Chemical Oceanography and the Marine Carbon Cycleassets.cambridge.org/97805218/33134/frontmatter/9780521833134... · Chemical Oceanography and the Marine Carbon Cycle Theprinciplesofchemicaloceanographyprovideinsightintotheprocesses

Chemical Oceanography and the MarineCarbon Cycle

The principles of chemical oceanography provide insight into the processes

regulating the marine carbon cycle. These topics are essential to under-

standing the role of the ocean in regulating the carbon dioxide content of

the atmosphere and climate on both human and geological time scales.

Chemical Oceanography and the Marine Carbon Cycle provides both a back-

ground in chemical oceanography and a description of how chemical

elements in seawater and ocean sediments can be used as tracers of physi-

cal, biological, chemical and geological processes in the ocean. The book

begins with a description of ocean circulation and biological processes, and

then moves on to discuss the chemicals that are dissolved in seawater.

Subsequent chapters focus on why the ocean has the chemistry that it does,

rather than on details of what is there. The first seven chapters present

basic topics of thermodynamics, isotope systematics and carbonate chem-

istry, and explain the influence of life on ocean chemistry and how it has

evolved in the recent (glacial–interglacial) past. This is followed by topics

essential to understanding the carbon cycle, including organic geochem-

istry, air–sea gas exchange, diffusion and reaction kinetics, the marine

and atmosphere carbon cycle and diagenesis in marine sediments. The

many figures in the book (including full-color versions) are available for

download at www.cambridge.org/9780521833134.

Developed by two well-known professors of oceanography, Chemical

Oceanography and the Marine Carbon Cycle is an ideal textbook for upper-

level undergraduates and graduates in oceanography, environmental

chemistry, geochemistry and earth science. It is also a valuable reference

for researchers in oceanography.

STEVEN EMERSON is Professor of Oceanography at the University of

Washington, specializing in inorganic geochemistry. He is a Fellow of the

American Geophysical Union and has worked on both air–sea interaction

and sediment geochemistry.

The late JOHN HEDGES was Professor of Oceanography at the University of

Washington, specializing in organic geochemistry. He was the recipient

in 2000 of the Geochemical Society’s Alfred R. Treibs Award for lifetime

achievement.

© Cambridge University Press www.cambridge.org

Cambridge University Press978-0-521-83313-4 - Chemical Oceanography and the Marine Carbon CycleSteven Emerson and John HedgesFrontmatterMore information

http://www.cambridge.org/0521833132

http://www.cambridge.org


Chemical Oceanography and

the Marine Carbon Cycle

Steven Emerson

John HedgesSchool of Oceanography, University of Washington, USA






CAMBR IDGE UN I VERS I T Y PR E S S

Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao Paulo, Delhi

Cambridge University PressThe Edinburgh Building, Cambridge CB2 8RU, UK

Published in the United States of America by Cambridge University Press, New York

www.cambridge.orgInformation on this title: www.cambridge.org/9780521833134

# S. R. Emerson and J. I. Hedges 2008

This publication is in copyright. Subject to statutory exceptionand to the provisions of relevant collective licensing agreements,no reproduction of any part may take place withoutthe written permission of Cambridge University Press.

First published 2008

Printed in the United Kingdom at the University Press, Cambridge

A catalog record for this publication is available from the British Library

ISBN 978-0-521-83313-4 hardback

Cambridge University Press has no responsibility for the persistence oraccuracy of URLs for external or third-party internet websites referred toin this publication, and does not guarantee that any content on suchwebsites is, or will remain, accurate or appropriate.






