Oceanographers collect 1.5 million year record of climate change in Africa

04/18/05

Scientists drill into sediments of one of the world's oldest, deepest lakes to improve understanding of global climate change

KINGSTON, R.I. April 18, 2005 Four University of Rhode Island oceanographers and colleagues from four other universities recently probed the ancient sediments beneath Lake Malawi in East Africa and recovered sediment samples that provide up to 1.5 million years of information about how climate in Africa has changed the longest continuous record of such data ever collected from that continent.

Just completed last month, the challenging expedition was managed by URI Associate Professor of Oceanography Kate Moran, and the URI scientific team included Professor John King and graduate students Meghan Paulson, Nathan Vinhateirot and Chip Heil.

Lake Malawi is considered by many scientists to be among the natural wonders of the world. It is one of world's deepest (700 meters) and oldest (more than 5 million years) lakes, and contains a rich assemblage of biological species found nowhere else on earth. Longer than Lake Michigan, it is situated in tropical latitudes that serve as the atmosphere's heat engine, and the region plays a major role in driving global climate dynamics.

"The role of the tropics within the global climate system is not well understood at present. The results of this project will significantly improve our overall understanding of the global climate system," explained King, a professor of oceanography at the URI Graduate School of Oceanography.

Results from the research will also contribute to a better understanding of African climate and improved weather predictions in this region of recurring drought, famine and human suffering. The project has the added benefit of recovering an archive of environmental change that occurred in concert with human evolution in East Africa.

"The lake has restricted circulation and virtually no oxygen at the bottom, so each year seasonal deposition of sediment creates a pattern like tree rings," King said. "With the cores we collected we'll be able to look at very old records of climate data simply by counting and analyzing the layers."

The researchers from URI, Syracuse University, the University of Minnesota-Duluth, the University of Arizona, and the University of Bergen (Norway) chose to drill Lake Malawi because its unique location and geology will enable them to reconstruct a high-resolution, tropical climate history stretching back through the time when massive ice sheets periodically covered high-latitude North America and Eurasia. The project was funded by the National Science Foundation and the International Continental Drilling Program.

In total, 623 meters of core samples were recovered from below the lake bottom, the oldest of which are about 1.5 million years in age. In the coming months, the scientists joined by those from the Malawi Geological Survey -- will undertake a variety of analyses and inspections of the sediment samples to predict the future impact of global warming.

The project faced very difficult engineering and logistical challenges, the first of which required construction of a drilling vessel on land-locked Lake Malawi. The project used an old, 160-foot, fuel barge as the drilling platform, but had to ship into interior Africa the drilling rig, custom-designed sampling tools, and a portable dynamic positioning system designed to stabilize the drilling vessel in one spot in deep water for weeks at a time in sustained winds as high as 35 knots and waves of up to six feet in height.

"No one has done this kind of drilling on an interior lake before, much less one in Africa, so the technical and logistical obstacles we faced were quite challenging," Moran said.

Source: Eurekalert & others

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