Poleward Flows Along Eastern Ocean Boundaries

383 Pages·1989·13.48 MB·English

by  Christopher N. K. Mooers (auth.)

Coastal and Estuarine Studies
Managing Editors:
Maleolm J. Bowman Richard T. Barber
Christopher N. K. Mooers John A. Raven
Coastal
and Estuarine Studies
formerly Lecture Notes on Coastal and Estuarine Studies
34
S.J. Neshyba Ch.N.K. Mooers
R.L. Smith R.T. Barber (Eds.)
Poleward Flows Along
Eastern Ocean Boundaries
Springer-Verlag
New York Berlin Heidelberg London Paris Tokyo Hong Kong
Managing Editors
Malcolm J. Bowman
Marine Sciences Research Center, State University of New York
Stony Brook, N.Y. 11794, USA
Richard T. Barber
Monterey Bay Aquarium Research Institute
Pacific Grove, CA 93950, USA
Christopher N. K. Mooers
Institute for Naval Oceanography
National Space Technology Laboratories
MS 39529, USA
John A. Raven
Dept. of Biological Sciences, Dundee University
Dundee, DDl 4HN, Scotland
Contributing Editors
Ain Aitsam (Tallinn, USSR) . Larry Atkinson (Savannah, USA)
Robert C. Beardsley (Woods Hole, USA) . Tseng Cheng-Ken (Qingdao, PRC)
Keith R. Dyer (Merseyside, UK) . Jon B. Hinwood (Meibourne, AUS)
Jorg Imberger (Western Australia, AUS) . Hideo Kawai (Kyoto, Japan)
Paul H. Le Blond (Vancouver, Canada) . L. Mysak (Montreal, Canada)
Akira Okuboi (Stony Brook, USA) . William S. Reebourgh (Fairbanks, USA)
David A. Ross (Woods Hole, USA) . John H. Simpson (Gwynedd, UK)
Absornsuda Siripong (Bangkok, Thailand) . Robert L. Smith (Covallis, USA)
Mathias Tomczak (Sydney, AUS) . Paul Tyler (Swansea, UK)
Editors
S.J. Neshyba
College of Oceanography, Oregon State University
Corvallis, OR 97331-5503, USA
Ch.N.K. Mooers
Institute for Naval Oceanography
Stennis Space Center, Mississippi 39529-5005, USA
R.L. Smith
College of Oceanography, Oregon State University
Corvallis, OR 97331-5503, USA
R. T. Barber
Monterey Bay Aquarium Research Institute, 160 Central Avenue
Pacific Grove, CA 93950, USA
ISBN-13 :978-1-4613-8965-1 e-ISBN-13 :978-1-4613-8963-7
001: 10.1007/978-1-4613-8963-7
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© Springer·Veriag New York, Inc., 1989
Softcover reprint of the hardcover 1st edition 1989
2837/3140-543210 - Printed on acid-free paper
PROLOGUE
This is the first volume to deal exclusively with an ubiquitous
feature of all the major ocean basins--the poleward-flowing surface
currents and undercurrents along the continental shelf and slope of their
eastern boundaries. The volume emanates from the First International
Workshop held on this topic, and which was hosted by the Naval Postgraduate
School, Monterey, California, in December 1986.
Organized initially by Steve Neshyba, Robert Smith, Dick Barber, and
Chris Mooers, the list of those interested in the workshop topic grew to
more than 90 investigators, worldwide, who were then directly involved
in or had previously carried out studies of eastern ocean boundary flows.
We had come to realize, ca. 1984, that such poleward flows were being
observed and described, and that hypotheses were being generated to
account for their cause, by many investigators within the context of
descripti ve theoretical and physical oceanography of regional phenomena.
It was timely to convene the scientific community involved for the
broad purpose of comparing the "anatomy" of eastern boundary flow
concepts, of deciding how to integrate theoretical and modeling tools more
effectively into future eastern boundary studies, and of recornrnending
future sampling recipes from which more wholesome descriptions could come.
And it was also high time to elevate the study of eastern boundary
flow processes to its rightful importance alongside that of intense
western boundary currents and of their concomitant rings and eddy
dynamies. Indeed, i t was the discovery of features along eastern
boundaries that we now call squirts and jets (made possible by the
technology of satellite ocean surveillance) that led us to conclude how
the comp18xity of eastern flow regimes might be organized into an
analytical framework, just as the study of the dynamics of western boundary
regimes has been given over to its broad-scale description and theory.
