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Frigid Forecast for Water Temperatures on Great Lakes This Summer

Photo: Ice on Lake Michigan. Source: Denise McDonough.
Ice on the west side of Beaver Island during the winter of 2014. (Photograph by Denise McDonough)

Of all the images of ice last winter, one of my favorites was a friend’s photo of crumpled sheets of blue ice on the west side of Beaver Island in northern Lake Michigan. With her smartphone, Denise McDonough snapped a photo that looked like it was taken by a polar explorer, not by one of the proprietors of McDonough’s Market, the family-owned grocery store on the island.

Her photo evoked childhood memories of the ice and snow in the Great Lakes region, so it makes sense to me that the forecast for this summer is for some of the coldest surface water we’ve seen since 1979.

At the end of May, small icebergs were still being spotted from a webcam mounted on Granite Island, an aptly named small, rocky island with a lighthouse about 5 miles from shore near Marquette, Michigan, on Lake Superior. The lake is normally ice-free by the end of April.

Photo: Granite Island lingering ice. Source: Great Lakes Evaporation Network (GLEN)
Photo from Granite Island Light Station on May 30, showing lingering ice on Lake Superior. (Photograph Great Lakes Evaporation Network)

With more than 90 percent of the Great Lakes covered in ice last winter, it should come as no surprise that summer water temperatures are expected to be colder than normal, but just how cold was anyone’s guess until now.

Researchers studying evaporation on the Great Lakes have developed a new forecasting tool for seasonal water temperatures on Lake Superior, funded in part by the University of Michigan.

Surface water temperatures above the deepest parts of Lake Superior are expected to be at least 6 degrees Fahrenheit colder than normal by August, the research team says. This temperature difference is about three times greater than at present, which was only about 2 degrees below normal at the end of May.

Figure: Lake Superior water temperature forecast 2014. Source: Great Lakes Evaporation Network (GLEN)

Why the big amplification by late summer? It has something to do with thermal memory and the way the lake mixes before and after 39 degrees Fahrenheit, the temperature that water reaches its maximum density, according to John Lenters of LimnoTech, one of the lead researchers on the project.

“Before 39 degrees, the lake mixes very deeply, which causes it to warm slowly, especially in deep, offshore waters,” said Lenters. “After 39 degrees, the top layer of the lake will warm much more rapidly. But this year, that rapid surface warming is not likely to happen in the offshore waters until well after the fourth of July. And it’s all because we started out just a few degrees below normal.”

My last post on this topic was about how “Ice Cover Affects Water Levels in Surprising Ways.” To summarize what this latest information means for lake levels, the cooler water this summer is good news because it will delay the evaporation season, allowing the lakes to continue their recovery from record lows last year.

The Summer of Fog

Photo: Fog Lake Michigan. Source: B. Borre
A fog bank on Lake Michigan on June 2, 2014. (Photograph by Betsy Borre)

Ice sightings are giving way to another weather phenomena: fog. Just the other day, my mom sent me the above photo of a thick, white fog bank taken from her deck overlooking Lake Michigan.

A fisherman’s video of a fog bank rolling in off the lake went viral after it was posted to YouTube on May 21:

Fog events are likely to continue with the combination of chilly water and warm, humid air.

“It’s going to be the summer of fog,” said Peter Blanken, a study co-investigator from the University of Colorado. “The water will stay really cold, but summer air tends to be warm and humid. And any time you get that combination, you’re going to have condensation and fog – basically evaporation in reverse.”

For more information about the new water temperature forecast tool and to view forecast maps, visit the U-M website.

Lisa Borre is a lake conservationist, freelance writer and avid sailor. With her husband, she co-founded LakeNet, a world lakes network, and co-wrote a sailing guide called “The Black Sea” based on their voyage around the sea in 2010. A native of the Great Lakes region, she served as coordinator of the Lake Champlain Basin Program in the 1990s. She is now an active member of the Global Lake Ecological Observatory Network.

Comments

  1. Joe
    Vaughan Ontario
    June 22, 12:22 pm

    i own a cottage at sauble beach Ontario, and the water temp. is only 7 degrees cel (the norm is 15 for June!). and it has stayed that way through all of April and all of may, why is this? should lake Huron ever warm up before august 2nd? (when i go to my cottage!), or will i just have to sit on the sand all summer wishing i could go in?

