For the first time, Juneau’s famous Mendenhall Glacier is not touching Mendenhall Lake, which was hidden beneath a thick sheet of glacial ice only a couple of hundred years ago. Scientists say this means the glacier has entered a new phase of its retreat.
Jason Amundson, a glaciologist at the University of Alaska Southeast who’s been studying the Mendenhall Glacier for years, said the glacier is the symbol of Juneau.
“There’s several glaciers around, but when someone says ‘the glacier,’ they’re definitely talking about Mendenhall,” Amundson said.
The inside of Juneau’s City Hall features a panoramic image of the glacier. It’s the most striking part of the landscape that travelers see when they fly into Juneau International Airport. It’s the capital city’s top tourist attraction, with roughly 700,000 visitors each year.
For generations, the glacier fanned out across the lake that it carved out. But it’s been rapidly retreating out of the lake over the past two decades. Now, scientists say it’s separated from the water completely.
Amundson flew over the scene in a helicopter about two weeks ago.
“That was the first time I had really thought, ‘Oh, it doesn’t look like it’s touching the lake anymore,’” he said, adding that photos posted on Facebook by local photographers confirmed it.
But he said glacial ice and water will probably touch again for brief periods over the coming seasons. Rainfall and snowmelt could cause the lake level to rise enough to meet the ice. Also, the glacier still pushes toward the lake a fraction in the winter, when gravity pulls on the added mass of the snowpack.
Eran Hood, an environmental scientist at the University of Alaska Southeast, said that despite these expected seasonal meet-ups, the Mendenhall is “functionally” no longer a lake-terminating glacier.
“It’s clear there’s a lot of shallow sediments through there that it’s kind of sitting on, or even perched up above,” Hood said. “There’s just not much chance at this point that it would really have meaningful interactions with the lake anymore.”
Climate change has accelerated the glacier’s retreat. Between 1941 and 2020, the local mean temperature rose by 2.5 degrees Fahrenheit.
In recent years, Amundson said that glacial ice on the lake has quickly disappeared.
“There was pretty rapid retreat that occurred because there was this shallow, pretty thin area of the glacier that was in the lake and that broke apart— like where the ice caves used to be,” he said.
According to a previously unpublished report shared with KTOO and written by Hood, Amundson and their colleagues, the Mendenhall Glacier retreated fastest between 2007 and 2011 — losing roughly a football field per year — because icebergs were calving off at a high rate as the glacier’s terminus moved through the deepest part of Mendenhall Lake.
Amundson said that’s because of the way that ice interacts with water.
“When you have a glacier that’s in deep water, there’s a lot of pressure at the bottom, so the glacier tends to flow faster,” he said. “Then, if it’s flowing faster, it can break apart.”
Now that the ice isn’t touching the water, Amundson said the Mendenhall’s retreat could slow down. In the report, the researchers found parts of the glacier that terminated on rock retreated substantially slower than parts that terminated on the lake. Between 1998 and 2020, the ice attached to bedrock receded about 56 feet per year, while ice on the lake vanished at more than two-and-a-half times that speed, at roughly 148 feet per year.
“So once you get out of the lake, it’s harder for the glacier to retreat as quickly as it has over the last 5, 10, 15 years,” Amundson said.
But the glacier is still receding. Using ice-penetrating radar, the research team is currently trying to predict when it will pull into another lake of unknown size, shape and location that’s currently hidden beneath the ice. That could speed up the glacier’s retreat again.
Losing a scenic view
One day in the not-so-distant future, scientists say Juneau’s symbol will disappear from the vantage point of the U.S Forest Service visitor center, which was built to feature its scenic vista.
Hood said he thinks that will happen sometime around 2050.
Alix Pierce, the visitor industry director for the City and Borough of Juneau, said that losing sight of Juneau’s most accessible glacier could change how the city markets itself as a tourist destination. But she suspects many cruise ship passengers will probably still come to see the Mendenhall.
“We’re going to need to be creative about how it changes, what it looks like, how we adapt,” Pierce said.
A few years ago, the Forest Service looked at several different options for how to address that foreseeable future.
“Some of those options were things like boating people across the lake to a satellite visitor center where they’d be able to see the glacier for longer,” Pierce said. “Those things weren’t ultimately selected in their final plan.”
Hood said the visitor center at Portage Glacier in Chugach National Forest could be a cautionary tale. In the 1990s, hundreds of thousands of people traveled there. Since that glacier pulled out of view, visitation has plummeted.
Paul Robbins, a spokesperson for Tongass National Forest, did not comment on how the agency might try to maintain scenic access once the current view of the glacier is lost.
“Our current plans are focused on improving access and increasing visitor capacity, safety and enjoyment through the Mendenhall Glacier Visitor Facilities Improvement project,” Robbins wrote in an email to KTOO. “The project adds a Welcome Center, an outdoor plaza, enlargement of parking areas, additional restroom facilities, three new trailhead parking lots, and improvements to the existing facility.”
But Pierce said those improvements don’t address the decline of the glacier.
“Things like that, that are vital and necessary for managing the traffic flow that we have out there today, but aren’t necessarily looking into the future for how we adapt to climate-related changes to how people use the area,” she said.