JOURNAL OF
JOURNAL
OF GEOPHYSICAL
GEOPHYSICAL RESEARCH,
RESEARCH, VOL.
VOL. 99,
99, NO.
NO. C4,
C4, PAGES
PAGES 7355-7370,
7355-7370, APRIL
APRIL 15,
15, 1994
1994
Comparison of
of the
the seasonal
seasonal and
and interannual
interannual variability
Comparison
variability
of
phytoplankton
pigment
concentrations
in
the
of phytoplanktonpigmentconcentrationsin the
Peru
Peru and
and California
California Current
Current systems
systems
A.
A. C.
C. Thomas
Thomas and
and F.
F. Huang
Huang
Atlantic
Atlantic Centre
Centre for
for Remote
RemoteSensing
Sensingof
of the
the Oceans,
Oceans,Halifax,
Halifax, Nova
Nova Scotia,
Scotia,Canada
Canada
P.
P. T.
T. Strub
Strub and
and C.
C. James
James
College
of Oceanic
Oceanic and
and Atmospheric
Collegeof
AtmosphericSciences,
Sciences,Oregon
OregonState
StateUniversity,
University,Corvallis
Corvallis
Monthly composite
composite images
images from
from the
the global
global coastal
coastal zone
zone color
color scanner
Abstract.
Abstract. Monthly
scanner
(CZCS)
data
set
are
used
to
provide
an
initial
illustration
and
comparison
(CZCS) data set are used to provide an initial illustrationand comparisonof
of seasonal
seasonal
and
concentration along
and interannual
interannualvariability
variability of
of phytoplankton
phytoplanktonpigment
pigment concentration
along the
the western
western
coasts
coastsof
of South
South and
and North
North America
America in
in the
the Peru
PeruCurrent
Current system
system(PCS)
(PCS) and
andCalifornia
California
Current
the entire
data
Currentsystem
system(CCS).
(CCS). The
The analysis
analysisutilizes
utilizesthe
entire time
time series
seriesof
of available
availabledata
(November
1978
to
June
1986)
to
form
a
mean
annual
cycle
and
an
index
of
interannual
(November 1978to June 1986) to form a mean annual cycle and an index of interannual
variability
for aa series
and cross-shelf
regions within
within each
each current
current
variability for
seriesof
of both
both latitudinal
latitudinaland
cross-shelfregions
system. Within
km of
of the
the coast,
coast, the
the strongest
system.
Within 100
100km
strongestseasonal
seasonalcycles
cyclesin
in the
the CCS
CCS are
are in
in
two
and the
the second
and 29°N,
each
two regions,
regions,one
onebetween
between34°
34øand
and45°N
45øNand
secondbetween
between24°
24ø and
29øN,each
with
maximumconcentrations
concentrations(>3.0
(>3.0mg
mgmm3)
in May-June.
MayJune. Weaker
seasonal
withmaximum
-3) in
Weaker
seasonal
variability
California
variability is
is present
presentnorth
northof
of45°N
45øNand
andin
inthe
theSouthern
Southern
CaliforniaBight
Bightregion
region(32°N).
(32øN).
Within
the PCS,
coastal region,
region, highest
highest (>45øS)
(>45°S) and
and lowest
lowest
Within the
PCS, in
in the
the same
same100-km-wide
100-km-wide coastal
(<20°S) latitude
latitude regions
regions have
have aa similar
seasonal cycle
cycle with
maximum concentrations
concentrations
(<20øS)
similar seasonal
with maximum
_3) during the
austral
spring,
summer,
and
fall,
matching
that
(>1.5
mg
m
(> 1.5mgm-3) duringtheaustralspring,
summer,
andfall,matching
thatevident
evident
throughout
throughoutthe
the CCS.
CCS. Between
Betweenthese
theseregions,
regions,off
off northern
northernand
andcentral
centralChile,
Chile, the
the
seasonal maximum
maximum occurs
occurs during
duringJuly-August
JulyAugust (austral
winter), contrary
contrary to
to the
seasonal
(austral winter),
the
influence of
of upwelling
upwellingfavorable
favorablewinds.
winds. Within
Withinthe
the CCS,
CCS, the
the dominant
dominant feature
feature of
of
influence
interannual
variability
in
the
8-year
time
series
is
a
strong
negative
concentration
interannualvariability in the 8-year time seriesis a strongnegativeconcentration
anomaly in
in 1983,
an E1
El Nifio
Niflo year.
year. The
The relative
anomaly
1983, an
relative value
value of
of this
thisnegative
negativeanomaly
anomalyis
is
strongest
central California
and is
is followed
followed by
by an
an even
strongestoff
off central
Californiaand
even stronger
strongernegative
negativeanomaly
anomalyin
in
1984off
offBaja
BajaCalifornia.
California.In
Inthe
the PCS,
PCS, strong
strong negative
negative anomalies
during the
the 1982-1983
El
1984
anomaliesduring
1982-1983E1
Niflo
period
are
evident
only
off
the
Peruvian
coast
and
are
evident
there
only
in
the
Nifio period are evidentonly off the Peruviancoastand are evidentthere only in the
regions 100
km or
or more
more from
from the
the coast.
regions
100km
coast.Although
Althoughnegative
negativeanomalies
anomaliesassociated
associatedwith
with
the El
20°S)
the
E1Niflo
Nifio were
were not
notpresent
presentat
athigher
higherlatitudes
latitudes(more
(morethan
thanapproximately
approximately
20øS)in
in the
the
PCS,
the
extremely
sparse
sampling
weakens
our
confidence
in
the
results
of
the
PCS, the extremelysparsesamplingweakensour confidencein the resultsof the
interannual analysis
analysis in
in this
this region.
region. An
An upper
upper estimate
the systematic
interannual
estimateof
of the
systematicwinter
winter bias
bias
remaining in
in the
the global
global CZCS
CZCS data
data after
after reprocessing
with
remaining
reprocessing
with the
the multiple
multiplescattering
scattering
algorithm
is given
given in
in the
algorithm is
the appendix.
appendix.
1.
1.
Coastal
Transition Zone
have provided
CoastalTransition
Zone programs
programshave
provideddetails
detailsof
of
Introduction
Introduction
both
both physical
physical and
andphysiological
physiologicalprocesses
processeson
on relatively
relatively
space and
A
major oceanographic
oceanographic characteristic
characteristic of
localized space
and time
time scales.
scales.
A major
of eastern
easternboundary
boundary localized
Previous
between the
currents
Previouscomparisons
comparisonsbetween
the dynamics
dynamicsof
of different
different
currents (EBCs)
(EBCs) is
is the
thepresence
presenceofofrecurring
recurringwind-driven
wind-driven
coastal
easternboundary
boundarycurrents
currents[e.g.,
[e.g.,Smith,
Smith,1981;
1981;Schulz,
Schulz,1982;
1982;
coastalupwelling
upwelling.Physical
Physicalforcing
forcingintroduces
introducesnutrient-rich
nutrient-rich eastern
subsurface water
water into
into the
the upper
in Minas
et al.,
which relied
relied on
on in
in situ
situ data
data were,
subsurface
upper water
water column,
column, resulting
resulting in
Minas et
al., 1986]
1986] which
were, by
by
increased
increased phytoplankton
phytoplankton production
production and
and concentrations.
concentrations. necessity,
necessity,restricted
restrictedin
in the
the time
time and
andspace
spacescales
scalesthey
they could
could
Large,
and multiyear
programs such
such as
data
Large, multidisciplinary
multidisciplinary and
multiyear programs
as address
addressand
and rarely
rarely had
had access
accessto
to temporally
temporallycoincident
coincidentdata
Coastal Upwelling
Upwelling Ecosystems
Ecosystems Analysis
Analysis (CUEA)
(CUEA) and
and CoopCoop- from
the different
synopCoastal
from the
differentregions.
regions.The
The repetitive,
repetitive,large-scale
large-scale
synoperative Investigation
Investigationof
of the
the Northern
Northern Part
Part of
erative
of the
the Eastern
Eastern tic
offered by
by satellite
satellite observations
observations are
tic views
views offered
are well
well suited
suitedfor
for
Central Atlantic
Atlantic (CINECA)
(CINECA) demonstrated
demonstrated the
the strong
tempo- estimating
Central
strong tempothe temporal
and spatial
estimatingthe
temporaland
spatialscales
scalesof
of variability
variabilityof
of
ral and
ral
and spatial
spatial variability
variability of
of both
both physical
physical dynamics
dynamics and
and
biological patterns
patterns in
in EBCs.
EBCs. More
More recently,
recently, programs
biological
programssuch
such
as the
as
the Coastal
CoastalOcean
OceanDynamics
DynamicsExperiment
Experiment(CODE),
(CODE), OrgaOrganization of
nization
of Persistent
PersistentUpwelling
Upwelling Structures
Structures (OPUS)
(OPUS) and
and
Copyright 1994
by the
the American
Copyright
1994 by
American Geophysical
GeophysicalUnion.
Union.
Paper
Paper number
number93JCO2146.
93JC02146.
0148-0227/94/93JC-02146$05.O0
0148-0227/94/93JC-02146505.00
near-surface oceanographic
oceanographic characteristics.
characteristics. Over
Over the
the last
near-surface
last
decade, satellite
of ocean
ocean color
color from
from the
the coastal
coastal zone
decade,
satelliteimages
imagesof
zone
color scanner
scanner (CZCS)
have revealed
revealed many
the larger-scale
color
(CZCS) have
many of
of the
larger-scale
time
and
space
features
of
biological
variability
time and space features of biological variability of
of the
the
California
Current
system
(CCS)
[Abbott
and
Zion,
California Current system (CCS) [Abbott and Zion, 1987;
1987;
Pelaez
Smith et
et al.,
Pelaez and
and McGowan,
McGowan, 1986;
1986; Smith
al., 1988]
1988] and
and some
some
details of
of structure
details
structure within
within the
the Peru
Peru Current
Current system
system(PCS)
(PCS)
7355
7355
7356
7356
THOMAS
ET AL.:
CURRENT
PIGMENT
VARIABILITY
THOMAS
ET
AL ßPERU
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
[e.g., Uribe
[e.g.,
Uribe and
and Neshyba,
Neshyba, 1983;
1983; Espinoza
Espinoza et
et al.,
al., 1983].
1983].
Substantially fewer
fewer CZCS
Substantially
CZCS data
data were
were collected
collectedover
overthe
thePCS.
PCS.
Sufficientimages
imagesare
are available,
available,however,
however, to
to obtain
obtain aa first
Sufficient
first
approximation
of the
the major
approximation of
major seasonal
seasonalfeatures
features that
that are
are evievident
dent in
in the
theavailable
available satellite
satelliteocean
oceancolor
colordata.
data.Although
Although
biased
biased by
by missing
missing data
data toward
toward certain
certain years
years and
andmonths,
months,
they
temporal
they allow
allow aa general
generalcomparison
comparisonof
of the
the larger-scale
larger-scaletemporal
and
and spatial
spatialvariability
variability of
of phytoplankton
phytoplanktonbiomass
biomassin
in these
thesetwo
two
Pacific
eastern boundary
Pacific eastern
boundarycurrents.
currents.
In
In this
this paper
paper we
we present
presentand
andcompare
comparethe
the mean
mean seasonal
seasonal
and
and interannual
interannualvariability
variability of
of phytoplankton
phytoplanktonpigment
pigmentconconcentrations
centrationsalong
along the
the west
west coasts
coastsof
of North
North and
andSouth
SouthAmerAmerica
Current systems.
ica in
in the
the Peru
Peru and
and the
the California
California Current
systems.The
The time
time
series of
a period
series
of CZCS
CZCS data
data includes
includes1982-1983,
1982-1983, a
period with
with aa
particularly
Barber and
and
particularly strong
strong El
E1 Niflo
Nifio event
event [Cane,
[Cane, 1983;
1983; Barber
Chavez,
1986].
The
analysis
is
offered
as
a
general
summary
Chavez, 1986]. The analysisis offered as a generalsummary
and synthesis
and
synthesisof
of the
the larger-scale
larger-scaletemporal
temporal and
and spatial
spatialfeafeatures
tures which
which can
can be
be deduced
deducedfrom
from the
the available
available CZCS
CZCS data,
data,
flawed though
thoughthat
that data
data set
set may
and
flawed
may be
be by
by poor
poor sampling
sampling and
potential
bias.
A
more
complete
analysis
of
features
on
these
potential bias. A more completeanalysisof featureson these
time and
and space
time
spacescales
scalesawaits
awaits the
the arrival
arrival of
of additional
additionaland
and
hopefully more
more complete
complete data
data from
hopefully
from future
future color
color sensors,
sensors,
such as
such
as the
the sea-viewing
sea-viewingwide-field
wide-field sensor
sensor(Sea
(Sea WiFS),
WiFS), supsupported
by
in
situ
measurements.
ported by in situ measurements.
Major
Major features
featuresof
of the
the temporal
temporalvariability
variabilityin
in the
the California
California
Current have
have previously
been shown
shown by
by Pelaez
Current
previously been
Pelaez and
and
estimatedthe
the accuracy
accuracy of
Gordon
et al.
Gordon et
al. [1983a]
[1983a] estimated
of the
the
CZCS-derived
to
CZCS-derivedpigment
pigmentmeasurements
measurements
tobe
belog(chlorophyll)
log(chlorophyll)
±0.5
--.0.5 (i.e.,
(i.e., within
within aa factor
factor of
of 22 in
in concentration).
concentration).A
A comparcompar-
ison
ison of
of CZCS
CZCS data
data with
with ship
shipmeasurements
measurementsoff
off southern
southern
California
[Smith et
et al.,
al., 1988]
showed the
the satellite
California [Smith
1988] showed
satellite data
data to
to be
be
±40%
within the
the chlorophyll
---40%within
chlorophyll concentration
concentrationrange
range0.05-10.0
0.05-10.0
Although the
the multiple-scattering
algorithm
used
mg
mgm
m-3. Although
multiple-scattering
algorithm
usedin
in
processing
the global
global data
data set
processingthe
set improves
improves the
the concentration
concentration
estimates,
at higher
estimates, especially
especially at
higher latitudes
latitudes during
during winter
winter
months
and Castano,
Gordon et
et al.,
months [Gordon
[Gordon and
Castano, 1987;
1987; Gordon
al., 1988],
1988], aa
systematic
bias may
may still
still be
be present.
systematicbias
present. This
This bias,
bias, as
aswell
well as
as
other
and random
other systematic
systematic and
random errors
errors associated
associated with
with the
the
CZCS
data set,
set, is
by Strub
CZCS data
is discussed
discussedin
in more
more detail
detail by
Strub et
et al.
al.
[1990]and
andisisnot
not repeated
repeated here.
here. An
An upper
upper estimate
estimate of
of the
the
[1990]
magnitude
of the
the possible
possible winter
winter bias
bias in
in the
the data
data is
in
magnitudeof
is given
given in
the
appendix.
Efforts
were
made
in
the
reprocessing
of
the
the appendix. Efforts were made in the reprocessingof the
data
to account
data set
set [Feldman
[Feldman et
et al.,
al., 1989]
1989] to
account for
for sensor
sensor degradegra-
dation
over the
the life
of the
et al.,
dation over
life of
the sensor
sensor [Gordon
[Gordon et
al., l983b;
1983b;
Mueller,
Mueller, 1985].
1985].
The
The mean
mean seasonal
seasonal cycle
cycle in
in pigment
pigment concentration
concentration over
over
the
extent of
of the
the PCS
the entire
entire latitudinal
latitudinal extent
PCS and
and the
the CCS
CCS was
was
calculated.
calculated. An
An overall
overall mean
mean image
image for
for each
each calendar
calendarmonth
month
was
formed
by
compositing
all
available
images
was formed by compositingall available imagesfor
for aa given
given
month
series. These
These images
are used
month to
to form
form aa 12-month
12-month series.
images are
used to
to
provide
provide a
a qualitative
qualitative description
description of
of spatial
spatial and
andtemporal
temporal
patterns
patternsover
over the
the year
year as
aswell
well as
asregional
regionaldifferences
differenceswithin
within
each
EBC.
