PALEOCEANOGRAPHY,
VOL. 12,
12, NO.
NO.2,
PALEOCEANOGRAPHY, VOL.
2, PAGES
PAGES191-205,
191-205,APRIL
APRIL 1997
1997
The
The California
California Current
Current of
of the
thelast
lastglacial
glacial maximum:
maximum:
Reconstruction
°N based
based on
on multiple
multiple proxies
Reconstructionat
at 42
42øN
proxies
Joseph Ortiz
Ortiz'• and
Joseph
andAlan
AlanMix
Mix
College of
of Oceanic
Oceanic and
and Atmospheric
Sciences,
Oregon State
State University,
University, Corvallis
Corvallis
College
Atmospheric
Sciences,
Oregon
Steve
Hostetler
Steve Hostetler
U.S. Geological
Protection
Agency,
U.S.
GeologicalSurvey
Surveyat
at U.S.
U.S. Environmental
Environmental
Protection
Agency,Corvallis,
Corvallis,Oregon
Oregon
Michaele Kashgarian
Michaele
Kashgarian
Lawience
LawrenceLivermore
LivermoreNational
National Laboratory,
Laboratory,Livermore,
Livermore,California
California
Abstract:
paleoceanographic
proxies
ininaazonal
across
the
Abstract:Multiple
Multiple
paleoceanographic
proxies
zonaltransect
transect
across
theCalifornia
CaliforniaCurrent
Current
near
42°N
record
modern
and
last
glacial
maximum
(LGM)
thermal
and
nutrient
gradients. The
near42øNrecordmodernandlastglacialmaximum(LGM) thermalandnutrientgradients.
The
offshore thermal
species
assemblages and
oxygen isotope
offshore
thermalgradient,
gradient,derived
derivedfrom
fromforaminiferal
foraminiferal
slx•iesassemblages
andoxygen
isotopedata,
data,
was
were
wassimilar
similarat
at the
theLGM
LGM to
to that
thatat
at present
present(warmer
(warmeroffshore),
offshore),but
butaverage
averagetemperatures
temperatures
were3.3°
3.3ø
± 1.5°Ccolder.
colder. Observed
gradients
require
flow
+1.5øC
Observed
gradients
requirethat
thatthe
thesites
sitesremained
remainedunder
underthe
thesouthward
southward
flowof
of the
the
California
Current,
and
thus
that
the
polar
front
remained
north
of
42°N
during
the
LGM.
Carbon
CaliforniaCurrent,andthusthatthepolarfrontremainednorthof 42øNduringtheLGM. Carbon
isotopic
flux
enhanced
nutrients
and
of
in
isotopicand
andforaminiferal
foraminiferal
fluxdata
datasuggests
suggests
enhanced
nutrients
andproductivity
productivity
offoraminfera
foraminfera
in
the
northern California
California Current
Current up
up to
to 650
650 km
km offshore.
offshore. In
marine organic
organic carbon
carbon and
and
thenorthern
In contrast,
contrast,marine
coastal diatom
diatom burial
burial rates
rates decreased
decreased during
during the
the LGM.
LOM. These
contradictory
results are
are
coastal
Theseseemingly
seemingly
contradictory
results
reconciled by
by model
LGM windfield, which
which suggest
suggest that
that wind
wind stress
stress curl
curl at
reconciled
modelsimulations
simulations
of the
theLGM
wind- field,
42°N (and
open-ocean upwelling)
upwelling) increased,
increased, while
while offshore
offshore Ekman
Ekman transport
transport (and
(and thus
thuscoastal
coastal
42øN
(andthus
thusopen-ocean
upweffing)
decreased during
during the
the last
last ice
ice age.
age. The
of
California
upwelling)decmasexl
Theecosystem
ecosystem
ofthe
thenorthern
northern
CaliforniaCurrent
Current
during the
the LGMapproximated
LOMapproximated that
in
during
thatof
ofthe
themodern
modernGulf
Gulf of
of Alaska.
Alaska.Cooling
Coolingand
andproduction
production
inthis
this
region was
by stronger
open-ocean upwelling
and/or southward
flow of
of high-latitude
high-latitude
region
wasthus
thusdriven
drivenby
stronger
open-ocean
upwellingand/or
southward
flow
water
rather than
watermasses,
masses,rather
thanby
by coastal
coastalupwelling.
upwelling.
