Lake bed sediments show rapid pace of climate change in arid region
By Summit Voice
SUMMIT COUNTY — Past climate change in the Dead Sea region was sudden and dramatic, with Mediterranean-type vegetation giving way to desert plants within just a few decades as the climate dried out.
One of those dry spells may have resulted in the Canaanites’ urban culture collapsing while nomads invaded their area, perhaps establishing a climate link to biblical events described in the Old Testament as the exodus of the Israelites to the Promised Land.
The new climate data from the area came from a detailed study by scientists with the Steinmann-Institute for Geology, Mineralogy and Paleontology at the University of Bonn, who tracked distinct dry periods during the pottery Neolithic Age (about 7,500 to 6,500 years ago), as well as at the transition from the late Bronze Age to the early Iron Age (about 3,200 years ago).
“Humans were also strongly affected by these climate changes,” said Dr. Thomas Litt, describing how the climate in the region shifted within just a few decades.
The researchers established their 10,000-year climatology record with lake bed sediment cores, using pollen analysis to determine the vegetation that prevailed during drier and wetter periods.
They matched the fossil pollen to indicator plants for different levels of precipitation and temperature. Radiocarbon-dating was used to determine the age of the layers.
“This allowed us to reconstruct the climate of the entire postglacial era,” Litt said. “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.
The pollen data helps determine what kinds of plants were growing at corresponding times. Meteorologists from the University of Bonn took this paleontological data and converted it into climate information. Using statistical methods, they matched plant species with statistical parameters regarding temperature and precipitation that determine whether a certain plant can occur.
“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,” said Dr. Andreas Hense, with 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,” said 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.”
In addition, this look back allows developing scenarios for potential future trends. “Our results are dramatic; they indicate how vulnerable the Dead Sea ecosystems are,” says Prof. Litt. “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.