And where it does, nutrients upwelling from the depths create lush planktonic feeding zones for the world's fisheries.
n a summer day, when a stiff
northerly wind blows along the
Oregon coast, and there's a line
in the sea where the color changes from
a clear cobalt blue to a murky green—
that's a day fishermen know they can
make a good catch. And catch they do.
The silver salmon, tuna, and other fish
congregate in certain greenish areas
where they feed on thriving pastures of
marine plants and animals—and if the
fishermen are there on the spot, the haul
is good.
Fishermen worth their salt in all
oceans have long known signals of wind,
sea color, frontal lines, and temperatures
in their special fishing areas—it's part of
the lore of the sea. Yet, although they
can recognize areas where the fish might
be, they have been unable to predict
these spots when winds and sea currents
change.
Now, after several years of research,
some of the factors that create good
catches are becoming beautifully clear.
In many slow and ponderous ways—
by action of the tide^ the rotation of
the Earth: and changes in seasons,
winds, and temperatures—the waters of
the world are constantly mixing, overiurr.ir.e. and wciim^ up, biir.ging dissolved chem^ai nutrient- irorn the sea
depths to the surface, and churning
oxygen-rich water from the surface
down again to the deep sea.
These complex vertical and horizontal
motions, vital to the living resources of
the sea, may occur in the middle of the
oceans, or at boundaries of different
water masses, in eddies around the lees
of island or land promontories projecting
into a current, or over ridges and canyons beneath the open sea.
However, the most dynamic ocean
turnover process is coastal upwelling, a
phenomenon by which nutrients from
the dark depths are periodically brought
up in certain areas to the sunlit surface
layers where photosynthesis can take
place and where they can become available to microscopic plant life. These
one-celled plants, phytoplankton, provide the base of the complex food chain
of ocean life. Provided with nutrients
and using energy from the Sun for photosynthesis, they multiply into large
masses, offering feasting grounds for
zooplankton and larger fish and creating
the most productive fish-producing regions in the world.
Fishing yields in these upwelling areas
and their immediate vicinity are at least
a thousand times higher than in other
oceanic areas. The coastal upwelling
areas, comprising only one-tenth of one
percent of the total area of the world's
oceans, are estimated to contain more
than half of the ocean's fish catch—a
total fishery yield of more than 40 million metric tons a year.
Progress in understanding the theory
of the upwelling phenomenon has
reached a point of worldwide significance, states Richard Barber of Duke
University's Marine Laboratory at Beaufort, North Carolina, and national coordinator of the Coastal Upwelling Ecosystem Analysis
(CUEA)
program.
CUEA, part of the International Decade
of Ocean Exploration, was started by
the National Science Foundation to investigate the physical and biological aspects of upwelling. With more than 29
principal investigators and 13 U.S. research and educational institutions and
organizations, CUEA has initiated a
series of experiments and theoretical
observations. Its purpose is to provide
systems models for predicting on a daily
basis the changing sites, courses, extent,
temperatures, and various other factors
of upwelling systems in particular locations. Eventually such system modeling
26
MOSAIC Winter 1974
would be used to predict the production
of the world fisheries on the basis of a
few significant meteorological and oceanographic measurements.
Where it happens
- lthough upwelling may take place
anywhere in the ocean, it occurs
more regularly and most conspicuously along the western edges of
continents in the. low and mid latitudes,
particularly along the western coasts of
the Americas and of Africa. In these
regions, the prevailing winds blow
equatorward, and this, in combination
with the Earth's rotation, causes the
surface water to move away from the
coast. The surface water is replaced by
water from the depths.
