science delivers an answer on Great Lakes water levels

Shame on me for repeating news from reporters without looking into the numbers in greater detail.  I’m not terribly surprised to find out that a swath of recent research on the dynamics of climate, ice cover, evaporation, and flow rates in the Great Lakes system has been published.  There’s a great article chock full of details and solid explanations of the research here on the National Geographic Water Currents blog.  Here’s the take-home message, which should settle the debate on why water levels are so low in the Great Lakes:

Lake water levels are heavily influenced by the amount of ice cover in the winter.  Ice cover in the winter affects when and how much the lake evaporates in the summer.  Ice cover has been at record lows, with a singularity in the winter of 1997-1998.  Since then, significant evaporation has started earlier in the summer, and the lake water has been getting steadily warmer.  This means that the annual onset of water level declines is starting earlier in the year, too, which all leads to lower average water levels.

The scientists apparently don’t want to speculate on the influence of climate change, since water levels aren’t yet statistically different from historical ranges.  Fine, but increasing surface temperature and decreasing ice cover/snowpack are two clear factors in favor of this explanation.  I suspect that the drought is the short-term driver of losses in the Great Lakes system, but climate change is the long-term driver, perhaps of both the Great Lakes system and the drought itself.

Happy Thanksgiving to all — let us be thankful for what we have to drink!

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