Topics in Atmospheric and Oceanographic Sciences

Editors: Michael Ghil Robert Sadoumy Jiirgen Siindennann

Eddies in Marine Science Edited by

Allan R. Robinson

With 268 Figures

Springer-Verlag Berlin Heidelberg New York Tokyo 1983

Dr. ALLAN R. ROBINSON Gordon McKay Professor of Geophysical Fluid Dynamics Harvard University, Division of Applied Sciences Pierce Hall, Cambridge, MA 02138, USA

Series Editors:

Professor Dr. MICHAEL GHIL Courant Institute of Mathematical Sciences, New York University 251 Mercer Street, New York, NY 10012/USA

Professor Dr. ROBERT SADOURNY Laboratoire de Meteorologie Dynamique, Ecole Normale Superieure 24 rue Lhomond, 75231 Paris Cedex 051France

Professor Dr. JURGEN SUNDERMANN UniversiHit Hamburg, Institut fUr Meereskunde Heimhuder StraBe 71, 2000 Hamburg 13/FRG

ISBN-13: 978-3-642-69005-1 e-ISBN-13: 978-3-642-69003-7 DOl: 10.1007/978-3-642-69003-7

Library of Congress Cataloging in Publication Data. Main entry under title: Eddies in marine science. (Topics in atmospheric and oceanographic sciences). Includes index. 1. Oceanic mixing. 2. Eddies. I. Robinson, Allan R. II. Series. GC299.E32 1983 551.47 83-4391.

This work is subject copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustra­tions, broadcasting, reproduction by photocopying machine or similar means, and stor­age in data banks. Under § 54 of the German Copyright Law, where copies are made for other than private use, a fee is payable to "Verwertungsgesellschaft Wort", Munich.

© by Springer-Verlag, Berlin Heidelberg 1983 Softcover reprint of the hardcover 1st edition 1983

The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

2132/3130-543210

Foreword

It is now well known that the mid-ocean flow is almost everywhere domi­nated by so-called synoptic or meso-scale eddies, rotating about nearly vertical axes and extending throughout the water column. A typical mid­ocean horizontal scale is 100 km and a time scale is 100 days: these meso­scale eddies have swirl speeds of order 10 cm s -1 which are usually con­siderably greater than the long-term average flow. Many types of eddies with somewhat different scales and characteristics have been identified.

The existence of such eddies was suspected by navigators more than a century ago and confirmed by the world of C.O'D. Iselin and V.B. Stock­man in the 1930's. Measurements from RIV Aries in 1959/60, using the then newly developed neutrally buoyant floats, indicated the main char­acteristics of the eddies in the deep ocean of the NW Atlantic while a se­ries of Soviet moored current-meter arrays culminated, in POLYGON-1970, in the explicit mapping of an energetic anticyclonic eddy in the tropical NE Atlantic. In 1973 a large collaborative (mainly U.S., U.K.) program, MODE-I, produced synoptic charts for an area of the NW At­lantic and confirmed the existence of an open ocean eddy field and es­tablished its characteristics. Meso-scale eddies are now known to be of interest and importance to marine chemists and biologists as well as to physical oceanographers and meteorologists. The geophysical fluid dy­namics of meso-scale eddies is difficult, and their small scale and long lifetime combine to make statistically significant observations time-con­suming and expensive. Cooperative work is necessary and sience 1975 scientists from the u.S. and U.S.S.R., together with groups sponsored by other nations, have been collaborating in such sprojects as POLYMODE and NEADS to make relevant theoretical studies and field observations in the N Atlantic.

It was with such joint studies in mind that the Scientific Committee on Oceanic Research created a Working Group, with Professor A.R. Ro­binson as Chairman, to "identify the critical scientific problems of the in­ternal dynamics of the ocean and to suggest the most appropriate ways to study them; and to advise on the design of mid-ocean dynamics experi­ments."

This book is one result of their work: with the kind help of many ex­perts in particular aspects the group has produced an account of the meso­scale eddies of the ocean, and of their influence in other fields of marine science, which will be of interest and value to a wide range of marine scientists. I welcome this volume, on behalf of SCOR, who are most grate­ful to its editor, Professor Robinson, and his colleagues for their efforts.

VI Foreword

Readers may also like to know that SCOR has invited Professor A.S. Monin to act as Editor of a more specialized account of the theoretical aspects of eddy dynamics, which it is hoped will be published in due course.

