Northern climate, ecosystems driven by cycles of changing sunlight

CHAMPAIGN, Ill. -- Emerging geochemical and biological evidence from Alaskan lake sediment suggests that slight variations in the sun's intensity have affected sub-polar climate and ecosystems in a predictable fashion during the last 12,000 years.

Researchers at six institutions report the findings in the Sept. 26 issue of the journal Science. The data, they say, help to explain past changes on land and in freshwater ecosystems in northern latitudes and may provide information to help project the future.

The scientists identified cycles lasting 200, 435, 590 and 950 years during the Holocene Epoch, said principal investigator Feng Sheng Hu of the University of Illinois at Urbana-Champaign. The pattern of environmental variations they found also matches nicely with cyclic changes in solar irradiance and the extent of sea ice in the North Atlantic.

"We found natural cycles involving climate and ecosystems that seem to be related to weak solar cycles, which, if verified, could be an important factor to help us understand potential future changes of Earth's climate," Hu said.

"Will changes in solar irradiation in the future mitigate or exacerbate global warming in the future? They may do both," said Hu, a professor in the plant biology and geology departments at Illinois. "A period of high solar irradiance on top of high levels of greenhouse gases could result in unprecedented warming."

The new data come from Arolik Lake sediment in the tundra region near the Ahklun Mountains, along the southwestern coast of Alaska. Hu and co-author Darrell Kaufman of Northern Arizona University in Flagstaff have conducted climate-change research in that region for more than a decade.

"To our knowledge, this is the first data set from the North Pacific high latitudes that has enough details to evaluate the effects of centennial scale solar cycles on climate and ecosystems," Hu said.

Sediment samples were tested for a variety of biolo

Contact: Jim Barlow, Life Sciences Editor
University of Illinois at Urbana-Champaign

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