Climate change has warmed Arctic lakes so much in the past two centuries that life in them has changed dramatically, according to an international group of scientists.
The team, led by John Smol at Queen's University in Ontario, travelled to 46 Arctic lakes from western Canada to Russia, taking sediment cores from the lake beds as they went.
"The cores are like history books. The further you go down into lake sediments, the further back in time you go and in that mud is a tremendously rich history of fossilised organisms that lived there at the time," says Smol.
By analysing slices of the cores, the scientists could piece together how the delicate ecosystems of the Arctic lakes had changed since the 1800s. They found that toward the end of the 19th century and throughout the 1900s, the types of creatures living in the lakes changed, with warmer water organisms becoming far more abundant. "Just as people associate polar bears with one climate and camels with another, we know of thousands of different organisms that only live in warmer and colder waters," says Smol. "What we're seeing is enough warming that the whole ecology of these ecosystems has changed dramatically and the changes in the past 100 to 200 years are greater than they have been for millennia."
Smol says the ecosystem changes can be put down to global warming because some parts of the Arctic, specifically north eastern Canadian regions, haven't warmed and lakes in those regions showed little, if any, change to the life they support. The study appears in Proceedings of the National Academy of Sciences.