Subsampling
each
of
the
mean
each EBC. Subsamplingeach of the meanmonthly
monthly images
images
by
within 100
100 xx 100
km boxes
boxes oriented
by averaging
averagingwithin
100 km
oriented by
by the
the
coast
a quantitative
of these
coast allows
allows a
quantitative analysis
analysis of
these seasonal
seasonalpatpatterns
regions of
of missing
missing data
data due
due to
to clouds.
clouds.
ternsand
andaids
aidsin
in filling
filling regions
The
location
of
these
boxes
is
shown
in
Figures
la
and
lb.
The location of these boxes is shown in Figures la and lb.
with any
any data
data set,
set, quantitative
quantitative interpretation
interpretation is
to
CZCS data
data set
set [Feldman
et al.,
CZCS
[Feldman et
al., 1989],
1989], is
is made
made and
and prepre- As
As with
is subject
subjectto
sented.
the errors
errors and
and bias
bias of
of the
the measurements
measurements(outlined
(outlined above).
above). In
In
sented.These
Thesedata
datawere
were processed
processedutilizing
utilizing aa multiple
multiple scatscat- the
tering algorithm
in the
the atmospheric
the vicinity
vicinity of
of the
the highly
highly complex
complex coastline
coastlineoff
off southern
southern
tering
algorithm in
atmosphericcorrection
correction [Gordon
[Gordon et
et the
Chile,
a
smoothed
coastline
oriented
along
the
western
al.,
1988],
which
reduces
the
errors
caused
by
large
solar
side
al., 1988], which reduces the errors caused by large solar Chile, a smoothed coastline oriented along the western side
zenith angles
(high latitudes
latitudes in
in winter
winter months).
months). In
In section
of the
the islands
islands was
was used.
used. Despite
Despite these
thesespatial
spatialand
and temporal
temporal
zenith
angles(high
section 2
2 of
we summarize
characteristics of the CZCS
averaging
procedures, some
some regions
regions of
of the
the PCS
we
summarize characteristics
CZCS data
data and
and details
details
averaging procedures,
PCS still
still had
had
data in
in some
some months.
months. Missing
data within
within aa box
of the
the analysis
methods. In
missing data
Missing data
box in
in
of
analysismethods.
In section
section3
3 we
we present
presentthe
the mean
mean missing
seasonal
variabilityinin the
the two
two EBCs
any month
month were
were supplied
suppliedby
by spatially
spatiallyaveraging
averagingthe
the concenconcenseasonal variability
EBCs and
and an
an analysis
analysis of
of any
interannual variability
variability in
in the
the PCS
PCS and
and CCS
over the
from the
the boxes
from the
the coast
trations from
boxes equidistant
equidistant from
coast and
and
interannual
CCS over
the 8-year
8-year trations
to the
the north
north and
extent of
the CZCS
CZCS data
data set.
set. A
comparison and
and discussion
discussion of
of immediately
immediately to
and south
south for
for the
thesame
samemonth.
month.
extent
of the
A comparison
patterns evident
in section
section 4,
4, and
and aa Total
data supplied
in this
this manner
manner were
were less
Total missing
missingdata
suppliedin
lessthan
than 5%
5%
patterns
evidentin
in the
the two
two EBCs
EBCs is
is made
made in
of
the
total
matrix
of
1836
data
points
(12
months
summary
and
conclusions
follow
in
section
5.
The
appendix
of
the
total
matrix
of
1836
data
points
(12
months
xx 33
summaryand conclusionsfollow in section5. The appendix
zones xx 51
presents an
offshore zones
51alorigshore
alongshoreboxes).
boxes).
presents
an empirical
empiricalestimate
estimateof
of magnitude
magnitudeof
of the
thesystemsystem- offshore
Previous
atic errors
Previousanalyses
analysesof
of interannual
interannualvariability
variability in
in the
theCaliforCaliforatic
errors which
which might
might remain
remain in
in the
the global
global CZCS
CZCS data
data set
set
owing to
to uncorrected
at high
nia Current
Current using
using CZCS
CZCS data
data [Pelaez
[Pelaez and
and McGowan,
McGowan, 1986;
1986;
owing
uncorrectedatmospheric
atmosphericscattering
scatteringat
high latilati- nia
Thomas and
and Strub,
Strub et
tudes in winter.
tudes
winter.
Thomas
Strub, 1989,
1989, 1990;
1990; Strub
et al.,
al., 1990]
1990] have
have
shown that
that the
to resolve
shown
the coverage
coverageis
is generally
generally sufficient
sufficient to
resolve
2. Data
2.
Data and
and Methods
Methods
features
features on
on time
time scales
scales of
of a month
month or less.
less. The
The CZCS
CZCS data
data
set for
for the
the Peru
Peru Current
less complete.
complete. To
To produce
produce
The
ocean
pigment
Current is
is much
much less
The ocean pigment concentration
concentrationmeasurements
measurementsprepre- set
aa time
sented
sented here
here are
are from
from the
the coastal
coastal zone
zone color
color scanner
scanner instruinstrutime series
seriesallowing
allowing examination
examination of
of interannual
interannualvariability
variability
ment
of the
ment aboard
aboard the
the Nimbus
Nimbus 7
7 satellite.
satellite. The
The entire
entire CZCS
CZCS data
data
of
the PCS
PCS over
over the
thelifetime
lifetime of
of the
theCZCS,
CZCS, large-scale
large-scale
temporal and
and spatial
is necessary.
necessary. This
set
spatial averaging
averaging is
This averages
averages
set has
has been
been reprocessed
reprocessed[Feldman
[Feldman et
et al.,
al., 1989]
1989] using
using a
a temporal
over
gaps
in
the
data
set
due
to
clouds
and/or
standard
epsilon
value
and
a
multiple
Rayleigh
scattering
lack of
of
standard epsilon value and a multiple Rayleigh scattering over gaps in the data set due to clouds and/or lack
collection effort
effort but
but obviously
reduces the
the amplitude
algorithm
in the
the atmospheric
atmospheric correction.
obviously reduces
amplitude of
of
algorithmin
correction.One
Oneof
of the
theproducts
products collection
McGowan [1986]
and Thomas
Thomas and
and Strub
and
McGowan
[1986] and
Strub [1989,
[1989, 1990]
1990] and
compared to
to wind
by Strub
A detailed
detailed
compared
wind forcing
forcing by
$trub et
et al.
al. [1990].
[1990]. A
description and
analysis will
will not
not be
be repeated
repeated here.
here. However,
However,
description
and analysis
a recalculation
a
recalculation of
of this
this variability
variability in
in the
the CCS,
CCS, warranted
warranted by
by
the recent
the
recentavailability
availability of
of the
the complete,
complete,global,
global,reprocessed
reprocessed
shorter time
of
is aa set
time scale
scale events.
events. To
To accomplish
accomplishthis,
this,8-month
8-month
of this
this reprocessing
reprocessingis
setofofglobal
globalfields
fieldsof
ofpigment
pigment shorter
concentration
km, composited
composited
concentrationwith
with aa spatial
spatialresolution
resolutionof
of 20
20 km,
within
calendar
months.
This
image
set
was
subsampled
to
within calendar months. This image set was subsampledto
provide
two
time
series
of
92
monthly
images
each,
extendprovide two time seriesof 92 monthly imageseach, extending
ing over
over the
theentire
entireCZCS
CZCS lifetime,
lifetime,from
fromNovember
November1978
1978to
to
June
One series
series covers
June1986.
1986. One
coversthe
the Peru
PeruCurrent
Currentregion
regionfrom
from6°
6ø
to
and the
the second
to 51°S,
51øS,and
secondcovers
coversthe
the California
California Current
Current region
region
from
from 21°
21 ø to 48°N.
48øN.
composite images
images temporally
temporally centered
centered on
on the
the midpoint
composite
midpoint of
of
summer
in
each
hemisphere
were
formed
within
each
year of
of
summerin each hemispherewere formed within each year
data coverage.
data
coverage. For
For the
the California
California Current,
Current, the
the8-month
8-month
summer
composite image
image in
in each
each year
year is
summer composite
is of
of months
months March
March
through October.
October. For
For the
through
the Peru
Peru Current,
Current, the
the8-month
8-month comcomposite image
was formed
posite
image was
formed from
from the
the months
months September
September
through April.
April. The
The resultant
resultant image
image time
time series
series extends
extends over
over
through
THOMAS
ET AL.'
AL.: PERU
CURRENT
PIGMENT
VARIABILITY
THOMAS
ET
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
I
[
I
] j[
]
I
7357
7357
I
a
45N
45N -
PACIFIC
REGION
ClFICNORTHWEST
NORTHWEST
REGION
40N
40N
CENTRAL CALIFORNIA REGION
-
'.....
NORTHERN
CHILE
tillZSS
4
35N -
35N
1
SOUTHERN CALIFORNIA BIGHT
SOUTHERN
CALIFORNIA
BIGHT•
_
•NTRAL C•
30N J30N
-
,
_
25N -
BAJA CALIFORNIA
REGION
BAJA
CALIFORN• REGION
125W
120W
115W
- SOUTHERN
CHILE-'
110W
125W 120W 115W 110•
I
I
I
I
(a) The
The California
California Current
Current system
system and
and (b)
(b)the
the Peru
Peru Current
Current system
system study
study areas
areas showing
the
Figure
Figure 1.
1. (a)
showingthe
regions
within which
which image
image data
data were
were spatially
averaged to
to extract
regionswithin
spatially averaged
extract seasonal
seasonaland
andinterannual
interannualvariability.
variability.
The
lines show
show the
the three
three 100-km-wide
stripsparallel
parallelto
tothe
the coasts
coasts extending
extending offshore
offshore and
and the
the extents
extents
The solid
solid lines
100-km-widestrips
of
four regions
regions used
used to
to illustrate
illustrate interannual
interannual variability.
of four
variability. The
The dashed
dashedlines
lines indicate
indicate the
the system
systemof
of 100
100 xx 100
100
km boxes
boxes used
used to
to spatially
average the
the image
image data
data for
for presentation
presentation of
of mean
mean seasonal
seasonal cycles.
cycles.
km
spatially average
8 years
8
years in
in each
each study
study region.
region. For
For the
the CCS,
CCS, the
the 1986
1986
compositeisis from
from March
Marchtoto June,
June, and
and for
for the
composite
the PCS
PCS the
the
1978-1979
composite is
is from
from November
November to
1978-1979 composite
to April.
April.
Quantitative analysis
Quantitative
analysisof
of interannual
interannualvariability
variability in
in pigment
pigment
concentration
was
carried
out
by
subsampling
and
concentration was carried out by subsampling and spatially
spatially
averaging within
within these
these 8-month
composite images
images to
to derive
averaging
8-month composite
derive
mean concentrations.
concentrations. These
These were
were calculated
calculated over
over each
each of
mean
of
four latitudinal
latitudinal zones
four
zones extending
extending 400
400 km
km or
or more
more alongshore.
alongshore.
An
annual
anomaly
was
formed
by
subtracting
An annual anomaly was formed by subtracting the
the overall
overall
mean concentration
concentration (the
mean
(the mean
mean of
of the
the 8-month
8-month period
period over
over all
all
8
years) for
for each
each zone
zone from
from the
the concentrations
8 years)
concentrationsfound
found in
in each
each
year. The
year.
The sample
sample zones
zones are
are oriented
oriented by
by the
the coastline
coastline in
in the
the
same
manner as
as the
same manner
the smaller
smaller boxes
boxes used
used above
above for
for the
the
seasonal
seasonalcycle.
cycle. To
To illustrate
illustrate cross-shelf
cross-shelfdifferences
differencesin
in interinterannual variability,
variability, each
annual
each latitudinal
latitudinal zone
zone was
was subdivided
subdividedinto
into
three 100-km-wide
areas, and
and aa separate
three
100-km-wide areas,
separate mean
mean was
was calcucalcu-
lated for
for each.
in aa time
each. This
This resulted
resulted
in
time series
series for
for each
each
lated
latitudinal zone
zone and
latitudinal
and each
each of
of the
the three
three offshore
offshore bands
bands (0-100,
(0-100,
100-200,and
and 200-300
200-300km)
km)shown
shownininFigures
Figuresl la
and lb.
lb.
100-200,
a and
is
substantially less.
less. In
is substantially
In many
many months,
months, some
someareas
areasof
of the
thePCS
PCS
are
to 33 years
years of
of data,
data, and
few areas
areas
are represented
representedby
by only
only 2
2 to
and a
a few
in
Lack of
in some
some months
months remain
remain completely
completely unsampled.
unsampled. Lack
of
coverage
is most
coverage is
most severe
severe during
during months
months of
of austral
austral winter
winter
(June,
(June, July).
July). These
These images
images are
are composed
composedof
of data
data from
from only
only
1-2
years.
1-2 years.
-3
Plate
shows that
that concentrations
Plate 11 shows
concentrationsgreater
greaterthan
than2.0
2.0 mg
mgm
m
are
are found
found within
within approximately
approximately 40
40 km
km of
of the
the coast
coastthroughthroughout
out the
the year
year and
and throughout
throughoutthe
thelatitudinal
latitudinalrange
rangeof
of the
theCCS
CCS
study
area.
High
concentrations
(>1.0
mg
m3)
studyarea.
concentrations
(>1.0 mg m-3) extend
extend
farthest
farthest from
from shore
shore off
off northern
northern and
and central
central California
California (ap(approximately
340
to 43øN)
43°N)and
and to
to aa lesser
proximately 34
ø to
lesserdegree
degreeoff
off Baja
Baja
California
(south of
California (south
of 30°N).
30øN). Higher
Higher pigment
pigment concentrations
concentrations
remain
most
closely
associated
with
the
coast throughout
throughout the
remain most closely associatedwith the coast
the
year
and southern
year in
in the
the California
California Bight
Bight and
southern California
California regions.
regions.
High
concentrations(>
(>1.0
mg m
m3)
farHigh concentrations
1.0 mg
-3) appear
appearto
toextend
extend
far-
thest
thest from
from shore
shore in
in November,
November, December,
December, and
and January,
January,
forming
diffuse pattern
pattern off
off northern
northern and
and central
forming aa diffuse
central California
California
with
these values
with no
no strong
strong zonal
zonal gradients.
gradients. Although
Although these
values from
from
late
and early
early winter
winter may
may continue
continue to
to be
be contaminated
contaminated by
late fall
fall and
by
incompletely
removed atmospheric
effects
[Strub
et
al.,
incompletely
removed
atmospheric
effects
[Strub
et
al.,
3.
Results
3. Results
1990],
in the
the appendix
appendix we
we estimate
estimate the
1990], in
the maximum
maximum magnitude
magnitude
3.1.
3.1. Seasonal
SeasonalCycles
Cycles
of
m3-3south
ofof40°N,
of such
sucherrors
errorsto
to be
beless
lessthan
than0.15
0.15 mg
mg m
south
40øN,
The multiyear
to 0.4 mg m
m3
risingto
-3 or
orless
lessatat48°N.
48øN.In
InFebruary
Februarythese
these
The
multiyear means
means of
of pigment
pigment concentration
concentration for
for each
each rising
month
the calendar
highest concentrations
concentrations are
are closer
closer to
to shore
this region,
month of
of the
calendar year
year are
are shown
shown in
in Plates
Plates 11 and
and 22 for
for highest
shore in
in this
region, but
but
the California
Current and
in March
March they
they appear
appear to
the
California Current
and Peru
Peru Current
Current regions,
regions, respecrespec- in
to extend
extendup
up to
to 700
700 km
km offshore
offshore again,
again,
tively. Spatial
resolution in
in these
these composites
composites is
is the
the 20
20 xx 20
as shown
and Strub
[1989]. In
In April
April the
shown by
by Thomas
Thomas and
$trub [1989].
the diffuse
diffuse
tively.
