Beyond the Surface: The Consequences of Shrinking Great Lakes Ice Coverage

Over the last 50 years, the Great Lakes have experienced increasing variations in ice coverage. Certain winters, such as 2014, witnessed near complete coverage while others had minimal ice. Nevertheless, a clear pattern emerges, indicating an overall decline in icy conditions. This trend has implications not only for the environmental landscape of the lakes, but also for vital regional industries like hydropower, fishing and commercial shipping. Cover graphic by Riley Walsh for Midstory.

The Great Lakes, impressive symbols of North America’s beauty, have enthralled the hearts of people across the United States and Canada for centuries. Encompassing the largest freshwater lakes on Earth, they serve as a sanctuary for outdoor adventurers and a hotspot for commerce and industry.

Both industrial and recreational uses of the lakes, however, change depending on seasonal conditions. And so recent extremes in ice coverage have raised alarm — and encouraged meticulous tracking of annual ice patterns.

“If you look at the time series of annual maximum ice coverage you can see a clear declining trend that goes back to 1973,” Dr. Ayumi Fujisaki-Manome, an assistant research scientist specializing in lake ice and hydrodynamics for the Cooperative Institute for Great Lakes Research, said. “I think an important thing to notice is that it’s not really a monotonic decrease, but a lot of year-to-year fluctuations.”

According to Fujisaki-Manome, ongoing research on global warming is attempting to explain the root causes of fluctuating yet declining ice coverage, and how much might be attributed to normal climatic variations.

“Our lake hold is only 50 years old, so it’s kind of hard to tell whether this declining trend is coming from global warming or part of this low-frequency oscillation,” Fujisaki-Manome said.

Environmental Effects

Ice coverage fluctuations play a pivotal role in shaping the health of the Great Lakes. From triggering algae blooms to balancing ecosystems, ice coverage shapes the lives of both animals and humans in the region. 

When ice melts early and the water becomes warmer, cyanobacteria — or blue-green algae blooms — plague the Great Lakes.

While cyanobacteria favor warm conditions, new research shows that blue-green algae blooms can occur in icy conditions, as well. Although blue-green algae blooms generally increase with declining ice coverage, they may still be present during icy oscillation periods.

“A few observations are being made under icy conditions and they have found some algae existing underneath the ice. Those scientists think that it might have some impact on springtime or even summertime biogeochemistry,” Fujisaki-Manome said.

The algae blooms produce toxins that are harmful to animals and people, and the depletion of oxygen that occurs during the blooms contributes to a decline in populations of fish.

The weather system also faces extreme impacts from declining ice coverage. Open water caused by melting ice can lead to lake-effect snow. This process occurs when cold air moves along warm open lake water, transfers warmth to the lowest part of the atmosphere, causes air to rise and forms clouds that produce snow.

“Even in January, we don’t get much ice cover. There is a lot of open water and if there is cold air coming up, that can cause a lot of lake-effect snow that can damage downwind communities a lot,” Fujisaki-Manome said.

Algal blooms in Lake Michigan, Lake Huron and Lake Erie. Image courtesy of Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC, via the NASA Earth Observatory.


In addition to its environmental effects, fluctuating ice coverage on the Great Lakes has significant industrial implications.

Hydropower, the use of fast-running water to generate electricity, is a vital industry in and around the Great Lakes. In a report written in 2014, Victoria Lubner and her colleagues revealed that hydropower already accounts for 9% of the power generation in the region. As the global trend toward sustainable energy gains momentum, the Great Lakes exhibit the potential to expand hydropower generation.

In years when ice cover is high, hydropower generation can be less efficient. As ice freezes the waterways, it hinders the flow of water and impedes optimal hydropower generation. Waters upstream can experience unintended flooding due to impeded flows, while hydropower plants downstream suffer from decreased water availability and lower levels of hydropower generation. 

Paradoxically, as ice cover and water levels drop, drought-like conditions can occur, creating different challenges for hydropower plants. The emerging trend of extreme weather creates the need for maintaining an equilibrium between ice cover and water levels — an endeavor that would require limiting greenhouse gas emissions and slowing down the potential impacts of climate change. 

Fishing & Recreation

The overall declining ice cover trend also has profound impacts on fishing — a powerful economic driver that generates more than $7 billion annually and supports about 75,000 jobs in the Great Lakes region. The disappearance of ice cover during warm winters disrupts fish habitats, spawning patterns and survival rates, which directly affects the productivity of the commercial fishing industry.

Great Lakes fish eggs are protected after cold winters with substantial icy conditions, generally increasing survival. 

“Research has discussed that ice cover protects fish eggs because if the ice is stable enough, and attached to the shore, it dampens waves when wind is blowing. Ice cover dampens wind stress and water can remain calm. That protects fish eggs and really helps with springtime spawning,” Fujisaki-Manome said. 

Most fish eggs in warmer temperatures faced challenges such as smaller egg size, waves and wind stress, leading to reduced chance of maturation and survival. 

Data from the Great Lakes Fishery Commission demonstrates that overall, the production of fish in pounds has decreased since 2014, one of the iciest winters in Great Lakes history.

