Delving into the past to predict the future

Delving into the past to predict the future

An Arctic researcher yields a treasure trove of climate change information from the bottom of lakes
March 1, 2007
When Arctic researcher Marianne Douglas looks at a lake, she doesn’t just think about taking a dip or getting a drink. She wonders what clues to the past are hidden in its watery depths.
 

Specifically, she wonders about diatoms. These minute organisms can be found in almost every pond and lake on earth, and when they die, they leave behind glass cell walls that pile up in layers at the bottom of lakes. Similar to rings in a tree trunk, these layers hold a lot of information about past climate.

“They’re like little jewels under the microscope,” Douglas says. “Each species has its own ornamentation and occupies its own specific niche. As environmental conditions changed, so did the species. We take core samples of the lakebeds, and as you go down in the sections, you're going back in time. Some of the changes are absolutely dramatic—huge, huge changes.”

Douglas’s passion is finding and unravelling those changes using a science called paleolimnology. What looks like Arctic pond scum to the average person is actually a clear timeline of ecological change under Douglas's trained eye. She uses 20 years of paleolimnological research to show how the Arctic’s climate is changing, to fill in the holes in Arctic climate data, and to test forward-looking climate models.

Douglas first looked to diatoms as a vehicle to the past in 1986 as a grad student working with John Smol, a paleolimnologist at Queen’s University. Smol sent her to Cape Herschel on Ellesmere Island, the most northerly island in the Arctic Archipelago, to collect samples from small lakes and ponds. Back in the lab that fall, Douglas started examining the sediment samples and was astounded at what she found. She had expected the types of diatoms in the sediment to change slowly over time as the climate gradually warmed from the Ice Age to present day. Instead, the samples showed that for 4,000 years, only three or four species of diatoms dominated. Then, surprisingly, the dating samples confirmed that after about 1850, diatom diversity jumped to more than 100 additional species.

“It would be like going to sleep having only three or four neighbours and then waking up in a new subdivision,” Douglas says. “In biological terms, it was a drastic change.”

Using ice core data, Douglas concluded that the post-1850 changes were caused by decreased volcanic activity and increased solar activity. This, along with possible early effects of human-influenced warming, caused the temperature to rise. That meant the Arctic lake ice melted earlier in the year than usual, providing a longer growing season for aquatic mosses and the like. That in turn created new niches for different types of diatoms to develop. “What we’re seeing is the tipping point,” she says. “The ecological threshold was reached.” Before 1850, the living conditions in the lakes were so extreme that only a few species could thrive. Around 1850, the environmental conditions in the lake changed and, suddenly, dozens of species could thrive.

Further study revealed another marked increase in life in the 1920s, which coincided with increased carbon dioxide readings in ice cores caused by the burning of fossil fuels. It prompted Douglas, in 1994, to publish one of the early scientific papers showing the effects of global warming in the Arctic.

“Her findings were very controversial at the time,” Smol says. Not so today. Most scientists now believe in global warming—in fact, physicists and climatologists use Douglas’s findings to predict how the weather will change in the future. Predictions are made with global climate models generated by powerful computers that forecast future land surface temperatures, sea ice, ocean currents, and more. Historical data is then used to test the model’s accuracy.

Richard Peltier, an astronomic physicist at the University of Toronto, is one of many scientists relying on Douglas’s research. He uses her results to confirm his models’ predictions about where climate change will be most extreme, and what ecological changes will result. “Our models show that global climate change should be most intense in high northern latitudes,” says Peltier. “We also expect to see changes in freshwater lake ecology. Marianne and John’s research results are very useful at confirming this.”

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The theory goes like this: if the models can accurately predict past climate conditions, given previous atmospheric carbon levels, then they’ll probably do a good job of predicting future conditions, given future carbon projections. Therefore, it is through Douglas’s examination of the past that scientists like Peltier can prepare for the future.

Benefits

Today, Douglas is one of the leading polar researchers and an expert on Arctic diatoms and climate change. In 2005, she collaborated with many of her former critics on a study using paleolimnology to demonstrate that warming began around 1850 throughout the Arctic and is increasing today. “Marianne’s ideas have gone from controversy to consensus,” Smol says. “She’s done a remarkable job.”

You don’t have to be a diatom specialist to know the Arctic climate is changing. Pack ice is noticeably thinner, smaller, and melting sooner, cutting hunters off from their prey. Never-before-seen wildlife, like swallows and robins, are appearing on the tundra. Even in Marianne Douglas’s short time in the Arctic, she’s seen dramatic changes. Last summer, a pond she was studying dried up for possibly the first time in 4,000 years. “The rate of change is unprecedented,” she confirms.

Arctic weather and climate records are too limited to record these changes, but Douglas’s research is putting science behind such observations. “The data I’m coming up with is helping corroborate what the people up North are seeing,” she says. “They know things are changing, but until I started my research, there was no way to know when these changes started.”

And that’s a real problem because “what happens in the Arctic affects us all,” says John Smol, a Queen’s University professor. “It’s an important bellwether for the rest of the planet.”

Now, along with the collection of lake sediment data, more extensive climate change research is being done. Just the presence of dedicated Arctic researchers to record the climate year to year is making a big difference. After more than 20 years of scientific visits, Cape Herschel is now one of the best-documented sites in the Arctic. Douglas hopes that knowledge will translate into help for the northern residents she has worked with for the last 20 summers. As part of Canada’s International Polar Year committee, Douglas is strongly supportive of incorporating a human dimension into the goals of the international science initiative. “It would be really nice if this project left a positive legacy on the culture of the North,” she says.

Partners

Just getting to the Arctic is extremely expensive and logistically difficult. Scientific collaboration is therefore a vital component of northern research. Douglas has collaborated with scientists in climatology and physics at the University of Toronto, paleolimnologists at Queen’s University, and more recently with Arctic paleolimnologists throughout the world on peer-reviewed papers. She spent a field season with the Bulgarian Antarctic Program on Livingston Island in Antarctica. Douglas is now collaborating with researchers at Université Laval and Queen’s University, and supporting many International Polar Year projects.

Learn More

Visit the Paleoecological Environmental Assessment and Research Laboratory.

Find out more about the Canadian Circumpolar Institute.

Discover the Canadian International Polar Year's website.

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