With a surface areas equal to the size of South Carolina and holding the same quantity of water as all the other Great Lakes added together, Lake Superior is a spectacular lake. However, it’s waters are warming up and it is slowly losing water, worrying scientists, businesses that rely on the lake, and local people alike. Are these changes down to ‘climate change’? Scientists aren’t sure.

Lake Superior’s water level is currently at it’s lowest point for eight decades; if it dips by another three inches, it will be the lowest ever recorded. The average temperature of the water is up by 4.5 degrees since 1979 – average air temperature has only risen by 2.7 degrees in the same period. For a freshwater lake that was created from a glacial melt at the end of the Ice Age and normally remains chilly, this is a big deal. On the western side of the lake, a weather buoy recently measured water temperature as 75 degrees – the warmest surface temperature that has been measured.

All the Great Lakes have suffered from lowering water levels since the late 1990s however Superior’s changes appear to be sudden and severe, causing concern from many corners. Shorelines are much wider than usual, and the mucky bottomland and rotting vegetation have been exposed.

Along the shores, some boats are unable to reach mooring points; marina operators have requested that the US Army Corps of Engineers help to dredge the shallow harbours. Some ferry services have been scaled back due to problems with docking. Low water levels have also had implications for the shipping industry – the shallower channels mean ships have to carry lighter loads of iron ore to avoid running aground. Local businesses are affected too – as the water’s warm up, some fish have moved from their traditional places to cooler waters in the lake.

However, it seems global warming may not be the culprit in this case. Many people in the area are suspicious of the government’s water movement – water is apparently being diverted to places with more people and therefore more political influence, to places such as Lake Huron, Lake Michigan and the Sun Belt. Not everyone believes this theory. There are locks, power plants and gates on the St. Mary’s River which allows some water from the Lake to exit, however the amounts that can leave are strictly regulated by the 1909 pact with Canada therefore the theory doesn’t stand.

Instead, the finger is pointed at precipitation which has tapered off across all over the Great Lakes in the past 40 years – in fact this year, nearly 6 inches less has fallen that is normal. Water evaporation rates are also up thanks to milder winters and this all adds up to lower water levels in the lakes.

Model predict that precipitation in the area should rise with the advent of global warming, however it appears the opposite is happening, meaning if the models are correct, something else other than global warming is to blame for the low water levels.

There are many theories such as the after-effects of El Nino and the warming of equatorial Pacific waters (that coincided with the lakes starting to recede) but no-one knows for sure.

Many people are concerned about the water levels receding and are sure to keep a close eye on the lake for the foreseeable future.

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