Here is another pretty clear indicator of the warming that has taken place over two decades. Lake Superior is a middle of the continent heat absorber that will actually accelerate the effect of an increase in temperature.
Anyway it also shows us what is truly in store for us in the Arctic. Heat will be absorbed every year and it will continue to eliminate and weaken remaining older sea ice.
The Arctic and its surrounds will become progressively warmer with the disappearance of the ice in summer. A number of these changes will be cumulative and help maintain the changes.
So long as the surplus heat is sustained then the changes taking place on these transition zones will also be sustained. It just will take a long time to fully mature.
Lake Superior is large enough to provide a high degree of confidence in terms of the quoted temperature changes.
Warmer Means Windier On World's Biggest
by Staff Writers
Rising water temperatures are kicking up more powerful winds on
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.
"The lake's thermal budget is very sensitive to the amount of ice cover over the winter," says Ankur Desai, atmospheric and oceanic sciences professor at the University of Wisconsin-Madison. "There is less ice on
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
"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 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.
"The warming of the lake is counteracting the mixing we would expect," says McKinley, as the annual period warm water "shoals," or remains shallow, grows longer by a few days every decade.
"If you look at an area like
Changes in the lake winds may also play out over neighboring land, Desai says, possibly in the way
"Large lakes are very interesting," he says. "They behave sometimes like an ocean and sometimes like a small lakes, but they're not studied as much as either."
That may change with the arrival of more than half a billion dollars promised by the federal government to
"We have more to do," McKinley says, pointing to Austin's mooring of underwater instruments and the researchers' continuing assessment of the carbon cycling in and out of Lake Superior as part of a four-year grant funded by the National Science Foundation.
"The new federal money is good, but it can't only be for remediation," she says. There's got to be some of that science to understand how these lakes work.