E.S.W. SIMPSON President SCOR

Preface

This book surveys the results of recent research in eddy science and ex­plores its implications for ocean science and technology. It attempts a comprehensive review suitable for a wide audience of marine scientists. Much progress has occurred and the subject is rapidly advancing. How­ever, the eddy-current phenomenon remains unexplored in vast areas of the world ocean and many of the most fundamental dynamical questions of eddy dynamics are unanswered or indeed as yet unasked. The inten­tion of a survey now is to contribute to a global synthesis, to help facili­tate researches in new regions and further reasearch into eddy dynamics, and to encourage applications. Eddy currents are energetically dominant and have the ability to trans porte and to influence mixing. Thus knowl­edge of the physical science of the eddies has important implications for biological, chemical and geological oceanography; for modern interdisci­plinary ocean science; and for practical activities in the sea including ex­ploitation and management of the marine environment and its resources. Hopefully, this book will contribute to the communication between spe­cialists in eddy dynamics and other marine scientists, engineers and man­agers, which is necessary for efficient utilization of the new physical knowledge.

The generic term "eddies" is used here without further qualification to encompass a large class of time and space variable ocean currents as discussed in the Introduction. The scales of variability range from tens to hundreds of kilometers and from weeks to months. These currents are usually approximately geostrophic, hence the name "geostrophic eddies" has been invoked. Many phenomena in the ocean are almost geostrophic and it is the nature of the small deviation from the geostrophic momen­tum balance which in fact subtly governs the dynamics of the flow. The general nature of this deviation for eddy currents is usually consistent with the assumption of the theory of quasigeostrophy. Thus the phenom­ena is sometimes referred to by the terminology "quasigeostrophic ed­dies". But eddies are usually, but not always, geostrophic and quasigeos­trophic. Other qualifications in common usage refer to scales. Horizontal eddy scales are on the order of the so-called Rossby internal deformation radius (the product of the vertical scale and the ratio of the Brunt-Vaisala frequency to the Coriolis parameter). Motions on the scale of the atmo­sphere's internal deformation radius are referred to by meteorologists as "synoptic scale" motions, since they include the midlatitude cyclones and anticyclones which are major features of weather maps. By dynami­cal scale analogy many authors refer to oceanic eddies as "synoptic ed-

VIII Preface

dies". Another term, in very common usage since the discovery of evi­dence for eddies as a major oceanic phenomena and still prevalent, is "mesoscale eddies". This phrase was coined simply to indicate motions of less than oceanic gyre scale. Referring to the overall phenomena inclu­sively simply as "eddies" reserves the role of qualifiers for the identifica­tion of important general subclasses of eddy-currents.

Eddies are a most important physical phenomenon in the ocean and have been the subject of a difficult and vigorous research effort which has required a large scale of international cooperation to be carried out. The foundation for eddy science today was constructed by the dedicated research programs carried out during the 1970's. A major role in the coordination, planning and communication of eddy science was per­formed by the Working Group on Internal Dynamics of the Sea (WG-34) of SCOR (The Scientific Committee on Oceanic Research of the Interna­tional Council of Scientific Unions). This multi authored book was pro­duced unter the auspices of WG-34 and constitutes the final scientific re­port ofthe Working Group (see SCOR Proceedings 1982 Vol 18 Annex 5).

The wealth of material presented here results from the scientific ef­forts and cooperation of numerous scientists, technicians, students and other around the world. Acknowledgements for support and help by the authors and the editor appear collectively in the Acknowledgement Sec­tion. In my introductory chapter I draw freely upon the material pre­sented in the book without specific references. The advice, encourage­ment and efforts of Henry Stommel, Henry Charnock, and Curtis Collins were instrumental in making this book possible.

ALLAN R. ROBINSON

Acknowledgements

1. Ove"iew and Summary of Eddy Science A.R. ROBINSON

I wish to express my thanks to numerous colleagues for their stimulating scientific interactions during our pursuit of eddy dynamics. I am espe­cially indebted to my graduate students and postdoctoral fellows. Mr. Robert Heinmiller helped in the initial organization of meetings and ma­terial and Ms. Marsha Cormier's assistance in the preparation and edit­ing of the final manuscript was invaluable. I am grateful for the support given to this project by grants from the National Science Foundation to Harvard University and the Massachusetts Institute of Technology and by contracts from the Office of Naval Research to Harvard University.

2. Gulf Stream Rings P.L. RICHARDSON

This is contribution number 4816 from the Woods Hole Oceanographic Institution and from the Mid-Ocean Dynamics Experiment (POLY­MODE). The manuscript was written with funds from the National Science Foundation (Grant OCE78-18017). Don Olson, Glenn Flierl, Tom Spence and Terry McKee made helpful comments on an earlier ver­sion of this paper.