There are only a few places in the
world where conditions exist to form
strong persistent upwelling over large
regions. One is along the Peruvian coast,
where the Peru Current flows northward
west of Chile and Peru. Another region
of marked upwelling occurs along the
coasts of Baja California, California,
Oregon, and Washington, where the
California Current flows south. Here the
upwelling peak moves up the coast with
the warming weather in May, June, and
July as the North Pacific atmospheric
high pressure cell intensifies and north-
erly winds develop along the coast. By
October it is finished. A third intensive
upwelling area is along Southwestern
Africa, with most intense activity in the
southern spring months of September
and October. A fourth dominant upwelling system occurs farther north—
along Northwestern Africa.
Contrary to the "west coast rule," important coastal upwelling also develops
in the region of Eastern Africa where,
during the annual southwest monsoon,
the Somali Current flows from the Southern Hemisphere up the east coast of
Africa and along the Arabian coast into
the Arabian Sea.
Upwelling also occurs in mid-ocean
spots around the Equator and in the
Antarctic. In the eastern equatorial region of the Pacific Ocean, for instance,
the Cromwell Undercurrent creates an
uprising in an area extending eastward
along the Equator from the 180-degree
meridian to the Galapagos Islands.
When the polar wind blows
: " he primary driving mechanism of
a "typical" coastal upwelling syst
tem is the wind system blowing
from an atmospheric high pressure toward the Equator and producing stress
at the surface of the sea. Because of the
effect of the Earth's rotation and fric-
tonal forces, however, the net transport
f the windblown surface water, called
,kman Transport or Drift, is directed
eaward, 90° to the right of the wind in
he Northern Hemisphere (to the left in
he Southern).
As the surface water is pushed offhore, cold water rises from several hunired meters deep, up and over the coninental shelf, to take its place. This
ipwelling may appear at the surface in
'arious patterns of tongues, plumes, and
latches. Such tongues or plumes indiate intense upwelling locally and may
.ssume many changing shapes, ranging
n length and depth from a few meters
o several kilometers. However, they
eldom exceed ten to 30 kilometers in
vidth, and ten to 20 meters in trackless. The tip of the tongue of intense
ipwelling usually can be found within
en to 20 kilometers off the coast.
:
rontal boundaries between the warm
old surface water) and cold (more
lewly upwelled) water masses are often
iharp and distinct. Some occur over long
listances, others over a space so small
hat a single ship may straddle the
>oundary.
An inherent feature of upwelling
seems to be the presence of a narrow
etlike surface current that flows along
he shore in the same direction as the
prevailing winds on the seaward side of
:he upwelling front. At the same time
is the surface current is flowing, a subsurface countercurrent is often observed
-lowing away from the Equator. This is
:onsidered a very important factor in
:he dynamics of upwelling and its asso:iated ecosystem. Just how much these
:urrents contribute to upwelling under
/arious conditions and what effect they
produce is not yet clear, points out physcal oceanographer Robert Smith of Oregon State University, which was the
renter of extensive upwelling experinents during the summers of 1972 and
1973.
Each regional upwelling ecosystem is
a separate, complex, and dynamic phenomenon that depends upon the physical
conditions of its setting. Each is subject
not only to variations within the system
itself—such as the configuration of the
:oast and continental shelf, the strength
and directions of ocean currents, and the
local wind conditions—but also to influences external to it, such as the seasons
and the world wind patterns.
What makes it happen. Strong winds blowing along the shore toward the Equator, combined
with the Earth's rotation and frictional forces, drive the warm surface water away from
the shore. It is replaced by cold, nutrient-rich water from the lower depths; phytoplankton
flourish, and fish congregate to feed on the plankton.
Unpredictable prodigy
-,' lthough the upwelling regions seem
well defined, the process itself
" has, as yet, no constant or dependable schedule of when it might
arrive or how long it will last. The
length of time an upwelling season may
prevail depends primarily upon how
long the dominating winds blow along
the coast. This in turn depends on the
strength and positions of the atmospheric highs that occur as spring and
summer arrive. During the season when
conditions are generally right for upwelling, the process may vary from
strong persistent upwelling to none at all
to strong again over a period of weeks.
