Ocean in the Earth System

Complexity is an intrinsic property of natural systems. In the oceanic system, it is linked to many interactions with the atmosphere, geosphere and biosphere with which it exchanges energy and matter.

Complexity of the ocean system has, at different spatial and temporal scales, hydrodynamic mechanisms of these exchanges and dynamics of elements and compounds, they are involved in biogeochemical cycles or used as tracers.

By its pedagogical approach, it defines the terms, methods, techniques and analytical tools used. Then, it analyzes the consequences of climate change, future projections, human impact and the concept introduced with planktonic pelagic ecosystem component.

André Monaco is Emeritus Director of Research for the French national research center (CNRS). His research interests concern marine sedimentology and geochemistry. He was responsible for part of the organizing committee for several French and European programs and has been guest editor for four special issues in international journals.

Patrick Prouzet is Director of Research focusing on the ecosystemic approach at Ifremer in France. He specializes in the biology and dynamics of anadromous fish such as Atlantic salmon and eels. He is the author or co-author of several works on these species or on estuary fishing.

FOREWORD xi

CHAPTER 1. THE OCEAN IN THE EARTH SYSTEM: EVOLUTION AND REGULATION 1
Philippe BERTRAND

1.1. The Earth system and its components 1

1.1.1. A system is a set of objects whose limit is arbitrary, but pertinent 1

1.1.2. One system is necessarily built into another 3

1.1.3. The Earth is a “closed” system  4

1.1.4. The major components of the Earth system 7

1.1.5. What is the biosphere? 8

1.2. The ocean, from its origins 9

1.2.1. Was there an ocean 4.4 billion years ago?  9

1.2.2. The origin of water on Earth (4.5 – 4 billion years ago)   9

1.2.3. The ocean and the end of the “Venus” phase of the Earth’s history (between 4.5 and 4 billion years ago)   10

1.2.4. Why are there oceans on Earth and a “Venus inferno” on Venus? 13

1.2.5. The ocean, cradle of the first living creatures (between 4.4 and 3.5 billion years ago) 16

1.3. The ocean, oxygen and the evolution of life forms 18

1.3.1. The essential characteristics had been selected in the ocean before the Cambrian period, over 540 million years ago 18

1.3.2. How did oxygen accumulate?  21

1.3.3. The first important accumulation of oxygen (around 2.5 billion years ago) 25

1.3.4. A moderate increase in oxygenation (between 2.5 and 0.5 billion years ago) 26

1.3.5. The second important accumulation of oxygen (between 500 and 350 million years ago) 27

1.4. The regulation of the greenhouse effect by the ocean 29

1.4.1. There is no life without a minimum greenhouse effect 29

1.4.2. The regulation of the greenhouse effect by the ocean 30

1.5. Oceanic photosynthesis regulates itself on a short timescale 36

1.5.1. When the ocean is deficient in nitrate  38

1.5.2. When the ocean has an excess of nitrate  40

1.5.3. The regulation of the N/P ratio  41

1.6. Conclusion 43

1.6.1. The ocean in the Earth system  43

1.6.2. The anthropogenic disturbance of the Earth system   45

1.6.3. And life among all that? 47

1.7. Acknowledgments 49

1.8. Bibliography  49

CHAPTER 2. THE OCEAN AND THE CLIMATE SYSTEM 55
Pascale DELECLUSE

2.1. Introduction 55

2.2. Climate change 55

2.2.1. The report on the findings   56

2.2.2. Interpretation of the observed changes 58

2.2.3. The Earth’s radiative equilibrium and greenhouse gases 59

2.2.4. The role of greenhouse gases – GHG60

2.2.5. Scenarios and projections 63

2.3. Physics and dynamics  67

2.3.1. Rotation, Coriolis, geostropy  69

2.3.2. An ocean moved by the wind  71

2.3.3. Ekman, spiral, transport, pumping, upwelling and downwelling 71

2.3.4. Interior ocean and western boundary currents 77

2.3.5. An ocean moved by thermohaline fluxes  80

2.3.6. Stratification, mixed layer, thermocline  82

2.3.7. Formation of water masses, convection and subduction  83

2.3.8. Schematization of global circulation: the great conveyor belt   85

2.4. Some key elements for understanding the ocean’s role in the climate  88

2.4.1. Typical times   88

2.4.2. Ocean–atmosphere in the tropics 90

2.4.3. Other types of variability 95

2.4.4. Climatic surprises  97

2.5. Some questions for the future 100

2.6. Bibliography 102

CHAPTER 3. OCEAN–ATMOSPHERE INTERACTIONS  105
Laurence EYMARD and Gilles REVERDIN

3.1. Introduction: what are ocean–atmosphere interactions?  105

3.2. Interface processes and their role in the coupled system   106

3.2.1. Radiative fluxes  107

3.2.2. Turbulent fluxes  109

3.2.3. Water exchanges between the ocean and atmosphere  115

3.2.4. Other exchanges of matter   118

3.2.5. Flux measurement  125

3.3. Examples of energy exchanges   129

3.3.1. Tropical cyclones  129

3.3.2. Surface temperature fronts   132

3.3.3. The interactions close to strong oceanic fronts 134

3.3.4. Marginal ice zones and associated air–sea fluxes 137

3.3.5. The example of the impact of the iron supply from Saharan aerosols 140

3.4. Conclusion 142

3.5. Bibliography 143

CHAPTER 4. MARINE BIOGEOCHEMICAL CYCLES  145
Louis LEGENDRE

4.1. Introduction: geochemistry, biogeochemistry and marine biogeochemistry 145

4.1.1. Geochemistry and cosmochemistry 145

4.1.2. Biogeochemistry and marine biogeochemistry 147

4.2. A fundamental characteristic of the Earth’s system: biogeochemical cycles  149

4.3. Carbon: at the heart of living matter  152

4.3.1. Carbon in large natural reservoirs 153

4.3.2. Biogeochemical cycles of carbon 156

4.4. Oxygen: a poison that Earth cannot do without 166

4.4.1. The Great Oxygenation Event  168

4.4.2. Biogeochemical cycles of oxygen 169

4.5. Nitrogen: a chemical element over which countries have fought in the past 174

4.5.1. Nitrogen, abundant but difficult to access  174

4.5.2. Biogeochemical cycles of nitrogen 176

4.6. Phosphorus: a chemical element over which countries may fight in future 182

4.6.1. Phosphorus, not very abundant or exploitable 182

4.6.2. Biogeochemical cycles of phosphorus 182

4.7. Biogeochemical equilibria and human societies: problems    185

4.8. Bibliography  186

CHAPTER 5. OCEAN ACIDIFICATION AND ITS CONSEQUENCES   189
Jean-Pierre GATTUSO, Lina HANSSON and Frédéric GAZEAU

5.1. Introduction 189

5.1.1. What is ocean acidification?  190

5.1.2. A brief history of research on the acidification of oceans  193

5.1.3. Main research programs  197

5.2. Observations 197

5.2.1. Past changes   197

5.2.2. Recent changes 199

5.3. Projections 201

5.4. Impacts of ocean acidification   204

5.4.1. Impacts on organisms and communities  204

5.4.2. Impacts on biogeochemical cycles 219

5.4.3. Economy and society 221

5.5. What are the solutions? 225

5.5.1. The reduction of CO2 emissions  226

5.5.2. Geoengineering techniques   227

5.5.3. Adaptation measures 228

5.6. Conclusion 229

5.7. Acknowledgments 231

5.8. Appendix 231

5.8.1. Carbonate chemistry of carbonates and biogeochemical processes 231

5.9. Bibliography 233

LIST OF AUTHORS 255

INDEX  257

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