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UMD research project adds 'new dimension' to understanding of African climate

Tom Johnson (center) stands with some crew members as they hold the final core sample drilled from the bed of Lake Malawi. Courtesy Tom Johnson1 / 2
A drilling barge gathers a core sample from Lake Malawi in eastern Africa on a UMD-led research project. Researchers used the cores to study changes in climate dating back 1.3 million years.2 / 2

One of the most challenging parts of a 22-year UMD research project on Africa's Lake Malawi was the 35 days on a noisy, hot fuel barge.

Anchored miles from the shore of the vast, ancient lake that spreads into three countries, the barge was run by a French, Dutch, Romanian and British crew, working amid faculty, students and technicians from the University of Minnesota Duluth and other schools from around the world.

Converted into a sophisticated drilling ship, the barge allowed researchers — using oil industry methods — to collect core samples from sedimentary layers far below the bed of Lake Malawi, one of the largest lakes in the world.

The nearly 1,250-foot long core that was collected tells the story of that part of the continent's climate over 1.3 million years. It shows that the area of southeastern Africa has become wetter over time, conflicting with a long-held theory that the entire continent has grown drier over time — a theory that came from research done in the northern half of Africa.

Tom Johnson"People took it a bit for granted that this is the story of the African climate," said Tom Johnson, professor emeritus and the first director of the University of Minnesota Duluth's Large Lakes Observatory, who led the project. "Now we have added a new dimension."

And that new dimension has implications for theories surrounding human evolution, and for climate change. The research project culminated last week with publication in Nature, a prestigious international science journal.

The work contributes to a better understanding of the African climate, and what may happen in the future for the people of Africa, who are "most vulnerable to whims of climate change," Johnson said.

"They are having to survive mainly on the products of their agricultural-based society, and are constantly hit by years of severe drought and flooding, and that leads to immense shifts in disease and famine, and in overall human welfare and political stability," he said.

Knowing what makes the continent tick, he said, will help predict what is to come as greenhouse gases in our atmosphere increase, and better prepare for it.

While proposals for funding began in 1994, the $4 million drilling project in Lake Malawi — which is bordered by Mozambique, Tanzania and Malawi — didn't happen until 2005. Since then, researchers from all over the world have been studying the samples for different projects. At UMD, they found that a type of plankton preserved in the sediment changes with water temperature. Because the core is so long, researchers could see the temperature of the water at different intervals in time, spanning 1.3 million years — the longest temperature record from anywhere on the African continent.

The core sample also helped researchers determine a vegetation history for the area, which points to how much rainfall there has been over time.

The research also showed that region of Africa goes through a wet and dry cycle every 100,000 years, in step with the coming and going of major ice ages. That means findings could affect human evolution theories focused on the idea that as the landscape in Africa changed, early humans migrated or evolved to adapt. It's been assumed that those early humans went from being forest-dwelling to living on grasslands, something called the "savanna hypothesis."

"These results are different, and demonstrate that African history has been more subtle ... there is more complexity," said Erik Brown, a professor of earth and environmental science with the Large Lakes Observatory. "The whole continent isn't responding in the same way."

Why Africa?

Johnson, who has traveled to Lake Malawi more than 30 times since the early 1980s, said Africa has been a major part of work for the Large Lakes Observatory for a couple of reasons.

"I always felt that we should have an institute that is No. 1, paying attention to Lake Superior," he said. "But No. 2, to have an institute that would be internationally recognized for its accomplishments, and global in its outlook. An institute that is very provincial and regional is not as exciting a place to work."

But it's about more than faculty recruiting efforts, he said, noting the study of large lakes is similar to the study of human anatomy. Studying different systems helps them better understand "the lake you care about the most, which of course is Lake Superior," Johnson said.

Lake Malawi is a tropical lake about as long as Lake Superior, created millions of years ago by by the tectonic forces that are slowly splitting the continent.

'Cutting-edge' research

UMD researchers have a history of gaining funding for major projects, Brown said. The Lake Malawi project was funded in part through the National Science Foundation, for example.

"But it's not just a handful of faculty doing something," he said. "It's affecting the research environment for students, as well, and I think that's really important."

He mentioned that the Lake Malawi research involved three graduate students. Melissa Berke was one of them. Now an assistant professor in the department of civil and environmental engineering and earth sciences at the University of Notre Dame, she is a co-author of the paper, and earned her doctoral degree from UMD in 2011.

Her time at UMD and traveling to Lake Malawi for the project, she said, "meant a great deal for my career."

The publication of the research in Nature — which "has been all over social media" — shows the results are important, she said, and validating for Johnson, who spent two decades working on it.

"All of the research at UMD and the Large Lakes Observatory is cutting-edge," Berke said. "I don't know if people really appreciate that in town. The world's leading researchers on (the processes of oceans and lakes) are at UMD ... Those faculty and students are at the forefront of their field."