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8 - Hydrologic cycling
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
Thermodynamic roles of water
So far we have dealt with radiative forcing and how differences in radiative heating result in motion that depletes differential heating, thereby following the second law. Our next step in the sequence of energy conversions from radiation to Earth system processes shown in Fig. 1.5 is to relate the differential heating and the resulting motion to hydrologic cycling and associated thermodynamic directions and limits.
There are two aspects closely related to water that greatly shape the thermodynamic setting of the Earth system. First, hydrologic cycling involves energy conversions of substantial magnitude that are associated with the different phases of water, so that the latent heat involved in the different phases contributes a considerable share of the heat fluxes in the atmosphere. Second, the presence of water in its different phases is associated with the abundance of ice and clouds, two aspects that greatly affect the albedo, the magnitude of the solar radiative forcing, and thereby the radiative environment of the Earth system. Furthermore, water vapor in the atmosphere and clouds contributes substantially to the atmospheric greenhouse effect, so that hydrologic cycling affects both absorption and reflection of solar radiation as well as the radiative transfer of terrestrial radiation. These highly relevant aspects illustrate how water and the magnitude of its cycling affects the overall thermodynamic state of the Earth system.
The thermodynamic treatment of hydrologic cycling starts with the thermodynamics of phase transitions. The different phases of water – solid, liquid, and gas – correspond to different intensities by which water molecules are bound to each other. The water molecules are bound most strongly in their solid state, and are unbound when in the gaseous state. When we consider the entropy of a system in which water is present in two states, for instance, liquid water and vapor then the total energy of the system involves thermal energy, but also uncompensated heat related to the water vapor pressure as well as intermolecular binding energies. Binding energies are described in thermodynamics by the mass and the respective chemical potential, as introduced in Section 2.3. The total energy of the system is thus spread over the thermal energy, the pressure of water vapor, and across the intermolecular bonds in the liquid state.
5 - Dynamics, structures, and maximization
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
Energy conversions, maximization, and evolution
So far, we formulated Earth system processes in terms of the different forms of energy that these involve and identified fundamental limits to the conversion of one form of energy into another. We have not yet discussed why processes should evolve to thermodynamic limits and how this evolution should take place. The goal of this chapter is to explore exactly these questions of why, how, and to what extent systems should be expected to evolve towards their thermodynamic limits.
At the core of these questions are the dynamics that take place within a system. The term dynamics is used here in a general sense on a thermodynamic system in disequilibrium that maintains fluxes that are directed towards depleting this thermodynamic disequilibrium. The extent of dynamics can thus be measured by how much free energy is being generated and dissipated. The motivation of this definition of dynamics is that a system in thermodynamic equilibrium would not show macroscopic dynamics. In contrast, a system with free energy generation can sustain fluxes and macroscopic changes taking place inside the system. As these fluxes and changes involve energy, mass, momentum, and other variables that are represented in the conjugated pairs of variables described in the earlier chapters, these dynamics relate to conversions of different forms of energy. We can thus view dynamics as the consequence of how a certain form of energy is generated and dissipated. The term evolutionary dynamics is then used here to characterize dynamics that go beyond energy, mass, and momentum balances and are specifically characterized by a change in free energy generation, dissipation, and the thermodynamic state of the system.
A general template for the conversions involved in a particular form of energy is shown in Fig. 5.1. At the top of the diagram is a driving gradient, for instance, a temperature difference, from which a certain form of free energy is generated. This form of free energy is then represented by a gradient in another variable. For kinetic energy, this gradient is represented by velocity differences within the fluid and its surroundings. Ultimately, this form of free energy is dissipated into thermal energy, with a greater amount of free energy being typically associated with a greater dissipation rate. For simplicity, conversions into other forms of energy during dissipation are not included here.
12 - The thermodynamic Earth system
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
Thermodynamic foundations of the whole Earth system
We have now dealt with the basics of thermodynamics and its application to a range of dominant Earth system processes, from the radiative forcing of the planet to human activity. At the end of this book, the goal is to synthesize these thermodynamic components to a comprehensive picture of how the Earth system functions as a whole and how its dynamics is a reflection of the second law, and to illustrate what insights this picture may provide for the questions raised in the motivation for the book. This chapter closes with a perspective of the possible future directions.