These modulations may occur several
times during a season of upwelling conditions. They occur when the prevailing
winds stop blowing in the direction
favorable to upwelling—equatorward
along west coasts—and come from other
directions, hence stopping the offshore
transportation of the warm surface water. This in turn shuts off the upwelling
circulation of water from lower depths.
The cold water remains below and the
warm water above in horizontal layers.
These wind changes of a few days' duration have large effects on water temperature over areas as wide as ten kilometers
from the shore and as deep as 20 meters.
Once the source of nutrients is stopped
or blocked, the growth of phytoplankton
halts, as does the concentration of fish.
The whole process collapses and the fish
disperse to find their own food where
they can, and fishing for the day, the
week, perhaps longer, can become a
haphazard affair for the fishermen.
MOSAIC Winter 1974
27
the diminished n u m b e r s of anchovies are
caused by overfishing d u r i n g el Nino, or
p e r h a p s by a n a t u r a l decrease in the
biological cycle of the fish. O t h e r tragic 1
failures blamed on similar circumstances
were the d i s a p p e a r a n c e of the California 1
sardine and H o k k a i d o h e r r i n g .
The sunlit zone
W i t h the r e t u r n of the prevailing
n o r t h e r l y w i n d s (or southerlies in t h e
S o u t h e r n H e m i s p h e r e ) , upwelling r e s u m e s , and p l a n k t o n g r o w t h and concentration of m a r i n e life reoccurs.
Some upwelling systems t a k e place
year after year in specific areas. O t h e r s
m a y continue for several years w i t h o u t
i n t e r r u p t i o n a n d t h e n fail c a t a s t r o p h i c a l l y — s u c h as t h e failures of upwelling in
1965, 1 9 7 1 , a n d 1972 off the coast of
Peru. In previous years, the P e r u v i a n
upwelling h a s created the w o r l d ' s m o s t
productive fishery area. In 1970, 22 p e r cent of the total world fish c a t c h — m o s t l y
28
MOSAIC Winter 1974
anchovies—was harvested. W i t h the absence of upwelling—el Nino or " T h e
C h i l d , " as it is called—in 1971-72, the
a n c h o v y catch d r o p p e d from 12.3 million
t o n s in 1970 to 4.5 million t o n s in 1972
— a t r a g e d y for Peru w h i c h for decades
h a d depended on the m o r e t h a n ten million tons of a n c h o v y catch, from w h i c h
n e a r l y 70 percent of the w o r l d ' s fishmeal
w a s produced. Scientists say t h e fish
stocks are slowly recovering w i t h the
r e s u m p t i o n of u p w e l l i n g in 1 9 7 3 , b u t
t h e y h a v e not yet multiplied to their
former n u m b e r s . T h i s d i s r u p t i o n has
raised several questions as to w h e t h e r
ithout d o u b t , coastal upwelling
systems p r o d u c e rich biological
g r o w t h and activity. This high
productivity of organic m a t t e r is limited
to the sea surface layers w h e r e sunlight
is sufficient for p h o t o s y n t h e s i s . Solar
radiation p e n e t r a t e s t h r o u g h this upper
sea layer, the euphotic z o n e , to d e p t h s
of about 11 to 28 m e t e r s , d e p e n d i n g on
the concentration of the m a r i n e p o p u l a tions or on turbidity. Into this zone are
b r o u g h t up the deep sea's n i t r o g e n , p h o s p h o r u s , and silicon; in ion form or as
c o m p o u n d s of nitrates, nitrites, p h o s p h a t e s , and silicates. Iron a n d traces of
other minerals are also p r e s e n t .
At first, the cold, n e w l y upwelled w a ter is low in plant and a n i m a l p o p u l a t i o n ; it takes a while for p r i m a r y biological activity to start, explains Richard
D u g d a l e , a biological
oceanographer
from the University of W a s h i n g t o n . As
one-celled p l a n k t o n m u l t i p l y , they gradually consume and reduce the a m o u n t of
n u t r i e n t s . At the same time, oxygen con-'
tent increases. A l o n g the surface w a t e r s ,
oxygen is near s a t u r a t i o n , and t o w a r d
the seaward edge of the s p r e a d i n g p l u m e '
it has been m e a s u r e d as h i g h as 130 percent of saturation.