Spatial resolution
20 as
pattern of
concentrations appears
km
of the
the original
global data
data set.
km pixel
pixel dimensions
dimensions of
original global
set. A
A pattern
of offshore
offshorehigher
higher concentrations
appearsto
toconsolconsolpresentation
idate closer
closer to
to the
the coast.
coast. By
the highest
concentrations
By May
May the
highest concentrations
presentation of
of the
the number
number of
of years
years(samples)
(samples)which
which make
make idate
up
each
pixel
in
each
monthly
mean
is
given
in
Figures
2
and
are
within
approximately
200
km
of
the
coast,
up each pixel in each monthly mean is given in Figures 2 and are within approximately 200 km of the coast, and
andaarelarelatively sharp
sharp frontal
3.
frontal gradient
gradient separating
separatinghigher
higher pigment
pigment concon3. In
In general,
general, pixel
pixel values
valueswithin
within the
themonthly
monthly composite
composite tively
images of
of the
the CCS
CCS are
are from
from 55 or
or more
more years
years of
centrations from
from very
very low
concentrations is
low offshore
offshore concentrations
is estabestabimages
of data.
data. As
As was
was centrations
previously stated,
stated, Figure
lished. In
In June
June this
takes on
this gradient
gradient takes
on aa scalloped
scalloped shape
shape off
off
previously
Figure 33 shows
showsthat
that coverage
coverageof
of the
the PCS
PCS lished.
THOMAS
ET AL.'
AL.: PERU
CURRENT
PIGMENT
VARIABILITY
THOMAS
ET
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
7358
7358
3.13
3.13
•..
[CHL]
ß
.
-
45N
-
40I
"
1.04
mgm-3
1.04
0.31
0.31
ß
I
- 35N
35N
-
0.06
- 30N
30N
-
-
25N
25W
•IAN
FEB
MAR
APR
MAY
[CHL]
mgm-3
JUN
I
3.13
3.13
1.04
1.04
0.31
0.31
-
I
35N
ø•"-'•'
"k, O.06
30N
- 30N
-
--
25N
25W
JUL
AUG
SEP
OCT
NOV
DEC
pigment concentration
concentration and
and spatial
spatial distribution
distribution along
along the
the west
west coast
coast
Plate
Plate 1.
1. The
The mean
mean seasonal
seasonalcycle
cycle of
of pigment
of North
(the entire
entire CZCS
global data
data set)
of
North America.
America. The
The images
images are
are 8-year
8-year composites
composites (the
CZCS global
set) of
of monthly
monthly
satellite-measured pigment
pigment concentration
concentration in
satellite-measured
in each
eachcalendar
calendarmonth
monthfrom
from the
theCZCS
CZCS 20-km-resolution
20-km-resolutionglobal
global
data set.
set.
data
central and
This zonal
zonal gradient
gradient remains
remains
central
and northern
northern California.
California. This
relatively steep
steep until
until September.
From May
relatively
September. From
May through
through SepSeptember, patterns
tember,
patterns off
off the
the Oregon
Oregon and
and Washington
Washington coasts
coasts
appear
relatively stable,
stable, with
with highest
highest concentrations
concentrations extendextendappear relatively
ing approximately
approximately 100
km offshore.
offshore. Off
Baja, relatively
relatively high
ing
100 km
Off Baja,
high
concentrations extend
extend farthest
concentrations
farthest from
from shore
shore(approximately
(approximately
200 km)
km) in
inMay
Mayand
andJune.
June. The
The gradient
gradient between
between low
low offshore
offshore
200
concentrations
and
higher
coastal
concentrations
is
concentrations and higher coastal concentrations is stronstrongest from
from February
February until
gest
until July.
July.
Inspection
of the
Inspection of
the individual
individual monthly
monthly images
images (not
(not prepresented
which make
make up
up these
these multiyear
multiyear means
means indicates
indicates
sentedhere)
here) which
that
that the
the relative
relative strengths
strengthsof
of the
the zonal
zonal gradients
gradients described
described
above
above are
are determined
determinedprimarily
primarily by
by interannual
interannual variability
variability in
in
the
concentration gradient
gradient than
the position
position of
of aa larger
larger pigment
pigment concentration
than
that
that evident
evident in
in these
these figures.
figures. The
The consistently
consistently lower
lower zonal
zonal
concentration
concentrationgradients
gradientswhich
which appear
appearin
in the
the multiyear
multiyear means
means
does
does not
not represent
represent the
the strength
strengthof
of the
the gradient
gradient on
on any
any given
given
year.
year.
A general
general mean
mean seasonal
seasonal cycle
cycle of
of pigment
pigment patterns
patterns in
in the
the
A
Peru Current
Current (Plate
to discern
Peru
(Plate 2)
2) is
is more
more difficult
difficult to
discern owing
owing to
to
lack of
of data.
data. The
The mean
mean images
images over
over the
the latitudinal
latitudinal extent
extent of
of
lack
the PCS
PCS for
for each
each month
month indicate
indicate that
that there
the
there are
are two
two regions
regions
THOMAS
ET AL.:
CURRENT
PIGMENT
VARIABILITY
THOMAS
ET
AL.: PERU
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
7359
7359
•:-_::::-:-:
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::::::::::::::::::::::::::::::::::::::::::::::::::::::
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::::::::::::::::::
=============================================================
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::::::::5:::::::::
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================================================
....:::::::::::::::::::::::::::::::::::::::::::::::::::::::
==============================================================
...=======================================================
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.--.:-:.:.:.:.:.:-:.:-:.:.:.:.:.:.:.:.:.:.:.:.:.:-:-:.:.....
--.-.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.........:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.....
===============================================================
===========================================
..........................................................
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::::::::::::::::::::::::::::::::::::::::::::::::::::
================================================
•:::.::::::'.
R1-2
3-4
•:::
:::::::'•:•::::::::::::::::::::::::::::::::::::::::
=========================================================
-:::
:::::::::::::::::::::::::
::::':::::::::::::::
:::::::::::::
:::::::
:::::
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::::':'":'•i•::•:'.•:::::":•::
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.:::::::::::::::::::::::::.•::::::::::::::::::•::::::::::.:.:.:.:.::::::•:::::::::::::::::::::•:•:•::::::::::::::::::::::::::.:::::.:.::::::::::::::::::::::::::::::::::•:::::::::::::::::::::::::..::......:::::::•::.::::::•:•:::•::::::::::::::
.....
JLtATJG
SEP
OCT
NOV
DEC
of data
data points
which make
make up
up each
each of
in
Figure
Figure2.
2. The
Thenumber
numberof
points(years)
(years)which
of the
themean
meanmonthly
monthlycomposites
composites
in
Plate
Plate 1.
1.
where
where zones
zones of
of higher
higher pigment
pigment concentrations
concentrations (>1.0
(>1.0 mg
mg
m -3)
3) closely
closely associated
associated with
the coast
coast are
throughm
withthe
arepresent
present
throughout the
out
the year.
year. The
The first
first region
region is
is north
north of
of 18°S
18øSalong
along the
the
Peruvian
coast, and
Peruvian coast,
and the
the second
secondis
is south
southof
of 30°S
30øSalong
along the
the
central and
central
and southern
southern Chilean
Chilean coast.
coast. Along
Along the
the Peruvian
Peruvian
coast, highest
and the
coast,
highest concentrations
concentrations and
the farthest
farthest offshore
offshore exextension of
of these
these concentrations
tension
concentrations appear
appear to
to occur
occur during
during the
the
austral summer
summer (December-March),
(DecemberMarch),with
withfall
fall(i.e.,
(i.e.,AprilApril
austral
km offshore.
offshore. ItIt is
km
is not
not possible
possible to
to determine
determine from
from the
the availavailable
data set
patch or
or
able data
set whether
whether this
this is
is aa spatially
spatially isolated
isolated patch
simply
the cloud-free
cloud-free portion
portion of
of aa more
more extensive
simply the
extensive region
region of
of
high
concentrations. Extreme
Extreme cloud
cover and
high concentrations.
cloud cover
and lack
lack of
of data,
data,
especially
during austral
austral winter,
winter, prevent
prevent aa better
especially during
better description
description
of
in this
this most
most equatorial
portion of
of the
the study
of seasonality
seasonality in
equatorial portion
study
area.
to
area. Along
Along the
the coast
coastof
of northern
northernChile
Chile (approximately
(approximately18°
18øto
30°S),
30øS), aa region
region of
of relatively
relatively low
low pigment
pigment concentrations
concentrations
June)
June) concentrations
concentrationsmore
more closely
closelyassociated
associatedwith
with the
the coast.
coast.
While lack
lack of
of data
data makes
makes the
the winter
While
winter concentrations
concentrations difficult
difficult
to interpret,
an area
to
interpret, from
from May
May through
through August
August an
area of
of increased
increased
concentrations centered
concentrations
centered at
at 15°S
15øSextends
extends approximately
approximately 200
200
winter
(JulySeptember). Concentrations
winter (July-September).
Concentrations in
in this
this region
region do
do
not
farther north
not reach
reach those
those found
found either
either farther
north or
or farther
farther south.
south.
(often
throughout
the
(often<0.3 mg
mg m3)
m-3)persists
persists
throughout
theyear,
year,with
with
slightly
elevated concentrations
concentrations appearing
appearing in
in the
slightly elevated
the austral
austral
THOMAS ET
ET AL.'
AL.: PERU
CURRENT
THOMAS
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT PIGMENT
PIGMENT VARIABILITY
VARIABILITY
7360
7360
3.13
3.13
[CHL]
-
-3
10S
mc3m
3. 04
1.04
-
20S
-
30S
0.31
0.31
0.06
0.06
-
40S
_
50S
APR '•'
JAN
MAY"'"
.JUN
I
lOS
-
20S
-
30S
-
40S
_
50S
3.13
3.13
1.04
1.04
0.31
0.31
I
Plate 2.
Plate
2.
UL
•
A .•
SEP
OCT '
0.06
0.06
NO
The
of pigment
pigment concentration
concentration and
and spatial
spatial distribution
distribution along
along the
the west
west coast
coast
The mean
mean seasonal
seasonalcycle
cycle of
of South
South America.
of
America.
Very low
are present
Very
low pigment
pigment concentrations,
concentrations,similar
similar to
to open-ocean
open-ocean nearshore
nearshore concentrations
concentrations are
present throughout
throughout the
the year.
year.
offshore extension
extension (up
(up to
concentrations far
far offshore
in the
concentrations
offshore in
the southern
southern Pacific,
Pacific, often
often Maximum
Maximum offshore
to 400
400 km)
km) of
of these
theseconconintrude to
within 40
40 km
km of
of the
the coast
coast during
during all
all months
months except
except centrations
centrationsappears
appearsto
to occur
occurduring
duringaustral
australsummer
summerininJanJanintrude
to within
July,
July, August,
August, and
and September.
September.Along
Along the
the southern
southernChilean
Chilean uary
uary and
and March.
March. Offshore
Offshoreextension
extensionappears
appearsto
to be
beminimum
minimum
coast (south
higher pigment
pigment concentrations
concentrations persispersis- in
July, and
coast
(south of
of 30°S),
30øS),higher
in winter
winter (May,
(May, July,
and August),
August), with
with a
a second
secondextension
extension
tently extend
extend up
in aa region
region centered
centered at
at offshore
evident in
in September.
tently
up to
to 200
200 km
km offshore
offshorein
offshore evident
September.
approximately 37øS
37°S during
during austral
austral fall,
fall, winter,
winter, and
A
more quantitative
quantitative presentation
presentation of
of the
the seasonal
seasonal cycles
approximately
and spring.
spring.
A more
cycles in
in
The
in Figures
Figures 44 and
and 5.
5. Variability
The July
July image,
image,showing
showingrelatively
relatively high
highconcentrations
concentrations the
the CCS
CCS and
and the
the PCS
PCS is
is given
given in
Variability
extending north
north of
of 37°S
and up
up to
to 400
km offshore,
offshore, results
results is
as contours
concentration in
in time
time and
and
extending
37øSand
400 km
is shown
shown as
contours of
of pigment
pigment concentration
from
over the
the extent
extent of
of each
latitude over
each EBC
EBC for
for each
each of
of three
three
from only
only 2
2 years
years of
of data
data(1979
(1979and
and1981),
1981), making
making it
it latitude
impossible
to determine
how well
100-km-widezones
zonesextending
extendingoffshore.
offshore. Averaged
Averaged over
over the
the
impossibleto
determine how
well this
this pattern
patternrepresents
represents 100-km-wide
mean July
July conditions.
conditions. Between
and 51°S,
relatively high
high 100-km-'wide
100-km-widezone
zoneclosest
closestto
to shore
shore (Figure
(Figure 4a),
4a), two
two regions
mean
Between370
37ø and
51øS,relatively
regions
THOMAS ET
ET AL.:
AL.: PERU
CURRENT
PIGMENT
VARIABILITY
THOMAS
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
7361
l-2
1-2
3-4
•,::::•i•:i:i•:ii::i•,:ii
3-4
ß
'•-::::•;.-'--..-•ii:
:'::.:':?-:•:..::7-•:':•.'•
ß
:.:.::::::::::::.:
>4
':'"i::•:i.:.•:
.•i.•'"
....-
..................
.
:::::::::::::::::::::::::::::::::::::
..
ß
Figure
Figure 3.
3. The
The number
number of
of data
data points
points(years)
(years) which
which make
make up
up each
each of
of the
the monthly
monthly composites
compositesin
in Plate
Plate2.
2.
Calculations
are the
the same
same as
as those
those for
for Plate
Calculations are
Plate II and
and Figure
Figure 2.
2.
of
cycles, and
of the
the CCS
CCS have
have relatively
relatively strong
strong seasonal
seasonalcycles,
and two
two
regions
regionsshow
show weaker
weaker seasonal
seasonalvariability.
variability. A
A region
regionof
of strong
strong
variability
to 30°N
variability reaching
reachingfrom
from approximately
approximately 22°
22ø to
30øN is
is cencentered
the Baja
tered at
at 26°N
26øN along
along the
Baja coast,
coast, and
and aa second,
second,reaching
reaching
from
to 45øN,
45°N, is
is centered
centered at
from approximately
approximately 340
34ø to
at 40°N
40øN along
along
the
the central
central and
and northern
northernCalifornia
California and
and southern
southernOregon
Oregon
concentrations
increase, beginning
beginningearliest
earliestinin the
the year
concentrations increase,
year at
at
37°N.
By May,
May, concentrations
concentrationsgreater
greaterthan
than3.0
3.0mg
mgmm3
37øN.By
-3 are
are
found
throughout this
this region.
region. Highest
Highest concentrations
concentrations appear
found throughout
appear
to
at 37°N
in summer.
North of
to remain
remain longest
longest at
37øN in
summer. North
of 45°N,
45øN, the
the
relatively
weak,
with
CZCS-estimated
seasonal
cycle
is
seasonal cycle is relatively weak, with CZCS-estimated
mean pigment
pigment concentrations
concentrations within
within 100
100km
km of
of the
the coast
mean
coast
-3
coasts.
Baja, mean
mean concentrations
concentrationsare
are <1.5
<1.5 mg
mg m
m3
remaining
above3.0
3.0mg
m3
the
coasts. Off
Off Baja,
remaining
above
mgm
-3 throughout
throughout
theyear.
year.Maximum
Maximum
from
through the
the winter
(>4.0 mg
mg m
m3)
from August
August through
winter into
into March.
March. By
By April,
April, concentrations
concentrations
(>4.0
-3)within
withinthis
thisregion,
region,however,
however,
concentrations
are
2.0
mg
m
and
increase
to
a
maximum
also
occur
during
summer
months.
Within
concentrations
are2.0 mgm-3 andincrease
to a maximum also occur during summer months. Within the
the Southern
Southern
of >3.0 mg
Between
central
California
Bight region
region (centered
(centered at
mg m3
m-3ininMayJune.
May-June.
Between
central
California California
California Bight
at approximately
approximately 32°N),
32øN),
and
and central
central Oregon,
Oregon, concentrations
concentrationsare
are approximately
approximately 2.0
2.0 the
the seasonal
seasonalcycle
cycle is
is also
alsorelatively
relatively weak.
weak. Concentrations
Concentrations
mg
September until
February. In
boxes do
averaged within
within the
the 100-km-wide
100-km-wide boxes
do not
not fall
fall below
below 0.5
0.5
mgm
m-3 from
fromSeptember
untilFebruary.
