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Bonn, Germany (SPX) Aug 27, 2012
The Dead Sea, a salt sea without an outlet, lies over 400 meters below sea level. Tourists like its high salt content because it increases their buoyancy. "For scientists, however, the Dead Sea is a popular archive that provides a diachronic view of its climate past," says Prof. Dr. Thomas Litt from the Steinmann-Institute for Geology, Mineralogy and Paleontology at the University of Bonn.
Using drilling cores from riparian lake sediments, paleontologists and meteorologists from the University of Bonn deduced the climate conditions of the past 10,000 years. This became possible because the Dead Sea level has sunk drastically over the past years, mostly because of increasing water withdrawals lowering the water supply.
Oldest pollen analysis
"This allowed us to reconstruct the climate of the entire postglacial era," Prof. Litt reports. "This is the oldest pollen analysis that has been done on the Dead Sea to date."
In total, there were three different formations of vegetation around this salt sea. In moist phases, a lush, sclerophyll vegetation thrived as can be found today around the Mediterranean Sea. When the climate turned drier, steppe vegetation took over. Drier episodes yet were characterized by desert plants. The researchers found some rapid changes between moist and dry phases.
Transforming pollen data into climate information
"This allows us to make statements on the probable climate that prevailed during a certain period of time within the catchment area of the Dead Sea," reports Prof. Dr. Andreas Hense from the University of Bonn's Meteorological Institute.
The resilience of the resulting climate information was tested using the data on Dead Sea level fluctuations collected by their Israeli colleagues around Prof. Dr. Mordechai Stein from the Geological Services in Jerusalem.
"The two independent data records corresponded very closely," explains Prof. Litt. "In the moist phases that were determined based on pollen analysis, our Israeli colleagues found that water levels were indeed rising in the Dead Sea, while they fell during dry episodes." This is plausible since the water level of a terminal lake without an outlet is exclusively determined by precipitation and evaporation.
Droughts led to the biblical exodus
"Humans were also strongly affected by these climate changes," Prof. Litt summarizes the effects. The dry phases might have resulted in the Canaanites' urban culture collapsing while nomads invaded their area. "At least, this is what the Old Testament refers to as the exodus of the Israelites to the Promised Land."
"They clearly show how surprisingly fast lush Mediterranean sclerophyll vegetation can morph into steppe or even desert vegetation within a few decades if it becomes drier." Back then, the consequences in terms of agriculture and feeding the population were most likely devastating. The researchers want to probe even further back into the climate past of the region around the Dead Sea by drilling even deeper.
Holocene climate variability in the Levant from the Dead Sea pollen record, Quaternary Science Reviews 49 (August 2012).
University of Bonn
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