Seminar

Studying the warm periods in geological history is essential to reveal the mechanism of natural variation and response process in climate system. As the most recent era, Cenozoic climate witnessed a general cooling process from “green-house” to “ice-house” punctuated by several warming episodes. Mid-Miocene Climatic Optimum (MMCO, 17-14.7 Ma) is the recent warming period in Neogene however related research focused on this time interval is very limited. In this study, 4 sites from global ocean were selected to reconstruct sea surface temperature (SST) and oceanic changes accordingly based on biomarker proxies, attempting to provide preliminary pattern of global ocean conditions during the MMCO. SST of Central Arctic Ocean generally decreased from ~10°C to ~3°C in the Mid-Miocene, displaying a cooling trend despite the ambiguity of chronology. Meridional SST gradient during the MMCO was reconstructed by compiling the results obtained in this research and other published records, exhibiting a smaller SST gradient than that of Pliocene and modern condition, with tropical warmth level extending to the mid-latitudes. Occurrence of strong ocean stratification during the MMCO was revealed at M0002A, 1208A and U1405A by biomarker-based records. The exploration and preliminary results obtained in this research provide a fundamental data support for model simulation as well as another perspective for describing oceanic conditions during the MMCO.