Great Lakes records fourth lowest ice cover in 50 years. How will that continue to impact us?

Ice fishermen stay close to shore off of Bay Shore Park in New Franken, Wis. The last bit of ice on the Great Lakes officially melted May 18.
Ice fishermen stay close to shore off of Bay Shore Park in New Franken, Wis. The last bit of ice on the Great Lakes officially melted May 18.

The Great Lakes recorded the fourth-lowest ice cover since scientists began keeping track a half-century ago, yet another sign of the impact of climate change on the environment.

The last bit of ice melted off the Great Lakes on May 18, marking the official end of this year’s ice season. “Ice-off” officially happens when all the ice has melted off the lakes and forecasters are sure it’s not coming back.

Average ice cover was only 6.2% this year, according to data from the National Oceanic Atmospheric Administration's Great Lakes Environmental Research Lab. Average ice cover over the past 50 years is 24.5%.

Coupled with historic flooding in the upper Mississippi River earlier this spring, Wisconsin is seeing how climate change is impacting weather and, in turn, affecting the bodies of water on three of its four sides. The Mississippi River flooding was due to an unusual abundance of heavy, wet snow and then unseasonably warm days in April that caused it to melt rapidly and rush down all at once.

Here’s what to know about how low ice cover can impact the lakes in the spring and summer.

More: It's mid-January and the Great Lakes are virtually ice-free. That's a problem.

Average ice cover was low throughout the season

In addition to the fourth-lowest ice cover overall, the Great Lakes ice cover hit a record-breaking low in mid-February.

The lowest average ice cover on record happened in 2012 with 4.2% average cover, followed by 5.9% in both 1998 and 2002.

Not only was average ice cover low throughout the season, but so was the maximum amount of ice observed across the lakes.

Across all the lakes, ice cover maxed out at only 21.6% on Feb. 4, the seventh lowest maximum ice coverage since 1973. The lowest on record was just above 12%, which happened in 2002.

The most amount of ice observed on Lake Michigan was 21.5% on that same day. And Lake Superior maxed out at 19.8 on Feb. 24.

Year-to-year extremes are expected with climate change

Ice cover in the Great Lakes has been declining for the past five decades due to climate change, a trend that scientists say will likely continue. But that doesn’t mean that ice cover is declining every single year.

Climate change is bringing more extreme year-to-year fluctuations, said Ayumi Fujisaki Manome, a scientist at the Cooperative Institute for Great Lakes Research at the University of Michigan who models ice cover across the lakes.

For more than a decade, average ice cover across the lakes has swung from near record lows followed by near record highs, such as 13% in 2012 to 92% in 2014.

Low ice cover can also lead to lower lake levels later in the summer as the lakes warm fast, favoring evaporation. But lake levels, which are also seeing more intense swings due to climate change, will depend on how much rainfall the lakes get in the spring and summer.

More: What's the state of the Great Lakes? Successful cleanups tempered by new threats from climate change

Warmer waters disrupt the food web in spring

Lake water mixes every spring when the surface water warms, bringing up nutrients and organic matter that was stuck on the bottom all winter. The freed up nutrients become available to phytoplankton — microscopic plants that form the foundation of the lakes’ food web.

When the surface water reaches a certain temperature, the lakes will stratify, creating layers that differ in their temperature, nutrients and oxygen levels.

But in years with low ice cover, the lakes warm up faster and stratify earlier, Fujisaki Manome said. The longer the lake is stratified, the less time that nutrients are available to phytoplankton throughout the open water.

This can impact the food web by decreasing overall productivity in the lake ecosystem, said Ed Rutherford, a fishery biologist who also works at the Great Lakes Environmental Research Laboratory.

The one exception is Lake Superior, Rutherford said, where it can actually cause a spike in productivity likely because the lake is already so cold.

Earlier spring warming may also cause disruptions in the food web, he said. Phytoplankton may bloom earlier than the zooplankton that normally feed on them. If there are no zooplankton around to eat them, it could have a ripple effect up the food chain, especially on the larval fish that depend on zooplankton.

More: Blue-green algae blooms, once unheard of in Lake Superior, are a sign that ‘things are changing’ experts say

Climate change creating perfect conditions for algae blooms

Climate change is intensifying rainfall as well as causing the waters to warm and reducing ice cover. This is creating the perfect conditions for algae blooms later in the summer.

These thick, green mats appear every summer in Lake Erie and the bay of Green Bay in Lake Michigan largely due to agricultural runoff. And now, these blooms are cropping up in Lake Superior.

The blooms consume oxygen and block sunlight from underwater plant, making it hard for aquatic life to survive.

More: Bay of Green Bay's dead zones could be getting worse, and scientists say climate change is the likely culprit

Caitlin Looby is a Report for America corps member who writes about the environment and the Great Lakes. Reach her at or follow her on Twitter @caitlooby.

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This article originally appeared on Milwaukee Journal Sentinel: Great Lakes average ice cover fourth lowest in more than 50 years