Lake Superior is the largest of the five Great Lakes of North America, with a surface area of more than 82,000 square kilometres – larger than the country of Austria. But how much of it is actually frozen?
According to a report by the International Institute of Space Studies (2002), up to 17% of Lake Superior can become ice-covered in winter, as measured by aerial photography. However, the extent of freeze-over varies from year to year; for example, in the 2019–2020 winter, only 8% of the lake’s surface was covered with ice.
The most important factor determining whether Lake Superior freezes is the weather. In general, the colder the winter, the more likely the lake is to freeze. This is largely due to the evaporation of water, which causes the water temperature to drop.
The effects of climate change can also be seen in the rise of seasonal water temperatures. As winters become warmer, the lakes take longer to freeze, leading to reduced ice cover. This can have a number of impacts on the aquatic life in the lake, as it disrupts their normal migratory patterns, reproductive cycles and food webs.
The increased temperatures can also lead to more evaporative water loss, which can alter the water chemistry of the lake. This can affect the lake’s primary productivity, causing the loss of nutrients essential to the fish populations.
In order to ensure the future health of Lake Superior, it is important to reduce greenhouse gas emissions and take other steps to mitigate the effects of climate change. This will help to ensure that winters remain cold enough for the lake to freeze, providing an important habitat for the lake’s aquatic species.
Impact on Water Levels
The amount of ice coverage on Lake Superior can also have an impact on the lake’s water levels. When the lake freezes, the ice acts as a barrier, preventing water from flowing out of the lake and into the rivers and streams that feed it. This can cause the lake levels to drop, leading to serious issues for shoreline communities who rely on the lake for their drinking water and other uses.
On the other hand, if the lake does not freeze, the ice layer that usually forms during the winter serves to keep the water in the lake instead of allowing it to drain out. This can help to maintain water levels, preventing water shortages for those who depend on water from the lake.
Economic Impact of Ice Cover
The amount of ice coverage on Lake Superior can also have an economic impact. Ice coverage on the lake provides an important habitat for fish, which attracts anglers and other recreational fishers looking to take part in ice fishing. This contributes significantly to the local economy, as people come to the area to take part in the activity.
Additionally, ice coverage enhances the shipping industry as it allows winter ports to open on the lake. This provides an important link between the communities situated around Lake Superior and the rest of the world.
In areas where there is significant ice coverage, the sport of ice-boating can also be enjoyed. This sport involves sailing on boats over the frozen lake and has become an increasingly popular pastime for many tourists.
In addition, ice coverage can also provide a source of income for those who live in areas affected by it. Ice harvesting is an industry that involves manually removing blocks of ice from the frozen lake, which are then sold for a variety of purposes, including cooling. This can provide an important source of income for those who live in the lake’s vicinity.
Geographic Impact on Freeze-Over Coverage
In addition to weather and climate, the geography of Lake Superior can also influence the amount of ice coverage it experiences. Areas of the lake that are sheltered from the wind by islands, peninsulas and other landforms experience less ice coverage, while areas that are open to the wind are more prone to freezing.
In addition, the depths of the lake can also have an effect; deeper areas of the lake tend to stay ice-free even in the coldest winters, while shallower areas are more likely to freeze. This is because deeper areas of the lake can store more thermal energy, preventing the water from reaching freezing temperatures.
Finally, the currents of Lake Superior can also play a role in determining the extent of its ice coverage. The warmer surface waters of the lake flow clockwise, which can lead to a lessening of the ice coverage in the east and a thickening in the west.
Impact of Pollution on Ice Coverage
Pollution can also play a role in determining the amount of ice coverage on Lake Superior. Many pollutants can end up in the lake, such as heavy metals and chemicals, which can collect on the ice and prevent it from forming. Additionally, runoff from urban areas containing fertilizers and other pollutants can add to the problem, limiting ice coverage and threatening the lake’s aquatic life.
In order to protect the lake from further pollution, it is important to reduce the amount of pollutants being discharged into the lake from urban and industrial sources. This will help to preserve the lake’s natural habitat and ensure that it remains healthy and ice-covered in the wintertime.
Effects on Species Populations
The amount of ice coverage on Lake Superior can have a significant effect on the species that inhabit the lake, as it affects their ability to feed, migrate and reproduce. Some species are better adapted to the cold temperatures associated with ice-cover, while other species are not. Although some species are able to survive in a frozen lake, others will be reduced in number or even die out.
In addition, the presence of an ice layer can also affect the amount of light entering the water, affecting the growth of aquatic plants, an important food source for the lake’s fish and other organisms. Reduced light availability can lead to lower levels of primary production, leading to reductions in species populations.
Finally, the ice coverage of Lake Superior has been linked to changes in the plankton populations of the lake. In some cases, freezing of the lake can lead to an increase in plankton biomass, due to the protection provided by the ice, as well as the abundance of food and oxygen found in the waters under the ice.
Public Access Issues
The amount of ice coverage on Lake Superior can also have an impact on public access to the lake. Areas of the lake that are covered in ice may not be safe for recreational activities, such as fishing or boating. This can limit the number of people who are able to access and use the lake, as well as the activities they are able to take part in.
In addition, ice-covered areas of the lake may be closed off to the public, as they are considered dangerous. This can limit access to certain parts of the lake, which may be important areas for fishing or other recreational activities.
Finally, the presence of an ice layer can also limit access to the lake in terms of transportation. For example, the lake may not be suitable for large ships or boats during the winter months, as the ice can be hazardous and cause vessels to become stuck, or even sink.
Community Education and Outreach
The extent of freeze-over on Lake Superior can have a significant impact on the local communities, so it is important for them to be aware of the risks associated with the lake and its ice coverage. As such, it is important for the local community to be educated about the lake and its environmental conditions, such as the amount of ice coverage and its possible effects.
In addition, it is important that the local community is also aware of the measures that can be taken to mitigate the effects of the lake’s ice coverage, such as reducing its sources of pollution and taking other steps to reduce the impacts of climate change.
Community outreach programs can be an important way to educate the public about the lake and to encourage them to take part in activities that help to protect it. These programs can also help to raise awareness of the importance of the lake and its ice coverage, and can help to foster a sense of community ownership of the lake’s future.
