Nonequilibrium thermodynamics and maximum entropy production in the Earth system

Abstract

The Earth system is maintained in a unique state far from thermodynamic equilibrium, as, for instance, reflected in the high concentration of reactive oxygen in the atmosphere. The myriad of processes that transform energy, that result in the motion of mass in the atmosphere, in oceans, and on land, processes that drive the global water, carbon, and other biogeochemical cycles, all have in common that they are irreversible in their nature. Entropy production is a general consequence of these processes and measures their degree of irreversibility. The proposed principle of maximum entropy production (MEP) states that systems are driven to steady states in which they produce entropy at the maximum possible rate given the prevailing constraints. In this review, the basics of nonequilibrium thermodynamics are described, as well as how these apply to Earth system processes. Applications of the MEP principle are discussed, ranging from the strength of the atmospheric circulation, the hydrological cycle, and biogeochemical cycles to the role that life plays in these processes. Nonequilibrium thermodynamics and the MEP principle have potentially wide-ranging implications for our understanding of Earth system functioning, how it has evolved in the past, and why it is habitable. Entropy production allows us to quantify an objective direction of Earth system change (closer to vs further away from thermodynamic equilibrium, or, equivalently, towards a state of MEP). When a maximum in entropy production is reached, MEP implies A. Kleidon (B) Max-Planck-Institut für Biogeochemie, Postfach 10 01 64, 07701 Jena, Germany e-mail: akleidon@bgc-jena.mpg.de that the Earth system reacts to perturbations primarily with negative feedbacks. In conclusion, this nonequilibrium thermodynamic view of the Earth system shows great promise to establish a holistic description of the Earth as one system. This perspective is likely to allow us to better understand and predict its function as one entity, how it has evolved in the past, and how it is modified by human activities in the future.

Vertical and horizontal processes in the global atmosphere and the maximum entropy production conjecture

“…In the real climateṠ ver can be thought of as the entropy production due to the sum of latent and sensible heat fluxes at the surface (Kleidon, 2009) and, to a minor extent, turbulent dissipation of kinetic energy. Lucarini et al (2011) have shown thatṠ hor is a lower bound of entropy production due to dissipation of kinetic energy.…”

Thermodynamic dissipation theory for the origin of life

“…Onsager's principle, and variations thereof, have been useful in describing the existence and stability of abiotic and biotic dissipative systems on Earth (Lorenz, 1960;Paltridge, 1979;Ulanowicz and Hannon, 1987;Swenson, 1989;Kleidon and Lorenz, 2005;Michaelian, 2005;Martyusheva and Seleznev, 2006;Kleidon, 2009).…”

“…These molecules, in the presence of water, are extraordinarily rapid at dissipating the high energy photons to heat. It is then plausible that life arose as a catalyst for absorbing sunlight at the surface of the shallow seas, dissipating it into heat and, thereby promoting still other irreversible processes such as the water cycle (evaporation/rain), and wind and ocean currents, all of which contribute to the entropy production of the biosphere (Peixoto et al, 1991;Kleidon 2009). This suggests a thermodynamic imperative for an origin of life which can be related to its thermodynamic function of entropy production (Michaelian, 2009.…”

The evolutionary approach to entropy: Reconciling Georgescu-Roegen's natural philosophy with the maximum entropy framework

“…This approach has gained in prominence with the recent rise of Maximum Entropy concepts in physics, especially in the earth sciences (Whitfield 2005; Kleidon 2009Kleidon , 2010. It builds on the statistical mechanics foundation of thermodynamics, and seems therefore plainly incompatible with Georgescu-Roegen's critique of Boltzmann.…”

“…Thus, the maximum power principle is treated as a correlate of the MEP principle. This view has been concisely developed by Kleidon (2009Kleidon ( , 2010 and states that open non-equilibrium systems such as the earth system will always manifest the tendency to approach the maximum entropy state, which is defined as the macroscopic state which is most probable, given energy and mass-balance constraints. This tendency is empirically complex because the respective manifold processes proceed in vastly different time scales.…”