Eastern ocean zones formerly labeled simply as "transition zones" for lack
of adequate tools of analysis, now become recognized as dynamic ocean
process regimes worthy of study in their own analytical domain.
And it was the development of the scientific understanding of Pacific
basin-wide equatorial waves, as processes integral to the large-scale
ocean-atmosphere coupling, that gave birth to explanations of events like
EI Nino, and that also elevated eastern ocean boundary processes to their
proper place in the dynamics of total ocean circulation.
Just as eastern boundary flow processes are important to the physical
understanding of ocean circulation, they are equally important to the
study of aphysical phenomena. It happens that eastern ocean boundary
VI
regimes of both the Atlantic and the Pacific also contain the four major
zones of coastal upwelling driven by gyre-dominated wind systems: Baja
California-California-Oregon-Washington in the NE Pacific; Peru to the central
Chilean coast in the SE Pacific; the Senegal-Mauritania region in the NE
Atlantic; and the Angola-Namibia coastal states in the SE Atlantic. Major
upwelling zones of the Indian Ocean are driven by monsoon-dominated wind
systems.
These are zones of major fisheries, particularly of the clupeoid
species from which the major part of world fishmeal production derives:
herring, anchovy and menhaden. One of the central problems, posed to
appropriate management of these fisheries, is to define the physical
constraints to the spawning-egg-larval-juvenile-adult life cycles of
members of their biotic communities. Accompanying the physical
biological aspect of these biomes is the chemistry of abiotic cycling on
which the biota depend. We recognized early in our design of the workshop
agenda how the several disciplines might contribute important insights
to one another, to the common goal of understanding how eastern ocean
boundary regimes function.
On a larger scale, there is the question of how eastern ocean boundary
flows participate in the basin-wide distribution of heat, salt, nutrients,
and water, i. e., the "budget" oceanography studies that are also key
aspects of global circulation models. An integral part of this same
question is whether or not the poleward flow is continuous in transport
from low to high latitudes, whether or not it is continuous in time, how
it is linked to the intensity and time scale of gyre circulation, and how
it is linked to the coastal upwelling process.
All such quest ions came to the fore during this workshop. We did not
find answers to them all. What we did accomplish, however, was a first
global scale recommendation for the methodology of proceeding with both
the field work of observations in situ and for the refining of theory and
models which will eventually need to assimilate these data. This volume
presents both of these achievements.
ACKNOWLEDGEMENTS
The authors express appreciation to all those persons whose efforts
have made this volume a reality.
Steve Neshyba deserves special recognition among the editors for
"staying the course" from inception of the Workshop on Poleward Flowing
Undercurrents on Eastern Boundaries held in Monterey December 1986, to
its completion in this text.
The Naval Postgraduate School (NPS) provided excellent facilities for
the workshop, and this within ten kilometers of an Eastern Boundary
Poleward Undercurrent, the (presumed) California Undercurrent off
Monterey Bay. Special thanks to Chris Mooers, then the Oceanography
Chairman at NPS, for arranging workshop details at the NPS.
Special thanks also to Bob Smith for assembling the initial list of
participants, from whose replies to inquiry we eventually compiled a
mailing group of over 70 scientists the world over, and to Florence Beyer
for her patient mailing effort. More than a third of us gathered in
Monterey.
Chris Mooers mobilized support for assembly of the camera-ready copy
through the Institute for Naval Oceanography (INO). A very special thanks
goes to Ms. Lydia Harper, INO, who performed exceptionally in coordinating
the final version with the authors and editors, as well as with Ms. Sabine
Kessler, technical editor of Lecture Notes on Coastal and Estuarine
Studies.
We thank the special efforts of Richard Barber in providing a
biological and chemical continuity to the workshop deliberations of
otherwise physics-oriented oceanographers.
We express appreciation also to the College of Oceanography of Oregon
State University for sustaining the costs of paper work and mailings and
telecommunication needed to bring this international effort to success.
The National Science Foundation supported travel for one international
participant to the workshop, and has supported the research of several
of the participants which resulted in their contributions to this volume.
This volume is a contribution of the Institute for Naval Oceanography,
which is sponsored by the Navy and administered by the Office of the Chief
of Naval Research. Any opinion, findings and conclusions or recommendations
expressed in this publication are those of the authors and do not
necessarily reflect the views of the Chief of Naval Research.
Lastly, we give our best thanks to all colleagues who participated
in the reviews of papers.
