Reports shed light on Great Lakes water levels

TRAVERSE CITY, Mich. — Scientists are reporting new findings about the relationship between evaporation, precipitation and changing water levels in the Great Lakes.

In a paper being released Tuesday, researchers say the role played by ice that covers sections of the lakes during cold winters is more complex than previously believed.

Lead writer John Lenters of the Ann Arbor consulting firm LimnoTech says ice doesn’t simply act as a “cap” that limits evaporation in winter. It also cools lake temperatures and helps delay the onset of evaporation later. But heavy evaporation can occur shortly before ice forms.

The other study by the University of Wisconsin says large-scale atmospheric patterns played a role in regular ups and downs of water levels until the late 1990s, when they began a slump for reasons that aren’t clear.