On average, ice coverage on the lakes has significantly declined in recent decades as average temperatures are increasing. In the Great Lakes regions, temperatures have warmed by as much as 5 degrees over the last 50 years.
Between 1973 and 2010, ice on the Great Lakes altogether declined 71%. Lake Ontario went down by 88%, Superior by 79%, and Michigan not far behind, recording a 77% ice loss over the 38-year timeframe. Lake Huron declined 62%, and Erie at 50%.
The maximum ice cover reached each year still shows an annual percent decrease, but it is less drastic, at a 22% decline for all lakes combined from 1970 to 2020.
Additionally, the variability of maximum ice cover is increasing over time. This makes sense when considering the weather patterns: big heat waves to big cold snaps leads to less ice and more ice, with the extremes occurring closer together.
In other words, the extreme from one year to the next is getting bigger and more frequent, which is an impact of climate change. That means even though this year is breaking records for low ice extent, next year or the year after could break records for max ice extent.
Low ice coverage has a wide range of impacts across industries and communities.
Hundreds of millions of tons of cargo are shipped on the lakes each year, a multi-billion dollar industry, and lower ice cover means shipping can operate longer throughout the year, increasing their profits.
Meanwhile, the Coast Guard can spend less time and fewer resources breaking ice and rescuing stranded ships since there is less ice cover, potentially saving taxpayer money.
Lower ice extent also means more evaporation, which means lower water levels. Not only does lower water levels negatively affect the commercial shipping industry, it can also affect hydroelectric plants, reducing their energy production — a cost that will trickle down to consumers when other means of energy production become necessary.
Less ice cover means more open-face water during winter, and this can lead to more lake-effect precipitation. For now, that means more lake-effect snowfall, but as temperatures continue to rise, this will lead to more lake-effect rainfall instead.
When there isn’t ice to dampen wave activity, there can be an increase to coastal erosion.
There is also a significant tourism industry that depends on the lakes icing over. Low ice extent can lead to a substantial negative impact on the tourism and recreation industry, such as ice fishing, and the businesses reliant on that.
When it comes to the ecosystem impact, the Upper Great Lakes are the most impacted by warmer waters throughout the year. Cold water fish are forced to compete with the warm water species that migrate farther north. Less ice can also leave the eggs of fish more exposed to the elements and lead to “dead zones,” where fish aren’t able to come to term.
Plus, with more heavy lake-effect precipitation, there can easily be more runoff with various nutrients loading into the lakes at higher levels, leading to more favorable conditions for toxic algal blooms.
Additionally, there are Indigenous communities who need ice cover to perform rituals.
And of course, safety is a bigger issue during low ice cover, because people who have been on the ice in years past may assume they can again without realizing how thin the ice that does exist is.
Among the repercussions are algal blooms like those that have choked western Lake Erie in recent years.
“Given enough nutrients in the water, algal blooms will thrive in warmer conditions,” Woolway said. “Heat waves will lead to those algal blooms becoming more persistent and longer-lasting.”
Warmer lakes also cause chaos for the ecology. Some fish and other aquatic species require colder temperatures and can’t adapt well to warmer ones. And the potential problems extend from there.
“Lake Superior is such a cold water system, much of our concern is about how warming surface waters open the door to invasive species that previously couldn’t tolerate the low temperature and lower nutrients — for example, zebra and quagga mussels,” Ashley Moerke, director of the Center for Freshwater Research and Education at Lake Superior State University, said. The center was not involved in Woolway’s research but is studying climate change’s impacts on the northern Great Lakes.
The effects of climate change are also apparent with a native Great Lakes species, the cisco, a slender, silvery fish that ranges in size from 8 to 16 inches in length and typically schools at between 60 and 175 feet. Its numbers were abundant enough to allow a thriving Great Lakes fishery at one point in the 20th century, but cisco numbers have dropped substantially in recent decades. Its last large refuge has been Lake Superior, but surveys have found an up to 48% decline in cisco numbers there as well in recent years.
Tiny aquatic organisms might feel outsize impacts from warming lakes, Claramunt said. And those creatures, such as zooplankton, are relied upon as food for small fish, that in turn feed medium-size fish, on up to the prized Great Lakes sport fish that fuel a multibillion-dollar industry in the Great Lakes region.
“I am very concerned that the base of the food web will be the most susceptible to these changes and that will cascade into impacts to our fisheries,” he said.
Woolway’s research includes modeling of potential lake heat wave impacts from continued warming, at varying scenarios of continued greenhouse gas emissions. At the more extreme, business-as-usual end, lake heat waves could become up to 25 times more likely by century’s end.
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