Introduction
Introduction
summer.
the
summer.By
By reconstructing
reconstructing
theLOM
LGM zonal
zonalthermal
thermalgradient
gradient
here
we infer
infer direction
direction in
in the surface
here we
surface water
water circulation
circulation and
and thus
in the
We
We report
report here
hereon
onconditions
conditionsin
thenorthern
northernCalifornia
California put limits on polar front movements.
put limits on polar front movements.
Previous
Current
during the
the last
(LGM).
Currentduring
lastglacial
glacialmaximum
maximum
(LGM). Previous
Hal
LGMpolar
polar front
front moved
moved south
south of
of these
these sites,
sites, flow
Hadthe
the LGM
flow
studies
suggest
that
NE
Pacific
surface
waters
cooled
by
2°-4°C
studiessuggest
thatNE Pacificsurfacewaterscooledby 2ø-4øC across the transect would have been northward, similar to the
across
the
transect
would
have
been
northward,
similar
to
the
[Moore,
1973; Moore
Moore et
e al.
[Moore, 1973;
al. 1980]
1980]and
andthat
thatexport
exportproduction
production
This would
AlaskanStream
Streamoff
off British
BritishColumbia
Columbiatoday.
today. This
would be
be
decreased relative to present values [Lyle et al. 1992; Sancetta Alaskan
decreased
relativeto presentvalues[Lyle et al. 1992; Sancetta
cores at
er al. 1992].
et
1992]. These
Thesepast
paststudies
studieswere
werelimited
limited to
to aa few
few cores
at
different
latitudes, which
which precludes
precludesresolution
resolution of
of water
different latitudes,
water mass
mass
we focus
To resolve
flows.
flows. To
resolveregional
regional currents,
currents, we
focus on
on zonal
zonal
temperature
andnutrient
nutrient structures
structures at
at42øN
42°Nin
in aa transect
transect of
of 10
temperature
and
10
cores
from
coresthat
thatspan
spanthe
theCalifornia
CaliforniaCurrent
Current
from125°W
125øWto
to 134°W.
134øW.
To
causes of
To evaluate
evaluate causes
of oceanographic
oceanographicchange,
change,we
wecompare
compare
geologic data
data with
with local
local wind
wind forcing
forcingsimulated
simulatedwith
with aa regional
regional
geologic
climate
climate model.
model.
and Cape
Our
Our transect,
transect, located
located between
between Cape
Cape Blanco
Blanco and
Cape
Mendocino,
is sensitive
translation of
Mendocino, is
sensitive to
to southward
southwardtranslation
of the
the polar
polar
front zone
zone (the
(the boundary
boundary between
between the
the subarctic
front
subarcticand
andsubtropical
subtropical
gyres) because
because itit is
is near
near the
the southern
southernboundary
boundaryof
ofthe
thetransition
transition
gyres)
Today,
year-round
flow is
is
zone
between
these
gyre
systems.
zonebetweenthesegyre systems. Today, year-roundflow
southward
(Figure1)and
1) andnear-coastal
near-coastalupwelling
upwellingisisstrong
strong in
in
southward(Figure
'Now at
Earth
of
University,
•Now
atLamcnt-Doheity
Lamont-Doherty
EarthObservatory
Observatory
ofColumbia
Columbia
University,
Palisades, New
New York.
York.
Palisades,
Copyright 1997
by the
the American
Union.
Copyright
1997by
AmericanGeophysical
Geophysical
Union.
Paper
96PA03
165.
Papernumber
number
96PA03165.
indicated
water
indicatedby
by warmer,
warmer,more
morenutrient-depleted
nutrient-depleted
waternear
nearthe
thecoast
coast
than
offshore. If
If the
polar front
front stayed
to the
the north,
north, our
thanoffshore.
theLGM
LGM polar
stayedto
our
sites
have remained
remained under
under aa southward
southwardflowing
flowing California
California
siteswould
wouldhave
Current, with colder nutrient-enriched water near the coast
coast and
and
warmer,
more
nutrient-depleted
waters
offshore.
warmer, more nutrient-depletedwatersoffshore.
