Late Miocene sea surface salinity variability and paleoclimate conditions in the Eastern Mediterranean inferred from coral aragonite d@u1@u8O

Coral skeletons are archives of chemical proxies which enable paleoenvironmental reconstructions to be made at subannual resolution. Stable oxygen isotope (d@u1@u8O) ratios of these archives reflect sea surface temperature (SST) as well as the d@u1@u8O composition of ambient seawater. The d@u1@u8O@ds@de@da@dw@da@dt@de@dr composition is not only controlled by global ice build-up, but river discharge and the hydrological balance of evaporation and precipitation, all influencing sea surface salinity (SSS), also play an important role in marginal seas. New sub-annually resolved coral d@u1@u8O data were measured and evaluated together with published data from reef coral communities of Late Miocene age from Crete (Eastern Mediterranean). This time-window is of particular importance for the paleoceanographic evolution of the Mediterranean Sea, because it covers the successive closure of the marine gateways connecting the Mediterranean with the Atlantic Ocean, which culminated in the onset of the Messinian salinity crisis (MSC) at 5.96 Ma. Corals were recovered from eight time-slices dated by @u8@u7Sr/@u8@u6Sr chronostratigraphy and cover a time-window from 610 to 67 Ma to monitor pre-MSC environmental changes. The oxygen isotope composition of the reef corals Porites and Tarbellastraea document significant changes in mean annual d@u1@u8O as well as in mean d@u1@u8O seasonality during the Late Miocene. Tortonian and Messinian coral mean annual d@u1@u8O values differ by up to 1.72ppt and exhibit substantial variability. Since SSTs can be considered rather constant over the Late Miocene according to lithological, paleobotanical and geochemical evidence, the mean annual d@u1@u8O variations in the corals appear to result from changing SSS during the Late Miocene prior to the MSC. This result is in contrast to earlier concepts that, despite increasing isolation of the Mediterranean basin starting at about 9 Ma ago, SSS did not change until only 300 kyr prior to the deposition of the first MSC evaporites. Mean seasonal d@u1@u8O amplitudes are lower by 0.4ppt in the Messinian compared to those of the Tortonian corals, which may be due to enhanced summer evaporation. Spectral analyses of Tortonian and Messinian coral d@u1@u8O records indicate significant interannual variability with periods of 2-3 and 4-5 years. Such variability is similar to that found in modern records. In the modern case, the Iceland Low and Azores High pressure centers influence climate in the Circum-