InMarch
Marchand
andApril,
April, averaged
7362
THOMAS
ET AL.:
CURRENT
PIGMENT
THOMASET
AL.' PERU
PERUAND
ANDCALIFORNIA
CALIFORNIA
CURRENT
PIGMENTVARIABILITY
VARIABILITY
7362
48
48
48
46
48
46
44
44
44
44
42
42
42
40
40
40
.0
38
'
40
36
3[5
i
36
36
34
•i 34
32
32
-
38
36
'
34
32 ;,;,,,,•.
5•.
.
i
'
34
5•
i
.
.
32
30
3O
3030
28
28
28
26
26
26
26
24
24
24
22
22
22
30
,,
.
NDJ
a(]
FM
AMJ
J
AS
OND
JF
NDJ F
b
b
0 - 100 KM OFFSHORE
100 -- •oo
200 n•
KM on,
OFFSHORE
•oo
s•o•.
.
NDJ FM AMJ I AS OND IF
c
OFFSHORE
200 - •oo
300 KM
•oo
• o•s•o•s
C
Figure 4. The mean seasonal cycle of surface pigment concentration in the California Current system.
Figure4. Theare
mean
seasonal
cycle
ofsurface
pigment
concentration
intheCalifornia
Current
system.
Concentrations
of
pigment
per
within
Concentrations
aremilligrams
milligrams
ofsatellite-measured
satellite-measured
pigment
percubic
cubicmeter
meterand
andare
aremeans
means
within
100-km-wide
zonesoriented
orientedparallel
parallelto
tothe
the coast
coast and
and contoured
contoured in
in time
time and
and latitude.
latitude. Data
Data were
sampled
100-km-wide
zones
were
sampled
from
shown
in
11and
Figure
22by
within
100
X 100 km areas oriented along the
fromthe
theimages
images
shown
inPlate
Plate
and
Figure
byaveraging
averaging
within
100x
100kmareas
oriented
along
the
coast
coast (see
(see Figure
Figure 1).
1).
mg m
the late
fall, and
and winter
winter and
and rise
rise to
to a scattering
mg
m-3 in the
latesummer,
summer,
fall,
scattering algorithm;
algorithm; and
and differences
differences in
in the
the land
landmasking
masking
maximum
of less
less than
than 2.0mg
in May
May and
and June.
June. Of
the processing
of
the two
maximum
of
2.0mgm
m-3 in
Of note
note used
usedin
in the
processing
of the
two data
datasets,
sets,which
whicheliminated
eliminated
is
is the
the fact
fact that
that no
nowinter
wintermaximum
maximumis
is found
found in the
the Southern
Southern some
concentrations next
next to the coast
some high pigment concentrations
coastin
in the
the
California
Bight in
in the
the reprocessed
CZCS
CaliforniaBight
reprocessed
CZCSglobal
globaldata
dataset.
set. previous
previousstudy.
study.
This
which
This is
is in
in contrast
contrastto
toprevious
previousanalyses,
analyses,
whichused
useddata
data
In
In the
the regions
regions100-200
100-200 km
km and
and200-300
200-300 km
kmoffshore
offshore
processed
with
atmospheric
4b and
and 4c),
4c), seasonal
seasonal variability
variability is
is minimal
minimal south
south of
of
processed
withthe
thesingle
singleRayleigh
Rayleighscattering
scattering
atmospheric (Figures
(Figures4b
correction
et al.,
al., 32°N.
In this
this southern
southern area,
area, concentrations
greater
correctionand
andfound
foundaa winter
wintermaximum
maximum[Michaelsen
[Michaelsen
et
32øN.In
concentrations
greaterthan
than0.5
0.5
1988].
1988].
mg m
m3
offshore
into
zone
mg
-3do
donot
notextend
extend
offshore
intothe
the200-to
200-to300-km
300-kmzone
Concentrations
over
range
(Figure 4c).
4c). Within
Within the
the 100to
200-km
zone
they
develop
Concentrations
overthe
thelatitudinal
latitudinal
rangeof
ofthe
theCalifornia
California (Figure
100-to 200-kmzonetheydevelop
Current shown
approximately
initially in
in April,
April, centered
centered at
at 27øN.
27°N. In
In May and
and June
June these
these
Current
shownin
in Figure
Figure4a
4a are,
are,on
onaverage,
average,
approximatelyinitially
0.5
than those
reported
by
rub etal.
concentrations are
are present
present throughout
this
portion
0.5mg
mgm
m-3higher
higher
than
those
reported
bySt
$trub
etal.[1990].
[1990]. concentrations
throughout
thissouthern
southern
portion
This
due principally
principally to
to three
three factors:
factors: the
the use
use of
Thisdifference
differenceis due
of of
until
only
of the
theCCS,
CCS,but
butthey
theypersist
persist
untilNovember
November
onlyatat27°N.
27øN.
the
the entire
entire CZCS
CZCS data
data set
setto
tocalculate
calculateconcentrations
concentrationsshown
shown Maximum
offshore
concentrations
(>1.5
and
>1.0
Maximumoffshore
concentrations
(> 1.5and> 1.0mg
mgm
m-3
here
as
previously;
zones)
hererather
ratherthan
thanthe
theuse
useof
ofaasubset
subset
aswas
wasdone
done
previously;in
in the
thetwo
twocross-shelf
cross-shelf
zones)are
arepresent
presentnorth
northof
of32°N
32øNin
in
the
global
CZCS
and
California
in
theuse
useof
ofthe
thereprocessed
reprocessed
global
CZCSdata
datawith
withaamultiple
multiple NovemberJanuary
November-January
andoff
offcentral
central
California
in the
thespring
spring
6
-6
c
-11
-11
-11
-11
-16
-16
-16
-21
-21L
-26
-2
-31
-31
a
-2
-31
ß
-36
-38
-41
-41
-41
-48
-46
-46
NDJ
FM
AMJ
JJ AS
JF
NDJ
FM
AMJ
AS OND
OND
JF
OFFSHORE
0
KM
0 -- 100
100
KMOFFSHORE
-51
b
(
-21
,
-36
-51
'.L.)(
)
51-L)I,
NDJ
AMJ
JJ AS
JF
ND J FM
FM
AMJ
AS OND
0 ND
JF
100
100 - 200
200 KM OFFSHORE
OFFSHORE
NDJ
AMJ
IJ AS
JF
ND J FM
FM
AMJ
AS OND
0ND
JF
C
200
200 - 300
300 KM OFFSHORE
Figure
seasonal
cycle
pigment concentration
concentration in
in the
the Peru
Peru Current
Current system.
Details
Figure5.
5. The
Themean
mean
seasonal
cycleof
ofsurface
surface
pigment
system.
Details
are
are the
thesame
sameas
asfor
for Figure
Figure4.
4.
THOMAS
ET AL.:
CURRENT
THOMAS
ET
AL.' PERU
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT PIGMENT
PIGMENT VARIABILITY
VARIABILITY
7363
7363
(beginning
in March).
March). Lowest
(<1.0 and
the same
and latitudinal
patterns described
(beginning in
Lowest concentrations
concentrations(<1.0
and the
same seasonal
seasonaland
latitudinal patterns
describedabove,
above,
<0.5mg
4b
are
with concentrations
approximately 0.5
0.5 mg
mg m-3 less
less than
<0.5
mgm3,
m-3in
, inFigures
Figures
4band
and4c,
4c,respectively)
respectively)
arepresent
present with
concentrations
approximately
than
initially
in May
May in
in the
the northern
portion of
of the
the study
those in
in the
the zone
zone 100-200
100-200 km
km offshore.
offshore.
initially in
northern portion
studyarea
area those
(north
and extend
extend south
south to
(north of
of approximately
approximately 41°N)
41øN) and
to include
include
the
the whole
whole study
studyarea
areanorth
northof
of32°N
32øNby
by late
late summer.
summer.
Contours
of pigment
in time
Contours of
pigment concentration
concentration in
time and
and latitude
latitude
within
the first
km of
of the
the South
South American
American coast
coast (Figure
within the
first 100
100 km
(Figure
Sa)
5a) indicate
indicate four
four regions
regionsof
of differing
differingseasonal
seasonalvariability;
variability;
however, lack
data (Figure
3) for
for austral
austral winter
winter presents
presents aa
however,
lack of
of data
(Figure 3)
3.2.
3.2.
Interannual Variability
Interannual
Variability
While
details of
of interannual
on time
While details
interannual variability
variability on
time scales
scalesas
as
short as
short
as 15
15 days
days are
are sometimes
sometimespossible
possible to
to resolve
resolve in
in the
the
California
Current system
system [Thomas
[Thomas and
and Strub,
California Current
Strub, 1989],
1989], the
the
sparse CZCS
CZCS data
data set
set over
over the
the Peru
Peru Current
Current prevent
prevent all
all but
but
sparse
severe
for interpretation.
The isolated
peaks of
severe problem
problem for
interpretation. The
isolated peaks
of the
the most
most coarse
coarseestimate
estimateof
ofinterannual
interannualvariability
variability (even
(even
concentrations
greater
during July
July (austral
but they
concentrations
greaterthan
than1.5
1.5mg
mgm
m-3 during
(austral these
these are
are suspect,
suspect, but
they represent
represent all
all that
that can
can be
be done
done
winter) in
in aa relatively
band centered
centered at
at with
winter)
relatively narrow
narrow latitudinal
latitudinal band
with the
the CZCS
CZCS data
data set).
set). The
The concentration
concentration anomalies
anomalies are
are
12°Sand
andin
inOctober
October over
over aa wider
wider latitudinal
latitudinal range
range come
come from
from for
temporal means
means within
within each
each year,
year, centered
12øS
for the
the 8-month
8-month temporal
centered
images
for the
the July-October
JulyOctober period
within each
each of
imagesfor
periodwith
withvery
veryfew
few data
datain
in this
this in
in midsummer,
midsummer, within
of the
the four
four alongshore
alongshoreoriented
oriented
region. Coverage
in Figures
Figures llaa and
and lb,
region.
Coverageimproves
improvesduring
during November
November through
throughMay
May zones
zones shown
shown in
lb, as
asdescribed
describedin
in section
section2.
2.
(austral
summer, and
and fall),
provide an
interannual differences
(austral spring,
spring, summer,
fall), and
and the
the data
data show
showrelarela- These
These anomalies
anomaliesprovide
an index
index of
of interannual
differences
tively high
high values
values in
in spring
spring and
and summer
summer and
and aa decrease
decrease in
fall in
the relative
pigment concentrations
concentrations over
over the
the time
time span
span of
of
tively
in fall
in the
relative pigment
data set
(AprilMay).
(April-May). Since
Sinceupwelling-favorable
upwelling-favorable winds
winds are
are most
most inin- the
the CZCS
CZCS data
set for
for the
the summer
summer period.
period. Because
Because two
two
tense off
zones within
within the
the PCS
latitudinal zones
PCS show
show maximum
maximum seasonal
seasonal
tense
off Peru
Peru in
in winter
winter [Bakun
[Bakun and
and Nelson,
Nelson, 1991]
1991] and
and latitudinal
surface
indicate strongest
strongest upa second
values in
in midwinter,
midwinter, a
secondanomaly
anomaly was
was calculated
calculatedfor
for
surface temperature
temperatureclimatologies
climatologiesindicate
up- values
welling (coldest
(coldest surface
surface temperatures)
temperatures) in
welling
in winter
winter [Weare
[Weare et
et the
the PCS
PCS using
using an
an 8-month
8-month mean
mean centered
centered in
in (austral)
(austral) midmidal., 1980;
Halpern et
al.,
1980; Halpern
et al.,
al., 1992],
1992], it
it seems
seemsmost
most likely
likely that
that winter.
winter. These
These means
means are
are therefore
therefore over
over aa period
period identical
identical to
to
chlorophyll
concentrations
remain
high
during
winter,
that
for
the
CCS
anomaly
calculations.
chlorophyll concentrations remain high during winter, that for the CCS anomaly calculations.
spring,
and summer,
although the
the data
data here
here document
Figure
6 shows
Figure 6
shows the
the pigment
pigment concentration
concentration anomalies
anomalies for
for
spring, and
summer, although
document only
only
the spring
four latitudinal
regions within
within the
the CCS
Northwest,
the
springand
and summer
summerperiods
periodswell.
well.
four
latitudinal regions
CCS (Pacific
(Pacific Northwest,
the Southern
Along the
the northern
Along
northern Chilean
Chilean coast
coastbetween
between18°
18øand
and33°S,
33øS, central
central California,
California, the
Southern California
California Bight,
Bight, and
and Baja
Baja
concentrations are
are less
less than
than 0.5
for each
each of
of the
the three
zones extendCalifornia) for
three 100-km-wide
100-kin-wide zones
extendconcentrations
0.5 mg
mgm
m-3 from
fromNovember
November California)
until April
offshore. Within
Within these
these latitudinal
latitudinal regions
regions the
the patterns
patterns of
ing offshore.
of
until
April (austral
(austral spring
springthrough
throughfall).
fall). Concentrations
Concentrations ing
greater than
are present
present only
July and
and August
variabilityare
are similar,
similar, but
but the
greater
than1.0
1.0mg
mgm
m-3 are
onlyin
in July
August interannual
interannual variability
the amplitude
amplitude dede(winter),
and creases
increasing distance
distance of
of the
the zones
zones from
from shore.
shore. A
creaseswith
with increasing
A
(winter), centered
centeredat
at 28°S.
28øS.In
In aa third
third region,
region, between
between33°
33øand
45°S,
concentrations
less
than
1.0
mg
m3
are
present
from
second
general
feature
is
the
reduced
relative
amplitude
45øS,concentrations
lessthan1.0mgm-3 arepresentfrom second general feature is the reduced relative amplitude of
of
January through
(summer). Maximum
Maximum concentrations
concentrations anomalies
in the
January
through March
March (summer).
anomalies in
the two
two lowest
lowest latitude
latitude regions
regions (Southern
(Southern
(>2.0 mg
m3)
latitudinal
region
are
in
Bight and
and Baja
Baja California).
California). Common
Common to
to all
regions
California Bight
all regions
(>2.0
mgm
-3)ininthis
this
latitudinal
region
arereached
reached
inMay
May California
(fall)
and again
again in
in July
July (winter),
(winter), with
with concentrations
concentrations greater
greater is
is aa negative
negativeanomaly
anomaly in
in 1983,
1983, in
in agreement
agreementwith
with previous
previous
(fall) and
persisting (except
in
at
from
Thomas and
and Strub,
Strub, 1990;
Strub et
than 1.5
studies[Ffedler,
[Fiedler, 1984;
1984; Thomas
1990; Strub
et al.,
al.,
than
1.5mg
mgm
m-3 persisting
(except
inOctober)
October)
at37°S
37øS
from studies
1990;
Abbott and
and Barksdale,
Barksdale, 1991]
that show
1990; Abbott
1991] that
show relatively
relatively low
low
pigment
concentrations during
(the El
pigment concentrations
during 1983
1983 (the
El Nino
Nifio period).
period).
anomaly in
in 1983
is strongest
strongest in
in the
with minimum
concentrations(<1.0
(<1.0mg
mgmm3)
minimumconcentrations
-3) in
in austral
austral The
The negative
negative anomaly
1983 is
the central
central
winter
(MayJuly) and
region and
and is
is accompanied
accompanied by
California region
by aa negative
negativeanomaly
anomaly
winter (May-July)
andconcentrations
concentrationsgreater
greater than
than 1.5
1.5 mg
mg California
m3
spring,
summer
and
in 1984
off Baja
Baja and
and in
in the
of similar
similar magnitude
magnitude in
1984 off
the Southern
Southern
m-3during
during
spring,
summer
andfall.
fall.In
Inthe
thezone
zone100-200
100-200km
km of
June until
June
until December
December (winter
(winter and
andspring).
spring).South
Southof
of45°S
45øSthe
the
seasonal
appears similar
to that
that at
seasonalcycle
cycle appears
similar to
at the
the lowest
lowest latitudes,
latitudes,
offshore
offshore(Figure
(Figure 5b),
5b), differing
differingseasonal
seasonalcycles
cycleswithin
withindifferdiffer-
California
Bight(in
(in the
the 0California Bight
0- to
to 100-km
100-km zone).
zone). This
This latter
latter
ent
regions are
are also
contrasts to
to the
anomaly contrasts
the situation
situation in
in the
the Pacific
Pacific Northwest
Northwest
ent latitudinal
latitudinal regions
also evident.
evident. At
At lowest
lowest latitudes
latitudes anomaly
(equatorward
concentrations are
are highest
region, where
where the
the largest
largest positive
positive anomaly
anomaly occurs
occursduring
during
(equatorward of
of 12°S),
12øS),concentrations
highest(>1.0
(> 1.0mg
mg region,
The largest
largest positive
positive anomalies
in central
m3)
until
and
and
1984. The
anomalies in
central California
California
m-3)from
fromOctober
October
untilMarch
March(spring
(spring
andsummer)
summer)
and 1984.
lowest
from April
April until
until September,
September, although
occur in
in 1981
1981 and
and 1986.