3. Western North Atlantic Interior C. WUNSCH

Supported in part by National Science Foundation Grant OCE78-19833. I am grateful to all those colleagues, technicians, seamen, students, and program directors, who have made possible the acquisition of these com­plex data sets. This chapter was largely written while I was a visitor at the Department of Applied Mathematics and Theoretical Physics, University of Cambridge, for whose hospitality I am grateful.

4. The Western North Atlantic - A Lagrangian Viewpoint H.T. ROSSBY, s.c. RISER, and A.J. MARIANO

We are grateful to our numerous Mode and Polymode colleagues for the many contributions that they have made to this research over the past decade. We would especially like to thank Dr. James Price of Woods

x Acknowledgements

Hole Oceanographic Institution for making some of his unpublished float dispersion results available to us so that this article might be as complete as possible.

We are thankful for the very generous level of support for this work that has been provided over the years by a number of grants from the Na­tional Science Foundation and the Office of Naval Research. One of us (S.c.R.) was supported by the Joint Institute for the Study of the Atmo­sphere and Ocean at the University of Washington during the prepara­tion of this paper.

5. The Local Dynamics of Eddies in the Western North Atlantic J.e. MCWILLIAMS, E.D. BROWN, H.L. BRYDEN, e.e. EBBESMEYER, B.A. ELLIOlT,

R.H. HEINMILLER, B. LIEN HUA, K.D. LEAMAN, E.J. LINDSTROM, J.R. LUYTEN,

S.E. McDoWELL, W. BRECKNER OWENS, H. PERKINS, J.F. PRICE, L. REGIER,

S.C. RISER, H.T. ROSSBY, T.B. SANFORD, e.Y. SHEN, B.A. TAFT, and J.e. VAN LEER

The LDE has required the efforts of many people. We are grateful for the financial support provided by the National Science Foundation (in parti­cular, we thank the program manager, Dr. Curt Collins) and the Office of Naval Research. We appreciate the counsel and organizational assist­ance from our colleagues in the POL YMODE Program (Drs. Allan Ro­binson and Henry Stommel, Co-Chairmen; Ms. Carol Ramey, Office Manager). Engineering, technical, and operational contributions were crucial to our experiment; in particular we thank Mr. Doug Webb and Dr. Albert Bradley for their work on the SOFAR floats, Mr. Bob Wil­liams who directed the CTD measurements made by the GEOSECS Op­erations Group, and Mr. Gerry Metcalf for his direction of the POL Y­MODE XBT program. We appreciate the assistance given us by the masters and crews of the ships involved in the LDE: R.Y. Atlantis II, USNS Bartlett, R.Y. Gillis, R.Y. Gyre, R.Y. Iselin, and R.Y. Oceanus. Fi­nally, we thank our scientific assistants, programmers, and secretaries for their direct contributions to our work.

9. Subpolar Gyres and the Arctic Ocean G.T. NEEDLER

In many of the northern areas, particularly the Arctic Ocean, information concerning eddies is very recent and/or unpublished. The author wished to particularly thank those people who have provided him with material not readily available.

12. The South Pacific Including the East Australian Current A.F. BENNElT

I am most grateful to the referees of this chapter and also to several of the authors of the following references, who have assisted me in assem-

Acknowledgements XI

bling this material. The help of Dr. George Cresswell is especially to be acknowledged.

13. Eddies in the Southern Indian Ocean and Agulhas Current M.L. GRONDLINGH

The author expresses his appreciation to his colleagues for their sugges­tions and gratefully acknowledges the help and constructive criticism provided by oceanographers of the Australian CSIRO in Cronulla, Aus­tralia.

14. The Southern Ocean H.L. BRYDEN

This work was supported by the Office for the International Decade of Ocean Exploration of the National Science Foundation under grants OCE 77-22887 and OCE 77-19403. Discussions with Dan Georgi, Terry Joyce and Ray Schmitt enlarged the scope of this review. Comments by Jim Baker, Nan Bray, Adrian Gill, Arnold Gordon, Worth Nowlin, John Toole and Dan Wright helped clarify the text. This is Contribution Num­ber 4773 from Woods Hole Oceanographic Institution.

15. Global Summaries and Intercomparisons: Flow Statistics from Long­Term Current Meter Moorings R.R. DICKSON

Travel funds for this work were provided by the National Science Foun­dation through the POLYMODE Office and the author gratefully ac­knowledges their assistance.

17. Eddy-Resolving Numerical Models of Large-Scale Ocean Circulation W.R. HOLLAND, D.E. HARRISON, and A.J. SEMTNER Jr.

The National Center for Atmospheric Research is sponsored by the Na­tional Science Foundation.

