Impact of Miocene Tectonics on Global and Neotropical Climate: A Modelling Approach

Abstract:

Latest studies suggest that the Miocene was a period of profound changes in Neotropical environments, with the rise of the Andes, the restriction of the Central American Seaway (CAS) and major modifications over the continent, with changing Amazon river-routing and long-standing inland seaways. Understanding how these perturbations have altered climate and in turn neotropical biodiversity require several steps, including the understanding of all physical mechanisms involved. Here we use the fully coupled general circulation model (GCM) IPSL-CM4 to quantify the impact of the uplift of the Andes and the closure of the CAS on global and regional climate, including Atlantic Meridional Overturning Circulation and South American temperature and rainfall patterns. A simulation with lower Andes helps understanding how the mechanical effect of this barrier affects surface winds and in turn, freshwater balances over the ocean and associated sea surface temperatures. In a second experiment, we include the continental effect of the Andean uplift, i.e. the changes in river routing within the Amazon basin and modified location of its freshwater outflow to the ocean, and show that mechanical and hydrological effects of the uplift are not acting in the same direction. Lastly, as the spatial resolution of GCMs can hardly be reconciled with the geographical scale required for paleobiogeographical studies, we suggest new methods to downscale climatic layers and bridge the gaps between large-scale models and intracontinental biotic studies.