Themainmotivation for formulating the Earth system in thermodynamic terms is that thermodynamics is so general that it is applicable to all Earth system processes. It thus provides a unifying basis for describing the directions, connections, and interactions of processes so that we can get an understanding of how the whole system functions and evolves. While for thermal energy and heat this thermodynamic formulation is common and straightforward, other processes such as radiation or motion are less commonly formulated in thermodynamic terms. Yet, when this is done with the use of conjugate variables, Earth system processes can be dealt with in the same units of energy, thus making them comparable, and the dynamics of these processes can be formulated in terms of energy conversions. Here, thermodynamics provides another critical component for a unifying basis. The second law of thermodynamics formulates the overall direction of these conversions and imposes a condition that results in thermodynamic conversion limits. These thermodynamic limits act as relevant constraints to the dynamics of Earth system processes. The first and second law of thermodynamics thus provide the bare minimum of essential physics to consistently formulate Earth system processes and their interactions.
Equally important in establishing a thermodynamic foundation of the Earth system is to place thermodynamics in the context of the Earth system. This was illustrated in the introduction by Fig. 1.5, which shows how the planetary forcing creates gradients that are further converted to motion, hydrologic and geochemical cycling, biotic and human activity and that result in the dynamics of the Earth system. This hierarchical view of Earth system processes allows us to separate the drivers from the driven processes and apply thermodynamic limits to these conversions.
7 - Motion
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
Transporting mass on the planet
With the radiative forcing being described in thermodynamic terms, in this chapter, we link this forcing to motion as the next step in the cascade of energy conversions of the Earth system that was shown in Fig. 1.5. Motion transports energy, mass, and momentum between different places of the Earth system. It is through large-scale energy and mass transports associated with motion that the processes in one region affect processes elsewhere. Motion thus plays the role of the global connector, allowing regions to interact. It is this global connection that makes the Earth system a highly interactive, planetary system with large-scale material cycling of geochemical elements.
The purpose of this chapter is to describe motion, the limits that it is exposed to as well as its planetary consequences from a thermodynamic perspective. This description is quite different from the common approach in which the natural starting point is the momentum balance in the form of the Navier–Stokes equation of fluid dynamics. The view formulated here does not contradict this common approach, but rather supplements it by placing motion explicitly into the context of the thermodynamic, planetary setting. Furthermore, the consequences of motion are then evaluated to show that motion can be interpreted as the result of a system advancing to its state of thermodynamic equilibrium at an accelerated rate.
Our starting point for the description of motion is kinetic energy and the processes that generate and dissipate this form of energy. Kinetic energy is then directly related to the velocity associated with motion and the magnitudes by which thermal energy and mass is transported. The generation of kinetic energy originates from differential heating. This differential heating causes density differences in fluids, which affect the potential energy of the system. The tendency of the system to deplete its potential energy to a lower value is associated with buoyancy in the system, which then drives the onset of motion. This mechanism to generate motion is very general and applies to most forms of motion found in the atmosphere, oceans, and the solid Earth. There are, however, also other forms of motion that result from different conversions that are either indirectly related to this generation mechanism or to other drivers. An example of an indirect relationship is the wind-driven oceanic circulation, which relates to atmospheric motion and its generation.
11 - Human activity
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
Human activity as a thermodynamic process
In the last chapter before the summary, we extend the thermodynamic description to human activity to formulate the last link represented in Fig. 1.5. This application of thermodynamics to human activity is rather important, as human activity increasingly shapes the functioning of the Earth system. As we will see in this chapter, thermodynamics can provide a generalized view of human activity, its limits as well as its impacts within the Earth system.
The impacts of human activity are noticeable at the planetary scale and are reflected in, for instance, the increase in atmospheric greenhouse gases such as CO2 resulting in global climate change, stratospheric ozone depletion, the expansion of croplands and pastures, with about 40% of the land surface being placed under human use (Foley et al. 2005), and the alterations of the global cycles of nitrogen and phosphorus. The impact of human activity has reached such an extent that it has been suggested that the present day can be referred to as the new geologic era of the “Anthropocene” (Crutzen 2002). As the size of the human population as well as its energy consumption is likely to grow in the future, the effects of human activity on the Earth system are likely to increase as well. A description of the thermodynamics of the Earth system would be incomplete without a characterization of human activity and its effect on the Earth system.