1986.
lowest(<0.5
(<0.5mg
mgm
m_3)
-3) from
although occur
lack
of
data
in
winter
may
obscure
the
true
signal
during
The
interannual
variability
pigment concentration
concentration along
lack of data in winter may obscure the true signal during
The interannualvariability of
of pigment
along
coast is
7 for
for the
the four
four
JulySeptember.
the South
South American
American coast
is shown
shown in
in Figure
Figure 7
July-September.InInaaregion
regioncentered
centeredatatapproximately
approximately15°S,
15øS, the
maximum
annual concentrations
concentrations (>1.0
are reached
reached latitudinal
regions and
and three
three cross-shelf
zones shown
latitudinal regions
cross-shelf zones
shown in
in
maximum
annual
(> 1.0mg
mgm
m_3)
-3) are
in
Figure lb.
lb. In
In discussing
discussingthe
the interannual
interannualvariability
variability off
off Chile,
Chile,
in JuneAugust
June-August(winter),
(winter),and
andconcentrations
concentrationsremain
remainabove
above Figure
0.5
mg m
m3
the
zone
is important
important to
to note
note that
that the
the anomalies
anomaliesduring
during the
the 1983
1983 El
El
0.5 mg
-3throughout
throughout
theyear.
year.In
Inthis
thisoffshore
offshore
zoneany
any itit is
Niflo are
are based
based on
on only
only one
one data
data point
within the
the
seasonal cycle
cycle has
point (1
(1 month
month within
seasonal
has aa relatively
relatively small
small amplitude
amplitudebetween
between17°
17ø Nifio
and 23øS.
23°S. Between
Between 23
23°
and41øS,
41°S,however,
however,there
there is
is an
an austral
austral 8-month
8-month averaging
averagingperiod).
period). Given
Given the
the scatter
and
øand
scatter of
of monthly
monthly
data points
points during
during periods
periods when
when more
more than
than one
one are
are available,
available,
winter maximum
maximum with
with concentrations
concentrations greater
greater than
than 1.0
winter
1.0 mg
mg data
present in July.
concentrations
(>0.5 mg
the most
conclusion isis that
that the
the available
data in
most reasonable
reasonable conclusion
available data
in
m -3 present
m
July.Increased
Increased
concentrations
mg the
associated with
with this
this maximum
begin earlier
earlier and
and persist
persist the
the global
CZCS data
data set
to document
m _3)
global CZCS
set are
are insufficient
insufficient to
document the
the
m
-3) associated
maximum
begin
response to
increasingly longer
longer at
at higher
higher latitudes
latitudes within
to the
the1983
1983El
El Niflo
Nifio off
off Chile.
Chile. The
The negative
negativeanomanomincreasingly
within this
this region.
region.In
In response
off Peru,
Peru, for
for which
which more
more data
data points
points are
are available,
are
the region
south of
the seasonal
seasonal cycle
cycle appears
appears similar
alies off
available, are
the
region south
of 43°S,
43øS,the
similar alies
more
credible.
Off
the
Peruvian
coast,
within
the
first
100
to
that
at
the
lowest
latitudes,
with
highest
concentrations
more
credible.
Off
the
Peruvian
coast,
within
the
first
100
to that at the lowest latitudes, with highest concentrations
km, maximum
positive anomalies
anomalies occur
occur in
in (the
present in
in early
early spring
spring and
and summer
summer(August-October,
(AugustOctober, Janumaximum positive
(the summer
summer
present
Janu- km,
period ending
aryMarch) and
concentrations (<0.5
(<0.5 period
ending in)
in) 1980
1980 and
and 1982,
1982, and
and maximum
maximum negative
negative
ary-March)
andan
anindication
indicationof
of lower
lower concentrations
during austral
austral fall
fall and
and winter
July),
occur in
and 1984.
Farther from
mg m
anomalies occur
in 1979
1979 and
1984. Farther
from shore
shore (100(100mg
m_3)
-3) during
winter(April
(Aprilthrough
through
July), anomalies
to
200and
200to
300-km
zones)
in
this
lowest
latitude
although
the
data
for
most
of
this
latter
period
are
few.
The
to
200and
200to
300-km
zones)
in
this
lowest
latitude
althoughthe data for most of this latter period are few. The
offshore zone
zone 200-300
km from
from the
the coast
region, the
the strongest
strongestsignals
signalsare
are negative
negativeanomalies
anomaliesin
in 1983
1983
offshore
200-300 km
coast (Figure
(Figure Sc)
5c) shows
shows region,
THOMAS
ET AL.:
THOMAS ET
AL.' PERU
PERU AND
AND CALIFORNIA
CALIFORNIA CURRENT
CURRENT PIGMENT
PIGMENT VARIABILITY
VARIABILITY
7364
7364
a
0-100
0-100 KM OFFSHORE
OFFSHORE
4.0
4.0
2.0
t
0
2.0
0.0
-2.0
-
*
o
*
79
79
80
80
4.0
40 2.0 o-
0
o
0
0.0
0 0
• o
Ii
82
83
84
82
83
84
Pac i;fic
f I c Northwest
Pac
Northwest
01
81
0.0
85
85
-2.0
-20
...... •
79
79
I
80
80
I
I
II
82
82
I
I
83
83
2.0-
20
-20
79
I
80
8
I
81
80
81
:
I
83
83
?.
84
84
I
I
B
E
79
79
3.0
3
0
-
1.5
15
-
-1.5
-15
I
85
85
86
83
83
82
82
84
84
0
79
79
0o
o
°
o
I
I
I
81
82
82
83
83
86
0
o
0
o
0
o
•
I
79
79
I
80
80
0o
a__._•_.• .......,_.
81
I
83
83
o
1.0
I
84
84
I
85
85
8
86
I
79
79
calculated
for each
each year
year
calculatedfrom
from the
the 8-month
8-monthcomposite
compositeimage
imagefor
formed
formed from
from all
all 20-km
20-km pixels
pixels available
availablewithin
within the
the 8-month
8-month
period.
period. Individual
Individual months
months with
with large
large amounts
amountsof
of missing
missing
data
data would
would therefore
therefore contribute
contribute little
little to
to the
the 8-month
8-month anomanomaly,
points in
in the
the
aly, although
althoughthey
they would
would appear
appearas
asindividual
individual points
figure
for the
the year
year in
figure for
in question.)
question.)
1.0
10
-
85
85
86
0
o
o
...............
0
I
80
80
81
83
83
82
82
0
o
0
o
8o
o
-..... ..-
S-0
6
-1 .0
I
E
• -1 0 79
79
2.0
2
0
84
84
Pacific
Pac; fic Northwe,t
Northwest
0.0
•
E
0
0
0.0
-1
-1.0 .0
' o
0
e
the
the monthly
monthly values
values presented
presented in
in the
the figure.
figure. They
They were
were
central
centralChile,
Chile, the
thepositive
positiveanomaly
anomalyin
in1983
1983becomes
becomesincreasincreasingly
ingly strong
strongwith
with distance
distancefrom
from shore.
shore.
I
82
82
2.0
anomalies
of
anomaliesshown
shownby
by the
the solid
solidcurve
curveare
are not
not aa simple
simplemean
mean of
from
from shore.
shore. At
At the
the highest
highestlatitude
latitude region
region of
of the
the PCS,
PCS, off
off
southern Chile,
Chile, the
the strongest
strongest signal
signal in
in all
all three
three zones
zones is
is aa
southern
positive
positive anomaly
anomalyin
in 1981.
1981. This
This is
is accompanied
accompaniedby
by positive
positive
anomalies
in 1982
and 1983.
1983.InIn aa trend
trend similar
to that
that off
anomalies in
1982 and
similar to
off
886
200-300
KM
200-300
KM OFFSHORE
OFFSHORE
C
c
2.0
2.0 -
anomaly
anomalyin
in 1982,
1982, with
with aa positive
positiveanomaly
anomalyin
in1983
1983becoming
becoming
increasingly
increasinglysimilar
similar to
to that
thatof
of1982
1982with
with increasing
increasingdistance
distance
85
85
Baja
Ba3a California
California
indicates
one or
or more
indicates one
more values
values off
off scale.
scale. (Note
(Note that
that the
the
and
and 1984
1984 and
and positive
positive anomalies
anomalies in
in 1982.
1982. Anomalies
Anomalies off
off
northern
northern Chile
Chile are
are the
the weakest
weakest in
in the
thefour
four regions
regionsand
and are
are
generally
generally positive
positive in
in 1981,
1981, 1982,
1982, and
and1983
1983and
and negative
negativein
in
other
years.
Off
the
central
Chilean
coast
the
other years. Off the central Chilean coast thestrongest
strongest
relative
in all
relative signal
signal in
all three
three cross-shelf
cross-shelfzones
zones is
is aa positive
positive
0....
Southern
California
Bight
Southern
California
Bight
Baja
Baja California
Cal ifornia
Eight-year time
time series
Figure
Figure 6.
6. Eight-year
series(solid
(solidcurve)
curve)of
of anomalies
anomalies
of
of pigment
pigment concentration
concentrationwithin
within three
three offshore
offshorezones
zones and
and
four
four latitudinal
latitudinal regions
regionsof
of the
the California
California Current
Current system
system(see
(see
Figure
Figure 1).
1). Units
Units of
of the
theanomalies
anomaliesare
aremilligrams
milligramsof
of pigment
pigment
per
per cubic
cubic meter
meter and
and are
arean
an8-month
8-monthmean
meanconcentration
concentration
(centered
(centeredon
on midsummer)
midsummer)minus
minusthe
the 8-year
8-year average
averageof
of these
these
concentrations
for that
that zone.
concentrationsfor
zone. Note
Note the
thechange
changeof
of scale
scalefor
for
the
the anomalies
anomaliesas
as distance
distancefrom
from shore
shoreincreases.
increases.Data
Data points
points
indicate
indicate the
the range
range and
and number
numberof
ofactual
actualmonthly
monthlymeans
means
available
the 8-month
8-month period
period in
in each
each year.
year. An
An asterisk
asterisk
availablewithin the
o
I
I
84
84
00•.....•....•.....o .''
85
0
õ
80
80
1.5
15
-1 .5
-15
84
e86
0
0.0
83
85
85
Central
California
Central
Cal iforn;a
3.0 -
0
82
8
86
6
00
84
84
I
85
85
0
E -1 .5
0
8
0
0
o.ek.4
0
o
o
o
0
0.00
Southern California
Bight
Southern
California
Oigh•
4
I
82
82
0
..... • --9•L•$
.....
81
I
81
Pacific
Northwest
Pacific
Northwest
15
o
0.0
I
80
80
-
1.5
0
o
Central
Cen•nai California
Cal ;fornia
2.0
20
79
79
3.0
30
82
83
84
85
-2 0 79
79 80
80 0181 82
83
84
85
86
4.0
40
-1
-15 .5
8
86
0
a
-2.0
15
o •o
0
0
0
0
6õ
3.0
3 0
0
0
100-200
KM OFFSHORE
100-200
OFFSHORE
b
-
I
I
I
I
Central Cal
Centra•
Cal ifornia
;fornia
0
o 88
o
0
I
80
81
85
8
80
81 82
82 83
83 84
84 85
86
0
•' 1.0610o
I
8
0.0.-.....0....i
o
0
ß 0
8
-p
0
1
00 .....•....o ...q....H.•
-1.0
-lO
o
6
79
79
I
80
II
81
I
I
82
82
84
84
83
83
85
85
8
86
Southern
California
Bight
Southern
California
Bight
2.0 1.0
0
0.0
0 I-.'
-•I -.......
-1
-1 .0
o
79
79
I
80
80
0o
•'
'•' .....
I
81
a
w
I
82
-
-I--- .•.
,..
I
83
83
' ' ''
C .....
I
84
84
Baja
Ba j a California
Ca t i forn i a
Figure
Figure 6.
6. (continued)
(continued)
.,
I
85
85
- - -
-u
86
86
7365
7365
THOMAS ET
ET AL.'
AL.: PERU
THOMAS
PERU AND
AND CALIFORNIA
CALIFORNIA CURRENT
CURRENT PIGMENT
PIGMENT VARIABILITY
VARIABILITY
0-100
0-100 KM
KM OFFSHORE
OFFSHORE
a
4.0
4.0
2.0
*
:0
oO
8
0
2o
o.•
0
79
79
80
80
81
8
8
9
'
I
82
82
83
83
84
84
Peru
4.0
4
0 -
Peru
-
,
E
-2.0
-2 0
....
79
I
80
80
I
I
81
•- ........
85
85
I
I
82
82
-1.55
•
II
II
I
84
84
85
85
8
-1.55
-1
I
86
B
E
E
0o
0.0
0.0
-2
0
-2.0
79
79
80
80
81
4.0
0
4
,
02
82
Centrat
Central
85
81
82
----.,
-
•
I
-
I
80
80
.
I
79
7g
80
80
81
86
I
I
I
I
84
84
03
83
1
.---,',_.•...
Northern
Northern
Chile
Chi[e
I
I
85
85
T
886
....
80
80
82
82
81
-
83
83
Central
,
04
84
85
85
86
86
85
85
86
86
Chile
Oh i le
0
0.0
o o
0
I
82
82
I
I
1.55
0
•
82
82
81
81
1
I
85
_
... ....
0
-2.0
-2
0
84
-
79
79
3.0
3
0
0
0.0
0 0
83
.....
8
86
o
2.0
2 0
-:
Peru
79
79
1.5
I
83
84
83
84
Chile
Chile
80
bO 3.0 1.5
1 5
I
79
79
0.0 -___
2
2.00
°o
-0 -_.r00 , _._,.,
• - • ..•. o
0
83
83
8
0o
0
3.0
30 1.5 -
NortI,ern Chile
Nor"•:h,),ern
Chi [ e
4.0 -
1.51 5
-1
886
*
ß
-c-.----
*
0.0
-o
2.0
0 0
0
3.0
-
3
0
o
0.0
0 0
-2.0
-2.0
100-200
KM
100-200
KM OFFSHORE
OFFSHORE
b
-1 .55
I
-1
83
83
84
84
85
85
86
86
79
79
80
I
84
84
Southern
Chile
Southern
Chi l e
Southern
Chile
Sou f. hern
Ch i[e
Eight-year time
time series
FIgure
Figure 7.
7. Eight-year
seriesof
of anomalies
anomaliesof
of pigment
pigment
concentration
concentrationwithin
within four
fourlatitudinal
latitudinalregions
regionsfor
for each
eachof
of three
three
cross-shelf
zones
in
Peru
Current
system
(see
Figure
1).
cross-shelf
zones
inthe
the
Peru
Current
system
(see
Figure
1).CC
The
The solid
solid curves
curvesrepresent
representanomalies
anomaliescalculated
calculated from
from the
the
8-month period
period (September-April)
(September-April) centered
centered on
on austral
austral sum8-month
sum-
mer. The
mer.
The dashed
dashedcurves
curvesrepresent
representanomalies
anomalies from
from the
the
8-month period
period centered
centered on
on austral
austral winter
winter (March-October).
(March-October).
8-month
Note the
concentration between
Note
the change
changeof scale
scalefor pigment
pigmentconcentration
between
the zone
the
zone closest
closest to
to shore
shore (0-100
(0-100 km)
km) and
and those
those farther
farther
offshore. Data
Data points
points are
are for
the austral
offshore.
for the
australsummer
summermonths
monthsand
and
are
are as
as described
describedfor
for Figure
Figure 6.
