September 26, 2003

A Lawrence Livermore National Laboratory scientist, in collaboration with an international team of colleagues, has reported that noticeable changes in the sub-polar climate and ecosystems appear to be linked to variations in the sun's intensity during the past 12,000 years.

The research, titled "Cyclic Variation and Solar Forcing of Holocene Climate in the Alaskan Subarctic," is reported in today's (Sept. 26) issue of Science.

Using core sediment samples from Arolik Lake in the tundra region along the southwestern coast of Alaska, Thomas Brown of Livermore's Center for Accelerator Mass Spectrometry measured the amount of carbon-14 in samples to provide a chronological framework for the biological and organic evidence of climate and ecosystem changes, which occurred during the Holocene Epoch (12,000 years ago to present).

By studying biological, geochemical and isotopic constituents of sediment samples (such as biogenic silica from single-celled algae, which reflects lake productivity), the researchers determined that variations of these components provided evidence of climate and ecosystem variations over the past 12,000 years.

The scientists identified significant cycles lasting 200, 435, 590 and 950 years in the 12,000-year record, which are consistent with previously recognized cycles of solar activity. By comparison of the Alaskan subarctic record to recent findings of North Atlantic ice cover variations and solar-activity-modulated production records of beryllium- 10 and carbon-14, the scientists showed that the changes in sub-polar climate and ecosystems are correlated with records related to slight variations in solar irradiance.

The data from biogenic silica, North Atlantic sea ice, and beryllium-10 and carbon-14 showed "remarkable correlation during the cycles", Brown said.

"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," said principal investigator Feng Sheng Hu of the University of Illinois at Champaign- Urbana.

"Will changes in solar irradiation in the future mitigate or exacerbate global warming in the future? They may do both. A period of high solar irradiance on top of high levels of greenhouse gases could result in unprecedented warming."

Other contributors come from Northern Arizona University, the Weizmann Institute of Science in Israel, Brown University and Columbia University.

This text derived from http://www.eurekalert.org/bysubject/atmospheric.php

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