ALPENA — Scientists for the National Oceanic and Atmospheric Administration have been researching a sinkhole near Center Island in Thunder Bay for several years. They are now extending their study to one further out in the Thunder Bay Marine Sanctuary to learn more about groundwater’s impact on the lake.

The headquarters for the study is based in Alpena at the NOAA Heritage Center and spearheaded by NOAA’s Great Lakes Environmental Research Lab in Muskegon, with assistance from scientists based in Alpena.

NOAA researcher Steve Ruberg said remotely operated vehicles are being used to set up sensors at the bottom of a sinkhole outside of Thunder Bay — but still within the sanctuary — to collect data about how much groundwater flows from the floor of the sinkhole and into the Great Lakes. The data will help scientists determine to what degree the groundwater has contributed, and will contribute, to the rising water levels in Lake Huron.

“We want to better understand the contribution groundwater has to things like lake levels and the sensors will measure the variable flow that will show it going in and out of the sinkholes,” Ruberg said. “We will come back next year and retrieve the sensors next year, review the data and write a paper on what we learn from the tests.”

Ruberg said once the equipment is retrieved it will take until the fall of 2019 to review the data and the report will be released shortly after that.

Ruberg said the ROV places the sensors in strategic locations in the sinkhole and they also will measure currents and take samples of the lake floor that will be analyzed. He said the meters sit in about 276 feet of water and the bottom of the sinkhole is about 360 feet from the surface.

Ruberg said finding sinkholes is easy because the groundwater discharged through them is warmer than the water at the deep depths. He said the lake water at that depth is about 38 degrees, while the groundwater is roughly 45 degrees.

“We notice the warm water disappears and reappears, so we have sensors that will measure flow and the speed of the currents going by,” he said. “We want to see why that warm water disappears. Does a current sweep it away? And, if it does, how long does it take to reestablish again near the surface of the sinkhole?”

NOAA scientists and staff in Alpena have aided in the sinkhole project, Ruberg said, and have helped to make the project go smoothly and efficiently. He said that although they belong to different segments of NOAA, they are all working toward the same goal, which is to preserve, protect and learn more about the history of water resources.

“The important thing to remember is that we are all on the same team and there are benefits from us working together,” Ruberg said. “We share their lab and they have provided personnel for a lot of our work and it is just great to work with our fellow, NOAA partners.”

Steve Schulwitz can be reached via email at sschulwitz@thealpenanews.com or by phone at 358-5689. Follow Steve on Twitter ss_alpenanews.