Background Information
Lake Superior is the biggest and deepest of the five Great Lakes in North America. With a surface area of 31,700 m2, it is regarded as the third-largest freshwater lake on the planet. It lies right on the border between Canada and the United States of America, with a shoreline that runs through three of the Great Lakes states: Minnesota, Michigan and Wisconsin. The lake is known for its frigid depths, where the average temperature is around 39°F (4°C). Consequently, one might expect the lake to freeze in the winter.
The Freeze Factor
There are several factors that determine whether or not Lake Superior freezes in the winter. The most significant factor is the lake’s temperature, which is determined by a number of other factors, such as wind, air temperature, and incoming solar radiation (the amount of heat coming from the sun). In summer, Lake Superior typically reaches peak temperatures of 71– 73°F (22–23°C). During winter, the surface water tends to become cooler, but the lake does not necessarily freeze.
The size of the lake is another factor, as it is so vast that the heat from the surface dissipates quickly and the water can stay liquid. In fact, Lake Superior has the largest surface area of any freshwater lake in the world, which means it takes longer for the temperature of the whole lake surface to drop. The depth also makes a difference, as the lake bottoms are so deep, it takes a prolonged cold spell for the lake to freeze solid.
Experts Views
Experts say that the lake rarely freezes over completely, but it has been known to do so only a few times in the last hundred years. There is speculation that climate change may be affecting Lake Superior’s freeze rate. A study published in 2019 by scientists from the Michigan Technological University found that while the rate of winter ice formation on Lake Superior has remained relatively stable since 1950, the lake is increasingly prone to thawing in spring.
The Great Lakes Integrated Sciences and Assessments Centre’s research scientist, Jan Bluyssen, said: “Climate change is affecting the lake in several ways. The lake is becoming warmer, deeper, and more variable. This could affect the ice formation rate, making Lake Superior less likely to freeze over in wintertime.”
Professor Houshuo Jiang from Michigan Tech, who co-authored the study on Lake Superior winter ice, said: “We see that in recent years the winter ice has not frozen over as much as it used to. This may be due to natural fluctuations in the climate, but it could also be a sign of a changing climate.”
Data and Insights
Analysis of the data gathered by the Michigan Tech researchers shows that surface ice coverage on Lake Superior is declining overall. According to the study, the average maximum ice cover of the lake was 75% between 1973 and 2010—down from 90% between 1946 and 1973. The research also showed that winter surface air temperatures in the region increased by an average of 0.86°C per decade between 1950 and 2017.
The research also revealed that the decreasing winter ice coverage could have implications for other aspects of Lake Superior’s ecosystem. It could lead to a decrease in water clarity as sediment from the lake floor is stirred up, and also lead to fluctuations in water levels as areas of melted snow and ice add to the lake’s surface.
Personal Insight
From my point of view, the evidence is clear that climate change is having an effect on Lake Superior’s rate of ice formation. As the average surface air temperature gradually increases, the lake is left more exposed to warmer temperatures and subsequently having an effect on the freeze rate. While it is rare for Lake Superior to be completely frozen in winter, the data shows that the lake is slowly accumulating less winter ice coverage than before.
Winter Impact on Lake Superior’s Wildlife
Lake Superior’s wide range of aquatic wildlife are affected by changes in ice formation. One example of this is the Great Lakes region’s beloved Ringed Seal. The ringed seal is an ice-dependent species, meaning that it requires ice for movement, escaping predators and exposing its young to different environments. With diminishing ice coverage, ringed seals are left more susceptible to predation and loss of their young.
Additionally, fewer areas of ice on Lake Superior disrupts the breeding cycles of some of its aquatic birds, such as the common loon. These birds feed near the edges of ice formations, and their nesting grounds are often located around these areas. If the ice formation rate continues to decline, the common loon risk losing these vital habitats.
Famous Winter Lake Superior
Perhaps due to its vastness and its reputation for unpredictability, Lake Superior has a long history in winter activities. It has long been used for winter transportation of goods and passengers and is home to a number of winter sports and activities, such as ice fishing, skiing and snowmobiling. The lake has featured on the reality television show ‘Ice Road Truckers’ and in the Oscar-winning 1993 film ‘Fargo’.
