Hydrological variability in northern Levant over the past 250 ka
1CEREGE, UMR6635, CNRS – (Aix-Marseille Université-CNRS-IRD-CdeF), BP 80, 13545 Aix-en-Provence cedex 04, France
2ECOLAB, UMR5245, (CNRS-Université de Toulouse-INPT), BP 24349, 31062 Toulouse cedex 9, France
*now at: Laboratoire Chrono-Environnement, UMR6249, CNRS – Université de Franche-Comté, 16 Route de Gray, 25030, Besançon cedex, France
**Invited contribution by F. Gasse, recipient of the EGU Hans Oeschger Medal 2010.
Abstract. The Levant features sharp climatic gradients from North to South and from West to East resulting in a large environmental diversity. The lack of long-term record from the northern Levant limits our understanding of the regional response to glacial-interglacial boundary conditions in this key area. The 250 ka paleoenvironmental reconstruction presented here is a first step to fill this geographical gap.
The record comes from a 36 m lacustrine-palustrine sequence cored in the small intra-mountainous karstic basin of Yammoûneh (northern Lebanon). The paper combines times series of sediment properties, paleovegetation, and carbonate oxygen isotopes, to yield a comprehensive view of paleohydrologic-paleoclimatic fluctuations in the basin over the two last glacial-interglacial cycles. Efficient moisture was higher than today during interglacial peaks around 240, 215–220, ~130–120 ka and 11–9 ka (although under different Precipitation minus Evaporation balance). Moderate wetting events took place around 170, 150, 105–100, 85–75, 60–55 and 35 ka. The penultimate glacial period was generally wetter than the last glacial stage. Local aridity culminated from the LGM to 15 ka, possibly linked to water storage as ice in the surrounding highlands. An overall decrease in local water availability is observed from the profile base to top. Fluctuations in available water seem to be primarily governed by changes in local summer insolation controlled by the orbital eccentricity modulated by the precession cycle, and by changes in precipitation and temperature seasonality.
Our record is roughly consistent with long-term climatic fluctuations in northeastern Mediterranean lands, except during the penultimate glacial phase. It shares some features with speleothem records of western Israel. Conversely, after 130 ka, it is clearly out of phase with hydrological changes in the Dead Sea basin. Potential causes of these spatial heterogeneities, e.g., changes in atmospheric circulation, regional topographic patterns, site-specific climatic and hydrological factors, are discussed.