There’s a lot going on beneath the surface, and researchers from the Great Lakes basin are out to solve mysteries of the deep in Lake Superior. Here are two exciting research headlines out of University of Minnesota-Duluth.
If at first you don’t succeed, try, try again. So goes research effort by Jay Austin, a professor from University of Minnesota-Duluth whose previous study to track Lake Superior’s currents and movements of ice sheets has been turned into something new. Austin and his fellow researchers attempted to track ice flow with sound, but ran into issues with data corruption due to Superior’s natural soundscape. Not to be deterred, they rejigged the experiment to address an entirely new focus – the lake’s soundscape in and of itself.
In conversation with Austin, CBC Thunder Bay reported that the researchers will use a hydrophone to record sound below the lake’s surface. Similar soundscape mapping has been done by oceanographers for decades, primarily for defence strategy and submarine warface. Austin told CBC that “no such threat [exists] in lakes, and so they’ve sort of gone unnoticed.”
As Austin and his fellow researchers have embarked on their fieldwork, they’ve detected sounds of wind, noise from passing lakers and salties, and – the most surprising – clicking sounds. Referencing existing research, Austin suggests to CBC that the mysterious clicks could be from burbot, a type of large freshwater cod. Austin’s hope is to work with biologist to decipher what the clicks might represent – whether they’re merely a function of the fish’s movement, or if they represent a form of communication. While Austin expressed skepticism that the clicks were communication, he mentioned that the researchers found the burbot appeared to stop making the sounds when ships passed nearby.
In addition to understanding more about the unique noises weaving their way through Superior’s soundscape, Austin believes the research could have positive benefits for those looking to efficiently take stock of fish populations, overcoming seasonal obstacles to tracking wind speed, and even use for experimental musicians who want to use Lake Superior sounds for their songs.
A recent article from Wisconsin Public Radio reports that research has begun on a National Science Foundation-funded initiative which will study internal waves in Lake Superior. The goal of the research is to gain an understanding of how these underwater waves affect lake temperatures. The National Science Foundation has granted roughly $1 million USD to support the project, which will focus on “[predicting] the strength of the waves, when they’re generated, how they spread, and when they break.”
In conversation with WPR, principal investigator Sam Kelly explained that temperature is integral to the formation of internal waves, which occur when warmer surface water and colder deep water meet and mix. Kelly is an assistant professor with the Large Lakes Observatory at the University of Minnesota-Duluth. Jay Austin, who is studying the underwater soundscape of Superior, is also affiliated with the Large Lakes Observatory, and acts as co-principal investigator in this project.
So far, researchers have installed 10 moorings in the western arm of Lake Superior between Grand Marais, MN, and Ontonagon, MI, to establish data on temperature and currents. This data will be used to inform preliminary findings by next year. Kelly identifies the following research benefits: to help predict how surface water temperatures may change during storm events, and potentially to help predict currents.
Kelly explains the mechanics of internal waves to WPR:
“These waves are generated when the wind blows over the lake and sort of pushes the surface water up against the coast, and that sort of pushes this interface up or down depending on the direction of the wind,” he said.
“The bottom of the lake is always 4 degrees Celsius, so the temperature at the surface that we measure really depends on how much mixing goes on between the surface and the bottom of the lake,” he said. “So you could have a very warm, very thin surface layer, or if you had a bunch of wind and it mixed up the colder, deeper water, you could have a relatively deep surface layer that’s much cooler.”
The research commenced in September 2016, and is expected to culminate in August 2020. To date, $626, 197.00 has been awarded to the project. The abstract, and updates for funding and completion dates, can be founded here.