Arctic Lake Sediments Show Warming, Unique Ecological Changes in Recent

Please download to get full document.

View again

of 2
8 views
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.

Download

Document Related
Document Description
Arctic Lake Sediments Show Warming, Unique Ecological Changes In Recent Decades ScienceDaily (Oct. 27, 2009) — 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, according to a new study led by the University of Colorado at Boulder. While environmental changes at the lake over the past millennia have been shown to be tightly linked w
Document Share
Document Tags
Document Transcript
  Arctic Lake Sediments ShowWarming, Unique EcologicalChanges In Recent Decades ScienceDaily (Oct. 27, 2009) — An analysis of sediment cores indicates that biological andchemical changes occurring at a remote Arctic lake are unprecedented over the past 200,000years and likely are the result of human-caused climate change, according to a new study led bythe University of Colorado at Boulder.While environmental changes at the lake over the past millennia have been shown to be tightlylinked with natural causes of climate change -- like periodic, well-understood wobbles in Earth'sorbit -- changes seen in the sediment cores since about 1950 indicate expected climate coolingis being overridden by human activity like greenhouse gas emissions. The research teamreconstructed past climate and environmental changes at the lake on Baffin Island usingindicators that included algae, fossil insects and geochemistry preserved in sediment cores thatextend back 200,000 years. The past few decades have been unique in the past 200,000 years in terms of the changes wesee 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 oneof the most remote places on Earth at a time when the Arctic should be cooling because of natural processes. The study was published Oct. 19 in the Proceedings of the National Academy of Sciences . Thestudy included researchers from CU-Boulder, the State University of New York's University atBuffalo, the University of Alberta, the University of Massachusetts and Queen's University inKingston, Ontario.The sediment cores were extracted from the bottom of a roughly 100-acre, 30-foot-deep lakenear the village of Clyde River on the east coast of Baffin Island, which is several hundred mileswest of Greenland. The lake sediment cores go back in time 80,000 years beyond the oldestreliable ice cores from Greenland and capture the environmental conditions of two previous iceages and three interglacial periods.The sediment cores showed that several types of mosquito-like midges that flourish in very coldclimates 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 lowestabundances of the last 200,000 years. Two of the midge species adapted to the coldesttemperatures have completely disappeared from the lake region, said Axford.  In addition, a species of diatom, a lake algae that was relatively rare at the site before the 20thcentury, has undergone unprecedented increases in recent decades, possibly in response todeclining ice cover on the Baffin Island lake. Our results show that the human footprint is overpowering long-standing natural processeseven in remote Arctic regions, said co-author John Smol of Queen's University. This historicalrecord shows that we are dramatically affecting the ecosystems on which we depend. The 20th century is the only period during the past 200 millennia in which aquatic indicatorsreflect increased warming, despite the declining effect of slow changes in the tilt of the Earth'saxis which, under natural conditions, would lead to climatic cooling, notes the University of Colorado's Dr. Axford.The ancient lake sediment cores are the oldest ever recovered from glaciated parts of Canadaor Greenland. Massive ice sheets during ice ages generally scour the underlying bedrock andremove previous sediments. What is unique about these sediment cores is that even though glaciers covered this lake, for various reasons they did not erode it, said study co-author Jason Briner of the University atBuffalo. The result is that we have a really long sequence of sediment that has survived Arcticglaciations. The study was funded by the National Science Foundation, the Natural Sciences andEngineering Research Council of Canada and the Geological Society of America.A study published in the journal Science last month that involved CU-Boulder researchers andreconstructed past temperatures in the Arctic using ice cores, tree rings and lake sedimentsconcluded that recent warming around the Arctic is overriding a cooling trend caused by Earth'speriodic wobble. Earth is now about 0.6 million miles further from the sun during the NorthernHemisphere summer solstice than it was in 1 B.C. -- a trend that has caused overall cooling inthe Arctic until recently.INSTAAR researcher and CU-Boulder geological sciences Professor Gifford Miller was a co-author on both the PNAS  study and the recent Science study. http://www.sciencedaily.com/releases/2009/10/091019162929.htm
Search Related
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks