THE MEDITERRANEAN SEA: A NATURAL LABORATORY TO STUDY GAS HYDRATE DYNAMICS?

Overview & Synopsis

Gas hydrates have been proven by coring at one site in the (eastern) Mediterranean Sea, but their wider extent remains uncertain. Here we present results from investigations of the potential Mediterranean gas hydrate system, suggesting that clathrates occur more widely and have been strongly impacted by glacial-interglacial climate forcing. Modeling of the methane hydrate stability zone (MHSZ) shows it to be present in most of the Mediterranean Sea, albeit in deep waters (>1000 m) due to warm bottom waters (12.5-14°C) and in greater thicknesses (200-500 m) in the geothermally cooler eastern basin. Comparison of the MHSZ with known or possible zones of gas flux to seabed suggests prospective areas for hydrate occurrence, mainly in the eastern basin. One is the Nile fan, where evidence of the first BSR in the Mediterranean Sea (presented sseparately, Praeg et al. this volume) confirms the potential for additional hydrate discoveries. During glacial stages, gas hydrate stability in the Mediterranean increased due to bottom waters up to 4°C cooler; even allowing for sea levels 125 m lower, the modeled glacial-stage MHSZ was up to 25% thicker and 300 m shallower on basin margins. Glacial-to-interglacial transitions thus corresponded to a marked reduction in hydrate stability, with downslope migration of the upper limit of the MHSZ across depths of c. 700-1000 m. A compilation of submarine landslides in the Mediterranean Sea indicates a peak in the age of slide deposits during the last deglaciation and includes abundant headwalls in mid-to upper slope depths (