Lake Malawi in East Africa is one of the oldest and largest lakes on Earth.
More than 7 million years old and reaching depths of more than 700 meters, Lake
Malawi could provide climatologists with a unique window into Earths climate
past. At least thats what Chris Scholz, associate professor of earth sciences
at Syracuse University, hopes.
The National Science Foundations Paleoclimate Program has given Scholz and his colleagues $2 million to drill Lake Malawi and analyze its sediment cores. The researchers hail from Syracuse University, University of Minnesota-Duluth, University of Rhode Island and the University of Arizona.
Lake Malawi is very large and very deep, Scholz says. And its an extremely sensitive recorder of changes in climate. Scholzs team will drill Lake Malawi at the southern end of the East African Rift Valley. The drilled cores should help in constructing a continuous, high-resolution record of past climates in the continental tropics over the past 800,000 years.
Although Malawi is an open-basin lake with an outlet, most of the water that enters the lake does not flow out. Instead, the water evaporates. So that means that lake is extremely sensitive to any changes in the precipitation/evaporation ratio, and that is reflected in huge changes in lake level, Scholz says. Early surveys reflect these lake-level changes, perhaps as large as 500 meters over geological time. On a seasonal basis, he says, the changes could amount to as much as 2 meters between wet and dry seasons.
Another exciting reason to study this lake is that in certain areas it contains annually laminated sediments, Scholz says. So we can potentially have not only a very long record of geologic change, a very sensitive record, but also one thats recording changes on a year by year basis.
But, Scholz adds, the site most uniquely distinguishes itself for the climate record with its location as a continental tropical site. Theres a lot of data from the marine realm, but relatively little from the continental tropics. So the global change research community really needs these reference sites in order to constrain modeling efforts. Lake Malawi is one of the few Southern Hemisphere tropical sites, sitting between 9 and 14 degrees latitude. Its also of course in the Great Rift Valley its the birthplace of mankind really. So, Scholz says, the coring research could provide a geological background for understanding the origin of early humans.
Lisa M. Pinsker