Yet, the human role is often described as if it were separate from the functioning of the Earth system. There are certain aspects that are taken from the Earth to sustain human activity, such as food production or fossil fuels, as shown in Fig. 11.1a. Human activity then has impacts on the Earth system, for instance, in terms of land cover changes associated with food production, or global climate change due to the emission of CO2 resulting from the combustion of fossil fuels. The purpose of this chapter is to describe human activity as a dissipative process that is embedded within the functioning of the Earth system, just as it was done for the other processes in the previous chapters.
3 - The first and second law of thermodynamics
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
The rules for energy conversions
The last chapter described how different Earth system processes are related to different forms of energy and entropy. This formulation in terms of energy sets a basis for making them comparable. The rules for converting one form of energy into another are described by the laws of thermodynamics. They ensure the conservation of energy during the conversion process, and set the direction into which these conversions occur.
Historically, these laws have grown out of the need to understand and improve the work output of steam engines in the mid-nineteenth century. Since then, their basis has been extended much beyond steam engines to all forms of energy transfer. The purpose of this chapter is to show those aspects of the laws of thermodynamics that have the most direct relevance to understand energy conversions by Earth system processes. The foundations set by the laws then allow us to make quantitative predictions of the direction in which the dynamics take place in Earth systems and set upper limits on energy conversion rates, as described in the following chapter. In total, there are four laws of thermodynamics that are numbered from zero to three. They are summarized in Table 3.1.
The zeroth law sets the basis for comparing thermodynamic systems. It establishes the state of thermodynamic equilibrium as a reference state, which is the state of a system in which there is no net transformation or exchange of any physical quantity. The zeroth law formulates that if two systems are in thermodynamic equilibrium with a third system, then the two systems are also in thermodynamic equilibrium. As we will see in the following, the state of thermodynamic equilibrium serves as an important reference point, as it sets the “target” state for the dynamics that take place within a system and the exchanges with other systems. The zeroth law also comes into play when the equilibrium between different forms of energy is needed to describe energy conversion processes. This is, for instance, the case for radiative processes, in which conversions between radiative and thermal energy are involved, or for phase transitions, in which conversions between liquid and gaseous phases are involved. However, as this law represents a more formal aspect, we will not deal with the zeroth law in greater detail here.
List of Symbols
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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References
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Frontmatter
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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2 - Energy and entropy
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
The central roles of energy and entropy
Different forms of energy and conversions among these are central to the dynamics of the Earth system and to the application of thermodynamics. Energy is defined as a property of matter and radiation that is linked to the capacity to perform work. Performing work relates to the conversion of one form of energy to another. The actual capacity to perform work is described by free energy, which is linked to the dispersal of energy across the microscopic scale of atoms and molecules and is described by its entropy. This chapter focuses on the description of different forms of energy and entropy relevant to the Earth system; but we should keep in mind that the dynamics of the Earth system are not shaped by the magnitudes of energy or entropy in the system, but rather by the conversion rates that are related to differences in energy and entropy. These conversion rates are subject to the laws of thermodynamics and are dealt with in the following chapters.
Earth system processes involve different forms of energy. Solar and terrestrial radiation involve radiative energy. Atmospheric motion is associated with kinetic energy, while cloud droplets are associated with gravitational, or simply potential, energy. Soil moisture on land is linked to the energy associated with the binding energy of water to the soil matrix and with potential energy. The concentration of constituents in air, water, and solids as well as biomass is linked to forms of chemical energy. Likewise, any other process within the Earth system is associated with some form of energy. In this chapter, the major forms of energy are described and broad estimates of their magnitude are given to illustrate how these are quantified. A more hidden aspect in these forms of energy is its spread at the scale of atoms and molecules that is described by entropy. At the microscopic scale, energy is stored in discrete, countable units. These units involve, for instance, photons, quanta of radiative energy, discrete energy levels of electrons in molecular bonds, and the distribution of kinetic energy over discrete number of molecules in a gas. When we describe Earth system processes at the planetary scale, such microscopic details are avoided to the extent possible, and aggregated, macroscopic variables, such as temperature, pressure, and density, are used instead that relate to macroscopic forms of energy.
