Lake bed sediment reveals climate history

Layers along the bottom of an Arctic lake show how the global climate has changed over last 200,000 years, and the impact humans have recently had

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SIGN OF THE TIMES By studying the sediment layers of Arctic lakes, researchers have a unique indicator of environmental changes over thousands of years.

Unearthed sediments from an ancient lake bed located on Baffin Island may shed light on the state of climate change in the Arctic — and the world. Scientists and activists alike have interpreted the findings as demonstrating that global warming is accelerating and requires a swift global response.

An international study of the lake, which included the University of Alberta and the University of Colorado, among other institutions, examined sediment layers dating back over 200,000 years. This predates three interglacial periods, one occurring 200,000 years ago, one occurring 120,000 years ago, and one including the last 10,000 ice-free years.

Most lake beds are eroded by the ebb and flow of glaciations, but this was a unique case in sediment preservation and it was largely untouched by passing glaciers.

“Every time there’s an ice age, the ice flows over [this] lake and doesn’t erode the sediments out from the bottom of the lake,” said Alexander Wolfe of the Department of Earth and Atmospheric Sciences at the U of A, and contributor to the study.

“We were able to collect data on flora, fauna, and geochemistry, and together all those things paint a really interesting picture of environmental changes over time,” said Yarrow Axford, a Paleoclimatologist from the University of Colorado, and the lead author on the study.

“This lake seems to follow a similar trajectory over time through each interglacial period — but in the past century, the lake has deviated from its usual course.”

According to Wolfe, the changes that are observed in the biogeography of the Arctic region are indicators of accelerating rates of climate change.

“The public refers to these things as things that are going to happen. Climate is changing. Climate is warming,” he said. “Our research traces natural patterns over hundreds of thousands of years and when you see the human fingerprint — there’s nothing subtle about it.”

Wolfe believes that real understanding of the scope of climate change is still only beginning.

“The Kyoto Accord failed in terms of controlling greenhouse gas emissions to the atmosphere, but it did succeed in emphasizing that carbon dioxide doesn’t know nation-state borders,” Wolfe noted.

Axford believes that a response to global warming is very personal.

“There is a mountain of scientific evidence that tells us humans are changing Earth's climate, but science can't tell us whether we should act to solve the problem — we all have to decide about that based on our values,” she said. “The faster we act, the more difference we can make.”

Wolfe shared his vision of a technology-based "greening" of industries.

“For better or worse, we’re heading into a kind of environmental terra incognito — we need to adapt,” he said. “I believe we can exploit existing technologies to embark on a ‘green’ trajectory.”

In the case of evolving greening economies, Andrew Fehr, an executive member of Greenpeace on Campus at the U of A, believes that change is quite natural.

“Obviously right now the coal and oil and gas companies are going to pollute more and people are going to be worried about losing jobs. When the DVD player came around, we didn’t feel bad for people who were making VHS players,” he said. “In the same way, industry just needs to adapt.”

Axford believes that the green trajectory in Wolfe’s vision can do more than green industries; she believes it will also increase general productivity.

“A new ‘green economy’ could solve a lot of our problems by creating new jobs and investment opportunities, reducing our dependence on foreign oil, making cities healthier and slowing climate change all at the same time,” she explained.

“Tackling climate change could be an opportunity to bring our economy into the 21st century.”