Just when you thought it was over, the jökulhlaup appears to have struck again.
Weather-watchers believe a second release of water from Suicide Basin above the Mendenhall Glacier has caused Mendenhall Lake and River to rise once again.
At press time Tuesday, the lake was just a tad above moderate flood stage, which is 10 feet, and still rising, said Meteorologist Edward Liske of the National Weather Service’s Juneau Forecast Office. Liske told the Empire the lake was expected to crest at about 11.6 feet by either late Tuesday or early today.
“Basically, after the first release earlier this year, pretty much the hole that (the water) went out of sealed up again ... and it basically just broke through again,” he said Tuesday.
The rising water levels prompted the National Weather Service to issue a flood warning for Juneau at 12:42 p.m. Tuesday afternoon. The warning is in effect until noon today.
The city, meanwhile, began alerting residents in the Mendenhall Valley to possible flooding, including areas along the lake and river corridor known to be affected by jökulhlaup flooding. The street department is on standby to close streets if they become flooded.
“We’ve dealt with flood levels at this level before, so we know what to do,” City and Borough of Juneau Emergency Programs Manager Tom Mattice said in a phone interview, noting that officials dealt with flooding last month when water erupted from the caves beneath the Mendenhall Glacier. “Obviously, we’re starting to look at View Drive again. Skater’s Cabin Road with the Forest Service just closed down. The biggest question is when is this going to peak, and/or what level.”
Earlier this summer, the water in Suicide Basin above Mendenhall Lake began rising about two feet per day until it burst through a glacial dam and dumped what is likely billions of gallons of water into the lake, which flowed into the river. It’s a natural phenomenon, known by the Icelandic term jökulhlaup, that has occurred every year since 2011.
The outburst on July 11 caused Mendenhall Lake to swell to record levels — 11.81 feet, topping the Sept. 11, 1995 record of 11.2 feet. The Mendenhall River reached 13.52 feet at the Mendenhall Loop Bridge, just shy of the 13.8-foot mark also recorded Sept. 11, 1995.
Liske said this isn’t the first time there has been a sequel to a jökulhlaup. After the 2011 release, there was a second about a month and a half later. That also occurred with a heavy rain event.
Liske believes Tuesday morning’s rain exacerbated the outburst, although there was only a quarter of an inch of rainfall at the airport and 0.44 inches at the forecast office on Back Loop Road.
It’s been raining steadily in Juneau for the past week, and there was a record 24-hour rainfall on Sunday. A recorded 1.53 inches of rain fell at the airport Sunday, beating the old 1944 record of 1.04.
It wasn’t immediately known how much water was in the basin when it released this time. It released last month when the basin water level rose to 88.67 feet.
The water levels were likely much lower than that because the water didn’t even reach the height of the sensor, which officials keep in the basin to monitor water levels. Rather than being alerted to the jökulhlaup by the sensor, weather-watchers were alerted by the rising level of the lake. They had been monitoring it because of all of the rain Juneau has experienced lately.
“We tried to determine what the cause was, considering it was still rising,” Liske explained. “So one of our people did call the Glacier Visitor Center to see if there was anything they could see from the glacier’s face, and they said they saw some ripples and white caps on the right side of the glacier, so it might be something coming out of there.”
The Mendenhall Glacier Visitor Center could not immediately be reached for comment, nor could the U.S. Forest Service. Reports indicated Skater’s Cabin was submerged in water by 1 p.m. Tuesday, as were some campsites at the Mendenhall Campgrounds.
• Contact reporter Emily Russo Miller at 523-2263 or at email@example.com.