Contents
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Glossary
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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9 - Geochemical cycling
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
Drivers of chemical disequilibrium in the Earth system
We have now dealt with the thermodynamics of mass cycling associated with water in relation to the planetary forcing. The next step in describing the thermodynamic view of the Earth system shown in Fig. 1.5 is to extend and connect the geochemical cycling of mass to this view. As we will see in this chapter, the thermodynamic formulation of geochemical cycling is similar to hydrologic cycling, except that the connections of geochemical cycling to energy fluxes and radiative effects is more subtle. This formulation then allows us to understand how and by which processes chemical energy is generated within the Earth system.We can then understand how chemical disequilibrium is maintained in the Earth system, how biotic activity as a specific geochemical process fits into this description, by how much biotic activity contributes to the maintenance of chemical disequilibrium, and how geochemical cycling interacts with the thermodynamic state of the Earth system.
This thermodynamic description of geochemical cycling in the Earth system relates back to one of the motivations of the introduction, in which it was described that the Earth's atmosphere reflects a notable state of chemical disequilibrium, reflected mostly in the simultaneous presence of methane, CH4, and oxygen, O2 (Lovelock 1965). If left alone, methane would react with oxygen to form carbon dioxide and water, so it requires a continuous exchange of these compounds between the atmosphere and other compartments of the Earth system to maintain the simultaneous presence of these chemical compounds. This remarkable state of chemical disequilibrium has long been recognized as being a unique signature of the Earth system when compared to other planetary atmospheres of the solar system. It possibly serves as a fundamental indicator of a planet with life (Lovelock 1965; Hitchcock and Lovelock 1967; Lovelock 1975), it motivated the development of the Gaia hypothesis (Lovelock and Margulis 1974), and is indicative of geochemical cycling through the Earth's atmosphere as exchange fluxes of chemical compounds are needed to maintain this disequilibrium state.
This chapter deals with geochemical cycling as a thermodynamic phenomenon of the Earth system that reflects the maintenance of geochemical reactions in a state of disequilibrium at the planetary scale. The description of geochemical cycling starts with a thermodynamic formulation of chemical reactions and with relating the concentrations of chemical compounds to states of chemical disequilibrium.
6 - Radiation
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
The main driver of the Earth system
Radiation – obviously – plays a major role in the Earth system. It is by far the most important driver for energy conversions on Earth, both in terms of the sheer magnitude of the energy flux of solar radiation, and also in terms of its quality, as solar radiation represents radiation with a very low entropy. In the thermodynamic view of the Earth system shown in Fig. 1.5, it is the start point and endpoint for most energy conversions taking place within the Earth system. Spatial and temporal variations in the absorption of solar radiation are the causes for various heat fluxes and associated dynamics that distribute imbalances in radiative heating and cooling rates. Variations in radiative forcing in combination with dynamics shape most of the observed climatic variations, from the seasons in mid-latitudes to the large-scale variation of surface temperature from the tropics to the poles. The focus of this chapter is to describe the thermodynamic nature of radiation which is then used to understand the dissipative nature of radiative transfer processes, to derive the limits of energy conversions from radiation to other forms, and to describe radiative transfer as a dominant process shaping the environmental conditions that affect other energy conversion processes.
In thermodynamic terms, the radiative exchange between the Earth and space generates the most important driving gradients, and it exports the entropy that is being produced by Earth system processes to space. The entropy of radiation is represented mostly by the spectral composition of the radiative flux. The spectral compositions of the incoming solar radiation and the outgoing radiation from the Earth system are shown in Fig. 6.1. Solar radiation is composed mostly of visible light which is characterized by relatively short wavelengths. This spectral composition essentially corresponds to the composition of the radiation when it was emitted from the Sun at a high temperature of about 5760 K. When solar radiation is absorbed by the Earth system, it is subsequently reemitted to space at a much lower temperature of about 255 K, which is approximately the Earth's radiative temperature. The associated spectral composition of the emitted radiation is centered at much greater wavelengths in the infrared, so that this radiative flux has a markedly different spectral composition.