Methods
Methods
Foraminiferal Faunas:
Faunas: Temperature
Foramlnlferal
Temperature and
and
Productivity
Estimates
Productivity
Estimates
We identified
identifiedforaminiferal
foraminiferalspecies
speciespercentages
percentagesin
in the
the >150>150We
size class using standard CLIMAP taxonomic
categories
taxonomic categories
[Parker,
one exception.
exception. In
[Parker,1962:
1962:Be,
BE,1977]
1977] with
with one
In this
thisstudy,
study,we
we
do not
pachyderma
do
not recognize
recognize the
the "Neogloboquadrina
"Neogloboquadrina
pachyderma -neogloboquadrina
dutertrei (P-D)
(P-D) intergrade"
intergrade"category
category of
of Kipp
neogloboquadrina
dutertrei
Kipp
tim
]Jxn
size class using standardCLIMAP
[1976].
[1976].
We compare
compare modern
modern foraminiferal
foraminiferalfaunas
faunasfrom
from sediment
sediment traps
traps
We
and
obtained
and plankton
planktontows
tows with
with local
local fossil
fossilassemblages
assemblages
obtainedfrom
from
wellpreserved LGM
LGMsediments
sediments(Table
(Fable1).
1). Core
Core top
top faunas
faunas in
in
well-preserved
this
area
are
highly
dissolved
and
thus
unusable
for
our
study
this areaare highly dissolvedand thus unusablefor our study
[Karlin
et al.
al. 1992;
1992; Zahn
Zahnetet al.
al. 1991b;
et al.
[Karlin et
1991b; Lyle
Lyle et
al. 1992].
1992].
0883-8305/97/96PA-03 165$ 12.00
0883-8305/97/96PA-03165512.00
191
ORTIZ
ET AL.:
AL.: GLACIAL
GLACIAL CALIFORNIA
CURRENT AT
AT 42øN
42°N
ORTIZ ET
CALIFORNIA
CURRENT
192
135
135
55
55
130
130
125
125
115
115
120
120
110
110
135
135
55
130
130
115
115
I
I
I
-
50
45
-
45
I
55
55
DNAMIC
(FMA
- 50
50
- 45
45
CAPE BLANCO
CAPE
BLANCO
w
ILl
I
110
110
DYNAMICHT (FMA)
500
0
120
120
I
•1
DYNAMICHT
DYNAMIC HT ( (AS
A S 00))
z
125
125
CAPE
CAPE BLANCO
BLANCO
Q
CAPE MENDOCINO
MENDOCINO
• 40
35
35
/Q
N
c%
30
30
-
40
-
35
-
30
A
^
25
25
135
CAPE
CAPE MENDOCINO
MENDOCINO
\ 'oo
40
40
35
- 35
- 30
30
B
130
1;30
125
125
120
120
115
115
110
130
130
155
LONGITUDE((°W)
øW)
125
125
120
120
115
115
110
110
LONGITUDE
LONGITUDE ((°W)
øW )
FIgure
Locations of
of the
the sediment
cores (solid
(solid circles)
and sediment
trap moorings
moorings (solid
Figure 1.
1. Locations
sediment cores
circles) and
sediment trap
(solid circles
circles
surrounded
bycircles)
circles) across
acrossthe
the California
California Current
Currentnear
near42øN.
42°N. Contours
Contours are
are the
the climatic
climatic average
surromxled
by
averagedynamic
dynamic
height
field relative
relative to
to 500
500 m
m in
in units
units of
of geopotential
(m2
2) Geopotential
is
measure of
of the
the geostrophic
geostrophic
heightfield
geopotential
(m2 s'2).
Geopotential
is aa measure
flow
during (a)
(a) August,
August, September,
September, and
March, and
flow during
andOctober
Octoberand
and(b)
(b) February,
February,March,
andApril,
April, using
usingdata
datafrom
fromLevitus
Levitus
[1982]. Closer
[1982].
Closercontours
contoursdenote
denotefaster
fastercurrents;
currents;arrows
arrowsshow
showthe
thedirection
directionof
of flow.
flow.
Table
Table 1.
