Evidence for abrupt changes in paleorainfall during the Holocene in the Eastern Mediterranean region as evident from speleothems
by
Miryam Bar-Matthews
Geological Survey of Israel
Coauthors: Avner Ayalon (Geological Survey of Israel)

The oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change. Among the key questions in paleoclimatic studies is the extent of the connection between the “local” records and regional and global events. Here we examine the changes in the rainfall amount in the Eastern Mediterranean (EM) region (central Israel) during the Holocene, and ask if these changes are evident in the archeological records of the area.

Estimates of annual paleorainfall amount, based on the present-day relationship between rainfall amount, temperatures and the isotopic composition of the speleothems, reveals that the time period with the highest rainfall (about 40% higher than the present-day average of ~500 mm) occurred during the earlier part of the Holocene, and coincided with the formation of sapropel S1. From 7.5 kyr toward the last ca. 500 years, there was a trend towards aridity and the annual rainfall was usually less than at present. A sharp drop in the rainfall amount occurred at 5.2 kyr. However although this was the most sever drop during the Holocene, it was also the shortest, lasting less than 200 years. Immediately after, conditions became wetter, and the highest rainfall during the later part of the Holocene occurred from 4.8 to 4.5 kyr. During the following 800 years there was a sharp 30-50% decrease in the rainfall amount, which caused an increase in the relative proportion of C4 type vegetation in the region. This was the only major change in the vegetation during the Holocene. These two aridity events overlap in time with periods of destruction of human civilization in the Middle East and North Africa. Since about 3.5 kyr, the amplitude of changes in the rainfall amount became smaller, but was still large enough to affect human population.

Date received: February 26, 2002

Copyright © 2002 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caiq-13.