NOAA/WDS Paleoclimatology - Vaks et al. 2003 Ma'ale Efrayim Cave, Israel Speleothem Stable Isotope Data

High-resolution 230Th/234U ages and d18O and d13C compositions of speleothems
in Ma'ale Efrayim Cave located to the east of the central mountain ridge of Israel
enable us to examine the nature of the rain shadow aridity during glacial and
interglacial intervals. Speleothem growth occurred during marine glacial
isotopic periods, with no growth during the two last marine isotope interglacial
intervals and during the peak of the Last Glacial Maximum. This contrasts
with speleothem growth in caves located on the western flank of the central
mountain ridge, in the Eastern Mediterranean semiarid climatic zone, which
continued throughout the last 240,000 yr. Thus, during glacial periods water
reached both sides of the central mountain ridge. A comparison of the present-day
rain and cave water isotopic compositions and amounts at the Ma'ale Efrayim Cave
site with those on the western flank shows that evaporation and higher temperatures
on the eastern flank are major influences on isotopic composition and the
lack of rainfall. The d18O and d13C profiles of the speleothems deposited
between 67,000 and 25,000 yr B.P. match the general trends of the isotopic
profiles of Soreq Cave speleothems, suggesting a similar source (eastern
Mediterranean Sea) and similar climatic conditions. Thus, during glacial periods
the desert boundary effectively migrated further south or east from its present-day
location on the eastern flank, whereas interglacial periods appear to have been
similar to the present, with the desert boundary at the same position. The decrease
in overall temperature and a consequent reduction in the evaporation to precipitation
ratios on the eastern flank are viewed as the major factors controlling the decay
of the rain shadow effect during glacial periods.