Arctic ponds disappearing as climate changes

Ponds which have provided water in polar regions for thousands of years are drying up - another sign of global warming according to Canadian scientists.

Dr John Smol takes a sample from a dried up bed of an Arctic pond

Dr John Smol takes a sample from a dried up bed of an Arctic pond

Two of Canada's leading environmental scientists, professors John Smol and Marianne Douglas, have been recording the levels, water chemistry and ecology of some 40 ponds on the Arctic Ellesmere Island for more than 20 years.

According to their latest paper, due to be published in the USA's Proceedings of the National Academy of Sciences, ponds which are ecologically vital are evaporating as temperatures in polar regions continue to rise.

Polar ecosystems such as these are very sensitive to the effects of climatic and other environmental changes

"In many respects, they are like the miner's canaries of the planet, showing the first signs of warming," said Dr Smol.

Ponds like these are the main source of surface water in many Arctic regions and as such are teaming with life, attracting birds, insects and other invertebrates.

The impact of the falling water levels will be widely felt throughout the ecosystem.

Another disturbing finding was the drying-up of neighbouring wetlands. In the 1980s, the regions around the ponds tended to be 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," said Dr Smol.

Dr Douglas said the study demonstrated the value of long-term monitoring programmes.

"Had we just arrived at Cape Herschel last year, we would have surmised that these were naturally temporary ponds," she said.

"But we know instead that this was not the case - these had been permanent water bodies for millennia."

In a controversial 1994 paper published in the journal Science, the Canadian team showed that the ponds existed more or less unchanged for thousands of years but that, beginning in the 19th century, they underwent a marked ecological shift, 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.

However, the ecological changes recorded in then pale in comparison to those noted in the current paper, where some sites had completely dried up by early summer.

Rising temperatures have seen some polar lakes disappear as the permafrost which creates an almost-waterproof bed has melted allowing water to seep away, but the process recorded by the Canadians is different.

Increasingly rich mineral concentrations suggest that the water is evaporating, a process Dr Smol's compared with boiling off soup.

"If you take the lid off, it is similar to what we are observing in these ponds," he said.

"The soup will slowly decrease in volume and it will get saltier and saltier as the water evaporates, leaving the salts behind."

Sam Bond



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