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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