    • Lisa Borre
      June 30, 4:18 pm

      Joe, I was on northern Lake Michigan on the day you submitted this comment and found similar temperatures near the shore. The researchers who developed the temperature forecast model for Lake Superior have not yet developed models for the other lakes, but they expect that the forecast would be similar in several ways: (1) all of the Great Lakes will be colder than normal this summer due to the cold winter and extensive ice cover, and (2) the shallow and nearshore surface waters will warm more rapidly than the deep portions of the lake. They also said that once the lake is above 39 degrees F (~4 degrees C), the water begins to warm more quickly. The lakes are so large that they have “thermal memory” that can last for months. If you want to see up-to-date temperature maps for Lake Huron, visit the NOAA GLERL website: http://coastwatch.glerl.noaa.gov/cwdata/lct/glsea.png.

  2. Psalmon
    June 9, 3:07 pm

    18 months ago you wrote:

    -The Great Lakes have lost 71% of their ice cover since 1973.
    -Summer lake temperatures are also on the rise.
    -The Great Lakes are among many lakes in the northern hemisphere experiencing a rapid warming trend.
    -LLO study found that summer surface water temperatures on Lake Superior have increased approximately 4.5°F (2.5°C) during the period 1979–2006.
    -Lake Superior evaporation … would explain the near-record low lake levels in October.
    -“Lake Superior’s rapid warming is like a canary in the coal mine,” Lenters told me.
    Just 9 months ago you replied:

    “Forecasters predict that it will take several years of wetter than normal weather to restore water levels in the upper lakes. And to remain there, this will have to offset climate-related trends such as warming water temperatures, loss of ice cover and increased evaporation rates, not to mention the increase in droughts and heat waves — all of which are contributing factors to low water levels and cause for other concerns about the ecological health of the lakes.”

    Today Superior is 7 inches above June’s average level and headed to near 603 feet. What a difference a few months make.

    Someone should re-run all those trends and you should post updated water level pictures. Everyone always asks what if we’re right about climate change? What if you’re wrong?

    • Lisa Borre
      June 11, 12:30 pm

      Psalmon, Even with the extreme cold this past winter in the Great Lakes region, this must be looked at within the context of longer term records. One cold and icy winter does not alter the basic trends cited above, but it certainly was a notable one because it had been 35 years since the region experienced a winter like it.

      I understand that it is hard to believe that the climate is warming after such a cold winter, but this past winter must also be looked at within the context of global trends. While it is true that the Northern U.S. was cooler than normal during January to May, many parts of the world were much warmer, according to NOAA. As of the end of April, global temperatures for this year-to-date are the sixth warmest since they began keeping records in the 1880s. I stand behind all of the basic facts I cited 18 months ago as well as the subsequent updates and replies to comments.

      And just to clarify one point you made: it’s been more than just a few months of favorable conditions that has resulted in higher water levels on Lake Superior. The extreme drought and heat wave occurred in 2012, and the extensive ice cover and snowfall over this past winter was even more than the forecasters could have predicted (or hoped for) in terms of the combination of cooler water temperatures, greater ice cover and lower evaporation rates. This wouldn’t be the first time that a weather forecast didn’t play out exactly as predicted.

      I should also point out that the response of the lakes to changing conditions over the past two years is further confirmation of the importance of climatic factors in water level fluctuations. And to your questions about being right or wrong: for me, the risks to the overall health of the Great Lakes — not just water levels — are too great to ignore these trends. I believe the lakes are like canaries. We need to listen to their call.

  3. Betsy
    Beaver Island, MI
    June 7, 1:07 pm

    I can watch this article playing out everyday from my deck on Beaver Island MI. However, the video of the fog bank by the fisherman was like nothing I have ever seen on the Lake.

    One unwelcome invader this summer is an enormous hatch of Mosquitos and some look like pests. Some visitors have left in dismay.

    I hope you will share more information on this most unusual summer.

    • Lisa Borre
      June 11, 7:04 pm

      I’ve heard that the insect hatches have been large these past two years. Thanks for braving the conditions to snap and send a photo of the fog last week! I’ll let you know if I find out more information about the hatch.

    • Lisa Borre
      June 30, 5:09 pm

      After seeing the “other” insects you mentioned with my own eyes last week, I can confirm that it was a hatch of midges. Enormous hatches were also being reported on nearby Mackinaw Island in late May. The midges look like mosquitos, but don’t bite or carry disease. Although the large swarms are annoying, midges are harmless to humans. The good news is that adult midges have a short life span (5-10 days) and the swarm typically lasts for about four weeks. They lay eggs their eggs in standing water, so this is why you see so many near the water’s edge. More good news: the midges are an important food source for fish and birds.