The Future of Lake Superior with Climate Disruption

Lake Superior is not just warming; it’s warming faster than its surroundings.

Jay Austin and a colleague published a study on Lake Superior warming about 15 years ago. Austin is a faculty member at the Large Lakes Observatory at the University of Minnesota, Duluth.

“We looked at summer surface water temperature increasing –and at the time it was only 25 years, but the message remains today with an extra 15 years of data- was faster than the change in air temperature,” he said.

Climate change is affecting Lake Superior in some volatile ways. Its surface temperature has been going up, but in wild fluctuations. The average wind speeds have been increasing five percent each decade since 1980.

And Superior has been pounded by three five hundred-year to one thousand-year storm events in the past eight years. (See here and here.)

“If it’s not climate change, what is it?” asks Peter Annin. He extensively documented the effects of climate change in his recently revised book Great Lakes Water Wars.

“I mean, that we have the largest lake in the world by surface area is not just seeing one extreme event, it’s seeing a series of scientifically documented extreme events that are creating a pattern that is changing the relationship that human beings are having with the Great Lakes that they love,” he said.

Waves of Lake Superior crashing against the rocks at higher levels than ever seen in recorded history. Photo LESTER GRAHAM / MICHIGAN RADIO

The ups and downs of the Great Lakes

The effects people are talking about now are the historically high lake levels of the Great Lakes. But, it wasn’t that long ago people were concerned about historically low water levels. The two most significant things that affect the water levels of the lakes are precipitation and evaporation.

“In 1998, Lake Superior’s temperature went up about two degrees Celsius (3.6 Fahrenheit) and it stayed there,” said Drew Gronewold, hydrologist at the University of Michigan’s School of Environment and Sustainability.

It stayed warm for more than 15 years. Gronewold said typically there’s more of a balance between precipitation and evaporation, but during that period evaporation was well above average and it dominated the hydrologic cycle of the Great Lakes, keeping water levels low.

Then the rains came. Gronewold says changes in how moisture is carried from the oceans and dumped into the Great Lakes region are also consistent with climate change. Add to that some cold weather, and things changed dramatically.

“In 2014, there was what we call in the media, the polar vortex, and lake temperatures went down by an order of one or two degrees Celsius and all of a sudden evaporation rates were low. So those changes in temperatures that you’re talking about, they are of a big magnitude and they have a huge impact on the hydrology and the physics of the lakes,” Gronewold explained.

And because Lake Superior is so big, it has a kind of a temperature memory. A super-cold winter means there will be a cool summer because a lot of heat energy has left the lake and it doesn’t come back immediately. So, there’s less evaporation over the summer.

Sand ripples in Lake Superior © Circle of Blue

You might be thinking ‘That’s not warming; that’s cooling’

The planet is warming. The regional effects caused by global warming fluctuate dramatically, but the trend does point to warming over decades.

Gronewold says weather in the Great Lakes region can vary dramatically by something as simple as the jet stream moving north or south by 100 miles and taking warmer or colder air with it. So, regional weather will be sporadic, but over the decades the mean temperature of the area is still trending higher.

It’s normal for the Great Lakes water levels to rise and fall over the years. They have throughout recorded history. However, things are changing.

“What’s different now is that we’re seeing an increase in extremes, an increase in higher highs, lower lows, the speed with which we’re rising, the speed with which we’re falling, we’re breaking records all over the place,” said author Peter Annin.

Lake Superior on a winter day. Photo © LESTER GRAHAM / MICHIGAN RADIO

Shorter hockey seasons and more invasive species

With the changes, there will eventually be less ice cover on Lake Superior. Human activities and some traditions will be disrupted.

“Maybe what used to happen in March might now be happening in February or January,” said Frank Seglenieks, Water Resources Engineer with Environment and Climate Change Canada.

“You can have ice hockey tournaments that are designed to be in mid-February at, let’s say, Thunder Bay, Ontario, where they’re going to use the ice surface because traditionally that ice has been frozen and you can have your hockey tournament. Maybe now, you can’t have that tradition because the water temperature is just too high,” he said, adding that less ice and thinner ice might happen every five years or so at first, but it could be every other year in the not too distant future.

Other activities such as ice fishing and snowmobiling also might not be possible as regularly on Lake Superior. These are part of the culture of the people who live near Lake Superior.

Besides higher lake levels and not as much ice on the Great Lakes, warming causes some other problems.

Researchers around the world measured the warming of more than 240 big lakes. Almost all of them are getting warmer, and Lake Superior is warming more quickly than many of those lakes.

“Temperature ends up being this giant control knob on ecosystems,” said Jay Austin at the University of Minnesota, Duluth.

He says temperature affects nutrient uptake rates in the regions where fish are comfortable spawning. That kind of warming also could make Superior more hospitable to invasive species.

“One of the things that has kept Lake Superior relative to the other Great Lakes less susceptible to invasive species is the fact that it is so cold. And so I think that the impacts on the ecosystem are what we really worry about,” Austin said, adding when the environment is changing in volatile ways, that’s going to be good for some species and bad for others. Some invasive species might thrive in a warmer Lake Superior.

In the Upper Great Lakes, invasive zebra mussels and quagga mussels brought in by shipping from the Caspian and Black seas have covered the bottoms of Lakes Huron and Michigan by the trillions. They filter out a lot of the nutrients from the base of the food web. That has meant some fish in Lakes Huron, Michigan, and fish the shallower, warmer parts of Superior where the mussels have invaded have suffered. For a couple of decades, whitefish populations have dropped and anglers say sometimes the whitefish they catch are skinny.

Looking through a window pane at a fisherman on an island near Isle Royale is removing a bit of the fish that researchers can use to determine the age of the fish.
CREDIT LESTER GRAHAM / MICHIGAN RADIO

Raising whitefish

Brad Silet with the Sault tribe says that’s why Native American fisheries experts are trying to figure out what they can do to save whitefish and other kinds of fish important to them.

“Right now, Sault Tribe is doing some experimental whitefish rearing. There’s another tribe (Little Traverse Bay Band of Odawa Indians) doing it also. We are seeing what it would take to raise whitefish and financially what it costs, space costs, so on, so on to see if we can potentially offset any changes to climate change or invasive species that are happening, at least in our area of the Great Lakes.”

The State of Michigan and the federal government long have operated fish hatcheries to raise sport fish. Government agents are now watching the Native American research to see how well the experiments in raising whitefish go. Besides being a cultural icon for Native Americans, whitefish bring in much needed money for the tribes and the other commercial fishers trying to make a living on the Great Lakes.