Porites corals from Crete (Greece) open a window into Late Miocene (10 Ma) seasonal and interannual climate variability

Variations in the biotic composition of marine shallow water carbonates document global climatic changes. However, a discontinuous stratigraphic record and uncertainties regarding the ages limit the significance of shallow water carbonates as palaeoclimatic archives on geological time-scales. Notwithstanding these deficits, the environmental information stored in the skeleton of reef biota is a unique source of information that resolves seasonal to interannual climate variability in geological time. Application of the method to corals from carbonate rocks is usually restricted to the past 130,000 yr, because the aragonite skeleton undergoes rapid diagenetic alteration. Consequently, reconstructions resolving seasonal to interannual climate variability of the more distant geological time are rare. We describe exceptionally well-preserved corals (Porites) as old as Late Miocene (10 million years) from the island of Crete (eastern Mediterranean, Greece). Stable isotope records (δ18O, δ13C) reflect seasonal changes in sea surface temperature and symbiont autotrophy. Spectral analysis of a 67-yr coral δ18O record reveals significant variance at interannual time-scales (2–5 yr) that show similarities to Late Quaternary eastern Mediterranean climate variability. Supported by simulations with a complex atmospheric general circulation model coupled to a mixed-layer ocean model, we suggest that climate dynamics in the eastern Mediterranean may reflect atmospheric variability related to the Icelandic Low 10 million years ago.