1. Multitracers
MultitracersCore
Core and
andTrap
Trap Locations
Locations
Age
A ge
Name
Conla
Controla
Latitude,
Latitude,
øN
Depth,
Depth,
m
Length,
Length,
cm
126.91
126.91
127.68
127.68
129.00
129.00
130.01
130.01
130.62
130.62
131.96
132.67
132.67
1120
1120
2717
2408
2408
2799
2799
3111
3136
3136
3136
3136
3330
3330
3680
3670
390
872
258
255
875
266
266
266
266
252
48
251
125.77
125.77
127.58
127.58
l32A)2
132.02
1000
1000
1000
1000
N/A
N/A
N/A
N/A
N/A
Longitude,
Longitude,
øW
Sediment
Cores
Sediment Cores
6706-2
6706-2
W8709A-13PC
W8709A-13PC
W8809A-53GC
W8809A-53GC
W8809A-21GC
W8809A-21GC
W8709A-O8PC
W8709A-08PC
W8809A-29GC
W8809A-29GC
W8809A-3IGC
W8809A-31GC
W8909A-57GC
W8909A-57GC
W8709A-OIBC
W8709A-01BC
W8909A-48GC
W8909A-48GC
type 1 and
2
type
and 2
type
type 3
type 3
type 33
type
type 3
type 33
type
type 3
type 3
type
type 11
type
type
type 1I
42.16
42.12
42.75
42.14
42.26
41.80
41.80
41.68
41.58
41.54
41.33
124.94
124.94
125.75
125.75
126.26
Sediment
Traps
SedimentTraps
Nearshore trap
trap
Nearshore
Midway trap
trap
Midway
Gyre trap
trap
Gyre
N/A
N/A
N/A
N/A
N/A
42.09
42.19
41.54
41.54
methods
of age
are used:
used: Type
Type II is
stiatigraphy, type
type 2
21s
aThree
methods
of
agecontrol
control
are
iscazbonate
carbonate
stratigraphy,
is
cweniional
'4C
dating
ciof
bulk
organic
matter
Lfrom
Spigai.
19711,
and
conventional
inc
dating
bulk
organic
matter
[from
Spigai,
1971],
andtype
type33is
isAMS
AMS'4C
•nc
on
onplanklic
plankticor
orbenthic
benthieforaminifera.
foraminifera.
25
25
193
193
ORTIZ ET
ET AL.:
AL.: GLACIAL
GLACIAL CALIFORNIA
CALIFORNIA CURRENT
CURRENT AT
AT 42øN
42°N
ORTIZ
Foraminiferal
sedimentIxap
trap fluxes
fluxes are
are from
Foraminiferal sediment
from Ortiz
Ortiz and
andMix,
Mix,
[1992],
but
were
modified
by
grouping
P-D
intergrade
[1992], but were modified by grouping P-D intergradewith
with
Age
Age Models
Models
Neogloboquadrina
dutertrei.
Neogloboquadrina
dutertrei.
Age
models are
are needed
neededboth
both for
for synoptic
synoptic sampling
sampling of
of the
Age models
the
LA3M
andfor
forcalculating
calculating sediment
sediment accumulation
rates. Core
LGM and
accumulationrates.
Core
locations
are given
Stratigraphic control
locationsare
given in
in Table
Table1.
1. Stratigraphic
controlincludes
includes
calcium
carbonatepercentages,
percentages, oxygen
oxygen isotope
isotope stratigraphy,
calciumcarbonate
stratigraphy,
and
dating. The
horizon, defined
and radiocarbon
radiocarbondating.
The LGM
LGM horizon,
defined here
here as
as
between
calendar-correctedradiocarbon
radiocarbonages
agesofof16-22
16-22ka,
ka, is
between calendar-corrected
is
Paleotemperature
estimatesuse
useaa version
version of
of the
Palcotemperatureestimates
the modem
modem
analog
method tested
tested on
on both
both core
core top
top and
and sediment
sediment trap
trap faunas
analogmethod
faunas
[Ortiz
and
Mix,
this
issue].
This
method
yields
unbiased
[Ortiz andMix, this issue]. This method yields unbiasedsea
sea
surface
temperature (SST)
(SST) estimates
estimates with
with an
anRMS
RMS error
error of
of 1.5°C
surfacetemperature
1.5øC
for the
include (1)
(1)
for
the core
core top
top dala
data set.
set. Additional
Additional checks
checks include
radiolanan paleotemperature
radiolarian
palcotemperatureestimates
estimates [Sabin
[Sabin and
and Pisias,
Pisias,
19961,
and (2)
(2) fi•aO
8"O measurements
of
1996],and
measurements
of G.
