PP43B-2279
Did high Neo-Tethys subduction rates contribute to early Cenozoic warming?
Thursday, 17 December 2015
Poster Hall (Moscone South)
Guilhem Hoareau1, Brahimsamba Bomou2, Douwe J J Van Hinsbergen3, Carry Nicolas4, Didier Marquer4, Yannick Donnadieu5, Guillaume Le Hir6, Vrielynck Bruno7 and anne-Véronique Walter4, (1)University of Pau and Pays de l'Adour, LFC-R, Pau, France, (2)University of Corsica Pascal Paoli, Geology department, Corte, France, (3)Utrecht University, Utrecht, Netherlands, (4)University of Franche-Comté, Laboratoire Chrono-Environnement, Besançon, France, (5)LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette Cedex, France, (6)Institut de Physique du Globe de Paris, Paris, France, (7)ISTeP Institut des Sciences de la Terre de Paris, Paris Cedex 05, France
Abstract:
The 58-51 Ma interval was characterized by an increase of global temperatures (+4 to +6°C) up to the Early Eocene Climate Optimum (EECO, 52.9-50.7 Ma), the warmest interval of the Cenozoic. It was recently suggested that sustained high atmospheric pCO2, controlling warm early Cenozoic climate, may have been released during Neo-Tethys closure through the subduction of large amounts of pelagic carbonates and their recycling as CO2 at arc volcanoes. To analyze the impact of Neo-Tethys closure on early Cenozoic warming, we have modeled the volume of subducted sediments and the amount of CO2 emitted along the northern Tethys margin. The impact of calculated CO2 fluxes on early Cenozoic climate have then been tested using a climate carbon cycle model (GEOCLIM). We show that CO2 production may have reached up to 1.55x1018 mol/Ma specifically during the EECO, ~4 to 37% higher that the modern global volcanic CO2 output, owing to a dramatic India-Asia plate convergence increase. The subduction of thick Greater Indian continental margin carbonate sediments at ~55-50 Ma may also have led to additional CO2 production of 3.35x1018 mol/Ma during the EECO, making a total of 85% of the global volcanic CO2 outgassed. However, climate modelling demonstrates that timing of maximum CO2 release only partially fit with the EECO, and that corresponding maximum pCO2 values (750 ppm) and surface warming (+2°C) do not reach values inferred from geochemical proxies, a result consistent with conclusions arise from modelling based on other published CO2 fluxes. These results demonstrate that CO2 derived from decarbonation of Neo-Tethyan lithosphere may have possibly contributed to, but certainly cannot account alone for early Cenozoic warming, including the EECO. Other commonly cited sources of excess CO2 such as enhanced igneous province volcanism also appear to be up to one order of magnitude below fluxes required by the model to fit with proxy data of pCO2 and temperature at that time.
