Thursday, November 7, 2013

Lake Superior Water Level

When I looked outside this morning I saw some minor snow accumulation along the fringes.  According to TV6, there are places in the Grand Marais area (probably south of town) with two inches on the ground as well as other areas in the U.P. with four inches of snow.  I guess it is November after all...

Since we have had SOOOOO much rain this year, I decided to research how the level of Lake Superior is doing.  Great Lakes water levels constitute one of the longest high quality hydrometeorological data sets in North America with reference gauge records beginning in 1860 and sporadic records going as far back as the early 1800's.  These levels are collected and archived by NOAA's National Ocean Service.

Lakes Superior and Michigan-Huron are 10 and 11 inches, respectively, above their levels of a year ago.   Lakes St. Clair and Erie are each 5 inches above what they were at this time last year, while Lake Ontario is 11 inches above last year.  Over the next month, the levels of Lake Superior and Lake Michigan-Huron are predicted to decline 3 and 1 inches, respectively.  Lakes St. Clair, Erie and Ontario are projected to each drop 3 inches over the next 30 days.  See our Daily Levels web page for more water level information.

Forecasted Water Level for November 1, 2013 (feet)
Chart Datum (feet)
Difference from chart datum (inches)
Difference from average water level for Oct 1, 2013 (inches*)
Difference from average water level for Nov 1, 2012 (inches*)


Most studies of future lake levels have concluded that climate change will cause lower lake levels in the future. Scientists are not sure.  Despite this uncertainty, there are reasons to be concerned about the future. Consider:

• Great Lakes ice cover has decreased 71 percent over the past 40 years. Less ice contributes to warmer water temperatures and increased evaporation —the single largest source of water loss in the lakes.

• Great Lakes water temperatures are rising, according to government data. Average summer water temperatures in the normally frigid Lake Superior, the world’s largest lake by volume, have increased 4 degrees since the 1980s and around 7 degrees since the 1970s. Superior is now one of the fastest-warming lakes on the planet.

• Evaporation has increased dramatically over the past 50 years, according to Army Corps of Engineers data. Evaporation has more than doubled in Lake Superior since the 1960s and has increased 44 percent in Lake Michigan-Huron, 45 percent in Lake Ontario and 17 percent in Lake Erie.

•  Most climate change models predict a continued increase in Great Lakes water temperatures, even less ice cover and more evaporation from the lakes. Climate change is also causing more extreme storms, which causes flooding that flushes more pollutants into the lakes.

The darker areas in the map below show where there has been significant water temperature increases.

Andrew D. Gronewold, Anne H. Clites, Joeseph P. Smith, Timothy S. Hunter:

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