The Middle Miocene climate as modeled in an atmosphere-ocean-biosphere model

We present the first simulations for the Middle Miocene using a fully coupled atmosphere-ocean-biosphere model. The Middle Miocene topography, which alters both large-scale ocean and atmospheric circulation, causes a global warming of 0.7 K compared to a modern control climate. Compared to temperature proxies this warming is too small. Applying higher CO₂ concentrations of 480 and 720 ppm, we are able to simulate a global warming of 2.8 K and 4.9 K compared to present-day, which is in line with proxy records. Still, a flatter equator-to-pole temperature gradient, as it is suggested by marine and terrestrial proxies, cannot be realized. One reason is that atmospheric and oceanic heat transport compensate leaving the total poleward heat transport nearly unchanged. In our contribution we will show the mechanisms that are responsible for these compensating effects in the atmosphere-ocean system.