Beyond commercial impacts on the fishing industry, fluctuating ice coverage could also affect the Great Lakes’ tourism industry. Recreational fishing is a key player in Great Lakes economies and relies on abundant fish populations; according to Michigan State University’s Michigan Sea Grant, “In 2017, charter captains logged 12,122 fishing trips in Michigan waters of Lake Michigan, generating tourism that created over $7 million in personal income and over 322,000 employment hours.”

Furthermore, the Great Lakes are also a prime destination for winter recreation. Ice fishing, a Midwestern cultural tradition, favors icy winters and has been called off in recent years due to the lower ice coverage.

Another study predicts an increase of unsafe ice for leisure activities such as ice fishing and skating as overall ice cover diminishes. The predictions indicate the availability of safe ice could decrease by 13-24 days in the future, posing an obstacle for recreation.

Fishing on Lake Huron. Image courtesy of the EPA. 

Commercial Shipping

While icy conditions may be preferred in fishing, the shipping industry favors the opposite. From some perspectives, the shipping industry benefits from the overall declining ice coverage, but it struggles when extreme icy oscillations occur.

The commercial shipping industry comprises a vast portion of economic growth in the Great Lakes region.

“It creates 227,000 jobs, $33.5 billion in business revenues, $14 billion in annual personal income, $6.4 billion in local purchases, $4.6 billion in tax revenue and it saves $3.6 billion in transportation rates,” Peace said.

A 2018 study estimated a loss of 10,000 jobs and $2 billion during the harsh winters of 2013, 2015 and 2017 because of inadequate equipment to deal with icy conditions and ice-locked ships. 

The first key to understanding commercial shipping is to understand the Soo Locks, essential passageways on the Great Lakes. These locks encounter remarkable obstacles during icy conditions, rendering them inoperable from mid-January to mid-March and halting shipping for the winter season. Due to treacherous icy conditions in the period before and after the lock closure, commercial ships can get caught in ice for days. 

An aerial view of the Soo Locks connecting Lake Huron and Lake Superior. Image courtesy of August Schwerdfeger via Wikimedia Commons. 

The onset of the ice season also disrupts the flow of vital raw materials from the upper Great Lakes to the lower Great Lakes. This disruption creates consequences for the lower Great Lakes region, a hub for manufacturing and processing these materials into steel and various goods. The far-reaching ripple effect poses a threat to the economy and puts a strain on job availability in the region.

“A heavy ice season impedes our ability to resupply critical facilities on the lower lakes with raw materials that come from the upper lakes,” Eric Peace, the vice president of the Lake Carriers' Association, said. “What that means is we cannot resupply those mills — those steel mills in the lower lakes — facilities lose manufacturing, people lose jobs and the economy withers.”

When ships are caught in heavy ice sheets, there are regional repercussions. Vital deliveries fail to reach their recipients, prompting widespread disruptions in supply chains. The icy challenges pose threats to the timely delivery of vital goods, contributing to economic instability.

“Of course, the perspective from the ports is if the ships are stuck in the ice out there, they aren’t getting to our ports, they are not delivering the cargoes that people need. Sometimes those cargoes are important to people, sometimes it’s iron ore for steel mills that make steel for the auto industry, or sometimes it’s salt for road safety, sometimes it’s limestone for construction, sometimes it’s grain for food production,” Steve Fisher, the executive director of the American Great Lakes Ports Association, said.

The only solutions for ships stuck in the ice are icebreaking fleets run by the United States and Canadian Coast Guard.

The region’s limited supply of available icebreakers has led to significant challenges in ice removal. According to Peace, the Great Lakes Region has downsized from 20 icebreakers back in 1979 to 11 icebreakers today. He attributes the reduction of resources to skewed data, which focuses on small waterways as opposed to the entirety of the region. The consequences include impeded trade efficiency and delays in the movement of vital commodities throughout the Great Lakes.

“I always use the analogy of snow plows on the highway. If somebody relied on the highway for the delivery of goods and there was a bad snowstorm, we assume the local city or county or state government has snow plows to come out and clear the highway. We all just sort of assume that will happen and I think we would all be shocked if it didn’t happen at all. That’s kind of what these icebreakers are — they are the snowplows of the Great Lakes,” Fisher said.

The Mackinaw, the Coast Guard’s largest icebreaking ship. Image courtesy of the United States Coast guard via Wikimedia Commons.

Amidst the challenges of icebreaking operations, however, a glimmer of hope emerges. With President Biden passing the infrastructure bill, $55 million of a $350 million project has been granted to the Coast Guard’s budget to construct a large icebreaking vessel around the same size as the Mackinaw, the biggest icebreaker on the Great Lakes, to combat heavy ice. 

“When President Biden proposes funding for anything in his budget, ultimately Congress has to approve that. That’s the phase we are in right now,” Fisher said.

From cyanobacteria blooms and disrupted fish habitats to challenges in hydropower generation, fishing and commercial shipping, ice coverage plays a vital role in maintaining the ecosystems and industries of the Great Lakes. Not only that, it’s a signifier of more climatic changes to come.

“Ice is a pretty major part of the response to global climate change. It’s very sensitive and it’s such a critical piece of the entire system,” Fujisaki said. “The change in lake ice is so manifest of the expression of all changes.”


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