Current Arctic heat wave among rarest in 200,000 years, study says

**GrnMachine** · #1 10-20-2009, 03:37 PM

Current Arctic heat wave among rarest in 200,000 years, study says

The Canadian Arctic is experiencing a heat wave that has seldom been matched in the past 200,000 years, says a new scientific paper based on the study of sediments found at the bottom of a remote lake on Baffin Island.
Scientists looking at the remains of microscopic plants and insects preserved in the lake's crusty bottom say a comparison of flora and fauna found in the remote past and in recent decades suggest temperatures are now so elevated they've rarely occurred.
Over the 200,000 years in question, the sediments revealed a natural ebbing and rising of various species that either favoured warmer or colder climate conditions. But recently there have been unprecedented increases of some algae types dependent on warmer conditions that were almost never found during the pre-industrial era.
“Our findings show that the last several decades have been the most ecologically unique in 200,000 years,” said Neil Michelutti, a research scientist at Queen's University in Kingston, Ont., and one of the members of the team that conducted the study, which is appearing this week in the online edition of the Proceedings of the National Academy of Sciences.
According to the study, the only times that summer temperatures were similar to current readings were just after the last ice age ended about 10,000 years ago, and also during an exceptionally warm period before the last glaciation.
The research also extends far back into time reconstructions of previous climate conditions in the Arctic. Up until now, past climates have been inferred from Greenland's ice cores and the 120,000 years of records they provide. But the data derived from the lake sediments predate the creation of Greenland's massive ice sheets by 800 centuries, allowing scientists to peer that much further back into the remote past.
The new finding is adding to the flurry of research suggesting dramatic and far reaching changes are under way in the Arctic, considered the part of the world most at risk from climate change. Last week, a team of British researchers said the Arctic Ocean is undergoing a swift melting that they predicted will leave it largely free of summertime ice in as little as 20 years.
Earlier this year, there was another report that suggested global warming in the decades ahead would allow for tree growth as far north as Baffin Island.
In the new research, scientists conducted a painstaking reconstruction of life at the site by looking at the fossilized remains of tiny algae and insects preserved in the sediments at the water body, located in an isolated part of the eastcoast of Baffin Island facing Greenland. The algae are microscopic, with hundreds fitting onto the head of a pin, and the insects are primarily midges, small two-winged gnats.
While the composition of the insect and plant communities varied over time, depending on the climate, recently the species have switched to those that thrive in ice free conditions, to a degree unlike anything previously seen.
“The lake has followed a trajectory through the 20th century toward increasingly exceptional environmental conditions with no natural analogues in the past 200,000 years,” the study said.
Over the period tracked by the researchers, there were two ice ages and three warmer so-called interglacial eras, highlighting the rarity of modern climate conditions.
“This historical record shows that we are dramatically affecting the ecosystems on which we depend. We have started uncontrolled experiments on this planet,” said Dr. John Smol, a biologist at Queen's University.
The lake was small and unremarkable by most standards – with less than a square kilometre in surface area and a maximum depth of only 10 metres. But scientists say it had one rare attribute that made it into a major scientific find: during previous ice ages, it wasn't covered with moving glaciers, but rather frozen solid. That meant the sediments at its bottom were preserved. They weren't scoured up and deposited elsewhere, bulldozer fashion, like lake bottoms throughout the rest of the area covered by the glaciers.
The study was conducted by researchers at five U.S. and Canadian universities, including the University of Alberta in Edmonton and the University of Colorado in Boulder.

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