As an indication of t h e extent to w h i c h
upwelling increases p r o d u c t i o n of prim a r y m a r i n e life, p h y t o p l a n k t o n cell
counts in the P e r u v i a n u p w e l l i n g ecosystem, in a good year, h a v e b e e n m e a s ured as high as 138,000 per liter. This
compares to a n o r m a l ocean density of
1,000 to 10,000 per liter.
Feeding directly on t h e p l a n t and animal p l a n k t o n are the h e r b i v o r o u s zoop l a n k t o n and fin fishes, such as t u n a ,
salmon, anchovies, mullet, a n d herring,
w h i c h are caught by fishermen or eaten
by other carnivorous p r e d a t o r s including
birds, b o n i t o , squid, a n d sea lions. In
the P e r u v i a n region, it is estimated t h a t
the a n n u a l n u m b e r s of fish captured by
fishermen are p r o b a b l y m a t c h e d b y those
c o n s u m e d by m a r i n e p r e d a t o r s .
As the upwelling t o n g u e of cold water
spreads over the sea surface a n d is
oved seaward by the wind, it carries
e products of this biological activity—•
e excreta, dead and decaying plants,
limals, and other organic compounds—hich gradually sink toward the bottom
• the sea. As this material drifts downard, it is acted upon by bacteria near
e surface which reduce it again to in•ganic nutrients that may be taken up
/ phytoplankton, dissolved into the sea,
• come to brief rest on the sea floor
;fore being upwelled again—a complete
:osystem recycling.
Moreover, though the processes are
3t yet well understood, there seems to
i nutrient recycling within various lay's arid currents of the sea in an upelling region—through local mixing and
mvection currents, or subsurface shoreard transport, or through injection at
ie source of upwelling. The proportion
: regenerated nutrients in a fully devel?ed upwelling ecosystem is quite high,
'ne estimate is that a dense school of
srbivorous fishes grazing on a phyto.ankton crop, through its excreta alone,
roduces the daily nitrogen requirements
" the phytoplankton in just two hours.
xpeditions for upwelling
cientists have been aware of upwelling for a long time, particularly along the coast of Peru,
'here the occurrence of el Nino has been
?corded by fishermen for more than
30 years. Scientific attempts to define
nd describe the upwelling system itself,
owever, did not occur until the early
900's. In the late 1920's and 1930's,
idividual oceanographers began making
tajor contributions to the studies. In
968 an Upwelling Biome Program was
icluded as ; part of the International
iological Program, and studies were
lade along the Peruvian coast and in the
lediterranean. With CUEA established
i 1971, four expeditions took place in
ie succeeding two years to investigate
ie biological and physical effects of
pwelling: MESCAL I and II off Baja
alifornia in the springs and summers
f 1972 and 1973; and CUE I and II off
\e Oregon coast in the same years.
The latest major experiment, CUE II,
perating from July through August
973, took place on a site some 80 kiloleters long along the Oregon coast
'om Newport to Cape Lookout, and
^tending some 60 kilometers into the
acific Ocean. CUE II, co-directed by
James O'Brien of Florida State University and Dale Pillsbury of Oregon State
University, was set slightly north of the
1972 CUE I site, at a place where the
topography of the continental shelf is
simpler and smoother. Here scientists
hoped to avoid the complicated sea circulations created by ridges and bumps
of the sea bottom and to simplify the
simulations of models.
