|
Axel Kleidon, Max-Planck-Institute for Biogeochemistry (Germany)
Susanne Arens, Max-Planck-Institute for Biogeochemistry (Germany)
Kristin Bohn, Max-Planck-Institute for Biogeochemistry (Germany)
Buendia Corina, Max-Planck-Institute for Biogeochemistry (Germany)
Ryan Pavlick, Max-Planck-Institute for Biogeochemistry (Germany)
Bjoern Reu, Max-Planck-Institute for Biogeochemistry (Germany)
Steffen Richter, Max-Planck-Institute for Biogeochemistry (Germany)
Stan Schymanski, Max-Planck-Institute for Biogeochemistry (Germany)
Kerstin Sickel, Max-Planck-Institute for Biogeochemistry (Germany)
|
|
Earth system models of various complexities have been built over the last decade or so to simulate the dynamics of the atmosphere, oceans, and land and how the biosphere interacts with these components. These models can be used to estimate and quantify biotic effects on Earth system functioning and this can serve as a tool to investigate whether biotic effects act to modify the Earth system in any particular direction, e.g. bring the system further away from thermodynamic equilibrium. Even though thermodynamic laws are widely recognized and to some extent represented in these models, quantitative expressions of the thermodynamic nature far from equilibrium of many Earth system processes, such as rates of entropy production and distance to thermodynamic equilibrium, are usually absent in these models. To address this deficiency, we develop a novel approach to simulate the Earth system that is based on non-equilibrium thermodynamics. We express the coupling between the different subsystems (atmosphere, ocean, land, vegetation on land) in terms of thermodynamic fluxes and gradients. While this is straightforward to implement for heat fluxes, the mass fluxes of water, carbon dioxide, etc. need to be adequately defined in terms of modified chemical potentials which account for concentrations, air pressure, and height. We show a first implementation of this model and use it to estimate the entropy balance for land with respect to energy, water and carbon fluxes. This modelling framework provides a basis for quantifying the non-equillibrium thermodynamic nature of the Earth system, how it changes with altered forcings and it allows us to estimate the thermodynamic consequences of biotic effects in future studies.
|
