A calving event at the Mendenhall Glacier on Wednesday revealed the bright blue of clean, ancient ice beneath.
Lead Naturalist Laurie Craig said Thursday that no employees of the visitor center witnessed the event. Despite this, she said, the scene is still amazing through the spotting scopes at the center and from the high-up perspectives offered by the East Glacier trail, for example.
“Close up the views are spectacular,” Craig said. “People will be able to see the breakup from the event and see the debris that has now frozen into place.”
As with all glaciers, Juneau’s own Mendenhall Glacier continues to move and change on a regular basis. Even in the winter, when Mendenhall Lake seems frozen and solid, a calving event at the glacier could turn the lake into what experts have described as a huge “slushy.”
Calving is when huge chunks of ice detach from the face of a glacier, often with little or no warning.
Despite the fact no one witnessed the event, which happened between 1 and 3 p.m. Wednesday, the University of Alaska Southeast cameras mounted at the visitor center recorded the entire scene. Craig said she has been in contact with Matt Heavner, who is able to access the UAS-managed cameras, and he is working to provide a video for the public.
“When you see the video, it shows how much the ice broke off the terminus, and you can see that some of it may be ‘shooters,’ which launch up from below the surface of the lake and then rupture the frozen surface,” Craig said.
What you don’t see is the lateral movement of ice chunks that can shoot out from the glacier’s face and move under the surface of the ice, like a rock skipping along the water. The sheer weight and force of the icebergs moving in this manner can weaken the ice in new and unexpected places, Craig said.
In the nine years Craig has worked at the glacier, she said she’s witnessed 22 calving events, and missed many more.
“Yes, they often seem to happen at night,” she said.
They also happen more often in the winter than one would expect.
The last witnessed calving event at the Mendenhall Glacier happened on Jan. 2, Craig said. Workers on the roof of the center heard a loud crack, and looked up to see huge bergs falling away from the face.
“So often when we do hear it, it’s already too late,” she said, “But they often come in multiples.”
Craig maintains that the ice is never safe at the Mendenhall Glacier, and as someone who has worked in the area for nearly a decade, she’s seen first-hand what can happen.
“It is never safe to be on the lake ice. I’ve seen it shattered to slush when a piece of glacier ice calved off the right side,” she said.
And despite her experience, Craig said she cannot predict the conditions that precipitate a calving event.
In December, a grandmother and her grandchild fell through the ice on Mendenhall Lake near the glacier’s terminus. Both were rescued and no injuries were reported. More recently, Scott Fischer, a volunteer groomer with the Juneau Nordic Club, found himself (and the snow machine he was using at the time) partially submerged after lake ice gave way. He managed to drag himself on his belly to safety, and the machine was recovered a day later.
It can’t be proven whether these events were tied to a calving of the glacier, but certainly big ice movements only weaken the lake’s surface in winter.
Craig said the visitor center will be open to the public from 10 a.m. to 4 p.m. Friday through Sunday.
• Contact Outdoors Editor Abby Lowell at firstname.lastname@example.org or 523-2271.