(photo credit: WIKIMEDIA COMMONS/IAN AND WENDY SEWELL)
There is a direct relationship between hydrological and chemical changes in the Dead Sea over 220,000 years, a time interval covering two glacial and three interglacial periods on Earth, according to research conducted at Ben-Gurion University of the Negev.
As one of the saltiest lakes on Earth in an arid region and the lowest point on Earth, the lake has recorded climate change in the region over geological periods, with lake-level rises during wet periods and lake-level drops during dry periods.
But until recently, there was no direct relationship between the lake composition and regional climate change over geological time.
The research, carried out with participation of the Israel Geological Survey and the Hebrew University of Jerusalem, was published recently in the leading geoscience journal Geology. It was part of doctoral research conducted by Elan Levy from Prof. Orit Sivan’s research group at BGU’s department of geological and environmental science.
The research focuses on reconstructing climate conditions in the past by using “pore water” (the pressure of groundwater held within soil or a rock in gaps between particles or pores) trapped within sediments in the Dead Sea. In the deep-drilling project conducted under the umbrella of the International Continental Drilling Project, and in cooperation with universities and research centers in Israel and abroad, a drilled core of some 450 meters long was extracted in 2011. The research group extracted pore fluids trapped in the drilled core sediments and measured geochemical and isotopic parameters.
The research results show that the chemical composition of the lake follows global climate changes. During glacial periods, when there was a drop in global temperatures, expansion of ice around the polar regions and a drop in oceanic sea level and atmospheric carbon dioxide concentrations, there was dilution of the lake, accompanied by the dissolution of Halite salt.
During the warmer interglacial periods, when there was a rise in oceanic sea levels and atmospheric carbon dioxide concentrations, the deep waters became more concentrated and Halite salt was precipitated.
The similarity between the global climate records and the pore water records from the Dead Sea core emphasizes a strong relationship between rainfall and humidity in the region and global climate changes, findings that are important for understanding and predicting climate change in Israel and the central Levant, the researchers wrote.
The results support modern observations showing a relationship between the amount of rainfall in the region and North Atlantic sea surface temperatures – during periods of relatively cold surface water in the northern ocean there is a relative increase in regional rainfall – and a decrease in regional rainfall during periods of relatively warm surface waters.