Lake Superior reaches record temperature

Beating the heat in Duluth, MN: Fearless swimmers take advantage of Lake Superior's record temps.
Beating the heat in Duluth, MN: Fearless swimmers take advantage of Lake Superior's record temps.Courtesy Mark Ryan
Last week, Lake Superior, which is bordered by Minnesota, Wisconsin, Michigan, and Ontario, Canada, recorded its highest average surface temperature ever, a balmy 68.3°F. People seeking relief from a very hot summer have been flocking to the shores and beaches and actually swimming in the lake! That is so unlike the Lake Superior I remember growing up in Duluth. Sure, we liked to spend a day on the sand beaches of Park Point or lounging on the rocky outcrops along the North Shore but swimming was usually not an option. On average, Lake Superior’s overall temperature is barely above freezing (39 °F), and back then it seemed you couldn’t even wade in ankle-deep without having your breath sucked out of your lungs and thinking your feet had fallen off. Standing knee-deep in the water for even a short time was unbearable and a true test of endurance. And for guys, going any further was just plain crazy, unless you wanted verifiable (and excruciating) proof of Costanza’sTheory of Shrinkage.

Those hell-bent among us would sometimes make a mad suicide dash across the burning sands and actually dive into the frigid waters only to set off the mammalian diving reflex and cause their vital organs to start to shut down. Their only hope was if the lifeguards were watching and were properly certified in CPR.

Temperature ranges on Superior have been recorded for more than three decades. In recent years, the normal average surface temperature for Lake Superior during the month of August has been only 55°, so this dramatic rise in the average is unusual. As expected, many people are quick to point a finger at global warming as the cause for the rise. That’s not a bad guess considering the National Oceanic and Atmospheric Administration (NOAA) just proclaimed the year 2010 as the hottest on record, globally.

But physicist Jay Austin at the University of Minnesota-Duluth’s Large Lake Observatory has been closely tracking the lake’s surface temperatures, and predicted the record high back in July. He says the warm water this summer is at least partially due to a recent El Niño event that had an unusual effect on the lake this past winter.

“2009 was a very strong El Niño year,” Austin said. “And that El Niño year led to a year at least on Superior where there was very little ice.”

That lack of ice led to a quicker and earlier warm up of Lake Superior’s surface waters. The other Great Lakes showed similar increases in their average warm temperatures as well. Although ice usually forms on the lake surface during the winter months, Lake Superior rarely freezes over completely. The last time was in 1979.

The following video illustrates the contrast between last winter and the one prior to that. Each day on their Coast Watch website, NOAA posts 3 or 4 photographs taken by a satellite in geosynchronous orbit above Lake Superior. Early in 2009 I began collecting the images regularly thinking they could come in handy for a future Buzz story such as this. From March 2009 to May 2010 I collected something like 1100 satellite photos. Edited together, they make for an interesting time-lapse video that illustrates the weather patterns over the big lake from one winter to the next. At the start of the video (March 2009) ice-cover is apparent over much of the lake and can be seen building then melting away as the spring thaw brings warmer temperatures. But later in the video, as summer passes into fall and fall into winter, no ice appears at all over the expanse of the lake’s surface. Other than that I don’t know how informative the time-lapse ended up being but it’s certainly interesting to watch, particularly the wind and cloud patterns seen flowing off the lake starting in late January 2010.

"This year is just tremendously anomalous," Austin said. "This year ranks up there with the warmest water we have ever seen, and the warming trend appears to be going on in all of the Great Lakes."

The big question is what effect these warmer temperatures have on the lake’s ecology? Austin admits it’s hard to say.

"Fish have a specific range of temperatures in which they like to spawn," he said. "It may be that for some fish this very warm year is going to be great for them, but for others, like trout which are a very cold-adapted fish, it's not going to be great."