18. Periodic and Regional Models D.B. HAIDVOGEL

This review was initiated while the author was a Visiting Senior Lecturer in the Department of Mathematics, Monash University. He thanks the members of that department and, in particular, Dr. A.F. Bennett, for their hospitality. This work has been supported by National Science Founda­tion Grant No. OCE 78-25700 (IDOE), whose support is gratefully ac­knowledged.

XII Acknowledgements

23. Eddies and Acoustics R.C. SPINDEL and Y.J.-F. DESAUBIES

This work was performed under Office of Naval Research Contract N00014-79-C-0071. This is Woods Hole Oceanographic Institution Con­tribution Number 4795.

24. Instruments and Methods R.H. HEINMILLER

The author wishes to acknowledge the help and support of many col­leagues over the years in his involvement with oceanographic instrumen­tation. In the preparation of this chapter, conversations with the follow­ing scientists and engineers were of particular value: John Dahlen, Russ Davis, Charles Eriksen, David Halpern, James Hannon, James Luyten, James McCullough, James McWilliams, Peter Niiler, Lloyd Regier, Dou­glas Webb, and Carl Wunsch.

Contents

Introduction

1. Overview and Summary of Eddy Science By A.R. ROBINSON ..... .

1.1 Eddy Currents in the Ocean

1.1.1 Observing the Eddies 1.1.2 Modeling the Eddies .

1.2 Status of Eddy Science

1.2.1 Distribution and Generation 1.2.2 Physics............. 1.2.3 Role in the General Circulation

1.3 Influences of Eddies . . . . . . . . . . .

1.3.1 Scientific Processes and Practical Consequences 1.3.2 Dispersion and Mixing 1.3.3 Description and Prediction

1.4 Evolution and Outlook ..... .

1.4.1 A Time of Transition ... . 1.4.2 A Decade of Eddy Research 1.4.3 Eddies in Marine Science . .

Regional Kinematics, Dynamics, and Statistics

2. Gulf Stream Rings By P.L. RICHARDSON

2.1 Introduction . . . 2.2 History . . . . . . 2.3 Cold-Core Rings

2.3.1 Formation 2.3.2 Structure and Velocity 2.3.3 Distribution and number 2.3.4 Movement . . . . . . . . . 2.3.5 Interaction and Coalescence with Gulf Stream 2.3.6 Decay .....

2.4 Warm-Core Rings 2.5 Gulf of Mexico Rings

1

3

3 4 5 6

6 6 8 9

9 11 11

12

12 13 14

17

19

19 19 21

21 22 29 31 32 38 39 41

XIV Contents

2.6 Eastern Rings . . . . . . . . . . . . . 2.7 Current Rings from Other Currents

3. Western North Atlantic Interior By C. WUNSCH . . . . . . . .

3.1 Introduction . . . . . . . . . . . . . . . 3.2 Observations ........... .

3.2.1 Spectrum and Time Scales 3.2.2 Spatial Scales . . . . . . . . . . 3.2.3 Kinetic and Potential Energy .

3.3 Other Data ........ . 3.4 Some Simple Conclusions . . . . . . .

4. The Western North Atlantic - A Lagrangian Viewpoint By H.T. ROSSBY, S.c. RISER, and A.J. MARIANO ..

4.1 Introduction . . . . . . . . . . . . . . . . . . . 4.2 The Data Base ................ . 4.3 The Mean Field ............... .

4.3.1 The Lagrangian View ........ . 4.3.2 The Equivalent Eulerian View, and the Eddy Kinetic

Energy Distribution ...

4.4 Mixing and Dispersion ........... . 4.5 Topographic Influences ........... . 4.6 The Eastward Flow in the Subtropical Gyre 4.7 Discrete Eddies ....... . 4.8 The Path of the Gulf Stream 4.9 Concluding Remarks . . . . .

5. The Local Dynamics of Eddies in the Western North Atlantic By J.C. MCWILLIAMS et al. ....... .

5.1 Introduction . . . . . . . . . . . . . . . . . 5.2 Scientific Objectives ....

5.2.1 Dynamical Balances ... 5.2.2 Synoptic Structures . . . . 5.2.3 Geostrophic Fine Scales . 5.2.4 Surface Layer Mesoscale Eddies ..... . 5.2.5 The General Circulation . . . . .

5.3 The Experiment . . . . . . . . . . . . . . 5.4 The Phenomena ......... . . . . . . 5.5 Summary ................... .

6. Gulf Stream Variability By D.R. WAITS .....

6.1 Introduction . . . . . . . . . . . . . . . . . . 6.2 The Gulf Stream Path .............. .

42 43

46

46 48 48 49 56 62 64

66

66 66 67

68

70

76 78 82 84 87 88

92

92 93

93 93 94 94 94 94 96

112

114

114 115

Contents

6.3 Current Structure and Transport ........ . 6.4 Water Masses ............... . 6.5 6.6

7.