6.
I
83
83
I
82
82
81
81
200-300
200-300
2
0
1
0
0
0
KM
KM OFFSHORE
OFFSHORE
o
-1
0
79
2
80
I
I
81
82
82
o
83
83
84
84
85
85
8
86
Peru
P
er u
0
1.0
1 0
Anomalies
in the
the PCS
Anomalies in
PCS formed
formed during
during the
the 8-month
8-month winter
winter
period (Figure
7,
curve)
do
differ
markedly
from
period
(Figure
7,dashed
dashed
curve)
donot
not
differ
markedly
from• 0.0
½½g
those formed
from
averaging
period.
Two
those
formed
fromthe
thesummer
summer
averaging
period.
Twodifdif- ? -1.0
79
79
ferences appear most notable. Off the Peru coast, negative E
anomalies in 1983 and 1984 are not as strong as those from
2.0
E
summer period
period. In
In the
the
the summer
the northern
northernand
andcentral
centralChilean
Chilean
where seasonal
occur in
in winter,
winter, the
regions,
regions,where
seasonalmaxima
maxima occur
the stronstron•1.0o
gest positive anomalies occur in 1981 rather than 1982 or
ferences
appear
most
notable.
Off
the
Peru
coast,
negative
• -• 0
anomalies
in1983
and
1984
are
not
asstrong
asthose
from• 20
- --' ----- -.----.g
----•-•
..... .-..-_,
e----•
I
80
80
ß
gest
positive
anomalies
occur
in1981
rather
than
1982
or
1983.
1983.
0.0
oo
-1.0o
-1
4.
Comparisons and
Comparisons
and Discussion
Discussion
between latitudinal
latitudinal patterns
patterns of
The
The strongest
strongestsimilarity
similarity between
of
in the
the CCS
seasonal
seasonalvariability
variability in
CCS and
and the
the PCS
PCS evident
evident in
in
Figures
Figures 4
4 and
and 55isisthat
thatminimum
minimumconcentrations
concentrationsand
and aa
low-amplitude
seasonal cycle
cycle are
are present
low-amplitude seasonal
presentat
atmidlatitude
midlatitude
locations
within these
these EBCs.
EBCs. This
This is
is counter
counter to
to the
the standard
locations within
standard
biological
patterns expected
expected in
in open
biologicalpatterns
open oceans,
oceans,where
whereminiminimum seasonal
variability is
is expected
mum
seasonal variability
expected at
at lower
lower latitudes.
latitudes.
Previous
Previouswork
work in
in the
theCCS
CCS [Lynn
[Lynn and
andSimpson,
Simpson,1987;
1987;Strub
Strub
2.0
20
79
79
I
I
I
83
84
I
I 83I 84I
Northern Chile
Nor
•hernOh
i [e
81
82
82
I
85
85
886
0
• ......••
--•:g-,•-..........
I
60
80
-
I
•
81
81
I
I
82
82
I
I
83
83
I
84
84
85
85
86
86
85
85
86
86
,1,Central
Chile
Central
Ch
i le
10
*
1.0
0 0
0.0
o
0
-1 .0
I
79
79
80
80
I
81
81
I
82
82
I
83
83
84
84
Southern
Chi
Sou•:hern
Chi l e
e
Figure 7.
(continued)
Figure
7. (continued)
THOMAS
ET
CURRENT
PIGMENT
VARIABILITY
THOMAS
ET AL.:
AL.' PERU
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
7366
7366
Summer
Summer
Winter
Winter
PaII
Fall
Spring
Spring
55 60 75 70
-85
-80
-75
-70
•
10
-10
2
10
-15
15
15
-2o
20
20
-25
25
25
30
30
-3o
35
-55
40
-40
.
-t t/;
.
,, %.
,,1.
"7'
35
-,
40
-.
*. %. 1-,o
45
-45
45
50
-50
50
65 60 75 70
-85
-80
-75
-70
65 60 75 70
-85
-80
-75
-70
-10
10
10
-15
15
15
-2O
20
20
25
-25
25
30
-3O
30
35
-35
35
40
40
45
-45
45
50
-5O
65 60 75 70
-85
-80
-75
50
-70
Figure
Filure 8.
8. The
The 10-year
10-year (1979-1988)
(1979-1988) mean
mean wind
wind seasonal
seasonal
cycle
cycle over
over the
the PCS
PCS calculated
calculatedfrom
from ECMWF
ECMWF wind
wind fields.
fields.
(top)
The 10-year
mean field
fieldfrom
fromsummer
summer(January-March),
(JanuaryMarch),
(top) The
10-year mean
fall
(AprilJune), winter
(Ocfall (April-June),
winter(JulySeptember),
(July-September),and
andspring
spring
(OctoberDecember);
tober-December); (bottom)
(bottom) the
the same
sameperiods
periods with
with the
the 1010year
removed to
to emphasize
emphasize seasonal
seasonal
year overall
overall mean
mean wind
wind field
field removed
differences.
differences.
large latitudinal
latitudinal range
range of
of the
the South
west coast
large
South American
American west
coast
during July.
July. In
In Plate
during
Plate 2
2 and
and Figure
Figure 3,
3, increased
increasedconcentraconcentrations
in the
the northern
region, both
both nearshare
nearshore and
and in
tions in
northern Chilean
Chilean region,
in
regions farther
farther from
km), are
are evident
evident in
in other
other
regions
from shore
shore(100-300
(100-300 km),
winter months
months (May,
(May, August,
August, and
and September).
September). The
The degree
degree to
to
winter
which the
the average
which
average July
July concentrations
concentrationsavailable
available from
from the
the
CZCS
data set
CZCS data
set shown
shown here
here represent
representlong-term
long-term mean
mean July
July
conditions
is unknown.
within
conditions is
unknown. Concentrations
Concentrations
within the
the middle
middle
latitudinal range
range of
of the
the PCS
PCS for
for July
July are
are calculated
calculated from
from data
data
latitudinal
from just
just two
from
two years
years (see
(seeFigure
Figure 3).
3). Examination
Examination of
of the
the
original
CZCS monthly
monthly images
images from
from each
each year
original CZCS
year (not
(not prepre-
sented
sented here)
here) indicates
indicates that
that the
thedata
dataare
arefrom
from1979
1979and
and1981.
1981.
Furthermore,
patterns and
within these
these 22
Furthermore, patterns
and concentrations
concentrations within
years
pigment values
values extend
extend
years are
are dramatically
dramaticallydifferent.
different. High
High pigment
both
than is
both farther
farther north
north and
andfarther
fartheroffshore
offshorein
in July
July 1981
1981 than
is
evident
in either
or other
evident in
either July
July 1979
1979 or
other winter
winter months
monthsin
in any
any
year
year (June
(June and
and August).
August).
In
In the
the CCS,
CCS, the
thetime-latitude
time-latitudeevolution
evolutionof
of the
thepigment
pigment
concentration
region closest
closest to
to the
the coast
coast
concentrationin
in the
the 00- to
to 100-km
100-kmregion
(Figure
4) is
is similar
to the
(Figure 4)
similar to
the time-latitude
time-latitudeevolution
evolutionof
of alongalongshore
wind stress
stress curl
curl discussed
discussed by
by
shorewind
wind stress
stressand
and offshore
offshorewind
Strub
[1990].This
Thisis
isconsistent
consistent with
with the
the hypothesis
hypothesis that
that
Strubet
et al.
al. [1990].
higher
higher surface
surface pigment
pigment concentrations
concentrationsare
are associated
associatedwith
with
coastal
[Strub et
et al.,
al., 1990]. Based
Based on
coastaland
andoffshore
offshoreupwelling
upwelling [Strub
climatological
wind data,
data, this
this does
does not
not appear
appear to
true over
climatologicalwind
to be
be true
over
much
much of
of the
the PCS.
PCS. Figure
Figure88shows
showsthe
the10-year
10-year(1979-1988)
(1979-1988)
mean
meanwind
wind stress
stressseasonal
seasonalvariability
variabilitywithin
within3-month
3-monthperiods
periods
over
wind stress
stress data
data
over the
the PCS.
PCS. These
These data
data are
are based
basedon
on daily
daily wind
from
the European
Weather Forefrom the
EuropeanCentre
Centrefor
for Medium-Range
Medium-RangeWeather
Forecasts
Wind stress
stress over
casts(ECMWF).
(ECMWF). Wind
over the
the PCS
PCS is
is persistently
persistently
upwelling
favorable from
from 66°
to 32°S,
upwelling favorable
ø to
32øS, in
in agreement
agreementwith
with
Bakun and
and similar
similar to
to the
Bakun
and Nelson
Nelson [1991]
[1991] and
the CCS
CCS equatorequatorward
the wind
wind
ward of
of approximately
approximately36°N.
36øN.Between
Between34°
34øand
and 50°S,
50øS,the
stress
stressover
over the
the PCS
PCS reverses
reversesitself
itself seasonally,
seasonally,with
with the
the most
most
seasonal
seasonalvariation
variationbetween
between34°
34øand
and44°S,
44øS,again
againsimilar
similarto
to the
the
CCS
CCS north
north of
of 38°N.
38øN.
Comparison
of the
the wind
Comparison of
wind and
and pigment
pigment seasonal
seasonalcycles
cycles in
in
the
that over
the PCS
PCS shows
shows that
over Peru,
Peru, northern
northern Chile,
Chile, and
and central
central
Chile,
pigment concentrations
concentrations do
Chile, pigment
do not
not have
have an
an obvious
obviousrelarelationship
to wind
forcing such
such as
as that
that seen
tionship to
wind forcing
seen in
in the
the CCS.
CCS. The
The
region
where the
region where
the surface
surfacepigment
pigment concentrations
concentrationsare
are maximaximum
in (austral)
(austral) fall,
fall, winter,
winter, and
mum in
and spring
spring is
is either
either the
the region
region
(approximately
32°
to 42øS)
42°S)where
where winds
winds have
have aa strong
(approximately 32
ø to
strong
seasonal
seasonal cycle
cycle (most
(most upwelling
upwelling favorable
favorable in
in summer
summer and
and
etal.,
favorable in
et al., 1987;
1987; Thomas
Thomas and Strub,
$trub, 1990;
1990;Abbott
Abbott and
and Barksdale,
Barksdale, downwelling
downwelling favorable
in winter)
winter) or
orthe
theregion
region(20°
(20øto
to32°S)
32øS)
1991] suggests
suggests that
that current
where winds
1991]
current structure
structure and/or
and/or wind-driven
wind-driven where
winds are
are persistently
persistentlyupwelling
upwellingfavorable
favorablewith
with little
little
physical
forcing can
can dominate
patterns, at
variation. Along
Along the
the northern
physical forcing
dominate seasonal
seasonalpatterns,
at least
least seasonal
seasonal variation.
northern Chilean
Chilean coast,
coast, the
the
within
this EBC,
CZCS data
data show
within this
EBC, and
and that
that seasonality
seasonalityis
is low
low within
within the
the CZCS
show that
that in
in aa region
regionwhere
wherewinds
windsare
areupwelling
upwelling
Southern
favorable throughout
throughout the
the year,
SouthernCalifornia
California Bight.
Bight. Figure
Figure 55 suggests
suggeststhat
that such
suchgengen- favorable
year, pigment
pigment concentrations
concentrations rereeralities
be extended
extended to
and that
that seasonality
is main
main very
very low
low at
at all
eralitiesmight
might be
to the
the PCS
PCS and
seasonalityis
all times
times along
along the
the coast.
coast. This
This pattern
pattern
also
contrasts strongly
also low
low within
within and
and immediately
immediately south
south of
of the
the large
largebight
bight contrasts
strongly with
with that
that evident
evident in
in the
the CCS
CCS even
evenwithin
within
formed near
near the Peru-Chile
formed
Peru-Chile border.
border.
the
same
latitudinal
region
(Baja
California).
Even
the same latitudinal region (Baja California). Even within
within 20
20
While
a similar
similar mean
mean seasonal
seasonal cycle,
km of
of the
the coast
coast off
northern Chile,
off northern
Chile, concentrations
concentrations in
in Plate
Plate 22
While a
cycle,albeit
albeitwith
with aa strongly
strongly km
varying
amplitude, is
and Figure
November through
varying amplitude,
is apparent
apparentthroughout
throughoutmost
mostof
of the
thelatilati- and
Figure 3
3 appear
appear relatively
relatively low
low from
from November
through
tudinal
the CCS
April. This
This argues
tudinalrange
rangeof
of the
CCS studied
studiedin
in this
thispaper
paper(Figure
(Figure4),
4), the
the April.
arguesagainst
againstaa simple
simplecoastal
coastaltrapping
trappingof
of high
high
CZCS
data indicate
indicatethat
that this
this isis not
pigment
values
which
may
be
missed
by
the
100-km-wide
CZCS data
not the
the case
case over
over the
the
pigment values which may be missed by the 100-km-wide
latitudinal range
range of
of the
the PCS
averaging boxes.
boxes. In
In the
latitudinal
PCS (Figure
(Figure 5).
5). The
The lowest
lowest and
and averaging
the northern
northernregion
regionoff
off Peru
Peru(equator(equatorhighest
latitude regions
ward of
where pigment
concentrations are
are high
highestlatitude
regionsof
of the
the PCS
PCS have
havemaximum
maximumpigment
pigment ward
of 18°S),
18øS), where
pigment concentrations
high in
in
concentrations
during summer,
summer, aa pattern
pattern similar
to that
that in
winter, spring,
in fall
fall
concentrationsduring
similar to
in winter,
spring, and
and summer
summer with
with aa distinct
distinctminimum
minimum in
the
ofofthe
(AprilJune), the
the CCS.
CCS. The
Themiddle
middlelatitude
latituderegions
regions
thePCS
PCS(17°
(17øto
to45°S)
45øS) (April-June),
the winds
winds are,
are,again,
again,upwelling
upwellingfavorable
favorable
exhibit
a mean
out of
of phase
phase with
throughout the
the year.
exhibit a
mean seasonal
seasonalcycle
cycle 180°
180ø out
with this.
this. throughout
year. A
A wider
wider analysis
analysisof
ofoceanographic
oceanographic
Plate
variables in
in this
shows that
that high
Plate 22 and
and Figures
Figures33 and
and55 show
showthat
thatthis
thiscycle
cycleis
isprimarily
primarily variables
this region
region by
by Bakun
Bakun [1987]
[1987] shows
high
aa result
pigment concentrations
concentrations in
in spring
resultof
of relatively
relativelyhigh
highpigment
pigmentconcentrations
concentrationsalong
along aa pigment
spring (Figure
(Figure 5)
5) are
are associated
associated
THOMAS
ET AL.'
AL.: PERU
CURRENT
PIGMENT
VARIABILITY
THOMAS
ET
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
7367
with the
with
the climatological
climatologicalseasonal
seasonalmaximum
maximumin
in wind
wind mixing,
mixing,
alongshore
wind stress,
stress, and
alongshore wind
and offshore
offshore Ekman
Ekman transport.
transport.
These data
These
data do
do not
not suggest
suggestan
an explanation
explanationfor
for the
the pigment
pigment
cently
CZCS data
data confirm
confirm the
the conclusions
conclusions of
of
cently released
releasedglobal
globalCZCS
minimum
minimum in fall.
fall.
cycle in
in the
the Southern
Southern California
California Bight.
Bight. The
The present
present analysis
analysis
cycle
extends
this
pattern
to
show
a
summer
maximum
off
extends this pattern to show a summer maximum off Baja
Baja
California.
This seasonal
seasonal evolution
evolution is
is consistent
California. This
consistent with
with the
the
hypothesis
hypothesisthat
that wind-driven
wind-drivencoastal
coastaland
andoffshore
offshoreupwellings
upwellings
are
are responsible
responsiblefor
for the
the summer
summermaxima
maxima in
in surface
surfacepigment
pigment
concentrations.
concentrations.