G. bulloides.
hulloides.
We infer
infer LGM
LGM nutrient
nutrient content
contentand
and foraminiferal
forarniniferal productivity
productivity
We
from (1)
(1) fi•3C
8'3C gradients
gradients of
of G. hulloides
bulloides across
across the
the transect
and
from
transect
and
associated
with
in cores
cores east
east of
of 129°W
associated
with high
high%CaCO3
%CaCO3in
129øW(Figure
(Figure2)
2)
[Lyle
et
al.
1992].
Farther
west,
the
carbonate
high
is
[Lyle et al. 1992]. Fartherwest, the carbonatehigh is broader,
broader,
and
the LGM
LOMhorizon
horizonisis chosen
chosen near
near the
the younger
andthe
youngerend
end of
of the
the
carbonate
carbonatehigh.
high. Carbonate
Carbonatepercentage
percentagedata
dataare
arein
in Table
Table2.
2.
Radiocarbon
dateson
on foraminifera
foraminiferacome
comefrom
fromLyle
Lyle et
et al.
al.
Radiocarbondates
(2)
rates of
of the
(2) shell
shell accumulation
accumulationrates
the heterotrophic
heterotrophicplanktonic
planktonic
are from
Modem shell
accumulation rates
rates are
foraminifera.
foraminifera.
Modern
shell accumulation
from
sediment
trap
fluxes,
subject
to
little
or
no
dissolution.
LGM
sedimenttrap fluxes, subjectto little or no dissolution. LGM
faunas
are well
well preserved,
preserved,but
butpossible
possible losses
losses due
due to
to partial
faunasare
partial
[1992], Gardner
and the
the present
[1992],
Gardneret
et al.
al. [this
[thisissue],
issue],and
presentstudy
study(Table
(Table
3).
that were
3). Dates
Dates from
from consecutive
consecutive 2-5
2-5 cm
cmintervals
intervals that
were not
not
statistically
independent were
were averaged.
averaged. Reservoir
corrections,
statisticallyindependent
Reservoircorrections,
needed
to adjust
adjustfor
for the
the apparent
apparent inc
'4C age
age of
of the
needed
to
thewater
waterin
in which
which
the
assume that
the foraminifera
foraminifera lived, assume
that benthic
benthic foraminifera
calcified
in North
4C = -250%
calcifiedin
NorthPacific
Pacificdeep
deepwaters
waterswith
with A14C
-250%o
[Ostlund et
et al.
al. 1987],
on
scale of
of Stuiver
Stuiver and
and
[Ostlund
1987],as
asdefmed
defined
onthe
theA'4C
A•nCscale
Polach [1977].
Polach
[1977]. The
Thebenthic
benthiereservoir
reservoircorrection
correction is
is thus
thus2380
2380
years,
'4C half-life
half-life of
of 5730
years,using
usingthe
the"Godwin"
"Godwin"inc
5730 years
years[Faure,
[Faure,
1977]. Subtracting
Subtracting the
the average
between
1977].
average'4C
•4Cage
agedifference
difference
between
benthic
benthieand
and planktonic
planktonicforaminifera
foraminiferain
in the
thesame
samesamples
samplesfrom
from
the
benthic reservoir
reservoir correction,
correction, we
we find
fmd aa planktonic
planktonic
the assumed
assumed
benthie
reservoir
reservoircorrection
correctionof
of 718
718 years.
years. This
This estimate
estimateis
is virtually
virtually
preserved accumulation
dissolution
imply that
rates are
are
dissolution imply
that preserved
accumulation rates
We assume
minimum
estimates for
for original
original shell
minimum estimates
shellfluxes.
fluxes. We
assumeaa
relationship
between
water
column
nutrient
content
and shell
shell
relationship betweenwater columnnutrient content and
fluxes
because nutrients
of
fluxes because
nutrients control
control the
the food
food supply
supply of
heterotrophic foraminifera
foraminifera [Ortiz
[Ortiz 1995;
1995;Ortiz
Ortizet
et al.
al. 1995;
heterotrophic
1995; Ortiz
Ortiz
and
and Mix,
M/x, 1992].