Dynamics Summary .....

The Northeast Atlantic Ocean By W.J. GOULD ........ .

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 General Oceanographic Conditions and Mean Circulation 7.3 Data Sources ................. .

7.3.1 Hydrographic Data ...... . 7.4 XBT Observations 7.5 Direct Observation of Currents .... 7.6 Satellite Observations . . . . . . . . . . . . . . 7.7 Surveys of Individual Eddies ........ . 7.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8. Eddy Structure of the North Pacific Ocean By R.L. BERNSTEIN .....

8.1 Introduction . . . . . . . . . . . . . . . . . . 8.2 Coastal Regions . . . . . . . . . . . . . . . . . 8.3 Mid-Latitude Open Ocean ........ . 8.4 Tropical Region . . . . . . . . . . . . . . . 8.5 Direct Current Measurements . . . .

9. Subpolar Gyres and the Arctic Ocean By G.T. NEEDLER

xv

124 131 137 143

145

145 145 146

146

147 149 151 151 156

158

158 158 161 164 166

167

9.1 Introduction . . . . . . . . . . . . . . 167 9.2 The Arctic Ocean . . . . . . . . . . . 167 9.3 Labrador Sea and Northwestern Atlantic ........... 171 9.4 The Norwegian and Greenland Seas and Their Overflows.. 174 9.5 The Northeast North Pacific and Bering Sea ......... 177 9.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 180

10. Tropical Equatorial Regions By G. SIEDLER ...... .

10.1 Latitudinal Changes of Mesoscale Processes ..... . 10.2 Eddy-Resolving Arrays in the Tropics ........ . 10.3 Mesoscale Features in Sections . 10.4 Mesoscale Energy in the Tropics

11. Eddies in the Indian Ocean By J.e. SWALLOW .....

181

181 183 187 198

200

11.1 Introduction . . . . . . . . . . . . . . . . . . 200 11.2 Kinetic Energy of the Seasonal Circulation ......... 200

XVI Contents

11.3 Arabian Sea 206 11.4 Somali Current . 209 11.5 Bay of Bengal .. 212 11.6 Equatorial Zone . 212 11.7 South Equatorial Current 214 11.8 Deep Currents in the Indian Ocean 217 11.9 Significance of Indian Ocean Eddies 218

12. The South Pacific Including the East Australian Current By A.F. BENNETT . . . . . . . . . . . . . . . . . . . . . . 219

12.1 Introduction: The Subtropical South Pacific 219 12.2 Observations: The Tasman Sea .... 223

12.2.1 The East Australian Current . 223 12.2.2 The Tasman Front . . . . . 235

12.3 Theories ............... . . . . . . . 237 12.3.1 A Line Vortex and a Wall .............. 237 12.3.2 A Free Inertial Jet . . . . . . . . . . . . . . . . . .. 237 12.3.3 Baroc1inic Instability of a Western Boundary Flow 239

12.4 The Significance of Eddies 240

12.4.1 Physical Significance ...... 240 12.4.2 Biological Significance ..... 241

12.5 Future Research ............. .

12.5.1 The Mid-Ocean ........ . 12.5.2 The East Australian Current ..

13. Eddies in the Southern Indian Ocean and Agulhas Current By M.L. GRONDLINGH . . . . . . . . . . . . . . . .

13.1 Introduction . . . . . . . . . . . . . . . . . . . . . 13.2 South Eastern Indian Ocean . . . . . . . . . . . .

13.2.1 Vicinity of the South Equatorial Current 13.2.2 West of Australia ............ . 13.2.3 Vicinity of the Subtropical Convergence

13.3 South Western Indian Ocean .......... . 13.3.1 Eddies South of Madagascar . . . . . . . 13.3.2 Larger Southwestern Indian Ocean ... 13.3.3 Adjacent to the Agulhas Current 13.3.4 The Agulhas Retroflection Area ........ . 13.3.5 The Vicinity of the Agulhas Plateau ..... .

13.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . .

