The modern and Last Glacial Maximum hydrological cycles of the Eastern Mediterranean and the Levant from a water isotope perspective

- We present a methodology for interpreting modern and paleo-isotopic data.
- Using modern data we model the Eastern Mediterranean isotopic hydrological cycle.
- Sea-land temperature gradient is an important control on the isotopic composition.
- We model the full Last Glacial Maximum paleohydrological isotopic cycle of the Eastern Mediterranean.
- Last Glacial Maximum moisture transport, humidity and distillation shifts altered rainfall composition.

The isotopic composition of precipitation (δP) is one of the most widely used and informative terrestrial paleoclimate proxies. δP integrates a series of hydrological processes; therefore, any interpretation of paleohydrology using δP requires a thorough understanding and quantification of the full hydrological cycle. In this paper, we use modern data to analytically model the full isotopic hydrological cycle of the Eastern Mediterranean and the Southern Levant, including oceanic evaporation, distillation during transport and precipitation over land. This model allows us to determine the important factors controlling this system. The model results underscore the significance of the isotopic distillation process driven by the land-sea temperature gradient as a significant factor controlling the long-term average isotopic composition of precipitation across Israel. Based on the understanding of the processes that govern the modern system, we model the isotopic composition of precipitation from the Last Glacial Maximum (LGM) using published data for speleothem oxygen isotopes in calcite, oxygen and hydrogen isotopes in fluid inclusions and clumped isotope values from Soreq Cave and the isotopic composition of East Mediterranean planktonic foraminifera G. ruber. The data and model results indicate two plausible scenarios for the LGM that entail changes in the magnitude of distillation over Israel, in normalized humidity over the Mediterranean and possible shifts of the moisture trajectories over the Mediterranean. The results presented in the paper illustrate the importance of understanding the full local hydrological cycle when reconstructing and interpreting the isotopic composition of precipitation.