A major study of Arctic lake sediments provides new evidence of human-induced climate change and concludes it may soon be impossible to find “pristine Arctic environments untouched by climate warming.”
Arctic lakes have undergone dramatic ecological change in the past 150 years, the study finds, and the timing of these changes mirrors the warming trend that commenced when humans began the widespread burning of fossil fuels.
The findings, which represent the largest study of its kind, were published this week in the “Proceedings of the National Academy of Sciences.”
Co-author Alexander Wolf said the new research provides key data on a region that is on the frontlines of climate change but can be difficult to study.
“Polar regions are expected to show the first signs of climatic warming, and are therefore considered sentinels of environmental change,” explained Wolf, an earth scientist from Queen’s University in Canada. “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.”
But microfossils of aquatic organisms preserved in lake sediment offer an archive of the lake’s history – and lakes are abundant in the Arctic.
“If you look at one lake at a time, you still get important information, but it is hard to make large scale, regional assessments,” said lead author John Smol, an Arctic lake expert from Queen’s University. “Once you compile the larger dataset of all these lakes and ponds, striking and consistent patterns become evident. Taken together, it is a very powerful message.”
To determine that message, the international team of 26 researchers analysed lake sediment from 46 Arctic lakes in four polar nations. They produced 55 historical profiles of algal and invertebrate animals, covering an area that extends halfway around the world and 30 degrees of latitude spanning boreal forest to high arctic tundra ecosystems.
Changes in the community composition of freshwater algae, water fleas and insect larvae in the majority of lakes reflect the impact of warming, the researchers said.
The study reports little change in these communities until the mid-1800s, with dramatic shifts occurring in the past three decades.
These organisms make up the base of most aquatic food webs, the researchers said, and impacts are likely to trickle up the food chain and affect larger animals.
The findings are consistent with data that show climate change has lengthened summers and reduced lake ice cover across much of the Arctic.
Image: Arctic Council