Preface
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- By Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
This book is about how thermodynamics applies to the Earth system. It is less about thermodynamics itself, but rather about how it applies to Earth system processes, their interactions, and the operation of the Earth system as a whole.
The motivation for writing this book stems from my interest in gaining a better, and more profound understanding of the Earth system, of the role that life plays within the system, and of how human activity changes the Earth system at a time when humans increasingly alter the operation of the planet. One way to deal with this challenge is to build increasingly comprehensive, yet also increasingly incomprehensible models of the Earth system. The other way is to search for a fundamental missing constraint that describes in comparably simple terms how systems operate and evolve. Since my doctoral work I have increasingly concentrated on this search. I looked into optimality approaches in vegetation, the Gaia hypothesis, and worked on the proposed principle of maximum entropy production (MEP). Over the years, I had many discussions with colleagues and took part in several workshops on these topics. I am tremendously thankful for these stimulating discussions, as these ultimately helped to shape my understanding that is now described in this book.
Today I think the answer to this missing constraint lies in the second law of thermodynamics. This law formulates a fundamental direction in physics that requires entropy to increase, at the small scale of an engine as well as at the scale of the whole Universe. Yet, its application to Earth system processes is almost absent, particularly when dealing with the whole Earth system. The second law, jointly with a thermodynamic formulation of the different processes yields a foundation to Earth system science that expresses processes in the same units of energy; it allows us to describe evolutionary dynamics as a thermodynamic direction imposed by the second law, and it sets fundamental limits and constraints on the emergent dynamics and interactions within the system. These limits can be quantified and yield estimates for Earth system processes that are largely consistent with observations, but require hardly any empirical parameters, substantiating that the second law provides missing constraints. It thus yields a grand picture of the Earth system in which its dynamics and evolution are a manifestation of the second law, […]
Index
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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4 - Thermodynamic limits
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
Limits to energy conversions
Energy conversions play a central role in driving the dynamics of Earth system processes. In the last chapter, we have seen how energy conversions are governed by the first and second law of thermodynamics. Energy conversions and the associated dissipative processes are sustained in natural systems by the entropy exchange across the system's boundary and are constrained by the second law. The subsequent generation of free energy out of this entropy exchange maintains the disequilibrium associated with a variety of variables and is reflected in the dynamics of the Earth system.
In this chapter, we take the laws of thermodynamics a step further.We first show how these laws yield fundamental conversion limits when combined, which then set the dissipative “speed limits” for the dynamics of a system. It sets the limit on the rate by which work can be performed through time, that is, the power that is associated with the conversion of thermal energy into another form. When applied to the Earth system, it is important to note that the work is performed inside the system, so that the consequences of the work need to be taken into account in the formulation of thermodynamic limits.
To illustrate thermodynamic limits qualitatively, consider the energy conversion associated with the heat engine shown in Fig. 4.1a. A heat engine is an abstract device that converts thermal energy into mechanical work and can represent a steam engine, a turbine, or atmospheric convection. The heat engine is driven by a heat flux Jin, from a hot reservoir, expels a certain fraction into a so-called waste-heat flux Jout, to a cold reservoir, and converts the other fraction into work at a rate G, with work performed through time representing the power of the engine. The heat flux Jout is referred to as a waste heat flux because its energy is not converted into free energy. The entropy exchange of the heat engine only consists of the heat fluxes between the reservoirs with their respective temperatures. This entropy exchange decreases the greater the value of G, because for the same entropy import associated with Jin, less is exported by Jout. The second law sets the ultimate limit to G, because the heat engine needs to at least export as much entropy as it is imported to maintain a non-negative entropy exchange.
