Widespread Arctic warming crosses critical ecological thresholds, scientists warn

Unprecedented and maybe irreversible effects of Arctic warming, linked to human intervention, have been discovered by a team of international researchers led by Queen's University biologist John Smol and University of Alberta earth scientist Alexander Wolfe. The researchers have found dramatic new evidence of changes in the community composition of freshwater algae, water fleas and insect larvae (the base of most aquatic food webs) in a large new study that covers five circumpolar countries extending halfway around the world and 30 degrees of latitude spanning boreal forest to high arctic tundra ecosystems.

"This is an important compilation of data that human interference is affecting ecosystems on a profound scale," says Dr. Smol, Canada Research Chair in Environmental Change and 2004 winner of Canada's top science award, the Gerhard Herzberg Gold Medal. "We're crossing ecological thresholds here, as shown by changes in biota associated with climate-related phenomena like receding ice cover in lakes. Once you pass these thresholds it's hard to go back."

The team's findings, in the largest study of its kind, will be published the week of February 28 in the Proceedings of the National Academy of Sciences (PNAS).

A total of 26 researchers from Canada, Finland, Norway, the UK, and Russia have produced 55 historical profiles of algal and invertebrate animal remains from the sediment in 46 Arctic lakes. Also on the team from Queen's are biologist Kathleen Rûhland and PhD student Bronwyn Keatley. John Birks, a professor at the University of Bergen and adjunct professor at Queen's, quantified the amount of biological change using statistical approaches.

The new study shows that climate change has lengthened summers and reduced lake ice cover across much of the Arctic. This in turn prolongs the growing season available to highly sensitive lake organisms, and opens up new habitats. The most intense population changes occurred in the northernmost study sites, where the greatest amount of warming appears to have taken place, the researchers say.

"Polar regions are expected to show the first signs of climatic warming, and are therefore considered sentinels of environmental change," says Dr. Wolfe. "Unfortunately, long-term monitoring data are generally lacking in these areas, which makes it difficult to determine the direction and magnitude of past environmental changes." Since lakes are ubiquitous to most Arctic environments, however, microfossils of aquatic organisms preserved in the sediment become an archive of the lake's history, adds University of Toronto Geology Professor Marianne Douglas.

"The timing of the changes is certainly consistent with human interference, and one of the major avenues is through climate warning," notes Queen's biologist Dr. Kathleen Rûhland. "This is another example of how humans are directly and indirectly affecting global ecology."

An earlier lake sediment study co-authored by Drs. Douglas and Smol, published in the journal Science in 1994, caused controversy with its interpretation of climatic warming in three high Arctic ponds. Now, says Dr. Smol, "the tide has turned, and some of the strongest skeptics of that 1994 study are co-authors on this paper."

One area in the Canadian sub-Arctic that appears not to be warming to the same extent is in Labrador and northern Québec. Team member Reinhard Pienitz, from Université Laval, notes that this represents an important control region for the study. The fact that no patterns of biological change are evident there supports the findings from other areas where warming has been inferred. "The changes have not been primarily caused by, for example, atmospheric deposition of contaminants," says Dr. Pienitz.

The study concludes that it may soon be impossible to find "pristine Arctic environments untouched by climate warming." And since changes in the Arctic are considered bellwethers of what is to come further south, the researchers consider this their most urgent environmental wake-up call to date.

"If you look at one lake at a time, you still get important information, but it's hard to make large-scale, regional assessments," says Dr. Smol. He compares this to viewing an Impressionist painting, where looking at one small section may only reveal dots, but on stepping back you see the whole picture. "Once you compile the larger dataset of all these lakes and ponds, striking and consistent patterns become evident. Taken together, it's a very powerful message."

Source: Queen's University

Related stories:

Climate negotiators reconvene this week in Ghana
(AP) -- Negotiators meet in Ghana this week to resume work on a new climate change treaty and discuss ways to prod developing countries to join the fight against global warming. But the latest round of talks comes at an awkward moment, with the world's poor more worried about the immediate cost of food and fuel than the uncertain long-term effects of climate change.
Future impact of global warming is worse when grazing animals are considered, scientists suggest
The impact of global warming in the Arctic may differ from the predictions of computer models of the region, according to a pair of Penn State biologists. The team -- which includes Eric Post, a Penn State associate professor of biology, and Christian Pederson, a Penn State graduate student -- has shown that grazing animals will play a key role in reducing the anticipated expansion of shrub growth in the region, thus limiting their predicted and beneficial carbon-absorbing effect. The team's results will be published in the online Early Edition of the journal Proceedings of the National Academy of Sciences sometime between 18 and 22 August 2008.
Canada to search for Arctic explorer's ships
(AP) -- For more than 160 years, the fate of British explorer Sir John Franklin and his men has remained locked in the frozen Arctic, but warming temperatures are threatening to change that.
Pacific shellfish ready to invade Atlantic
As the Arctic Ocean warms this century, shellfish, snails and other animals from the Pacific Ocean will resume an invasion of the northern Atlantic that was interrupted by cooling conditions three million years ago, predict Geerat Vermeij, professor of geology at the University of California, Davis, and Peter Roopnarine at the California Academy of Sciences.
Russian subs explore world's deepest lake (Update)
Two Russian mini-submarines on Tuesday dove to the bottom of the world's deepest lake to draw attention to its fragile environment but failed in a record-setting attempt, organisers said.
Russian scientists begin trial exploration of world's deepest lake
Russian scientists leading a submarine expedition to probe the world's deepest lake on Thursday carried out test dives ahead of the start of the operation next week, reports said.
Whale playground offers glimpse into Russia's melting Arctic
A young whale pokes its melon-shaped head into the cool morning air near this remote island, a sign its herd is thriving despite mounting threats in Russia's melting Arctic.
Russian researchers 'rescued from melting ice floe'
Twenty Russian scientists have been rescued from their camp on an ice floe in the Arctic that was melting faster than expected, a spokesman for the expedition told AFP on Monday.

News discussion:

Space & Earth science news