The
The present
presentanalysis
analysisof
of the
the global
global data
data set
setalso
alsoincludes
includes
the
for the
the first
the winter
winter months
months for
first time.
time. These
These data
data show
show an
an
offshore
extension of
of pigment
offshore extension
pigment concentrations
concentrationsgreater
greater than
than
0.5-1.0 mg
pattern off
central and
0.5-1.0
mgm
m-3 in
in aa diffuse
diffusepattern
offcentral
andnorthern
northern
California
and extending
extending north.
north. This
This offshore
offshore extension
extension of
of
California and
higher
pigment
concentrations
creates
a
winter
maximum
in
higherpigmentconcentrationscreatesa winter maximum in
the seasonal
km offshore
at
the
seasonalcycle
cycle for
for regions
regions more
more than
than 100
100 km
offshore at
these higher
latitudes. A
these
higher latitudes.
A winter
winter maximum
maximum is
is consistent
consistentwith
with
that seen
and 40°N
in an
an
that
seenby
by Lewis
Lewis et
et al.
al.[1988]
[1988]between
between250
25ø and
40øN in
analysis of
of seasonal
seasonal cycles
cycles evident
evident in
in Secchi
analysis
Secchi disk
disk depths
depths
Comparisons
between the
the time
Comparisons between
time series
seriesof
of concentration
concentration
anomalies
in the
the CCS
anomaliesin
CCS and
and the
the PCS
PCS (Figures
(Figures66 and
and 7)
7) allow
allow
some
general statements
statements of
somegeneral
of differences
differencesand
and similarities.
similarities.Most
Most
significantly,
visual inspection
inspection indicates
indicates that
significantly, visual
that interannual
interannual
anomalies
of pigment
pigment concentration
concentrationininthe
the PCS
PCS are
anomalies of
are not
not
correlated with
with those
correlated
those in
in the
the CCS.
CCS. Unlike
Unlike the
the CCS,
CCS, interaninterannual anomalies
anomalies in
in the
the four
four regions
regions along
along the
the latitudinal
latitudinal extent
extent
nual
of the
the PCS
PCS do
do not
not have
have aa common
commoncharacteristic.
characteristic. in
In addition,
addition,
of
most of
of the
in the
the PCS
most
the strongest
strongest relative
relative anomalies
anomalies in
PCS are
are
positive,
positive,whereas
whereasstrong,
strong,and
andoften
oftenthe
thestrongest,
strongest,anomalies
anomalies
in all
all regions
regions of
of the
the CCS
CCS are
are negative.
in the
the highestin
negative.Only
Only in
highestlatitude
region
of
southern
Chile
and
in
the
100latitude region of southernChile and in the 100-to
to 200-km200-kmoffshore zone
zone off
Peru do
offshore
off Peru
do relatively
relatively strong
strongnegative
negativeanomaanomalies occur.
occur.
lies
A
feature in
in these
these EBCs
is present
A common
common feature
EBCs is
present in
in the
the PeruPeru-
Strub et
et al.
there is
in most
Strub
al. [1990]:
[1990]' there
is aa summer
summer maximum
maximum in
most
locations
closest to
to the
the coast,
locations closest
coast, with
with aa very
very weak
weak seasonal
seasonal
vian coast
coast region.
vian
region. The
The year
year 1983
1983 appears
appears as
as aa negative
negative along 180°W in the central North Pacific. It is also consistent
along 180øWin the central North Pacific. It is also consistent
anomaly (Figure
(Figure 7),
7), especially
especially strong
offshore zones,
zones, as
anomaly
strongin
in offshore
asitit
does throughout
throughout the
does
the CCS.
CCS. Anomalous
Anomalousoceanographic
oceanographiccondiconditions
with aa major
tions associated
associatedwith
major El
E1Niflo
Nifio event
event were
were present
present
throughout the
the CCS
throughout
CCS in
in1982-1983
1982-1983 [e.g.,
[e.g., Simpson,
Simpson,1983;
1983;
Huyer
Huyer and
and Smith,
Smith, 1985;
1985;Rienecker
Rienecker and
andMooers,
Mooers,1986].
1986].
Although
the strongest
strongest anomalies
in sea
sea surface
surface temperature
temperature
Althoughthe
anomaliesin
(SST)
along
the
South
American
coast
associated
with this
this
(SST) along the South American coast associatedwith
El Niflo
occurred north
E1
Nifio occurred
northof
of approximately
approximately20°S
20øS[Cane,
[Cane, 1983;
1983;
Rasmusson
Rasmusson and
and Wallace,
Wallace, 1983],
1983], positive
positive SST
SST anomalies
anomalies
occurred
at least
occurred at
least as
as far
far south
southas
as40°S
40øS[Rasmusson
[Rasmusson and
and
Wallace,
Results presented
presented here
Wallace, 1983].
1983]. Results
here (Figure
(Figure 6)
6) agree
agreewith
with
with large
large sedimentation
sedimentation rates
rates recorded
recorded 100-300
km offshore
offshore
with
100-300 km
of Cape
Cape Blanco
in winter
winter and
and spring
[Sancetta,
of
Blanco (43°N)
(43øN) in
spring 1988
1988 [Sancetta,
1992],which
whichwere
wereattributed
attributed to
to plankton
plankton productivity
productivity char1992],
characteristic of
of the
the coastal
acteristic
coastal regions.
regions. Both
Both the
the CZCS
CZCS seasonal
seasonal
distribution and
these offshore
distribution
and its
its magnitude
magnitude in
in these
offshoreregions
regionsagree
agree
with chlorophyll
chlorophyllconcentrations
concentrationsgreater
greaterthan
than1.0
1.0mg
mgmm3
in
with
-3 in
FebruaryMay
February-May reported
reportedby
byLandry
Landryetetal.
al.[1989]
[1989] for
for distances
distances
more than
than 50
km from
from the
the coast
coast of
and greater
greater
more
50 km
of Washington
Washington and
than 0.51 mg
mg m
m3
reported
than
-3 ininNovemberDecember
November-December
reportedby
by
Thomas
and Emery
for the
the outer
Thomas and
Emery [1986]
[1986] for
outer southern
southernBritish
British
Columbia continental shelf. Although the cause of the diffuse
previous
previous work
work [Fiedler,
[Fiedler, 1984;
1984; Thomas
Thomas and
and Strub,
Strub,1990;
1990; Columbia continental shelf. Although the causeof the diffuse
offshore maxima
maxima in
in winter
winter remains
remains to
to be
be determined,
determined, winter
offshore
winter
Strub
Strub et
et al.,
al., 1990]
1990]showing
showingthat
that pigment
pigmentconcentrations
concentrationsin
in
surface
nutrient
concentrations
presented
by
Landry
et
surface
nutrient
concentrations
presented
by
Landry
et al.
al.
the
CCS
during
1983,
especially
in
regions
more
than
50
km
the CCS during 1983, especiallyin regionsmore than 50 km
[1989]
are
high
enough
to
support
phytoplankton
growth,
[1989]
are
high
enough
to
support
phytoplankton
growth,
offshore,
were
anomalously
low.
In
a
time
series
of
transects
offshore,were anomalouslylow. In a time seriesof transects
and previous
previous analysis
analysis by
by Thomas
indicates
Thomas and
and Strub
Strub [1989]
[1989] indicates
off
off the
the Peruvian
Peruvian coast,
coast, Barber
Barber and
andChavez
Chavez [1983]
[1983] show
show aa and
similar response
response to
to the
the El
similar
E1Niño,
Nifio, with
with maximum
maximumreduction
reductionin
in
chlorophyll
concentrations and
chlorophyllconcentrations
andlongest
longesttemporal
temporalpersistence
persistence
of
of this
this condition
condition in
in areas
areas more
more than
than 50
50 km
km offshore.
offshore. In
In the
the
three
Niflo year
threehighest
highestlatitude
latituderegions
regionsof
of the
the PCS,
PCS, the
the El
E1Nifio
year of
of
1983
is slightly
slightly positive
positive and
and does
does not
not appear
1983 is
appear anomalous
anomalousin
in
the 8-year
time series
the
8-year time
series (for
(for both
both the
the winter
winter and
and summer
summer
anomalies). This
This result
result must
must be
be treated
treated with
with caution
caution because
because
anomalies).
of the
sparse data
data over
over the
the PCS
of
the relatively
relatively sparse
PCS and
and also
also the
the
smoothing
effect of
of the
the temporal
temporal mean.
smoothingeffect
mean. The
The 8-month
8-month mean
mean
for
(September 1982
for 1983
1983(September
1982to
to April
April 1983)
1983)is
is heavily
heavilyweighted
weighted
toward
September
because
of
missing
data,
and this
this is
toward Septemberbecauseof missingdata, and
is early
early
in the
the E1
El Nifio
Niño episode,
episode, especially
at higher
higher latitudes
latitudes [Barber
[Barber
in
especiallyat
and Chavez,
Cane, 1983].
This is
is not
not true,
true, however,
and
Chavez, 1983;
1983; Cane,
1983]. This
however,
for the
the (austral)
(austral) winter
for
winter 8-month
8-month mean
mean anomaly
anomaly also
alsoshown
shownin
in
Figure
7, where
Figure 7,
where the
the entire
entire period
period MarchOctober
March-Octoberisisrelarelatively well
well represented.
represented. This
This period,
period, however,
tively
however, is
is obviously
obviously
weighted by
by months
weighted
monthsafter
after the
themaximum
maximumEl
E1Niflo
Nifio anomalies
anomalies
when near-surface
when
near-surfacenutrients
nutrientsand
and chlorophyll
chlorophyll concentrations
concentrations
were recovering
were
recovering to
to normality
normality [Barber
[Barber and
and Chavez,
Chavez, 1983].
1983].
Thus it
Thus
it seems
seemslikely
likely that
that the
the CZCS
CZCS missed
missedthe
the maximum
maximum
amplitude of
the 1982-1983
El Niho signal
signal at
at higher
higher latitudes
latitudes
amplitude
of the
1982-1983E1Nifio
in the
in
the PCS.
PCS.
Summary
Summary and
and Conclusions
Conclusions
In
the
California
Current
the seasonal
In the California Current system,
system, the
seasonalcycles
cycles of
of
surface
surface pigment
pigment concentrations
concentrationsrecalculated
recalculatedusing
usingthe
therere5.
$.
that light
may not
not be
be limiting,
limiting, at
at least
least in
in late
late winter,
winter, at
at these
that
light may
these
latitudes.
latitudes.
The
The analysis
analysis of
of interannual
interannual variability
variability shows
shows aa common
common
feature throughout
throughoutthe
the CCS
CCS to
to be
feature
be low
low values
values in
in 1983,
1983,
following the
the strong
strong 1982-1983
El Nifio.
Niflo. These
These low
following
1982-1983 E1
low values
values
persist through
off Baja
Baja California
California but
but are
are followed
persist
through1984
1984 off
followed by
by
the major
the
major peak
peak in
in the
the 8-year
8-year record
record off
off the
the Pacific
Pacific NorthNorthwest.
west.
Although lack
lack of
of data
data for
for the
the Peru
Peru Current
Current system
Although
systemsomewhat
somewhat
reduces our
our confidence
in the
the results
results of
of the
reduces
confidence in
the analysis,
analysis, the
the
available CZCS
CZCS data
data do
do suggest
suggest fundamental
fundamental differences
differences in
in the
the
available
seasonal
cyclesof
of the
the two
two EBCs
seasonalcycles
EBCs and
and point
point to
to important
important
oceanographicquestions
questionswhich
whichneed
need to
to be
oceanographic
be addressed
addressedwith
with
future data
data sets.
a
future
sets. The
The seasonal
seasonalcycle
cycle south
south of
of 45°S
45øS shows
shows a
summer
maximum, which
which may
may be
be consistent
summer maximum,
consistentwith
with wind
wind forcforcing,
providing one
one of
of the
the few
few similarities
to the
the CCS.
ing, providing
similaritiesto
CCS. Between
Between
17°
and 45øS,
45°S, however,
however, maximum
maximum values
values occur
occur in
17
ø and
in austral
austral
winter, despite
the fact
winds are
are either
winter,
despite the
fact that
thatclimatological
climatologicalwinds
either
persistently
favorable (off
northern Chile)
persistentlyupwelling
upwelling favorable
(off northern
Chile) or
or cycle
cycle
between conditions
favorable (austral
(austral summer)
and unfavorbetween
conditions favorable
summer) and
unfavorable
central Chile
able (austral
(australwinter)
winter) to
to wind-driven
wind-drivenupwelling
upwelling(off
(off central
Chile
between
and 40øS)
40°S) [Bakun
[Bakun and
and Nelson,
Nelson, 1991].
northern
between 30°
30ø and
1991]. Off
Off northern
Chile,
even within
20-40 km
km of
of the
Chile, even
within 20-40
the coast,
coast,relatively
relatively low
low
pigment
concentrationsare
arepresent
presentfor
for much
much of
of the
the year
pigment concentrations
year
despite
winds. Off
Off Peru
Peru between
between
despitepersistent
persistentupwelling-favorable
upwelling-favorablewinds.
6°
and 17°S,
there is
is aa minimum
in fall,
fall, despite
despite the
the fact
fact that
that
6ø and
17øS,there
minimum in
winds
favorable (the
winds are
are persistently
persistentlyupwelling
upwellingfavorable
(the lack
lack of
of data
datain
in
7368
THOMAS
ET
CURRENT
PIGMENT
VARIABILITY
THOMAS
ET AL.:
AL.' PERU
PERU AND
AND CALIFORNIA
CALIFORNIA
CURRENT
PIGMENT
VARIABILITY
winter
scatterometersshould
shouldclarify
clarify the
therelationships
relationshipsglimpsed
glimpsedonly
only
winter may
may mask
mask what
what is
is really
really aa broad
broadwinter,
winter,spring,
spring,and
and scatterometers
partially
and imperfectly
imperfectly with
with the
the CZCS
summer maximum).
partially and
CZCS data
data set.
set.
summer
maximum).
The
The analysis
analysisof
of interannual
interannualvariability
variability off
off South
SouthAmerica
America
shows
a
decrease
in
relative
pigment
concentration
shows a decrease in relative pigment concentration in
in offoffAppendix
shore
shore zones
zones off
off the
the Peru
Peru coast
coast(lowest
(lowest latitudes)
latitudes) after
after the
the Appendix
The
pattern of
1982-1983
El Nifio.
Niño. This
This parallels
The diffuse
diffuse pattern
of surface
surfacepigment
pigment concentration
concentrationvalval1982-1983 E1
parallels observations
observationswithin
within the
the
ues,
shown
stretching
far
offshore
in
Plate
andFigure
Figure4,
4, is
is
CCS
which show
CCS during
during1983
1983which
showthat
thatmaximum
maximumdifferences
differencesdue
due ues, shown stretching far offshore in Plate 11and
similar to
to the
the pattern
pattern caused
caused by
by the
the single
singleRayleigh
Rayleigh scatterscatterto
were offshore
and that
that very
very nearshore
nearshore similar
to El
E1Niflo
Nifio conditions
conditions were
offshore and
atmospheric correction
correction used
ing atmospheric
used in
in previous
previous versions
versionsof
of the
the
pigment
pigment concentrations
concentrationsremained
remainedhigh
high[Fiedler,
[Fiedler,1984;
1984;ThoTho- ing
CZCS data,
data, although
although much
much lower
lower in
in magnitude
magnitude [Strub
[Strub et
et al.,
al.,
mas
mas and
and Strub,
Strub,1990].
1990].This
This pattern
patternis
isalso
alsoin
in agreement
agreementwith
with CZCS
1990]
(hereinafterreferred
referred to
to as
as SJTA).
1990] (hereinafter
SJTA). Although
Although the
the global
global
in
in situ
situ observations
observations from
from aa cross-shelf
cross-shelf transect
transect at
at 5°S
5øSprepreCZCS
data
set
uses
the
multiple
Rayleigh
scattering
algoCZCS
data
set
uses
the
multiple
Rayleigh
scattering
algosented by
Barber and
Chile, the
the historical
historical
sented
by Barber
andChavez
Chavez[1983].
