Likely Date of Last Freeze Over
Lake Superior is the largest and deepest of the five Great Lakes that straddle the boundary between the United States and Canada. Lake Superior stands out for its size and deepness, as well as its status as the world’s largest freshwater lake by area. It is renowned for its sometimes-extreme weather, winter storms, and in more recent years, an ice bridge to cross over the lake. While it is not the coldest of the Great Lakes, it has an extensive and variable freeze-over history. Based on the current climate record and other factors, experts suggest that the last freeze-over period likely occurred in 2019.
This speculation is based on several factors, including Lake Superior’s freeze-over pattern and its present climate requirements. In general, the lake typically freezes over in the winter, with a later freeze date than the other Great Lakes and a somewhat earlier break-up in the spring. Because of its large surface area, Lake Superior is considered to be the first to freeze and last to break.
The break-up date of Lake Superior’s ice cover is largely determined by its prevailing air temperature, water temperature, and degree of air movement. The ease of freeze-over is further determined by wind and current speed and direction, ice thickness, as well as the presence of other material such as snow and debris on the lake’s surface. All these variables have teamed up to create a variable and inconsistent freeze-over pattern over the past two centuries.
Historically, Lake Superior has frozen completely over several times since the 19th Century, however, none in the recent years. Since January 2000, temperatures around Lake Superior average a couple of degrees warmer, resulting in less frequent freeze-over occurrences. As a result, the frequencies of fully frozen Lake Superior and faster break-up between winters has decreased significantly while the length of the duration of freeze-over has grown shorter.
This decrease in the number of forms and break-ups, as well as the duration of freeze-overs, has in turn made it difficult for scientists and climatologists to pinpoint an exact date of the last freeze-over of Lake Superior. However, based on the data available and prevailing temperatures, experts speculate that the last freeze-over occurred in 2019, though this cannot be said with absolute certainty.
Impact of Climate Change
The decrease in the number of freeze-overs has largely been attributed to the effects of climate change and global warming. Studies from the U.S. Climate Data Initiative have reported lower temperatures during the winter freeze-over season compared to previous decades and a longer ice-free season in the summer months. In addition, higher air temperatures are causing the atmosphere to hold more moisture and creating more heat stress on the lake.
This has had an effect on both the frequency and length of Lake Superior’s freeze-over cycles. As temperatures continue to rise, it is likely that the amount and duration of freeze-over events will decrease even further. In fact, some experts suggest that by the next century, Lake Superior’s freeze-over period could come much later in the winter and end up being much shorter in duration.
Climate change has been having a direct effect on Lake Superior and its ice cover dynamics, resulting in drastic shifts in the lake’s freeze-over period and other water-related events. This, in turn, has driven up the availability of safe navigation and fishing grounds, leading some to suggest that Lake Superior could become more accessible than ever before.
Changes in Lake Superior’s freeze-over pattern due to climate change have also resulted in a shift in the availability of resources. For example, with increased air temperatures, more sunlight is now able to penetrate the ice, allowing for increased algae and other aquatic life that are essential for the health of the lake’s ecosystem. Warmer temperatures also melt the snow faster, resulting in more nutrients for the lake’s plant life. This in turn has had a positive impact on the species of fish in the lake.
Human Impact on Lake Superior’s Freeze-Over
Though the discussion surrounding Lake Superior’s freeze-over period has largely focused on the effects of changing climate, there is another factor that experts believe is having a direct influence on the lake’s freeze-over pattern: human activity. In other words, many of the lake’s freeze-over patterns are direct results of man-made activities that are occurring in and around the lake.
For example, the development of a hydroelectric plant near the lake and the use of asphalt and other construction materials near the lake can cause water temperatures to warm up more quickly than normal, especially during the winter months. This can lead to relatively shorter freeze-over times and higher breakup dates. In addition, the presence of ships and other large vessels can disrupt the lake’s freeze-over period due to their own heat sources and the force of their movement.
However, these impacts are relatively small when compared to the effect of global climate change. Nonetheless, these potential influences are something that scientists and experts need to take into consideration when considering the freeze-over of Lake Superior.
Rising Eutrophication Levels
Climate change is not the only factor having an effect on Lake Superior’s freeze-over pattern. Researchers have identified a dramatic increase in the lake’s eutrophication levels over the past several decades. Eutrophication is the process of nutrient enrichment of water bodies, and Lake Superior has seen its nutrient levels increase significantly in recent years.
This nutrification is thought to be caused by increased runoff from agricultural land, as well as industrial pollutants that are making their way into the lake. This nutrient-rich water can make the lake warmer and act as an insulator, making it more difficult for the lake to freeze over. The warming of the lake water can also make the ice thinner, making it more fragile and difficult to traverse.
These nutrient-rich conditions have also had a direct effect on the lake’s aquatic life. Increased levels of nutrients such as nitrogen and phosphorus have caused an increase in algae growth, leading to algal blooms that can have a direct effect on the lake’s fish population. Warmer lake temperatures can also lead to a decrease in the amount of oxygen in the water, potentially leading to the death of aquatic species.
Conclusion of Impact
Overall, Lake Superior’s freeze-over patterns and climate requirements have experienced a gradual shift over the past two centuries. Rapidly changing air temperatures, increased eutrophication levels, as well as man-made activities near the lake have all had a direct impact on the lake’s freeze-over period. It is therefore difficult to pinpoint an exact date of the last freeze-over of Lake Superior, though experts suggest that this happened in 2019.
The effects of climate change and other factors have had a profound effect on the lake’s resources and ecosystems, leading some to question how long the lake will remain frozen in the future. As temperatures continue to rise, it is likely that the number of freeze-overs will decrease even further, resulting in Lake Superior becoming more accessible than ever before.
