TEMPERATURE DYNAMICS OF THE MIDDLE MIOCENE CLIMATIC TRANSITION IN SOUTHERN EUROPE AS RECORDED IN PEDOGENIC CARBONATES

Global warming during the Middle Miocene Climatic Optimum (MCO; ca. 16.9 to 14.7 Ma) represents an important transition in Earth’s climate system with an interruption of long-term Cenozoic cooling. Between 14.5 and 12.9 Ma the Earth’s climate changed from warm conditions with a low latitudinal temperature gradient during the MCO to a colder phase with accelerated Antarctic ice sheet formation. Middle Miocene δ¹⁸O records indicate increased temperature variability (e.g. Mi2 & Mi3) and define the Middle Miocene Climatic Transition (MMCT). While Middle Miocene ocean temperatures, ocean chemistry, varying pCO₂, and faunal assemblages have been studied at high temporal resolution, continental climate change during the MCO and MMCT as well as the precise magnitude and rate of continental temperature variation are currently not well-understood. This especially applies for the transition out of the MCO and into the MMCT (ca. 14.2 to 13.8 Ma). Resolving the dynamics of climate change is essential to evaluate and forecast the natural dynamics of the Southern European climate system in an area vulnerable to anticipated future climate change which could result in large natural and socioeconomic hazards.

Here we present a comprehensive and well-dated terrestrial clumped isotope (Δ₄₇) paleosoil carbonate dataset from Southern Europe (Spain) that ranges from 15.33 to 12.98 Ma and therefore includes the end of the MCO and the complete MMCT. After a short-termed cooling at 14.18 Ma (ca. Mi3a), Δ₄₇-based soil temperatures strongly decline at 13.94 (midpoint; ca. Mi3b). The data is in agreement with oceanic sea surface temperatures, δ¹³C, and δ¹⁸O isotope records and shows that the continental climate during the MMCT was highly dynamic and characterized by substantial fluctuations in temperature.