On the thermodynamics of the oceanic general circulation: Irreversible transition to a state with higher rate of entropy production

Abstract

SUMMARYThe mechanism of transitions among multiple steady states of thermohaline circulation is investigated from a thermodynamic viewpoint. An oceanic general-circulation model is used to obtain the multiple steady states under the same set of wind forcing and mixed boundary conditions, and the rate of entropy production is calculated during time integration. Three states with northern sinking and four states with southern sinking are shown to exist in the model by perturbing the high-latitude salinity. It is found that for transitions among southern sinkings the transition tends to occur from a state with a lower rate of entropy production to a state with a higher rate of entropy production, but the transition in the inverse direction does not occur. These transitions can thus be said to be irreversible or directional , in the direction of the increase of the rate of entropy production. For transitions between northern sinking and southern sinking, the rate of entropy production can either increase or decrease depending on the direction of the perturbation. The decrease is found to be associated with a collapse of the northern sinking circulation by a certain amount of negative salt (positive fresh water) perturbation to the northern hemisphere. After this collapse, a new southern sinking circulation develops, and the corresponding rate of entropy production increases. All these results tend to support the hypothesis that a nonlinear system is likely to move to a state with maximum entropy production by perturbation.

The climate sensitivity to human appropriation of vegetation productivity and its thermodynamic characterization

“…Furthermore, entropy production provides a unifying perspective of seemingly different processes in the climate system (energy vs. water vs. carbon fluxes) and it is well suited in that it provides a clear reference point defined by states of maximum entropy production (e.g. Paltridge, 1978;Grassl, 1981;Ozawa and Ohmura, 1997;Shimokawa and Ozawa, 2002;Lorenz et al, 2001;Ozawa et al, 2003;Kleidon et al, 2003Kleidon et al, , 2006Kleidon and Fraedrich, 2005). This thermodynamic interpretation of climate sensitivity would seem worthy of further development and applications to other topics related to global climatic change.…”

The mechanics of granitoid systems and maximum entropy production rates

“…One of the tenets of modern non-equilibrium thermodynamics is that systems not constrained to be at steady state will evolve to that state which tends to maximize entropy production. Such a principle has proved invaluable in explaining aspects of the Earth's climate (Paltridge 1975(Paltridge , 1978(Paltridge , 2001, the oceanic general circulation (Shimokawa & Ozawa 2002), and the fundamental mechanical, hydraulic and chemical behaviour of solids (Ziegler 1983a,b;Coussy 1995Coussy , 2004Houlsby & Puzrin 2006). The principle has a basis in statistical mechanics (Dewar 2005) where it has been shown that a state of maximum entropy production rate is the most probable state for large systems not at equilibrium and not constrained to be at steady state.…”

A discussion on maximum entropy production and information theory

“…It is important to keep in mind that (contrary to what is claimed in [2]) the constitutive equations derived from the above Lagrangian are only compatible with (18) and (23) when ij F ij ∂A ij,kl ∂F lm = 0. It is clear that this restriction does not hold in the non-linear regime of our model with constitutive equations (11).…”