Three research vessels—the "workhorse" Cayuse which can make a 180°
turn "on a quarter" to place or pick up
buoys and objects from the sea; and
the more elegantly equipped Oceanographer and Yaquina—made
repeated
journeys back and forth over the area
to measure temperatures, salinities, densities, and changes in currents. On another vessel, the Thomas G, Thompson,
scientists made detailed studies on chemical nutrients, plankton, and fish, and
compiled maps charting temperature
zones, flow of currents, and areas of
nutrients and biological activity. An instrumented aircraft from the National
Center for Atmospheric Research operated over the area during August, measuring sea surface temperatures, air humidity and temperatures, and wind
systems.
Since 1965, arrays of buoys moored
on Oregon's continental shelf have been
used to record currents and temperatures. During CUE II more buoys were
installed in arrays extending from land
out to sea some 60 or more kilometers—
across the continental shelf and over the
edge of the continental slope. These
buoys—spaced several kilometers apart,
depending on the configuration of the
sea floor or the currents—recorded temperatures and currents from the surface
to the sea floor. They helped scientists
"follow" various ebbs and flows of currents as the winds changed and the season progressed. Buoys from NOAA's
Pacific Marine Environmental Laboratory
were moored at single points along the
array to measure the wind, solar radiation, and currents near the surface.
Buoys from Oregon State University
MOSAIC Winter 1974
29
Taking the sea's temperature, Equipment is placed at strategic points off the Oregon coast
during CUE-ll.
measured current velocities and directions at different depths.
Scientists found the 1972 data lacking
in adequate information on wind directions and changes. Since wind is recognized as the major driving force in
upwelling systems, emphasis was made
in 1973 on increasing wind data from
anemometers on land and sea stations.
In addition to new data-gathering
techniques and equipment, a wholly new
shipborne computerized data storage,
processing, and display system was used
in 1973, packed totally in a van about
half a room large, and placed on board
the Thomas G. Thompson. This system
acquired data on the spot, processed it,
and provided scientists with a nearly
"real time" look at the area they were
studying to help them update their plans
during the cruise.
A step closer to prediction
ome parts of the upwelling process
have been successfully simulated
on
two-dimensional,
two-layer,
t i m e - d e p e n d e n t numerical models over
coastal regions of simple t o p o g r a p h y
u n d e r steady wind conditions.
James
O'Brien a n d J o h n J. W a l s h , University
of W a s h i n g t o n , are w o r k i n g o n models
t h a t e n c o m p a s s basic f e a t u r e s — t h e slope
a n d configuration of the coastal shelf,
t h e direction and speed of w i n d , b i o logical variables, t h e flow of c u r r e n t s
30
MOSAIC Winter 1974
a n d c o u n t e r c u r r e n t s , a n d t h e size a n d
m o v e m e n t of the upwelling.
But since upwelling is a t h r e e - d i m e n sional affair, actually four w h e n o n e considers the time factor, O'Brien a n d his
c o - w o r k e r s are developing a t h r e e d i m e n s i o n a l , time-variable
circulation
m o d e l to handle the m a n y variables occ u r r i n g during upwelling. " W i t h this
m o d e l , " O'Brien says, " w e h o p e to p r e dict factors such as w i d t h of t h e u p w e l l ing t o n g u e , the times and areas for
u p w e l l i n g to appear, a n d t h e flow of
currents.
" N u m e r i c a l models of t i m e - d e p e n d e n t
oceanographic phenomena have a particularly promising f u t u r e , " h e says.
" W i t h models from e x p e r i m e n t s C U E I
a n d II already feeding forecasts o n a
general scale, we h o p e n u m e r i c a l studies
will b e applied to other u p w e l l i n g r e gions t h r o u g h o u t t h e w o r l d . "
T h e accumulation of d a t a a n d testing
of h a r d w a r e and techniques d u r i n g CUE
II a n d other CUEA e x p e r i m e n t s h a v e
been building u p to a large i n t e r n a t i o n a l
project, J O I N T I, scheduled for February
t h r o u g h M a y 1974 off t h e n o r t h w e s t e r n
coast of Africa.
