Partitioning meridional heat transport in Early Eocene Climatic Optimum model simulations

The meridional heat transport is primarily governed by the geometry between the Earth and the Sun and it has been shown in previous studies that it is nearly invariant in different climates. Nevertheless, the processes, which contribute to the whole transport, do not stay invariable, but their changes compensate each other. Thus, the changes in the various transport processes give an insight into the climate system and its changes in different conditions, such as the high CO₂ concentrations of the Early Eocene Climatic Optimum (EECO).

In our work we investigate the meridional heat transport and its elements in climate model simulations from DeepMIP focusing on the EECO. The meridional heat transport is divided into atmospheric and ocean heat transport. The atmospheric heat transport is further divided into moist and dry energy transport and also into transport by the meridional overturning circulation, transient eddies and stationary eddies. Annual and seasonal changes are compared in the preindustrial control simulation, in the 1xCO₂ simulation and in simulations with high CO₂ concentration values (3xCO₂, 4xCO₂, 6xCO₂). We found that in a warmer climate, where the hydrological cycle is expected to be stronger, the transport of the meridional overturning circulation at the tropics, so the circulation of the Hadley cell, is more intense. Also, at the subtropics the energy transport of monsoon systems and at the mid-latitudes the energy transport of cyclones and anticyclones is different than in the control climate.