Freighter entering Duluth Harbor, Minn.
High Resolution (Credit: U.S. E.P.A. Great Lakes National Plan Office)
Studies of future climate change scenarios on the Great Lakes have pointed to falling water levels, but a new N.O.A.A. study gives a more optimistic outlook.
Scientists at the N.O.A.A. Great Lakes Environmental Research Lab (GLERL) in Ann Arbor, Mich., have devised a new approach to modeling future water levels. Their work, now accessible online in the Journal of Great Lakes Research, predicts either a smaller drop or an actual rise in lake water levels under varying climate change scenarios.
The impact of climate change on Great Lakes water levels is a critical question for the region's economy and environmental resources, as well as for one of the nation's key shipping corridors.
"Even small drops in lake water levels create problems for shipping and navigation, hydroelectric energy production, and recreational boating," said Brent Lofgren, Ph.D., a GLERL scientist and lead author of the study. "While there are still many unknowns about how climate change will unfold in the Great Lakes region, our results indicate less loss of water than earlier studies."
The researchers used a different method than previous studies to account for how water evaporates into the atmosphere from the soil and plants in the drainage basin that surrounds the lakes, a variable known as evapotranspiration. Earlier studies used air temperature alone to estimate this variable. The new GLERL study uses an "energy budget-based approach" to better reflect the balance between energy coming in from the sun and energy given off from the Earth, which drives evaporation.
Color satellite image of the Great Lakes. How climate change impacts Great Lakes water levels is critical to the region's environment and economy.
High Resolution (Credit: NOAA)
This approach also better represents the influence of greenhouse gases in the atmosphere on evaporation. The scientists applied this approach to computer models that predict lake levels and crunched various climate change scenarios.
"The models show lower loss of water to vapor, meaning that more water is staying in the Great Lakes basin," explained Lofgren.
While greenhouse gases add a small influx of energy to the land surrounding the lakes, they are much more effective at raising the temperature by hindering energy from leaving.
The study, Effects of using air temperature as a proxy for potential evapotranspiration in climate change scenarios of Great Lakes basin hydrology, can be found online.
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