" J O I N T I is the first major e x p e r i m e n t
w i t h all c o m p o n e n t s of t h e C U E A p r o g r a m functioning t o g e t h e r , " says Barber.
T h e international research project will be
conducted in the area of C a p e Blanc in
cooperation with scientists from France,
G e r m a n y (East a n d W e s t ) , U.S.S.R.,
Tracks of winds, Arrows on this vector
chart show how the wind blew daily aiory,
the Oregon coast during July and Auguj-i "f
1972. Prevailing winds blew from the nc.!->
most of the time, but reversed around
July 2, 6, 31, and August 15. During theo<
reversals, upwelling slowed, shore watei
temperatures rose, and fishing was
generally poor until north winds picked
up again.
Spain, the United Kingdom, and Mauritania—all participants in an even larger
international program called Cooperative
Investigations of the Northern Part of
the Eastern Central Atlantic.
"The primary research objective of
JOINT I is exactly the same as the cen-
al scientific objective of the CUEA pro•am," he says: "to develop a total sysm model of the complex process of
swelling."
The complete understanding of the
swelling phenomenon depends on the
entification and correlation of changes
. global atmospheric and ocean current
rculations and in local mesoscale epilations—essentially on the dynamics
lat drive, or fail to drive, upwelling.
More data on physical processes and
lechanisms are still needed. For in:ance, what are the effects on upwelling
'om irregularities of the sea bottom
)pography? What energy transfers ocxv from the wind to the ocean surface
i different wind velocities and under
iffering conditions of surface sea roughess? What are the qualitative apporonments of sources of upwelled water
nder different conditions of temperaires and currents? These are some of
\e questions that scientists plan to exlore during the JOINT I expedition.
rotecting the ocean's resources
he major practical benefit of an upwelling prediction system for locations throughout the world is that
shermen will be able to obtain an
bove-average harvest with less time
'asted searching for fishing locations.
. potential hazard, of course, is that
nee the actual time and place of up'elling can be predicted, fishermen will
verfish the resources of the sea.
"Scientists are aware of the possibilies that, with scientific and technolog:al knowledge such as we are finding,
shermen may take more from the sea
aan can be naturally replaced," says
arber. Any kind of control over fishing
ghts and international legal codes is
Dmplex and hard to enforce, especially
>r the smaller coastal nations. Cerlinly, lack of regulation has contributed
} the ruin of several fishing industries—le California sardines, for instance, or
ae menhaden on the East Coast.
Overfishing as well as other factors
ach as ocean pollution is a serious threat
) be considered and controlled in order
D maintain life and productivity of the
ea. "Yet we have to be careful in interreting what we think affects the marine
opulation," points out Barber. "Other
actors have to be considered—for intance, the natural biological cycles of
International rendezvous. In the summer of 1974 scientists from more than half a dozen
nations will fake part in JOINT I to study upwelling dynamics off the West African coast.
fish population. At times a species of
fish may become abundant; at other
times in their biological cycle there may
be a natural decrease in their numbers."
By gaining a deeper understanding of
the physical and biological dynamics of
upwelling, scientists, fishermen, and national legislators will have more potential control over the supply of fish stock.
"In other words," Barber says, "scientists can forecast the possibility of upwelling and hence productivity of fish
in certain local areas. The fishing industry and national resources offices can
then be alerted as to whether they
should reduce their fishing quota or
shorten the fishing season to let the fish
stock be replenished. Or in a good year
they can increase their fishing harvest
without damaging the stock."
Already, In some countries, fishing
controls have been Instituted. In Peru,
for instance, fishing regulations are extremely strict. For the small, newly developing coastal countries it is important
that their marine resources be under
legal protection.
"For the world as a whole," says Barber, "there is a high payoff in the new
scientific and technological knowledge of
upwelling and fish harvest. Large and
small nations need cooperation in order
to preserve, protect, and manage these
resources of the sea." •
MOSAIC Winter 1974
31