Published June 01, 2011, 12:00 AM

Rising water temps not unique to Lake Superior

On opposite sides of the earth, the two largest lakes are warming at similar rate.

By: John Myers, Duluth News Tribune

The world’s largest lake by volume is warming at almost the same rate as the world’s largest lake by area, and scientists say reduced winter ice cover may be behind both.

The surface water of Lake Baikal in Siberia warmed about 3.8 degrees Fahrenheit from 1977 to 2003 and has continued increasing since then, according to scientists who presented their findings Tuesday at the International Association of Great Lakes Research convention in Duluth.

That warming is nearly as striking as the 4.5 degree surge that University of Minnesota Duluth scientists found from the surface waters of Lake Superior from 1979 to 2006.

In both cases, the water temperature increases are more than double the land temperature increase nearby each lake. And in both cases scientists hypothesize that reduced ice cover each winter on both lakes (caused by shorter, warmer winters) is allowing more sunlight to warm the dark open water rather than be reflected back into space off of white ice.

Lake Baikal, which freezes entirely every winter, lost 18 days of ice cover, on average, over the study period. Lake Superior, while it rarely freezes entirely, has seen a steady decline in the average percentage covered by ice each winter over the past 40 years.

Different scientists “looked at the two largest lakes in the world from vastly different perspectives… and found essentially the same results. Both lakes are warming very rapidly on the surface,’’ said Marianne Moore, one of the keynote speakers at the Duluth conference, which has drawn more than 600 large-lake researchers from around the world.

The scientists come together annually to share new research and compare notes and say they are finding amazingly similar issues facing lakes in astonishingly diverse places — air pollution, agricultural and urban runoff, exotic species and climate change are affecting lakes from Africa to Asia.

In the case of the temperature studies, Jay Austin, a researcher at UMD’s Large Lake’s Observatory, said there’s no escaping the data.

“It just points to this warming of lakes being a global phenomenon and not just a local or regional issue,’’ Austin said. “They all obey the same laws of physics.’’

Lake Baikal, about 400 miles long and averaging about 35 miles wide, is the largest lake in the world by volume, with nearly twice as much water as Superior because of its vast depths. It’s in an incredibly remote area — a six-hour flight from Moscow — with virtually no development or even roads along its shores.

The lake holds almost 20 percent of all the fresh water on Earth.

Because the lake is so old, some 25 million years, species have had millennia to adapt and evolve. It’s considered one of the most ecologically diverse places on Earth, with 2,500 animal species and more than 1,000 plant species, many of them found no where else — from freshwater seals and sponges to single-cell critters that can be seen only under a microscope.

Moore, an aquatic ecologist from Wellesley College in Massachusetts, along with her Russian colleagues already have seen impacts from a warmer Lake Baikal, including a 300 percent increase in algae at one location. Other small critters that thrive in warmer waters are up as much as 335 percent.

Lyubov Izmest’eva, one of the Russian scientists involved with the Baikal research, said temperatures have continued to climb since 2003, the last year previously analyzed.

“The last 10 years, the frequency of above normal days has been increasing,’’ she said Tuesday through an interpreter.

Scientists predict Lake Baikal will increase another 6-7 degrees by the end of the century, with vastly diminished ice cover each winter. That could mean tough times for the lake’s unique seals as well as tiny diatoms that depend on longer ice cover to thrive.

In addition, warmer temperatures on land already have been increasing forest fires in Siberia, causing more nutrients in ash to fall into the lake.

In a lake as cold and deep as Baikal it takes centuries for many things to change much, Moore noted.

“But we are already seeing changes in our lifetime,’’ she said. “By 2099 there could be one to possibly two months fewer months of ice cover. And that’s going to have a dramatic impact on both ends of the’’ lake’s food chain.