Each winter, Lake Superior become enveloped in a thick layer of ice, which is said to be thickest at its deepest points. The lake is frozen solid for days, weeks, and even months at a time, rendering it a spectacular winter wonderland for anyone brave enough to visit. But just how much of Lake Superior is actually frozen?
According to the U.S Environmental Protection Agency, Lake Superior has an average area of 31,700 square kilometers. While this region is affected differently year to year, the lake typically experiences peak ice levels in March, when around 12.5 percent of the surface area of the lake becomes frozen. This year, the National Oceanic and Atmospheric Administration reported that the maximum ice coverage on Lake Superior since 1976 was 28 percent in 2014.
Dr. Michael Carroll, a professor of physical geography at the University of Wisconsin who studies the changing nature of ice on freshwater lakes, sheds some light on the situation. “The amount of ice on Lake Superior is largely determined by weather conditions,” he says. “In any given winter, you can expect that the southern portion of the lake will generally have less ice than the northern portion. This is because that region receives more sunlight and less wind.”
This pattern is also echoed in corresponding measurements of the thickness of the ice on the lake. According to Dr. Carroll, Lake Superior can reach up to 0.5 meters of ice thickness at its northernmost points, but this is usually rare. The average thickness of the ice on the entire lake is around 0.2 meters.
However, this does not necessarily mean that the lake is impenetrable. Mike Schoonveld, a public safety instructor for the National Ski Patrol, has fished and skimmed the lake in the winter. “It’s not impossible to get out on the lake,” he says, “but obviously there are a lot of dangers to consider. Without appropriate clothing, you won’t get very far. You also have to be careful not to overload your boat, as too much weight has the potential to break the ice.”
Despite the dangers associated with venturing out on the lake, it is still a popular practice among seasoned fishermen and winter sports enthusiasts alike. According to Schoonveld, “Ice fishing and snowmobiling on the lake can be an incredibly rewarding experience. Watching the sunrise over the frozen lake is something I don’t think I’ll ever get tired of.”
The Effect of Climate Change On The Ice Coverage
Climate change has made a significant impact on the amount of ice present on Lake Superior. According to research conducted by Dr. Carroll and his team, the mean annual ice coverage on the lake has declined by 4.6 percent since records dating back to the late 1960’s. Additional research conducted by the Intergovernmental Panel on Climate Change (IPCC) has determined a further 17.3 percent drop in the mean ice coverage since the early 20th century.
These decreases in the mean ice coverage can be attributed to a number of factors, the most prevalent of which being an increase in average air temperature and an increase in wind intensity. While the increases are both inherently linked to climate change, they also impact each other. For example, warmer temperatures mean that the lake takes longer to freeze, while high wind velocity deflects solar radiation emanating from the lake’s surface, making the lake take even longer to freeze.
The long-term trends in the ice coverage of Lake Superior is of particular interest to researchers. According to Dr. Carroll, the “lake is likely to experience reductions in winter ice coverage in its future as climate change progresses”. It is also unlikely that the lake will ever reach its peak ice coverage of 28 percent again due to the fact that the lake’s average ice coverage has steadily declined over the course of the last several decades.
The Benefits To Having Ice Coverage
Despite the fact that the ice coverage of Lake Superior has declined due to climate change, there is still a large presence of ice in the winter time. As such, there are a number of benefits associated with have a healthy amount of ice coverage on the lake.
One of the most important benefits of having ice coverage is its role in protecting aquatic wildlife. “The ice serves as a sort of shield to the fish,” explains Dr. Carroll. “In the winter, fish take refuge in the deeper, colder sections of the lake under the ice. This makes it more difficult for predators to locate them. The ice also prevents the water temperature from dropping too low, as it serves as an isolator for the lake.”
The ice on the lake also provides a habitat for a variety of birds and mammals, including bald eagles and otters. With the lake frozen over, these animals can access parts of the lake’s shoreline that they would otherwise not be able to reach. “The shoreline provides a lot of food to these animals, including various insects and small fish,” adds Dr. Carroll.
The Implications Of Changes On The Ice Coverage
Any changes in the ice coverage of Lake Superior could have dire consequences on its aquatic ecosystem. While research indicates that fish populations have so far not been negatively impacted by the decrease in ice on the lake, this could very well change in the future.
Research conducted by the IPCC has concluded that a further decrease in the lake’s ice coverage could result in an increased rate of fish mortality during the winter months. This is due to the fact that fewer fish will be able to take refuge in the deep, colder depths of the lake, leaving them susceptible to predation from avian and mammalian predators. In addition, the decrease in ice coverage could lead to more algal blooms, as warmer water and increased exposure to sunlight lead to more nutrients entering the ecosystem.
The implications of this increase in algal blooms is, unfortunately, not positive. Algal blooms lead to an increased rate of eutrophication in the lake, resulting in the accumulation of toxins, decreased water clarity, and decreased oxygen levels. These factors will, in turn, further decrease the population of fish in the lake, and could potentially lead to the extinction of some species.
The Impact Of Human Activities
Climate change is not the only factor affecting the ice coverage of Lake Superior. Human activities, such as boat traffic, can have a significant impact on the amount of ice on the lake. According to Schoonveld, “Boats generate a lot of wake when they navigate the lake, which can cause ice to break and move further away from the shoreline. In extreme cases, the wake from boats can be felt up to a couple miles away from where the boat passes”.
The impact of these activities is not only seen in the ice coverage, but also in the mobility of the ice. When a lake experiences significant boat traffic, the ice will typically become fragmented, resulting in blocks of ice that can move freely on the lake. This is why Schoonveld advises, “it’s very important to understand where the ‘safe zones’ are on the lake, so you don’t end up in a difficult situation with limited options”.
Another factor to consider when discussing the impact of human activities is the presence of pollutants. According to Dr. Carroll, “in recent years, the health of Lake Superior has been significantly compromised by human activities, specifically air pollution, discharge of industrial waste and nutrient runoff from agricultural lands”. These pollutants can have a profound effect on the ice coverage of the lake, as pollutants and their accompanying toxins can negatively affect the freezing process.
The Importance Of Taking Action
Given the current health of Lake Superior and the potential implications of further damage, it is important that action is taken to reverse this trend.
Dr. Carroll offers a few potential solutions. “The most important way to minimize the effects of climate change on ice coverage is to reduce our emissions of carbon dioxide and other greenhouse gases”. He also suggests increasing the amount of protected land surrounding the lake and regulating the amount of boats that are allowed on the lake at any given time.
Schoonveld agrees and adds, “there needs to be more awareness about the fragility of the lake, so that people can take the necessary steps to protect it”. It’s also important to understand that this is not just a regional issue, as the lake is an important part of the global environment.
Lake Superior is an incredible natural feature that should be celebrated and protected. By taking the necessary steps to preserve its health, we can ensure that its ice coverage will remain healthy for years to come.