1992]. Given
Givenaalife
lifespan
spanof
ofabout
about11month
month[Hemleben
[Hemleben
et
et al.1988],
a/.1988], foraminifera
foraminiferalike
like other
otherzooplankton
zooplanktoncan
can respond
respondto
to
changes
in prey
related to
to upwelling
events of
changes in
prey abundance
abundancerelated
upwelling events
of
several
weeks duration,
duration, in
in addition
to advective
changes on
several weeks
addition to
advectivechanges
on
longer
[Barnard, 1994].
longertimescales
timescales[Barnard,
1994].
W8709a-O8PC
W8 709a-08PC
W8809a-21GC
W8 809a-21GC
W8809a-53GC
W8809a-53GC
%CaCO3
%CaCO3
%CaCO
3
%CaCO33
%CaCO
20
20
0
0
0
m•
I 100-ui100
I
%CaCO
3
00
40
40
E
200
200 -,-
500
500
20
00-3:;i
100100 -
200 200
200
200
-
'S 300
300-
¬ i
i
100 lOO
E
U
200
200-
II
5
.5
100 -.':
100
200
200-
300 0
300- 0
400 400-
400
400-
400
400--
500
500
500 J
500
500
500
-•
5 10
10 15
15
! i
0
00•
!
.5 300300
1)
500
500
-•
I
100
lOO --
400-400
U.
0o
I
6706-2
6706-2
%CaCO3
%CaCO
3
00 51015
5 10 15
20
20
10
10
00
_
300
300--
300
-
300
400
400- -
10
W8709a-13PC
W8709a-13PC
%CaCO3
%CaCO
3
--
W8909a-48GC
W8909a-48GC
W8709a-01BC
W8709a-01BC
W8909a-57GC
W8909a-57GC
W8809a-3 1GC
W8809a-31GC
W8809a-29GC
W8809a-29GC
%CaCO3
%CaCO
3
%CaCO3
%CaCO
3
%CaCO3
%CaCO
3
%CaCO33
%CaCO
%CaCO3
%CaCO
3
0 20
20 40
40 60
60
00 20
20 40
40 60
60
0 20
20 40
40 60
60
0
•
1010-
20 30- 30
40 4020-
5050
I
0..
El.
!
I
0I
II
0
o=L
I
i
i
1010-
20 'S 30
30- 40 4020-
50
5O
I
0
o
•:•
•
0...
20 40
40- 60
60--80 80100
100
-
i
II
0
I
I
20 40 4060 60-80
•o- 20-
0
fl
Q-.
0
0 20
60
20 40
40 60
20 40
40 60
60
0 20
.5
100
lOO
0
0
p.
1
'ii
0'II
0
I
'5
0
_
25 50 75
75-25-
1
%,
100
100-125
125
-
150
150
Figure
carbonate stratigraphies
stratigraphies for
for the
the 10
10 cores
cores in
in the
the transect,
orderedby
by distance
distance from
from the
the
Figure 2.
2. Percent
Percentcarbonate
transect,ordered
coast:
while
mark the
the last
last
coast:6706-2
6706-2 is
is closest
closestto
tothe
thecoast,
coast,
whileW8909A-48GC
W8909A-48GCis
is farthest
farthestoffshore,
offshore.solid
solidsquares
squares
mark
glacial
maximum(LGM)
(LGM)samples
samplesidentified
identifiedby
bycarbonate
carbonatestratigraphy
stratigraphy and
and AMS?C
AMS-'4Cdating.
dating. Some
glacialmaximum
Somecarbonate
carbonate
data
for 6706-2
6706-2 are
Spigai [1971].
datafor
are from
from Spigai
[1971]. Carbonate
Carbonatedata
data for
for W8709A-I3PC,
W8709A-13PC, 13TC,
13TC,W8709A-8PC,
W8709A-8PC, TC,
TC, and
and
W8709A-1BC
W8709A-1BC from
from Lyle
Lyle et
et al.
al. [1992].
[1992].
ORTIZ
El AL.:
ORTIZ ET
AL.: GLACIAL
GLACIAL CALIFORNIA
CALIFORNIA CURRENT
CURRENT AT
AT 42°N
42øN
194
Table
Stratigraphies
for
Table 2.
