The Associated Press reports that, “A first-of-its-kind NASA study is finding nice cool lakes are heating up — even faster than air. Two NASA scientists used satellite data to look at 104 large inland lakes around the world. They found that on average they have warmed 2 degrees since 1985. That’s about two-and-a-half times the increase in global temperatures in the same time period. The study was published Wednesday in the journal Geophysical Research Letters.”
The study’s lead author Phillipp Schneider says, “Our analysis provides a new, independent data source for assessing the impact of climate change over land around the world.”
ScienceNews notes that, “Globally, the average increase has hovered around 0.045 degrees Celsius (0.81 degrees Fahrenhenit) per year, but in some regions the increase has been more than twice that — or about 1 degree Celsius (1.8 degree Fahrenheit) per decade.”
A NASA media release states that, “In certain regions, such as the Great Lakes and northern Europe, water bodies appear to be warming more quickly than surrounding air temperature.”
The study says that, “The results have implications for lake ecosystems, which can be adversely affected by even small water temperature changes.” The NASA media release adds that, “Small changes in water temperature can result in algal blooms that can make a lake toxic to fish or result in the introduction of non-native species that change the lake’s natural ecosystem.”
The Canadian Press reported in July that, “Normally frigid Lake Superior has warmed up faster than usual this summer due to a winter with little ice and a record-warm spring, according to researchers.”
“Surface temperatures are about 11 degrees Celsius higher than normal for this time of year and could be on their way to record highs, said researchers at the University of Minnesota Duluth’s Large Lakes Observatory. In the spring, the sun warms the water fairly uniformly as deep and shallow water mix. Once it reaches about 3.8 degrees Celsius, however, the behaviour of the water changes and warmer water starts to form a layer floating on the colder water below. The process, known as lake turnover, usually happens in mid-July on Lake Superior, but this year it happened in early to mid-June instead.”
“Climate change is responsible for the warming effect, the researchers said. ‘Lake Superior is responding to global climate shifts as clearly as anywhere on Earth,’ they said. …’There’s a climate momentum going on out there,’ (Steve) Colman (director of the University of Minnesota Duluth’s Large Lakes Observatory) said. ‘The traditional thought was that there really wasn’t any carry-over from one year to the next with this kind of system. But it looks like there is.’”
The pattern is, “The warmer the air and water, the less ice forms. The less ice, the warmer the water gets. Then less ice forms next winter.” It is unclear what effect the warmer water will have on the lake say the scientists. It could mean “a more fertile lake with more organisms that thrive in warmer conditions” or Colman says it could cause “cascading biological effects to fish and other species that we can surmise but haven’t confirmed as yet.”
“(Research Jay) Austin said UMD researchers don’t track water temperatures in the other four Great Lakes.”
And a major new report by International Upper Great Lakes Study Board released in December 2009 found that climate change has also caused a discernible drop in the water levels of the Great Lakes. The report, that involved more than 100 scientists and engineers, estimates that Lake Huron and Lake Michigan have fallen about a quarter metre relative to Lake Erie over the last fifty years with 40-74 percent of that reduction due to climate change.
The NASA media release is at http://www.nasa.gov/topics/earth/features/earthb20101123.html.