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Lake Superior Lake Levels
Lake water levels are systematically measured all around Lake Superior. GLERL has an great interactive web page showing the base levels of the Great Lakes, and facilitating the thorough public exploration of this important data.
Lake Superior’s base level has been generally decreasing since about 1993, and has decreased by about 50 cm in 20 years (about 2.5 cm or ~1 in/yr). This decrease is small compared to seasonal changes, so it seems muted unless one has a decadal perspective. While it is good for our geological goals of seeing wave-washed shoreline exposures, this decline has many local residents quite concerned. In the past few months, the lake level has rebounded to about its long term average, a change that is driven in part by groundwater levels bouyed by increased precipitation, that broke a decade of drought.
Are Great Lakes levels linked to global warming? This is an issue of focus. It appears that correlation of decreasing lake levels and rising local temperatures is happening, but it isn’t clear whether they are causally related. A futuristic look at the likely environmental changes we can expect from global warming is available from the Union of Concerned Scientists. These forecasts do include lower lake levels.
A leader in research on Lake Superior lake levels is Walter Loope of the USGS, who lives at Pictured Rocks. His work on Lake Superior lake levels gives a record of lake changes since the last glaciation. Understanding this record is important to forecast future lake levels.
Some Climate Change Links
Annual averages of global sea level. Red: sea-level since 1870; Blue: tide gauge data; Black: based on satellite observations. The inset shows global mean sea level rise since 1993 - a period over which sea level rise has accelerated. More information: Coastal Sensitivity to Sea Level Rise (USGCRP) and Climate Change 2007: The Physical Science Basis.
Global Sea Levels are rising as Earth’s glaciers melt (see below). This trend does not directly link to the Great Lakes, however. USGS: Uncertainty in Great Lakes Water Levels
