Historical Evidence of Tides in Lake Superior
Lake Superior, the largest of the Great Lakes, has long been thought to be immune from the ebb and flow of tides. The truth is much more complicated, however. Evidence of rhythmical water levels has been observed by European settlers and Native American tribes for centuries.
In the early 1800s, noted French explorer Alexander Henry reported the unusual phenomenon of the the lake rising and falling, much like the tide. He and other early explorers observed the water ebbing and flowing almost exactly six hours apart. The Native Americans living on the shores at the time were eyewitnesses to this as well, and have legend of a giant fish and serpent spirit which caused the lakes to rise and fall.
Modern Research Into Tides
In more recent times, extensive research has been done in a bid to fully understand the tidal behavior in Lake Superior. Studies have shown that the lake does in fact experience small, rhythmic fluctuations in water levels which correspond to the lunar cycle and tides in the nearby Atlantic Ocean.
The lake’s tidal range is around 6mm, a fraction of what some coastal oceans experience, but nevertheless, these tides are enough to cause fluctuations in fish behavior and concentrations, as well as shifts in the formation of beaches and shoreline topography.
Why Does Lake Superior Experience Tides?
The reason that Lake Superior experiences tides is due to a combination of its size and shape, as well as geological and atmospheric forces. Its size, combined with the expansive shoreline and the open connection to the Atlantic Ocean, creates a gravitational pull that is enough to cause small but perceptible changes in water levels. Its shape also adds to the pull, as it is longer vertically than it is horizontally, which helps to amplify the tidal forces.
What Affects The Magnitude of the Tides?
Atmospheric and weather patterns can also have an effect on the magnitude of the tides. Low pressure systems act to draw water towards them and correspondingly, high pressure systems will push away the water, resulting in increased and decreased tidal magnitudes respectively.
Winds from different directions also affect the magnitude. Northerly winds result in more pronounced tides as they cause a piling up of water along the north shore of the lake, whereas easterly winds result in a higher rate of flow as the tide exits into the Atlantic.
How Do the Tides Affect the Surrounding Environment?
The ebb and flow of the water can create waves and currents which have a significant impact on the shape of the shoreline. The size of the waves is small, meaning they don’t reach the beaches, but they are still large enough to cause erosion of the sand and rock by churning the sediments. This gradual erosion can cause a shift in the shape of the shoreline and even create coves and tidal basins.
The presence of the tides also affects fish behavior and concentrations. The presence of tides in a lake can lead to an increase in fish concentration, as the variations can disorient certain species. It can also cause the fish to seek out calmer waters and concentrate there, which can make them easier to catch.
Effects on Water Quality
The presence of tides can also have an effect on water quality in the lake. As the tide ebbs and flows, it can bring in or take out pollutants or pollutants that are suspended in the water. This can cause an imbalance which affects the pH of the water and the presence of nutrients which can lead to an increase in algae growth and poorer water clarity. Additionally, the presence of tides can speed up sediment transport and erosion, resulting in deeper and more stable shorelines.
The Scientific Explanation
The scientific explanation for the phenomenon is fairly simple. As the moon orbits around the Earth, its gravity causes the atmosphere to bulge in the direction that the moon is in, and this causes the lake to be pulled toward it. When the moon is at its furthest away, the lake falls in a “spring tide” that is roughly 6 hours apart. This would explain the observation made by early Europeans and Native Americans of the lake rising and falling in the same 6-hourly pattern.
The Effect of Climate Change on the Tides
Climate change poses an even greater threat to the tides in Lake Superior. As temperatures continue to rise and the ice continues to melt, the lake levels are expected to rise further. This is likely to cause an increase in the magnitude of the tides, which can then lead to changes in fish behavior and shoreline formations.
The increased water levels also pose a threat to beach and dune ecosystems, as the higher tides will accelerate erosion and reduce the amount of usable beach area. Additionally, the higher water levels could cause an influx of pollutants, as the increased force of the tides can draw more pollutants onto the beaches and into the lake.
The Impact of Tourism
Although the presence of tides in Lake Superior is a naturally occurring phenomenon, it is now being affected by human activities. The increased traffic of ships, boats, and recreational watercraft have all have been blamed for increasing the rate of erosion and fouling of the shoreline. Additionally, as more people visit the lake and use it for recreation, the more likely it is to become a breeding ground for pollutants.
The increased human activity around the lake could also result in greater amounts of debris and other waste. This could speed up the rate of erosion and reduce the shelf life of beaches and dunes, as the debris will reduce the amount of natural material available for the waves to work with and can even result in altered habitats.
How to protect the lake?
In order to protect the lake and its tidal systems, governments, conservationists and local communities need to take action to reduce the impact that human activities have on the lake. This would involve implementing regulations on human activities that could disrupt the lake’s environment, such as motorboat restrictions and improved waste management.
It is also important for local communities to take responsibility for the lake and its environment. This could involve organizing beach and shoreline clean-ups, maintaining a low-impact approach when using the lake and respecting any regulations that are in place.
Ultimately, it is up to everyone to do their part to protect Lake Superior and its tidal systems, both now and for the future.