[1983]. Off
Off Chile,
rithm [Gordon
[Gordon et
etal.,
1988;
Feldman
et
al.,
1989],
itit is
natural
rithm
al.,
1988;
Feldman
et
al.,
1989],
is
natural
CZCS
data
are
too
sparse
to
document
interannual
variabilCZCS data are too sparseto documentinterannualvariabilto wonder
wonder how
how much
much systematic
systematic error
error may
still be
be caused
caused by
by
to
may still
ity
ity with
with any
any confidence.
confidence.
incompletely
corrected
atmospheric
scattering
at
high
sunThe
The most
most robust
robust result
result of
of our
ouranalysis
analysis concerns
concerns the
the incompletely corrected atmospheric scattering at high sunsatellite angles (high latitude, winter).
seasonal cycle
where the
seasonal
cycle off
off Chile
Chile between
between 30°
30ø and
and 40°S,
40øS, where
the satellite angles (high latitude, winter).
SJTA developed
developed aa technique
for estimating
this error
SJTA
technique for
estimating this
error
spring-summer data
data coverage
coverage is
is best
best and
and where
where the
the seasonal
seasonal
spring-summer
empirically for
for the
the previous
previous data.
data. That
That technique
empirically
techniqueis
is repeated
repeated
increase
in
upwelling-favorable
winds
is
greatest
during
the
increasein upwelling-favorablewinds is greatestduring the here. The assumptions of the technique are that (1) the error
here. The assumptionsof the technique are that (1) the error
same period
same
period (OctoberMarch).
(October-March). Here,
Here, pigment
pigmentconcentraconcentrawith latitude;
latitude; (2)
(2) the
the error
increases monotonically
monotonically with
error should
should
tions in the 100 km next to the coast only briefly exceed 1.5 increases
tions in the 100 km next to the coast only briefly exceed 1.5
have the
at times
have
the greatest
greatest magnitude
magnitude at
times around
around the
the winter
winter
mg m
m3,
below
This
mg
-3 dropping
dropping
below1.0
1.0 mg
mg m3
m-3ininsummer.
summer.
This solstice; and (3) winter values of pigment concentration far
solstice;
and
(3)
winter
values
of
pigment
concentration
far
contrasts to values
contrasts
valuesgreater
greaterthan
than3.0-4.0
3.0-4.0mg
mgm
m-3 during
during offshore are uniformly low, without a monotonic increase
offshore are uniformly low, without a monotonic increase
spring
and summer
km of
of the
the coast
coast in
the region
springand
summerwithin
within 100
100 km
in the
region
of
of seasonality
seasonalityin
in upwelling-favorable
upwelling-favorablewinds
windsoff
off California.
California.
Thus forces
Thus
forces other
other than
thanlarge-scale
large-scaleseasonal
seasonalwind
wind forcing
forcing
appear
appear to
to dominate
dominate the
the seasonal
seasonalcycles
cyclesof
of surface
surfacepigment
pigment
with
with higher
higher latitude.
latitude.
The technique
uses the
The
technique simply
simply uses
the CZCS
CZCS pigment
pigment concentraconcentra-
tion
in aa north-south
tion values
values in
north-south band
band far
far from
from the
the coast
coast in
in an
an
empirical
orthogonal function
function (EOF)
(EOF) analysis
empirical orthogonal
analysis and
and examines
examines
concentration
concentration over
over large
large portions
portions of
of the
the PCS.
PCS.
the
the space
spaceand
and time
time series
seriesfor
for the
the properties
propertieslisted
listed as
asassumpassumpThe significance
The
significanceof
of this
this difference
differencegoes
goesbeyond
beyondthe
thephytophyto- tions
tions 1
1 and
and 2 above.
above. Since
Since SJTA
SJTA used
used data
data from
from the
the West
West
plankton response
response to
plankton
to local
local wind
wind forcing.
forcing. It
It raises
raisesthe
the question
question Coast
from the
the coast,
Coast time
time series,
series, which
which extended
extended only
only 5°
5ø from
coast,
of
whether the
of whether
the surface
surfacesignature
signatureof
of the
thephytoplankton
phytoplanktonstanding
standing they
band separated
separated from
they formed
formed aa 2.5°-wide
2.5ø-wide band
from the
the coast
coastby
by
stock
can be
be used
of 2.5°
stock (as
(as seen
seenfrom
from aa satellite)
satellite) can
used as
as an
an indicator
indicator of
of longitude.
longitude. The
The first
first EOF
EOF accounted
2.5ø of
accountedfor
for 71%
71% of
of the
the
the
of the
the coastal
ocean system
system at
at the
the overall
overall productivity
productivity of
coastal ocean
the variance,
variance, with
a temporal
temporal function
with a
function that
that had
hadmaximum
maximum values
values
higher
trophic levels.
levels. The
The productivity
the coastal
ocean off
highertrophic
productivityof
of the
coastalocean
off of
of 3.0
3.0 in
in December
December and
and January
January and
andapproximately
approximately 0.0
0.0 in
in
Chile,
fish
Chile, as
as measured
measuredby
by the
theharvest
harvestof
ofphytoplankton-eating
phytoplankton-eating
fish June
Juneand
and July.
July. The
The spatial
spatialfunction
function ramped
ramped up
up from
from approxapproxspecies
species(anchovies
(anchoviesand
and sardines),
sardines),is
is reportedly
reportedly55 to
to20
20times
times imately
imately 0
0 at
at 25°N
25øN to
to 1.3
1.3 between
between40°
40øand
and 50°N.
50øN. Thus
Thus errors
errors
greater than
occurred in
in winter
greater
than that
that off
off California
California (P.
(P. Smith
Smith and
and R.
R. Parrish,
Parrish, of
4.0
of approximately
approximately
4.0mg
mgm
m-3 occurred
winternorth
northof
of
personal communications,
The harvest
harvest of
predator fish
personal
communications,1992).
1992). The
of predator
fish 40°N.
40øN.
species
jack mackerel
Although
the global
global data
data set
set is
not restricted
speciessuch
suchas
asjack
mackerelis
is also
alsolarge.
large. Why,
Why, then,
then, do
do the
the
Although the
is not
restrictedto
to the
theregion
region
satellite
satellitecolor
color data
data suggest
suggestmuch
much lower
lower surface
surfaceconcentrations
concentrations near
near the
the coast,
coast, there
there are
are more
more data
data for
for that
that region.
region. For
For this
this
of
of chlorophyll
chlorophyll (and
(and phytoplankton)?
phytoplankton)?Are
Are the
thephytoplankton
phytoplankton reason
reason and
and in
in order
order to
to facilitate
facilitate aa comparison
comparison to
to the
the results
results
located
can see?
see? of
data set
located deeper
deeper in
in the
the water
water column
column than
than the
the satellite
satellite can
of SJTA,
SJTA, the
the technique
technique was
was applied
applied to
to the
the global
global data
set in
in
Is
that higher
concentrations of
phytoplankton exist
exist two
bands: one
one based
Is it
it possible
possiblethat
higher concentrations
of phytoplankton
two latitudinal
latitudinal bands:
based on
on 1°
1ølatitude
latitude by
by 2.5°
2.5ø
in
to resolve
blocks separated
in aa very
very narrow
narrow nearshore
nearshoreregion
regiondifficult
difficult to
resolve in
in this
this longitude
longitude blocks
separatedfrom
from the
thecoast
coastby
by2.5°
2.5øofoflongilongirelatively
relatively low
low spatial
spatialresolution
resolutiondata
dataset?
set?Do
Do very
veryhigh
highprimary
primary
productivity
rates
maintain
the
fishery,
with
biomass
so
productivity rates maintain the fishery, with biomassbeing
being so
heavily
grazed that
heavily grazed
that higher
higherconcentrations
concentrationseither
eitherdo
donot
notbuild
build up
up
or
or do
do not
not spread
spreadoffshore?
offshore?These
These are
are questions
questionsthat
that the
the CZCS
CZCS
data
data set
setcan
canonly
only pose.
pose.Answers
Answersrely
rely on
onthe
thecombination
combinationof
of
future
data and
and more
color data.
data.
future field
field data
more reliable
reliable satellite
satellite color
Thus,
the relative
relative lack
lack of
Thus, acknowledging
acknowledging the
of data,
data, the
the time
time
series of
series
of CZCS
CZCS data
data suggest
suggestthat
that there
thereare
arefundamental
fundamental
differences
in the
differences in
the seasonal
seasonalvariabilities
variabilitiesof
of surface
surfacepigment
pigment
concentrations
concentrations in
in the
the Peru
Peru and
and California
California Current
Current systems,
systems,
even
wind forcing
is similar.
even though
though large-scale
large-scale wind
forcing is
similar. A
A more
more
complete understanding
understanding of
complete
of this
this variability
variability and
and its
its relation
relation to
to
wind
wind forcing,
forcing, upwelling,
upwelling, and
and horizontal
horizontal transport
transport within
within
these current
a more
these
current systems
systems will
will be
be possible
possible only
only when
when a
more
complete data
data set
complete
set becomes
becomesavailable.
available. As
As always,
always, the
the need
need
for in
for
in situ
situ observations
observations over
over aa wide
wide range
range of
of spatial
spatial and
and
temporal scales
is tantamount.
tantamount. In
temporal
scalesis
In the
the future,
future, combinations
combinationsof
of
pigment data
data from
pigment
from SeaWiFS
SeaWiFS (and
(and other)
other) sensors,
sensors,current
current
data
TOPEX and
and other
data from
from TOPEX
other altimeters,
altimeters, and
and wind
wind data
data from
from
tude,
tude, and
and another
another based
based on
on1°
1ølatitude
latitude by
by3.0°
3.0ølongitude
longitude
blocks
separated
from
the
coast
by
5.0°
of
longitude.
blocks separatedfrom the coast by 5.0ø of longitude.The
The
data
data are
are from
from the
the first
first 4
4 years
years of
of the
the global
global data
data set
set
(1979-1982),
whendata
data coverage
coverage was
was better.
better. The
(1979-1982), when
The results
results are
are
shown
in Figures
Figures Ala
Ala and
shown in
and Alb,
Alb, respectively.
respectively.
The
The average
average seasonal
seasonaltime
time series
seriesof
of each
eachfunction
function show
show
low
values (0.1-0.2)
(0.1-0.2) in
in spring
spring and
and summer
summer and
values
low values
and higher
higher values
(0.5-0.9)
in fall
(0.5-0.9) in
fall and
and winter.
winter. The
The spatial
spatialfunctions
functions show
show
localized
maxima superimposed
superimposed on
on aa gradual
gradual increase
increase with
localized maxima
with
latitude
which isis more
latitude which
more evident
evident farther
farther from
from shore.
shore. An
An
identical
dashed curve
curve based
identical dashed
based on
on the
the increase
increase in
in minimum
minimum
values
from the
the more
band (Figure
Aib)
values from
more offshore
offshore band
(Figure A
lb) has
has been
been
drawn
by hand
in both
The fact
fact that
drawn by
hand in
both figures.
figures. The
that it
it fits
fits the
the
minimum
values in
in Figure
Figure A
Ala
that
minimum values
1a gives
gives us
us some
someconfidence
confidencethat
it
it describes
describesan
an upper
upper estimate
estimate of
of the
the bias
bias caused
causedby
by uncoruncorrected
rected atmospheric
atmospheric scattering
scattering (or
(or other
other systematic
systematicoptical
optical
effects).
Using the
the more
band, where
effects). Using
more offshore
offshore band,
where we
we expect
expect
lower
lower true
true pigment
pigment values,
values, the
the maximum
maximum value
value for
for the
the
averaged
and occurs
averagedseasonal
seasonaltime
time series
seriesis
is 0.4
0.4 and
occursin
in November
November
THOMAS
ET AL.'
AL.: PERU
THOMAS ET
PERU AND
AND CALIFORNIA
CALIFORNIA CURRENT
CURRENT PIGMENT
PIGMENT VARIABILITY
VARIABILITY
7369
3.5
;5.5
!
3.0
3.0
1.0
1.0
'2.5
0.8
10.6
2.0
0.6
0.6
1.5
1.0 A A
0.4
0.4
0.2
0.2
0.5
0.5
0.0.
0.0
.......
, I I•
Jon Feb
Mar Apr
Apr MoyJun
May Jun Jul
Jon
FebMot
JulAug
AugSep
SepOct
OctNov
NovDec
Dec
Time
.rea
Time sir;el
bL2
l.2
.-.." .......
20
20
30
50
40
40
/
3.5
3.0
1.0
1.0
50
50
LoUtud.
Latitude('N)
2.5
,•' 2.5
•, o.s
110.8
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JonFebMorAprMoyJunJulAugSepOctNovD.c
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Time seriI
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.........
20
20
I
.........
I
30
40
•0
40
Lotituds ("N)
('N)
Lot;tude
....
50
50
Figure AI.
Al. Latitudinal
Latitudinal dependence
dependence and
in
Figure
and time
time series
seriesfor
for monthly
monthlypigment
pigmentconcentrations
concentrations
in two
twooffshore
offshore
zones of
of the
orthogonal function
function (EOF)
(EOF) decompositions.
decompositions. (a)
(a)
zones
the CCS
CCS shown
shownas
asthe
thefirst
firstmodes
modesof
of empirical
empiricalorthogonal
The first
first EOF
EOF mode
variability, accounting
accounting for
for 63.7%
63.7% of
of the
the total
total variance,
variance, of
The
modeof
of pigment
pigmentvariability,
of aa zone
zone2.5°
2.5øof
of
longitude wide
wide and
and 2.5
2.5°ø(approximately
(approximately 300
300km)
km)away
awayfrom
fromthe
thecoast
coast of
of North
North America.
America. (b)
longitude
(b) The
The first
firstEOF
EOF
mode of
of pigment
pigment variability,
variability, accounting
accounting for
for 62.9%
62.9% of
of the
the total
total variance,
variance, of
mode
of aa zone
zone3.0°
3.0øof
of longitude
longitudewide
wide
and
(approximately 600
600 km)
km)away
awayfrom
from the
the coast
coast of
of North
North America.
and 5°
5ø (approximately
America.
through
January. The
through January.
The spatial
spatialfunction
function increases
increasesto
to 0.25
0.25 at
at
approximately
and 0.75
which would
approximately 38°N
38øN and
0.75 at
at 48°N,
48øN, which
would indicate
indicate
maximum
errors
ofof0.0.1-0.4
1-.0.4 mg
maximum
errorsin
inNovember-January
November-January
mgm
m-3 at
at
these latitudes.
these
latitudes.
Whether
these maxima
are aa result
Whetherthese
maximaare
resultof
of advection
advectionof
of pigment
pigment
or
byproducts from
from closer
closer to
to the
the coast
coast or
or represent
represent
or pigment
pigmentbyproducts
local
production is
local production
is not
not known.
known.
Others may
draw their
Others
may draw
their own
own curves
curvesand
and conclusions,
conclusions,but
but
Acknowledgments.This
This work
work was
was supported
supportedby
by NASA
NASA grant
grant
we estimate
estimate any
any error
error caused
caused by
by these
these systematic
systematic processes
processes Acknowledgments.
we
NAGW-2475.
PeterBugden
Bugdenand
andSerge
SergeL6vesque
Lvesque assisted
with
NAGW-2475.
Peter
assisted
with
to
be
less
than
0.1-0.4
mg
m
in winter
winter at
at latitudes
latitudes between
between aspects
tobelessthan0.1-0.4mgm-3 in
aspectsof
of the
the plotting
plottingand
andimage
imageprocessing.
processing.We
We thank
thankSatlantic
Satlantic
40°
and 50øN
50°Nand
and negligible
negligibleatatother
other times
times and
and latitudes
latitudes less
less Inc.
40
ø and
Inc. of
of Halifax,
Halifax, Nova
Nova Scotia,
Scotia, for
for access
accessto
to their
their archive
archive of
of CZCS
CZCS
global monthly
monthly composites.
composites.
than 40°N.
This is
is supported
supported by
by data
data from
from the
the Peru
Peru Current
Current global
than
40øN. This
system
(Figure 5),
5),where
wherevalues
valuesremain
remainless
lessthan
than0.5
0.5mg
system
(Figure
mgmm3
-3
in winter
winter at latitudes of
in the
the band
band farthest
farthest from
of 45°
45 ø to 51°S
51 øS in
from
the coast.
the
coast.
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The analysis
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Approximately 300
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(Figure
Ala), there
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ET
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THOMAS
ET AL.:
AL.: PERU
PERU AND
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