The Gulf Stream: Tiny Plankton, Giant Bluefin, and the Amazing Story of the Powerful River in the Atlantic

229 Pages·2008·2.64 MB·English

by  Stan Ulanski

The Gulf STReam
T he Gul f S Tre a m
T he Gul f S Tre a m

Tiny Plankton,
Giant Bluefin,
and the Amazing
Story of the
Powerful River
in the Atlantic
Stan Ulanski
The University of North Carolina Press | Chapel Hill
© 2008 The University of North Carolina Press
All rights reserved
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Library of Congress Cataloging-in-Publication Data
Ulanski, Stan L., 1946 –
The Gulf Stream: tiny plankton, giant bluefin, and the
amazing story of the powerful river in the Atlantic /
Stan Ulanski.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-8078-3217-2 (cloth: alk. paper)
1. Gulf Stream. I. Title.
gc269.u43 2008
551.46'2131 — dc22 2008004746
A Caravan book. For more information, visit
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ConTenTS
Preface ix
Acknowledgments xv
PaRT 1 CominG full CiRCle:
flow in The aTlanTiC
1 Swirls and Conveyors 3
2 Anatomy of the Gulf Stream 23
3 Flowing Down the Hill:
The History of Ocean Circulation 39
PaRT 2 life in The Gulf STReam
4 Floaters and Drifters 63
5 Bluefin Tuna: The Great Migration 87
6 Fishing the Blue Waters 107
PaRT 3 SailinG The aTlanTiC
7 Exploration and Discovery 131
8 Colonization of America 155
Epilogue 193
Bibliography 197
Index 207
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illuSTRaTionS
5 Simplified view of an ocean gyre
8 Ocean currents in the North Atlantic
10 Currents in the Caribbean and the Gulf of Mexico
12 Opening of the Atlantic Ocean, 200 million years ago to
the present
16 Gulf Stream meanders and rings off the mid-Atlantic coast
18 Carta Marina by Olaus Magnus
21 Conveyor-belt circulation, surface component and deep
component
31 Infrared image of the Gulf Stream departing the North
Carolina coast
32 Warm-core rings, north of the Gulf Stream
33 Weakening of the Gulf Stream at higher latitudes
34 Winslow Homer’s The Gulf Stream
55 Ekman spiral and transport
58 Hill of water and geostrophic flow
59 Western intensification of gyre
65 Diatoms
74 Portuguese man-of-war
76 By-the-wind sailor
78 Sargassum weed
83 Pipefish
89 Bluefin tuna
viii Illustrations
114 Dolphinfish
117 Wahoo
120 Gulf Stream sailfish
133 Caravel with lateen sails
141 Voyage routes of Columbus, Cabot, and Alaminos
145 Bermuda high-pressure center
156 Square-rigged ship
178 Molasses-rum-slave triangle
PRefaCe
I winced slightly when my fishing companion, Matt, queried me
about the effects of the Gulf Stream on the game fish that we were seeking
on a charter out of a North Carolina marina. As a professor, I have come
to expect, though reluctantly accept, almost a complete unawareness of
the Gulf Stream from students in my introductory oceanography class.
Even Matt, an experienced angler, had woefully little knowledge about
the mighty, warm, and deep current, flowing like a river just off the At-
lantic coast. Matt listened eagerly to my explanation of how water tem-
perature gradients of the Gulf Stream concentrate game fish prey, and how
this powerful current affects all life forms, from the tiniest bioluminescent
plankton to the largest bluefin tuna.
In retrospect, there was a time when my own knowledge of the Gulf
Stream was at best scanty, but that started to change more than three de-
cades ago, when I took my first research cruise. Like the mariners of a bygone
period, I sailed into the realm of the Gulf Stream, experiencing firsthand
this relentless flow of the Atlantic — where cobalt-blue water rushed past
our ship, and where tuna and marlin roamed in search of an easy meal.
But my early sea adventure would not start off smoothly; I was seasick
most of the way out. I soon learned that queasiness was no excuse for avoid-
ing the routine task of taking measurements at sea. Called on deck by the
senior scientist one evening, I was startled to see the bow of the ship aglow
with a pale light. Little did I know at that time that large accumulations
of microscopic plants, called dinoflagellates, in the Gulf Stream produce
“phosphorescent seas,” where the waters glow an electric blue. But my enjoy-
ment of the light show was short-lived; the ship growled to a stop. A heav-
ily rolling ship, a heaving stomach, and swinging instruments don’t make
for a pleasant sea experience. But persevering, I soon came to realize that
my measurements yielded one of the defining characteristics of the Gulf
Stream: its relatively high temperature, above 80°F (27°C). As I retired to