GLOBAL WARMING IS EVAPORATING ARCTIC PONDS: NEW STUDY

High Arctic ponds – the most common source of surface water in many polar regions – are now beginning to evaporate due to recent climate warming, say two of Canada’s leading environmental scientists.

Queen’s biology professor John Smol, Canada Research Chair in Environmental Change, and Marianne Douglas (professor of eEarth and aAtmospheric sSciences and director of the Canadian Circumpolar Institute at the University of Alberta) will publish their startling conclusions this week in the on-line edition of the journal, Proceedings of the National Academy of Sciences (PNAS).

“The final ecological threshold for an aquatic ecosystem is loss of water,” says Dr. Smol. “These sites have now crossed that threshold.”

Since 1983, Drs. Smol and Douglas have been regularly sampling the water quality and biota of about 40 ponds on Cape Herschel, east-central Ellesmere Island, in the Canadian High Arctic. Polar ecosystems such as these are very sensitive to the effects of climatic and other environmental changes, they note in their paper. “In many respects, they are like the ‘miner’s canaries’ of the planet, showing the first signs of warming.”

But this new discovery by the Canadian researchers has surprised even them. In the 1990s they were alarmed when they began to recognize a trend of declining water levels and changes in water chemistry. When they arrived to begin another field season in July of 2006 (the warmest year on record for that portion of the Arctic), some of the ponds were dry, and others had dramatically reduced water levels.

“This study shows the value of long-term monitoring programs,” says Dr. Douglas. “Had we just arrived at Cape Herschel last year, we would have surmised that these were naturally temporary ponds. But we know instead that this was not the case – these had been permanent water bodies for millennia.”

As well as monitoring the ponds for 24 years, the researchers have also reconstructed ecological trends over the past several thousand years in some of the ponds, using paleoecological techniques. In a controversial 1994 paper published in the journal Science, they showed that the ponds existed for millennia, but that, beginning in the 19th century, they underwent marked ecological changes, consistent with warming.

“We had a bit of a rough ride with that paper for a few years, but now there is almost universal scientific consensus concerning our 1994 conclusions,” says Dr. Douglas. In 2005, she and Dr. Smol, along with 24 co-authors, used similar techniques to document widespread ecological changes, consistent with warming, across the circumpolar Arctic.

However, the ecological changes recorded in the 1994 study pale in comparison to those noted in the current paper, where some sites had completely dried up by July.

While some subarctic lakes have recently disappeared because the permafrost that formed a largely waterproof barrier has melted, this is not the case here, say Drs. Smol and Douglas. Instead, the high Arctic ponds are evaporating due to warming. By measuring changes in water quality over their 24-year sampling window, they have shown that the concentration of salts has been steadily increasing.

Using the analogy of a pot of soup simmering on a stove, Dr. Smol explains: ”If you take the lid off, it is similar to what we are observing in these ponds. The soup will slowly decrease in volume and it will get saltier and saltier as the water evaporates, leaving the salts behind.” The same process is happening with the Cape Herschel ponds, he continues. Water levels are declining and the remaining water is more concentrated with evaporation due to warming.

Another disturbing finding was the drying-up of neighbouring wetlands. In the 1980s, portions of their study region were also characterized by water-saturated wetlands, where the team would need to don hip waders to sample the surface pools of water persisting throughout the summer. However, in 2006, the wetlands had dried to such an extent that they could easily be ignited with a lighter. “The ecological consequences of shifting wetlands such as these from carbon sink to potential carbon sources are frightening,” they say.

Ponds, the dominant source of surface waters in many Arctic regions, are “hot spots” of biodiversity, as well as habitat for many birds, insects, and other organisms, the researchers point out. The resulting ecological changes will likely cascade throughout the ecosystem.

“In the past, researchers like us have sometimes been accused of being alarmist when we discussed climate warming,” says Dr. Smol, winner of the 2004 NSERC Herzberg Gold Medal as Canada’s top scientist or engineer. “We now think we have been overly optimistic – the speed and magnitude of environmental changes are worse than even we imagined!”

The research was funded primarily by the Natural Sciences and Engineering Research Council of Canada and the Polar Continental Shelf Project.

(Source: http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2007/2007070325354.html)

Arctic ocean history is deciphered by ocean-drilling research team

Sediment cores retrieved from the Arctic’s deep-sea floor by the Integrated Ocean Drilling Program’s Arctic Coring Expedition (ACEX) have provided long-absent data to scientists who report new findings in the June 21 issue of Nature.

A team of ACEX researchers report that the Arctic Ocean changed from a landlocked body of water (a ‘lake stage’) through a poorly oxygenated ‘estuarine sea’ phase to a fully oxygenated ocean at 17.5 million years ago during the latter part of the early Miocene era.

The authors attribute the change in Arctic conditions to the evolution of the Fram Strait into a wider, deeper passageway that allowed an inflow of saline North Atlantic water into the Arctic Ocean. Scientists believe that the deep-water connection between the northern Atlantic and Arctic Oceans is a key driver of global ocean circulation patterns and global climate change.

In 2004, the offshore ACEX research team cored a 428-meter thick sediment sequence from the crest of the Lomonosov ridge in the central Arctic Ocean, near the North Pole. These sediments provide the first geological validation of the Cenezoic paleoenvironmental history of the Arctic Ocean. Current evidence of the onset of the ventilated circulation system is preserved in the chemical and physical properties and the micropaleontology of the recovered seafloor sediments.

Co-chief scientist Jan Backman, Stockholm University, comments on the significance of the new findings, saying, “If we can learn what has happened in the geological past, we can begin to use that knowledge to look into the future. Scientists engaged in climate change studies are advancing an important area of knowledge about the planet we live on.”

Source: Integrated Ocean Drilling Program Management International

(Source: http://www.physorg.com/news101566538.html)