It is also home to some of the most beautiful ice formations in the world. Every winter, the lake is known to produce large sheets of clear ice, sometimes over 50 feet (15 m) thick, in locations close to the shore, such as Little Presque Isle near the city of Marquette and the shore of the harbor in the town of Duluth.
Long-term Weather Forecasts
Winter temperatures on Lake Superior are difficult to predict in the short-term, but long-term forecasts of lake surface air temperatures could be more accurate. Research published by scientists at the University of Michigan Water Centre in 2018 concluded that meteorological forecasting can predict winter air temperatures and ice cover on Lake Superior more accurately than traditional climate models.
The study showed that the accuracy of the forecasts improves as the forecasts get longer. In the study, the five-day forecasts were the most accurate, and the forecasts from 10 to 14 days in advance were almost as reliable. In some cases, the forecasts for even further ahead were reliable enough for planning ‘ice off’ dates for navigation.
Winter Recreational Activity on Lake Superior
Despite there being a risk of areas of ice on Lake Superior, winter recreational activities are still undertaken without any major restrictions. People still enjoy kayaking, sailing, and fishing during the winter season. The lake usually does not freeze in its entirety which allows for safe water-based recreational activities for residents of the Great Lakes counties and visitors.
Ice boats, sloop-rigged sailboats with three skates beneath them, are also thriving on Lake Superior. These vessels are particularly abundant in Duluth, Minnesota. The city has banned shore-based ice-boating to ensure safety of ice-skaters. However, they still promote ice-boating and encourage others to take part in the recreational activity each winter.
What is an Ice Bridge?
Sometimes Lake Superior can freeze over sections of shallow shorelines, but rarely ever its entire length. On these occasions, an impressive natural phenomenon occurs: an ice bridge forms between two sites on either side of the shore. This is known as an ‘ice bridge’ – a natural pathway made up of thick ice that spans the entire breadth of Lake Superior.
These bridges are created by a combination of forces, the most significant of which is wind. As cold, dry air circulates around the lake, it causes the surface water to freeze and form an icy layer. On rare occasions these conditions can coincide and create an immense bridge of ice.
The ice bridge is an incredible sight, but also a dangerous one. With temperatures falling below -30°C, the cold can take its toll, and should someone venture onto the bridge they risk the lethal danger of hypothermia.
The Phenomenon of ‘Snow Squalls’
Lake Superior is notorious for its unpredictable weather patterns, and in the winter months, it can be especially hazardous. The lake has a unique phenomenon that is known as ‘snow squalls’ which can occur suddenly and turn the lake into a raging blizzard.
Snow squalls are caused by the rapid and sudden convergence of cold air and warm air temperatures. This causes winds of up to 60mph that whip up snowdrifts and can create near-white-out conditions. Snow squalls can last anything from a few minutes to hours and can be hazardous for anyone out on the lake.
All these unpredictable weather patterns and conditions make Lake Superior especially hazardous for winter activities such as ice sailing and snowmobiling. Ice forms on the lake, but it is equally possible that it may not freeze solid, making it dangerous for anyone venturing out on it. As a result, I believe that it is important that people take precautions before venturing out on Lake Superior in winter.
The Extreme Environment in Lake Superior
Lake Superior is an extreme environment, as water temperatures can drop below 0°C during the winter. This chilly environment can be harsh on living organisms, forcing them to migrate to warmer waters or depths, out of the reach of the extreme cold. The lake is home to over 80 species of freshwater fish, such as walleye, trout and whitefish, that migrate to the deeper areas of the lake during the winter season.
The icy depths of the lake can also pose a challenge to boaters, fishermen, and swimmers. The extreme cold temperatures can quickly cause severe hypothermia, and prolonged exposure to the lake in poorly equipped vessels can be fatal. It is, therefore, important that people take precautions before venturing out onto Lake Superior in winter.
The lake is also home to mammals, such as the common loon, harbor seal and grey wolf. These creatures are well-adapted to the harsh environment and can survive even during the coldest temperatures.
