Fwd: CC No turning back on Arctic warming
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No turning back on Arctic warming
Scientists fear effects on polar lakes irreversible
Climate changes traced back to 1850s, study finds
OTTAWA-A circumpolar investigation led by Canadian scientists has
discovered clear signs of climate change in scores of Arctic lakes
dating back to the mid-19th century, when the Industrial Revolution
kicked off widespread burning of fossil fuels.
Warmer temperatures have pushed some plant and animal life in the
lakes over an ecological threshold that won't be reversed for
generations, if ever, the scientists conclude in a study released
"We're seeing big changes occurring in lakes and ponds all around the
Arctic. It's not just algae but also invertebrates like water fleas
higher up the food chain," said University of Toronto professor
Marianne Douglas, a polar lake expert and one of the lead researchers.
The study also found the ecological changes became greater the farther
north the lakes were located, just as average temperatures have risen
more in the High Arctic than farther south at the Arctic Circle.
The lakes don't look much different, lacking anything as dramatic as
the green scum that coated parts of Lake Erie when over-fertilized
with nutrients in the 1970s. One scientist compared the change to the
ecosystems being shifted into overdrive.
Douglas said mud cores from 46 Arctic lakes in Canada and three other
countries showed clear evidence of a longer growing season beginning
as far back as the 1850s, well before thinning pack ice and starving
polar bears currently being linked to global warming. Russia, Norway
and Finland provided the other research sites.
The long-term evidence comes from the distinctive glassy casings of
single-celled algae called diatoms that rain to the lake bottom as the
algae die. Experts can read the past climate from the layers of
sediment since some diatoms do better under ice and others in clear
Douglas said the sediment cores suggest that many of the lakes were
now ice-free a month longer than in the mid-1800s, doubling the
growing season for some diatoms. This has produced a surge in
Cyclotella, a diatom that thrives only under open water conditions.
Lead researcher John Smol of Queen's University said the study should
put the final nail in the coffin of arguments that climate change is
"This is a completely new independent set of data and wasn't included
in earlier studies the skeptics spend so much time attacking," said
Smol, who pioneered the study of Arctic lake sediments in Canada.
This view was echoed by John Hobbie, a leading American expert in
Arctic lakes who was not one of the 26 researchers involved in the
unprecedented circumpolar investigation.
"We had thousands of years with no changes in the algae species. Now
they've shown that changes occur in places where warming is going on
and, more importantly, don't occur where there is no warming," said
Hobbie, co-director of the renowned Marine Biological Laboratory at
Woods Hole in Maine.
Smol also said ecosystems in the Arctic lakes would need several
generations to switch back to their previous condition and that could
happen only if the world actually reduced atmospheric levels of
greenhouse gases like carbon dioxide.
The study, published by the U.S. National Academy of Sciences, is
something of a vindication for Smol and the UofT's Douglas.
In 1994, they ran into widespread doubts among colleagues after
publishing similar diatom results from just three lakes on Ellesmere
Island in Canada's Arctic archipelago.
"Some thought the changes couldn't have started as early as the
mid-1800s and that there must be some other explanation," said Smol,
the 2004 winner of Canada's premier science award, the Herzberg Gold
One of those earlier skeptics, Alex Wolfe, is now a co-author of the
new paper and a paleoecologist at the University of Alberta. He became
convinced after finding the same evidence in his own lake sediment
"We have low-productivity, sensitive ecosystems that are essentially
cast into overdrive," Wolfe said, speaking from the remote Norwegian
island of Svalbard, where he is doing research.
"I would stake my reputation against the lakes reverting back to what
they looked like 1,000 years ago ... Ever," Wolfe added.
Additional articles by Peter Calamai
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