Contents

Preface page ix

Acknowledgements x

I Introduction to chemical oceanography 1

1 Oceanography background: dissolved chemicals, circulation

and biology in the sea 3

1.1 A chemical perspective 3

1.2 Constituents of seawater 5

1.3 Ocean circulation 17

1.4 Ocean biology 24

2 Geochemical mass balance: dissolved

chemical inflow and outflow from the ocean 33

2.1 Mass balance between input from land andauthigenic mineral formation 34

2.2 Reverse weathering 43

2.3 Hydrothermal circulation 46

2.4 Summary and conclusions 57

Appendix 2.1 An extremely brief review of rocksand minerals 58

Appendix 2.2 The meaning of residence time 59

3 Thermodynamics background 63

3.1 The properties of water and ions 64

3.2 Ion–ion interactions and activity coefficients 70

3.3 Thermodynamic basics 73

3.4 Equilibrium constraints on chemical activities 77

3.5 Redox reaction basics 89

4 Carbonate Chemistry 101

4.1 Acids and bases in seawater 103

4.2 Carbonate equilibria: calculating the pH of seawater 112

4.3 Kinetics of CO2 reactions in seawater 116

4.4 Processes that control the alkalinity and DIC of seawater 118






Appendix 4.1 Carbonate system equilibrium equationsin seawater 127

Appendix 4.2 Equations for calculating the equilibriumconstants of the carbonate and boratebuffer system 130

5 Stable and radioactive isotopes 134

5.1 Stable isotopes 137

5.2 Radioactive isotopes 153

Appendix 5.1 Relating K, �, �, and " in stable isotopeterminology 169

Appendix 5.2 Derivation of the Rayleigh distillation equation 170

6 Life processes in the ocean 173

6.1 A simple model of ocean circulation and biologicalprocesses 174

6.2 The euphotic zone 179

6.3 Biologically driven export from the euphotic zone 188

6.4 Respiration below the euphotic zone 203

7 Paleoceanography and paleoclimatology 219

7.1 The marine sedimentary record: 0–800 ky 220

7.2 The ice core record: 0–800 ky 243

7.3 Abrupt (millennial-scale) climate change 249

II Advanced topics in marine geochemistry 259

8 Marine organic geochemistryCo-author: Kenia Whitehead 261

8.1 The nature of organic matter 264

8.2 Methods of characterizing organic matter 266

8.3 Major organic carbon compounds as biomarkers 277

8.4 Dissolved organic matter in seawater 294

9 Molecular diffusion and reaction rates 303

9.1 Molecular diffusion 304

9.2 Reaction rates 310

9.3 Reaction rate catalysis 326

vi CONTENTS






10 Gases and air–water exchange 340

10.1 Air–sea gas transfer models 343

10.2 Measurements of gas exchange rates in nature 350

10.3 Gas saturation in the oceans 357

10.4 Surface films and chemical reactions 366

11 The global carbon cycle: interactions

between the atmosphere and ocean 372

11.1 The global carbon cycle 373

11.2 The biological and solubility pumps of the ocean 376

11.3 The fate of anthropogenic CO2 in the ocean 384

12 Chemical reactions in marine sediments 404

12.1 Diagenesis and preservation of organic matter 406

12.2 Diagenesis and preservation of calcium carbonate 419

12.3 Diagenesis and preservation of silica 428

12.4 Diagenesis and preservation of metals 433

12.5 Conclusions 439

Index 445

The color plates are between pp. 212 and 213.

CONTENTS vii






Preface

The field of chemical oceanography has evolved over the past severaldecades from one of discovery to an interdisciplinary science thatuses chemical distributions to understand physical, biological, geo-logical and chemical processes in the sea. The study of chemicaloceanography includes much of the background required to under-stand the global carbon cycle on all time scales because of the pri-mary role of themarine carbonate system. Thus,we present this bookabout Chemical Oceanography and the Marine Carbon Cycle as a naturaloutgrowth of the evolution of our scientific field and a necessarybackground for building intuition to manage the anthropogenicintrusion into the global carbon cycle.

After a long deliberation about whether we had the time, staminaand personalities to write a book about our subject, John Hedges andI decided to do it, using as a guide, the notes we had compiledfrom teaching Chemical Oceanography together in the School ofOceanography at the University of Washington. During the firstthree years of the new century we used sabbatical leaves and timeborrowed from teaching and research to compile about half of thebook. Then, in 2003 John died suddenly and unexpectedly. EveryoneJohn touched was thrown into a state of shock at the loss of a goodfriend, reliable colleague and brilliant organic geochemist. At thispoint we had put so much of ourselves into this undertaking thatI felt there was no turning back, and I continued to complete whatyou see here.