One problem for the trout could be that scourge of the Great Lakes, the jawless sea lamprey. Lampreys are invasive parasites and attach themselves to lake trout and live off their blood. It’s unknown what changes, if any, the warmer waters will have on their life-cycle. They may lay eggs faster and in larger quantities, increasing their populations, and their impact on the trout species.

Lake Superior has probably passed through its peak time for temperature this summer so more than likely the 68.3°F record will stand for the rest of the year. If you want to keep track you can go to the Michigan Sea Grant website where you can follow all the Great Lakes’ daily surface temperatures. But who knows? This summer may not be the height of the 30-year warming trend. Let’s see what next year has in store.

Personally, I’m concerned these warm water temperatures will spoil us. Being able to endure extremely cold temperatures is a Minnesota tradition, and helps build character. It makes you tough and able to withstand all sorts of adversity as well as the harshest of elements. Which brings to mind the time when my wife (then girlfriend) and I were in Glacier National Park and decided to go for a swim in St. Mary’s Lake. There were only a few other people goofy enough to be swimming in the glacial lake at the same time. It didn’t surprise us to learn they were all from Minnesota.

We were so proud of ourselves.

Minnesota Public Radio story
Lake Superior facts
More about Lake Superior
Great Lakes info

Your Comments, Thoughts, Questions, Ideas

arielle's picture
arielle says:

While this may be good news for recreation, it is bad news in almost every other way. Years ago when I would go camping on the shores of Lake Superior, I recall that your skin would turn red upon wading in the water; even in the height of summer! Warming waters clearly seem to be a reflection of climate change. This could result in ecological changes in the lake's biology, creating higher densities of bacteria but lower densities of larger game fish. Or could it be an unseasonable but not foretelling change in the lake's temperature?

posted on Sat, 08/21/2010 - 1:15pm
mdr's picture
mdr says:

Since I posted this story, there have been some changes that need to be updated. First off, the new record average temperature rose a bit to 68.7 °F on August 12th. Secondly, the party's over. No more excessive frolicking in the waters. Three days of high winds have returned the lake's surface waters back to their not-so-warm typical average temps. Oh, well. It was fun while it lasted. Read more about the turnabout here.

posted on Sun, 08/29/2010 - 11:41am
Ben's picture
Ben says:

Ha ha so you would think i was crazy to have gone snorkeling for several hours each week an hour at a time at least. up until October 15th last year(2009).

posted on Sat, 09/04/2010 - 10:06am
Gene's picture
Gene says:

It could also just be bad data.

posted on Sun, 09/05/2010 - 11:20pm
bryan kennedy's picture

That story seems to be more about the perils of posting live data feeds from satellites on public websites in this politically charged, everybody's an expert, media environment.

posted on Tue, 09/07/2010 - 9:16am
Anonymous's picture
Anonymous says:

Wow - 68 degrees !

I grew up on Lake Superior, North of Sault Ste Marie Ontario - We have a pool in our backyard in Ottawa, Canada now - and today (Sept 25) the temperature of the pool dropped to a low of 68 so I guess I'll go for a swim, and pretend like it's August back on Horseshoe Bay.

posted on Sun, 09/26/2010 - 6:23pm
michigan gal 's picture
michigan gal says:

what is the coldest lake superior has ever beeb??

posted on Mon, 05/14/2012 - 12:48pm
mdr's picture
mdr says:

That's hard to say. The lake is never the same temperature throughout. If your talking surface temperature then it's certainly been at least 32 °F and lower when its frozen over. Of course, you'd have to take air temperature into consideration (the coldest recorded air temperature around the Lake Superior region was -60 °F in Minnesota, reached on Feb. 2, 1996, beating out Wisconsin, Michigan, and Ontario, Canada). The lake rarely freezes over its entire surface, and even when it does it doesn't freeze all the way to the bottom, so while the surface temp might be below freezing, the water underneath would be warmer. Average annual temperature for the lake is 40° F, but that's the average. Still pretty cold.

posted on Mon, 05/14/2012 - 2:13pm

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