Rising water temperatures are kicking up more powerful winds on Lake Superior, with consequences for currents, biological cycles, pollution and more on the world's largest lake and its smaller brethren.

Since 1985, surface water temperatures measured by lake buoys have climbed 1.2 degrees per decade, about 15 percent faster than the air above the lake and twice as fast as warming over nearby land.

A wide temperature differential between water and air makes for a more stable atmosphere with calmer winds over the relatively cold water. However, as warming water closes the gap, as in Lake Superior's case, the atmosphere gets more turbulent.

"You get more powerful winds," Desai says. "We've seen a 5 percent increase per decade in average wind speed since 1985."

Those findings will be published Nov. 15 in the journal Nature Geoscience.

Desai, fellow atmospheric and oceanic sciences professor Galen McKinley and graduate research assistant Val Bennington of UW-Madison and physics professor Jay Austin of the University of Minnesota-Duluth used more than 20 years of temperature and wind data collected by three lake buoys and Earth-observing satellites to model Superior's water and wind system in three dimensions.

"We can look at how the currents are changing based on changes in the wind," McKinley says. "What we saw was a significant increase in the speed of the currents, nearly 10 percent per decade."

In theory, that increase in wind and current strength would make for more mixing within the lake and, in turn, a boost in the growth of organisms that make up the earliest links in the food chain.

"A November storm on Lake Superior with Split Rick Lighthouse in the distance. Rising water temperatures are kicking up more powerful winds on Lake Superior, with consequences for currents, biological cycles, pollution and more on the world's largest lake and its smaller brethren. (Credit: iStockphoto/Lawrence Sawyer)"

Source: University of Wisconsin-Madison