10 - Land
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
The thermodynamic setting of land
The next step in describing the thermodynamics of the Earth system deals with the conditions on land. The land surface – in contrast to the oceanic surface – has a particular relevance in the Earth system. While it covers less than a third of the Earth's surface, it harbors a disproportionately large share of the biosphere, culminating in the lush and highly productive tropical rainforests that show among the highest levels of photosynthetic activity on the planet. These high levels of photosynthetic activity on land are achieved by large, complex, and highly organized vascular plants rather than by small and comparatively primitive microorganisms that are the primary producers of the oceans. On land, the high rates of photosynthetic activity are associated with a physical imprint on the characteristics of the surface. Note how different the land surface covered by rainforest is compared to an ocean surface, which is almost entirely described purely by its physical state, as exemplified by Fig. 10.1. On land, forest canopies provide dark and heterogeneous surfaces which absorb solar radiation while their root systems reach deep into the soil where they are able to extract water and transport it into the canopies to sustain an evaporative flux into the atmosphere. By dominating the absorption of solar radiation and evaporation, forests shape the partitioning of the surface energy balance. Biotic effects on the functioning of the Earth system are thus particularly strong at the land surface. In this chapter, we want to understand the conditions that allow for and favor these strong biotic effects and how these feed back to biotic activity from the insights gained so far from thermodynamics.
We have seen in the previous chapters that the partitioning of absorbed solar radiation into radiative and convective cooling in the surface energy balance is constrained by the maximum power limit as it results from a close interaction of the convective heat flux with its driving temperature difference between the surface and the atmosphere. Hence, the effects of forests on the surface energy balance extend further into the atmosphere and have the potential to alter the thermodynamic limit of the surface–atmosphere system. As convection drives the mass exchange between the surface and the atmosphere, this potentially feeds back on the gas exchange between vegetation and the atmosphere and thus on the level of biotic activity, as was hypothesized in the previous chapter.
1 - Thermodynamics and the Earth system
- Axel Kleidon, Max-Planck-Institut für Biogeochemie, Jena
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Summary
A thermodynamic basis for Earth system science
The Earth is a vastly complex system. This complexity is reflected in the broad range of processes that it entails, from the solar radiative forcing to the highly dynamic circulatory patterns in the atmosphere, ocean and the interior, to high level and diversity of metabolic activity of life, and to human activities. The complexity is further enhanced by strong interactions by which processes alter their own drivers. Atmospheric motion, for instance, transports such vast amounts of heat that it alters the radiative exchange with space. The activity of the Earth's biosphere, the sum of all living organisms, has strongly altered the chemical composition of the atmosphere, as for instance reflected in its high abundance of molecular oxygen, resulting in altered physical and chemical conditions. And finally, human activity over the last century has released such large amounts of buried organic carbon by its industrial activities that it has substantially altered the global carbon cycle resulting in enhanced concentrations of carbon dioxide in the atmosphere and global climate change. With such complexities in mind, it would seem almost impossible to make robust predictions of magnitudes, the strength of interactions, and the overall evolutionary direction of the Earth system as a whole in order to get a robust, physical understanding of how the whole Earth system functions and responds to change.
Yet there is a range of fundamental, practical, and relevant questions that require such a robust understanding. What determines, for instance, the strength of the atmospheric circulation and its ability to transport and mix heat and mass? The answer to this question would help us to make better predictions of the magnitude of climate system processes and how these would respond to perturbations and change. Does the climate system, and the planet as a whole, regulate its climatic state to some particular reference level? Is climate even regulated to a point that is most suitable to life, because of the presence of life, as proposed by the Gaia hypothesis (Lovelock 1972b,a; Lovelock and Margulis 1974)? If this is so, how would human activity play into such a planetary regulation? A better understanding of these questions would provide information about the role of the biosphere at the planetary scale and the factors that shape planetary habitability.
Thermodynamic Foundations of the Earth System
- Axel Kleidon
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Thermodynamics sets fundamental laws for all physical processes and is central to driving and maintaining planetary dynamics. But how do Earth system processes perform work, where do they derive energy from, and what are the limits? This accessible book describes how the laws of thermodynamics apply to Earth system processes, from solar radiation to motion, geochemical cycling and biotic activity. It presents a novel view of the thermodynamic Earth system explaining how it functions and evolves, how different forms of disequilibrium are being maintained, and how evolutionary trends can be interpreted as thermodynamic trends. It also offers an original perspective on human activity, formulating this in terms of a thermodynamic, Earth system process. This book uses simple conceptual models and basic mathematical treatments to illustrate the application of thermodynamics to Earth system processes, making it ideal for researchers and graduate students across a range of Earth and environmental science disciplines.