14. The Southern Ocean By H. BRYDEN .. .

14.1 Introduction .... . 14.2 Observations of Eddies in the Southern Ocean

242

242 242

245

245 246 247 248 251

252 254 254 259 260 261 261

265

265 267

Contents XVII

14.3 Eddy Generation and Decay . . . . . . . . . . . . . . .. 270 14.4 Effects Eddies and Implications for Models the Southern

Ocean. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 275

15. Global Summaries and Intercomparisons: Flow Statistics from Long-Term Current Meter Moorings By R.R. DICKSON . . . . . . . . . . . . . . . . . . . . . . .. 278

15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .. 278 15.2 Global Kinetic Energy Estimates from Shift-Drift Analysis 279 15.3 The North Atlantic ................. 282

15.3.1 Introduction ................ 282 15.3.2 Ocean-Scale Patterns of Kinetic Energy 293 15.3.3 A Transect of the Western Basin 294 15.3.4 A Transect of the Eastern Basin 296

15.4 The North Pacific . . . . 301

15.4.1 The Kuroshio 301 15.4.2 Western Pacific 304 15.4.3 East-Central Pacific 305 15.4.4 Central and Eastern Tropical Pacific 306

15.5 The Equatorial Zone 307 15.6 South Atlantic . . . . . . . . . . . . . . . . . 311 15.7 High Latitudes. . . . . . . . . . . . . . . . . 311

15.7.1 The Antartic Circompolar Current . 311 15.7.2 Weddell Sea .......... 318 15.7.3 The West Spitsbergen Current 318 15.7.4 Arctic Ocean . . . . . . . . . . 321

15.8 Summary . . . . . . . . . . . . . . . . . 323

15.8.1 Horizontal Distribution of Eddy Kinetic Energy at Midlatitudes ....................... 323

15.8.2 Vertical Structure of the Eddy Field at Midlatitudes 324 15.8.3 Vertical Eddy Structure in Ice-Covered Seas 327 15.8.4 Eddy Time Scales at Midlatitudes . . . . . 327 15.8.5 Eddy Time Scales in the Equatorial Zone 328 15.8.6 Relationship of KE to KM Worldwide . . . 328

16. Global Summary: Review of Eddy Phenomena as expressed in Temperature Measurements By W. EMERY . . . . . . . . . . . . . 354

16.1 Introduction . . . . . . . . . . . . . . 354 16.2 Standard Deviation of Temperature 355 16.3 The North and Equatorial Atlantic 359 16.4 The North and Equatorial Pacific 369 16.5 Discussion .............. 373

XVIII Contents

Models .. 377

17. Eddy-Resolving Numerical Models of Large-Scale Ocean Circulation W.R. HOLLAND, D.E. HARRISON, and A.J. SEMTNER, Jr. 379

17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 379 17.2 Review of EGCM Results .................. 380

17.2.1 What Processes Account for the Presence of Mesos-cale Variability? ..................... 381

17.2.2 Do Mesoscale Phenomena Playa Fundamental Role in the Character and Dynamics of the Time-Mean Circulation? ....................... 385

17.2.3 Where the Effects of Mesoscale Circulations Are Im­portant, Can They Be Parametrized in Terms of Mean-Field Quantities? . . . . . . . . . . . . . . . .. 390

17.2.4 How Do the Answers to Questions About the Role of Mesoscale Eddies Change as the Model Physical Processes Change? . . . . . . . . . 393

17.3 Comparisons with Observations . . . . . . 395 17.4 Unsolved Problems and Future Prospects 401

18. Periodic and Regional Models By D.B. HAIDVOGEL ..... 404

18.1 Introduction . . . . . . . . . . 404 18.2 Two-Dimensional Turbulence 407 18.3 The Effects of P . . . . . . . . 411 18.4 Mean Flow Generation by Localized Forcing 414 18.5 Turbulent Cascades in a Stratified Fluid . 418 18.6 Scattering by Topography ......... 423 18.7 Regional Models and Non-Local Effects 426 18.8 Comparison with Observations .. 432 18.9 Conclusions and Future Directions 436

Effects and Applications

19. Eddies in Relation to Climate By A.E. GILL ........ .

19.1 Introduction ......... . 19.2 Heat Flux Carried by Eddies 19.3 Indirect Effects of Eddies on the Heat Balance

20. Eddies and Coastal Interactions By P.e. SMITH ...... .

20.1 Introduction . . . . . . . . 20.2 Theoretical Considerations

439

441

441 441 443

446

446 448

Contents XIX

20.2.1 Stratification, ~-Effect . . . . . . . . . . . . . . . 448 20.2.2 Abrupt Topography: Scattering and Reflection 450 20.2.3 Refractive Effects . 453 20.2.4 Bottom Friction .................. 454 20.2.5 Longshore Currents ................ 454 20.2.6 Generating Mechanisms and Initial Value Problems 455

