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From a Minnesota webpage: (with pic.)
Link is long dead. No archived version found. MIA article seems to be quoted in full below.
Link is long dead. No archived version found. MIA article seems to be quoted in full below.
Mystery hole in North Long Lake: Thermal images, divers used to explore two acre spot of open water
By Peter Frank
[email protected]
Six people found themselves in ice cold water on the west bay of North Long Lake late last winter after chancing on a large area of open water. It killed one of them, Ronald Piekarski, on March 1.
As ice fishermen set up their houses and snowmobilers make trips across the lake this winter, that fatal spot of open water in the midst of an otherwise solid ice sheet is back. It has members of the Long Lake Association and the Thirty Lakes Watershed District worried and searching for an explanation.
The search hasn’t turned up any answers, said Allan Cibuzar, president of A.W. Research. His firm is working with the Thirty Lakes Watershed District to collect data on the nearly two acre gash in the ice sheet.
He showed results of a thermal imaging camera overflight flown on December 24 to Thirty Lakes Watershed District workers and members of the Long Lake Association December 26.
The hole, over 1,300 feet long and 500 feet wide, glowed white around the edges, showing the presence of warm water. Along the sides of the still intact ice sheet were signs of eddying currents further weakening the remaining ice.
“It’s growing,” said Cibuzar.
After the hole’s appearance last year, Cibuzar placed sensors on the lake bottom to record temperature and chemical levels in the water. The results of those tests didn’t show anything conclusive.
Those sensors and an underwater camera will be going back in the water this year, with the help of divers Todd and Bill Matthews from the Minnesota School of Diving. While they are on the bottom sometime this week, they plan to use dye to check for currents and take temperature readings. The divers will also give the whole area a thorough going over in an effort to find any clues to the open water on the bottom.
The two divers are just as puzzled by the open water as anyone else. Todd, who has been under water on that spot of North Long Lake already this winter, said he didn’t experience anything abnormal.
“It didn’t seem warm to me…usually I feel it on my face,” he said. At least one rumor that is being passed around claims that water temperatures in that area of the lake are around 60 degrees.
Todd also doubted a rumor that there was a trench on the bottom. In that area of the lake, he said, the bottom is silty and flat.
“I don’t know of any volcanos we’re sitting on,” said Bill, only half joking. “In 44 years of this [diving], I haven’t seen anything like this,” he added.
He had a hard time believing that the open water had a natural explanation. The water is about 16 feet deep in the area of the hole, and as part of a shallow bay, it should freeze quickly and remain frozen. Long Lake, which is 97 feet deep at its deepest point, is only 20 feet deep at its deepest points in the bay.
According to Bill, lakes begin to freeze after the temperature throughout the entire body of water reaches 39 degrees. Until that happens, the water simply turns over, with the water that is 39 degrees moving to the bottom of the lake and warmer water rising to the top. Once the water reaches a uniform 39 degree temperature, it can become successively cooler without turning over and eventually freeze.
Cibuzar didn’t rule out some type of natural volcanic activity. However, he noted that his sensors didn’t pick up any sulphates in the water. Somewhere, he said, there has to be a big chunk of energy, either in the form of heat, or water movement regularly coming into the lake at the area of the hole in the ice.
Tom Ebnet, manager of the Thirty Lakes Watershed District, said he was surprised that so far no one but the lake association and his organization has invested time in trying to understand what is going on.
“Nobody seems to care to check it out,” he said.
For the lake association, the main concern is safety, said Chuck Bartells, president. Ideally, there would be a fence around the hole or some other way to alert winter anglers and recreationists of the danger. However, he’s not sure who would install and maintain a fence.
“It freezes and thaws. It moves so much,” he said.
The Crow Wing County Sheriff’s department has the authority to mark hazards on water bodies; however, said Bartells, they have been reluctant to fence the opening. Signs have been installed, warning of thin ice at entrances to the lake, said Sergeant Neal Gaalswyk.
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