Istituto Nazionale di Geofisica e Vulcanologia, Italy

A key reason for both the ANDRILL (ANtarctic geological DRILLing Program) and the ACEX (Arctic Coring EXpedition, Integrated Ocean Drilling Program Expedition 302) drilling efforts is to understand 1) when, why and how ice started developing at the two poles and 2) the role of the cryospheric evolution/dynamics in the global climate system from direct archives. While it is already well established that Antarctica's major glaciation started some 34 Ma ago (the greenhouse to icehouse transition), a gap of about 26 Ma (between approximately 44 and approximately 18 Ma) in the ACEX IODP 302 record has possibly hampered a direct reconstruction of the timing of the onset of major glaciations in the Arctic. A robust history of Neogene glaciation and climate evolution at both poles is yet to be achieved. ANDRILL recently drilled more than 1000 meters of sediment from the Southern McMurdo Sound, and successfully recovered sediments younger than early to middle Miocene. This record is essential to evaluate the history, derived from global proxy records, that invoke a change from a warm climatic optimum ( approximately 17 Ma) to the onset of major cooling ( approximately 14 Ma) and the formation of quasi permanent ice-sheet on East Antarctica. Records are already available from the central Arctic Ocean showing a warmer than expected Miocene Climatic Optimum, with Sea Surface Temperature (TEX86-derived SST) of 15 to 19 degrees C, and a perennial ice cover on the Arctic Ocean over the last 14 Ma. Here we present preliminary sea surface temperature (SST) reconstructions of the Miocene Climatic Optimum and the Mid-Miocene Climate Transition for the ANDRILL Southern McMurdo Sound Project record and compare results to the available data from the central Arctic Ocean to discuss Neogene bipolar glaciation/climate dynamics.