20.3 Observations and Analysis . . . . . . . . . . . . . 459 20.3.1 The New England Continental Rise. . 459 20.3.2 The East Australian Shelf. . . . . . . . . 461 20.3.3 The Southeastern Coast of the U.S. 462 20.3.4 The West Florida Shelf . . . . . . . . . . 463 20.3.5 The Scotian Shelf .............. 464

20.4 Anatomy of a Warm-Core Ring Interaction with the Conti-nental Margin ........................... 465

20.4.1 Low-Frequency Current Data, Summer 1976 . . . .. 467 20.4.2 Offshore Forcing . . . . . . . . . . . . . . . . . . . .. 471 20.4.3 Analysis and Interpretation . . . . . . . . . . . . . .. 474

20.5 Conclusions ............. .

21. Eddy-Induced Dispersion and Mixing D.B. HAIDVOGEL, A.R. ROBINSON, and e.G.H. ROOTH

21.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Two-Dimensional Dispersal in the Mid-Ocean ....... . 21.3 Streakiness . . . . . . . . . . . 21.4 Particle Motions ............. . 21.5 Gyre-Scale Dispersal Effects ...... . 21.6 Tracer Evidence for Dispersal Processes

22. Eddies and Biological Processes By M.V. ANGEL and M.J.R. FASHAM

22.1 Introduction . . . . . 22.2 Frontal Eddies . . . . . . . . . . . . . .

22.2.1 Formation .......... . 22.2.2 Air-Sea Interaction Within a Ring . . . . . . . . . . . 22.2.3 Horizontal Exchanges Between the Ring and Its Sur-

roundings ........................ . 22.2.4 Horizontal Exchange of Plankton Between a Ring

and Its Surrounding Water ...... .

22.3 Mid-Ocean Eddies .............. . 22.3.1 Biological Processes in a Single Eddy . . 22.3.2 Spatial Spectrum . . . . . .

22.4 Observational Data . . . . . . . . . . . .

22.4.1 Scripps Transects ...... . 22.4.2 Gulf Stream Ring Structures ..

480

481

481 482 483 488 489 489

492

492 493 493 494

495

498

499

500 501

504

504 506

XX Contents

22.4.3 East Australian Current Rings . 515 22.4.4 Incidental Observations . . 517

22.5 Sampling Procedures 521 22.6 Conclusions ............. 523

23. Eddies and Acoustics By R.C. SPINDEL and Y.J-F. DESAUBIES 525

23.1 Introduction . . . . . . . . . . . . . . . . . 525 23.2 Dynamic Ocean . . . . . . . . . . . . . . . 527 23.3 Sound Propagation in a Range-Dependent Environment 529

23.3.1 Geometrical Acoustics ........ ..... 529 23.3.2 Normal Modes . . . . . . . . . . . . . . . . . . . . 530 23.3.3 The Parabolic Approximation ........... 532

23.4 Analytical and Numerical Studies of Sound Propagation Through Eddies . . . . . . . . . . . . . . . . . 533

23.5 Acoustic Measurements in Eddies 535 23.6 Acoustic Eddy Monitoring 540 23.7 Conclusions ............... 541

24. Instruments and Methods By R.H. HEINMILLER 542

24.1 Introduction . . . . . . . . 24.2 Moored Instrumentation . . . . . . . . . . . .

24.2.1 Moorings ............... . 24.2.2 Fixed Depth Moored Current Meters

24.3 Moored Profiling Current Meters . . . . 24.4 Temperature Recorders . . . . . . . . . . 24.5 Other Moored Instrumentation 24.6 Drifting Instruments ..

24.6.1 Surface Drifters .... 24.6.2 Deep Drifters . . . . . . 24.6.3 Problems and Interpretations . . . .

24.7 Profiling Instruments ............ . 24.7.1 Temperature and Salinity Instruments 24.7.2 Nansen Bottles ..... 24.7.3 CTD and STD . . . . .

24.8 Expendable Bathythermographs 24.9 Current Profilers ........ . . . . . .

24.9.1 Electromagnetic Velocity Profiler 24.9.2 The White Horse ....... . 24.9.3 Schmitz-Richardson Profiler .. . 24.9.4 Other Velocity Profilers ..... . 24.9.5 Calibration and Intercomparison

542 543 543 547 552 554 555 556 556 556 557 559 559 559 560 561 563 563 564 564 565 565

Contents

24.10 Remote and Inverse Techniques

24.10.1 Satellite and Airborne Measurements 24.10.2 Tomography ............. .

24.11 Intercomparison Between Instrument Types

References ..

