Robot divers to report on Lake Superior's depths

Dan Whiteman
Dan Whiteman, an engineering technician with Wet Labs, installs various components into one of the Autonomous Moored Profiler, which is a device that will record various measurements at differing depths in Lake Superior. The device will allow scientists to track trends in Lake Superior and take measurements during the winter when conditions were either unsafe or unfavorable for traditional methods.
Derek Montgomery for MPR

With its frigid, often ice-choked water and legendary storms, Lake Superior can be a dangerous place for scientists to conduct research.

"In Lake Superior, the season where it's nice to go out there is relatively short," University of Minnesota Duluth physics professor Jay Austin said. But he said "there's science year round out there."

Aiming to tap the wealth of information deep inside Lake Superior, Austin and other researchers are preparing to send two mechanical divers in the big, cold lake for a long time. They plan to test one of the divers Wednesday.

Funded by a $485,000 National Science Foundation grant, the new devices, called "Autonomous Moored Platforms," will travel up and down the depths on cables anchored to the lake bottom. They'll collect readings on water temperature, currents and a long list of other data points.

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In the long run they could actually save researchers money. A single day on a research vessel costs roughly $7,000.

Austin, lead investigator on the new project at the school's Large Lakes Observatory said the technology will offer a view of Lake Superior science has never had before.

"We're very interested in being able to have something where it's collecting a wide variety of data over the course of the year," he said.

"Typically, people have just assumed during the winter, it's cold and nasty and dark and nothing happens. That may not be the case. We don't know what we don't know."

That's where the platforms come in. The devices are big cylindrical tubes, about seven feet tall and contain instruments that measure nitrates, light intensity, dissolved oxygen, and a slew of other properties.

The cylinders, called profilers, are made by WET Labs of Philomath, Ore. They sit on a platform moored to the bottom of the lake.

At the click of a mouse button, they'll travel up a cable towards the lake's surface, taking measurements along the way. When they pop to the surface they'll transmit the data back to the lab.

Austin said the profilers will help eliminate a phenomenon known as "fair weather bias," because they can operate below the water in any season.

"What this is doing is it's giving us a really continuous presence in the lake," he said.

By using the profilers, researchers will be able to gather data under the ice in the depth of winter for the first time, said Erik Brown, acting-director of the Large Lakes Observatory at UMD.

"Making under-ice measurements is complicated and dangerous, and it's just never been done," Brown said. "Typically, people have just assumed during the winter, it's cold and nasty and dark and nothing happens. That may not be the case. We don't know what we don't know."

Brown said the devices also will help monitor the effects of a changing climate. He cites the recent record flooding that dumped tons of sediment into Lake Superior and raised the water level by several inches.

"When we were writing the proposal, if we would have said, 'we're going to look at big flood events,' people would have said you're crazy," he said. "But it turns out this instrumentation is really well-suited for looking at the effects of events like the Duluth flooding."

Biologist Liz Minor, another researcher on the project, said the system will also provide a much clearer view of long-term trends.

"With sensors moving up and down in the water at programmed times, we can get a nice long continuous record of what's going on, which to us is very exciting," she said.

For the past several years the Large Lakes Observatory has been tracking unprecedented changes in Lake Superior.

Total ice cover on the lake has shrunk. Water temperatures are the highest they've been in a century. But Austin stresses that the profilers aren't meant to measure the influence of climate change on Lake Superior.

"We purchased them because there are a lot of basic things about the ecosystem of the lake that were trying to understand, and we're trying to establish a more robust presence in the lake," he said.

Austin said the primary goal is to know more about the lake and its processes. But he said eventually that could inform practical applications such as expanding the Lake Superior fishery.