The first part of the book (Chapters 1–7) covers a one-quarter-longcourse for beginning graduate students. Because of the backgroundsof students in this class, we taught the course so that little previousknowledge of oceanography or chemistry was required. All oneneeded is some experience in thinking scientifically and the desireto learn. We feel this part of the book should also be appropriate forsenior-level undergraduate courses on this subject. The finalfive chapters of the book are compiled from parts of other, moreadvanced seminars and should serve well as a guide for research andmore advanced courses in Chemical Oceanography and the Carbon Cycle.

Steven Emerson






Acknowledgements

Many people played a role in seeing this book to the finish. I’d firstlike to thank Michael Peterson, who drafted all the figures, editedthe text and equations and helped to mold the very different styles ofthe two authors into a common voice. Bruce Frost, while he wasdirector of the School of Oceanography, helped support this effortwith the Karl Banse Fund of the School of Oceanography. Parts of thisbook were written on sabbaticals, where freedom from normalactivities and our generous hosts made life conducive to writing.These include time spent at the Water Research Laboratory ofthe Swiss Federal Institute of Technology (EAWAG-ETH); CambridgeUniversity; the OceanResearch Laboratory (LOCEAN) of the Universityof Pierre and Marie Curie (SE); and the Hanse Institute forAdvanced Studies in Delmenhorst (JH). We appreciate the hospitalityof our colleagues, Werner Stumm, Harry Elderfield, Lillian Merlivatand Juergen Rullkoetter, respectively. At home we both tookadvantage of the writing-friendly environment of the WhiteleyCenter at the Friday Harbor Laboratories of the University ofWashington.

Many of the chapters were reviewed by colleagues, post-docs andformer students. We owe special acknowledgement to KeniaWhitehead, who, as co-author of Chapter 8, was responsible fortaking a partly finished manuscript left by John Hedges and moldingit into a comprehensive chapter on organic geochemistry. DieterImboden helped with the discussion about diffusion in Chapter 9.Others who played valuable roles in reviewing individual chaptersare Curtis Deutsch, Burke Hales, Roberta Hamme, David Hastings,Taka Ito, JenniferMorford, JimMurray, Paul Quay, Amelia Schevenelland Stuart Wakeham. We would like to thank the editors atCambridge University Press for their patience and skill in presentingthe book. Mistakes that persist after these conscientious effortsshould be attributed solely to the authors.

John and I believed that the unlikely birth of a textbook aboutoceanography from two people raised on farms in Ohio resulted fromthe influence of our early mentors. Our curiosity and approach toscience was instilled at the beginning of our careers by WallaceBroecker of Columbia University and Werner Stumm and DieterImboden at EAWAG-ETH (SE), and by Pat Parker of the University ofTexas and Tom Hoering of the Carnegie Geophysical Laboratory,Washington D.C. (JH). We feel that collaborations with our PhDgraduate students have stimulated our discoveries in the field ofchemical oceanography and taught us valuable lessons about scienceand life along theway. These people are: Rick Jahnke, Lucinda Jacobs,John Ertel, Dan McClorkle, David Archer, Greg Cowie, Miguel Goni,David Hastings, Ann Russell, Brian Bergamaschi, Burke Hales, Matt






McCarthy, Jennifer Morford, Peter Hernes, Anthony Aufdenkamp,Kenia Whitehead, Roberta Hamme, Angie Dickens, Susan Lang andDavid Nicholson.

Finally, we dedicate the book to our wives, Julie Emerson andJoyce Hedges, whose support, encouragement and love made it pos-sible to complete this endeavor.

ACKNOWLEDGEMENTS xi






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Chemical Oceanography and the Marine Carbon Cycleassets.cambridge.org/97805218/33134/frontmatter/9780521833134... · Chemical Oceanography and the Marine Carbon Cycle Theprinciplesofchemicaloceanographyprovideinsightintotheprocesses