Subject Index

XXI

565 565 566 567

568

602

List of Contributors

ANGEL, MARTIN V., Institute of Oceanographic Sciences, Brook Road, Wormley, Godalming, Surrey GU8 5UB, Great Britain

BENNETT, ANDREW F., Institute of Ocean Sciences, P.O. Box 6000, Sid­ney, B.C., Canada V8L 4B2

BERNSTEIN, ROBERT L., University of California, Scripps Institution of Oceanology, La Jolla CA 92093, USA

BRECKNER OWENS, W., Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

BROWN, E.D., Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

BRYDEN, HARRY L., Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

DESAUBIES, Y.J.-F., Woods Hole Ocenaographic Institution, Woods Hole, MA 02543, USA

DICKSON, ROBERT R., Ministry of Agriculture, Fisheries and Food, Di­rectorate of Fisheries Research, Fisheries Laboratory, Lowestoft, Suf­folk NR33 OHT, Great Britain

EBBESMEYER, c.c., Evans-Hamilton, Inc. 6306 21st Avenue, NE, Seattle, WA 98115, USA

ELLIOTT, B.A., Ocean Physics Department, Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA

EMERY, WILLIAM J., Department of Oceanography, University of British Columbia, 6270 University Boulevard, Vancouver, B.c., V6T 1 W5, Canada

FASHAM, M.J.R., Institute of Oceanographic Sciences, Brook Road, Wormley, Godalming, Surrey GU8 5UB, Great Britain

GILL, ADRIAN E., Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge, CB3 9EW, Great Britain

GOULD, W. JOHN, Institute of Oceanographic Sciences, Wormley, Go­dalming, Surrey GU8 5UB, Great Britain

GRUNDLINGH, MARTEN L., NRIO, P.O. Box 17001, Congella 4013, South Africa

XXIV List of Contributors

HAIDVOGEL, DALE B., Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

HARRISON, D.E., Department of Meteorology and Physical Oceanogra­phy, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

HEINMILLER, ROBERT H., OMET, 70 Tonawanda Street, Boston, MA 02124, USA

HOLLAND, WILLIAMS R, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307, USA

LEAMAN, K.D., RSMAS, University of Miami, 4600 Rickenbacker Cau­seway, Miami, FL 33149, USA

VAN LEER, J.C., RSMAS, University of Miami, 4600 Rickenbacker Cau­seway, Miami, FL 33149, USA

LIEN HUA, B., Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

LINDSTROM, E.J., Department of Oceanography, University of Washing­ton, Seattle, WA 98195, USA

LUYTEN, J.R, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

MARIANO, ARTHUR J., Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02881, USA

McDoWELL, S.E., EG & G Environmental Consultants, 300 Bear Hill Road, Waltham, MA 02254, USA

MCWILLIAMS, JAMES C., National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307, USA

NEEDLER, GEROLD T., Atlantic Oceanographic Laboratory, Bedford In­stitute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada

PERKINS, H., NORDA, NSTL Station, MS 39529, USA

PRICE, J.F., Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

REGIER, L., Scripps Institution of Oceanography, La Jolla, CA 92093, USA

RICHARDSON, PHILIP P., Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

RISER, S.c., Department of Oceanography, University of Washington, Seattle, WA 98195, USA

ROBINSON, ALLAN R, Pierce Hall, 100-C, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA

List of Contributors xxv

ROOTH, CLAES G.H., RSMAS University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA

ROSSBY, H. THOMAS, Graduate School of Oceanography, University of Rhode Island, Kingston, RI 02881, USA

SANFORD, T.B., Ocean Physics Department, Applied Physics Lab, Uni­versity of Washington, Seattle, WA 98105, USA

SEMTNER JR., ALBERT J., National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307, USA

SHEN, C.Y., Department of Oceanography, University of Washington, Seattle, WA 98195, USA

SIEDLER, GEROLD, Institut fUr Meereskunde an der UniversWit Kiel, Ab­teilung fiir Meeresphysik, Diisternbriicker Weg 20, D-2300 Kiel 1, Fed. Rep. of Germany

SMITH, PETER C., Atlantic Oceanographic Laboratory, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia, Canada B2Y 4A2

SPINDEL, ROBERT c., Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

SWALLOW, JOHN C., Institute of Oceanographic Sciences, Brook Road, Wormley, Godalming, Surrey GU8 5UB, Great Britain

TAFT, B.A., PMELlNOAA, Seattle, WA 98195, USA

WATTS, D. RANDOLPH, Graduate School of Oceanography, Narragansett Bay Campus, University of Rhode Island, Kingston, RI 02881, USA

WUNSCH, CARL, Department of Earth and Planetary Sciences, M.I.T., 54-913, Cambridge, MA 02139, USA