Washington, October 20 A new study has determined that an analysis of sediment cores indicates that biological and chemical changes occurring at a remote Arctic lake are unprecedented over the past 200,000 years and likely are the result of human-caused climate change.

The new study included researchers from University of Colorado at Boulder, the State University of New York's University at Buffalo, the University of Alberta, the University of Massachusetts and Queen's University in Kingston, Ontario.

While environmental changes at the lake over the past millennia have been shown to be tightly linked with natural causes of climate change, the changes seen in the sediment cores since about 1950 indicate that expected climate cooling is being overridden by human activity like greenhouse gas emissions.

The research team reconstructed past climate and environmental changes at the lake on Baffin Island using indicators that included algae, fossil insects and geochemistry preserved in sediment cores that extend back 200,000 years.

"The past few decades have been unique in the past 200,000 years in terms of the changes we see in the biology and chemistry recorded in the cores," said lead study author Yarrow Axford of CU-Boulder's Institute of Arctic and Alpine Research.

"We see clear evidence for warming in one of the most remote places on Earth at a time when the Arctic should be cooling because of natural processes," he added.

The sediment cores were extracted from the bottom of a roughly 100-acre, 30-foot-deep lake near the village of Clyde River on the east coast of Baffin Island, which is several hundred miles west of Greenland.

The lake sediment cores go back in time 80,000 years beyond the oldest reliable ice cores from Greenland.

The sediment cores showed that several types of mosquito-like midges that flourish in very cold climates have been abundant at the lake for the past several thousand years.

But, the cold-adapted midge species abruptly began declining in about 1950, matching their lowest abundances of the last 200,000 years.

Two of the midge species adapted to the coldest temperatures have completely disappeared from the lake region, according to Axford.

In addition, a species of diatom, a lake algae that was relatively rare at the site before the 20th century, has undergone unprecedented increases in recent decades, possibly in response to declining ice cover on the Baffin Island lake.

"Our results show that the human footprint is overpowering long-standing natural processes even in remote Arctic regions," said co-author John Smol of Queen's University. "This historical record shows that we are dramatically affecting the ecosystems on which we depend," he added. (ANI)