Table of Contents
I. Workshop Summaries 1
Workshop Summary: Poleward Flow-Observational
and Theoretical Issues by Christopher Mooers 2
Poleward Flows Along Eastern Ocean Boundaries:
An Introduction and Historical Review by Robert Smith 17
Theoretical Understanding of Eastern Ocean Boundary
Poleward Undercurrents by Allan Clarke 26
Poleward Flow Along Eastern Boundaries: What Next?
by Adriana Huyer 40
11. Geographical Reports: Atlantic Ocean 46
The Baroclinic Circulation of the West Spitsbergen
Current by Robert Bourke and Alan Weigel 47
A Brief Sketch of Poleward Flows at the Eastern
Boundary of the North Atlantic by Thomas McClimans 68
On the Northeast Atlantic Slope Current
by John Huthnance and W. J. Gould 76
The Poleward Undercurrent on the Eastern Boundary
of the Subtropical North Atlantic by E. o. Barton 82
The Subsurface Circulation Along the Moroccan Slope
by Ekkehard Mittelstaedt 96
Poleward Motion in the Benguela Area
by Greville Nelson 110
11. Geographical Reports: Pacific Ocean 131
Observations of the Low-Frequency Circulation off the
West Coast of British Columbia, Canada
by Howard Freeland 132
Poleward Flow in the California Current System
by Adriana Huyer, Michael Kosro, Steven Lentz, and
Robert Beardsley 142
Poleward Flow Near the Northern and Southern
Boundaries of the U.S. West Coast by Barbara Hickey 160
Poleward Flows off Mexico's Pacific Coast
by Antoine Badan-Oangon, J. Robles, and J. Garcia 176
An Overview of the Poleward Undercurrent and
Upwelling Along the Chilean Coast
by Tomas Fonseca 203
11. Geographical Reports: Indian Ocean 229
The Leeuwin Current by John Church,
George Cresswell, and J. Stuart Godfrey 230
IX
III. Special Topies 255
An Applieation of Turbulenee Oata to the
California Undereurrent by Rolf Lueek and
Hidekatsu Yamazaki 256
Model Simulations of a Coastal Jet and Undereurrent
in the Presenee of Eddies and Jets in the California
Current System by Mary Batteen 263
00 Nitrogen Transformations in the Poleward
Undereurrent off Peru and Chile Have a Globally
Signifieant Influenee? by Louis Codispoti,
Riehard Barber, and Gernot Friederieh 281
Topographie Stress in Coastal Cireulation Oynamies
by Greg Holloway, Ken Brink, and Oale Haidvogel 315
IV. Epilogue 331
V. Referenees 342
Appendix A: List of Partieipants 371
PART I:
WORKSHOP SUMMARIES
WORKSHOP SUMMARY: POLEWARD FLOW-OBSERVATIONAL AND THEORETICAL ISSUES
Christopher N.K. Mooers
Institute for Naval Oceanography
Stennis Space Center, MS 39529-5005
I will summarize from my own perspective what I think the essence
of the workshop has been, to help set the stage for discussion of scientific
futures. With that, let me fill in some of the historical background
leading to this workshop.
Some of us, who over the past 10 to 30 years of association with the
coastal upwelling studies which "bumped" into po1eward undercurrents,
have long wondered about their greater importance, but not a great deal
has been done about the topic in general. I always thought the topic
deserved more attention on its own. Beginning a half-dozen years ago,
through the Eastern Pacific Oceanic Conference (EPOC) where western North
American physical and other oceanographers gather annually for informal
discussions, the undercurrent continually "popped up" as a topic for
discussion. And we kept hoping that someone, like Bob Smith or Dudley
Chelton or Andrew Willmott, who were "designated hitters" for awhile,
would produce an organized research effort on poleward undercurrents.
The opportunity for this workshop arose about two years ago when Steve
Neshyba proposed holding a topical session on poleward flows in the context
of a Fall AGU meeting. Both Joe Reid and I were then invol ved as officers
of the Ocean Sciences Section of the AGU, and we supported the idea. As
it was, the date was a bit late for scheduling it that year, and the event
was rescheduled as a poster session for the following year, the 1986 Fall
AGU. In the sequence of events that followed, I offered the facilities
of the Naval Postgraduate School for an expanded workshop on the topic
just prior to the AGU meeting, the bett er to organize a more comprehensive
discussion than is possible within the AGU context, but still designed
to interact with the AGU. Bob Smith joined the organizers, drawing up
a first list of invited participants who were then encouraged to suggest
others wi th demonstrated interest in the poleward undercurrent topic. The
list grew and here we are.
The 1986 AGU meeting next week has special interest to our group
because of its sessions celebrating the centennial of scientific