacier for more than 10 years, says the glacier will do one of three things in the next few years:

-- Retreat farther and faster up into Portage Valley. The glacier would become landlocked - lifted up and back from the water - producing no icebergs and retreating up into the unnamed ice field that feeds it.

-- Stop its retreat and remain at the edge of the shoreline, advancing enough to continue some calving into the lake. Crossen said this is the most likely possibility.

-- Reverse its 300-year retreat back from Turnagain Arm. This is the least likely possibility, Crossen said. The newly exposed shoreline would provide new material for the glacier to grind up, allowing a shelf for the ice to push out onto. It would take decades or centuries for the glacier to again reach Portage Lake's western shore, where the glacier's face began pulling back to reveal the lake in 1914.

But if Portage is about to enter a less active phase, it's at least going out with a bang.

"I've never seen so much ice," said John Toomer, the visitors center's director, who has worked at the shoreside facility since it opened in 1986. "The ice is right up against the building and blocking the view of the glacier at times."

Last weekend, as the 200-passenger tour ship Ptarmigan circled in a downpour a few hundred yards in front of the glacier's face, Crossen cheered as walls of ice capable of flattening two fast-food outlets crashed into the lake's silty water. Two waterfalls, previously hidden under ice, gushed down the newly exposed bedrock face.

Janis Hammock, a deckhand on the Ptarmigan for the last three years, also cheered. She said the crew had noticed more calving than usual this summer and a rapid retreat in July.

"We recorded a 748-foot retreat from July 1 to August 1 of this year alone," Hammock said.

Faster-than-expected calving throughout the 1980s resulted in the shoreline prediction being off by 26 years, Crossen said.

Warm weather in the last two years was a contributing factor in the retreat, but the lake's depth - more than 600 feet in some areas - was the biggest reason for the massive calving, Crossen said. Deep water means no shelf to support the ice, allowing it to break off into the lake.

Both Toomer, from the U.S. Forest Service visitors center, and Hammock, from Holland America Line, which operates the Ptarmigan, think business will still be good even if the glacier retreats out of the lake.