2. Carbonate
Carbonate
Stratigraphies
forthe
theMultitracers
MultitracersCores
Cores
Depth,
Depth,
cm
cm
CaCO,
CaCO,,
Depth,
Depth,
CaCO,,
CaCO,,
%
cm
cm
%
6706-2PC
6706-2PC
11.5
102.5
124.5
152.5
175.5
0.72
0.72
5.5
1.19
1.06
1.95
1.95
1.68
703
70.5
2.36
2.36
8.88
12.44
202.5
202.5
215.5
249.5
252.5
3.12
3.12
5.84
7.94
7.94
6.07
6.07
3.65
4.42
4.42
2983
298.5
352.5
352.5
W8809A-3IGC
W8809A-31GC
5.5
303
30.5
39.5
50.5
59.5
70.5
86.5
96.5
122.5
27.77
27.77
45.58
45.58
52.38
52.38
5032
50.32
46.78
31.22
31.22
14.83
2.87
52.54
52.54
1532
15.52
3.25
1137
11.37
8.73
5.55
5.5
60.5
1233
123.5
140.5
160.5
180.5
198.5
216.5
254.5
254.5
0.98
0.98
7.16
7.16
10.80
9.56
9.91
6.93
8.46
8.46
7.14
7.14
12.61
Depth',
Depth',
CaCO,
CaCO,,
cm
W8809A-29GC
W8809A-29GC
135.5
155.5
155.5
173.5
184.5
198.5
208.5
208.5
220.5
220.5
230.5
230.5
250.5
250.5
6.05
6.05
19.91
34.92
34.92
29.02
37.71
3733
37.53
40.48
40.48
30.21
1.85
6.30
6.30
W8909A-S7GC
W8909A-57GC
5.5
20.5
30.5
40.5
47.5
55.5
64.5
73.5
73.5
91.5
CaCO,
CaCO,,
%
%
W8809A-2JGC
W8809A-21GC
W8809A-S3GC
W8809A-53GC
137.5
150.5
170.5
185.5
202.5
222.5
222.5
241.5
255.5
255.5
Depth,
Depth,
cm
cm
W8909A-48GC
W8909A-48GC
11.95
55.67
52.35
46.69
47.75
48.76
26.41
32.25
26.08
3.5
7.5
7.5
12.5
15.5
10.72
31.20
31.20
32.18
32.18
30.49
30.49
18.5
20.5
21.5
23.5
31.5
30.49
34.92
34.92
32.98
32.98
25.26
25.26
26.39
26.39
'Core top
at
135
•Core
topoccurs
occurs
atapproximately
approximately
135cm
cmdepth
depthdue
dueto
todouble
doublecoring.
coting.
identical to
to that
that of
of Zahn
Zahnet
etal.
ci. [1991a].
[1991a].The
Thebenthic-planktonic
benthic-planktonic
identical
age comparison
comparison in
in five
five samples
samples of
of up
up to
age
to 25,000
25,000 '4C
•4Cyears
years
suggests
that
the
average
reservoir
age
of
the
surface
water
suggeststhat the averagereservoirage of the surfacewaterwas
was
roughly
constant over
over that
that time
time interval.
interval. We
roughly constant
We thus
thussubtracted
subtracted
718 years
years from
fromeach
eachof
of the
the planktonic
planklonic foraminiferal
dates, and
718
foraminiferaldates,
and
2380
2380 years
yearsfrom
from each
each of
of the
thebenthic
benthicforaminiferal
foraminiferaldates,
dates,for
for
corrections on
on bulk
reservoir
reservoircorrections.
corrections. Reservoir
Reservoir corrections
bulk organic
organic
carbon dates
dates are
are calculated
calculatedto
toalign
aligntheir
theirages
ageswith
withthose
those of
of the
the
carbon
reservoir-corrected
This empirical
reservoir-correctedcalcite
calcite dates.
dates. This
empirical correction
correction
(4300 years)
years) is
open-ocean
(4300
is larger
largerthan
thanany
anyreasonable
reasonable
open-oceanreservoir
reservoir
age.
It
implies
that
some
older
reworked
material
is present
present as
age. It implies that some older reworkedmaterial is
as
part
of the
the bulk
bulk organic
part of
organic carbon.
carbon.The
The conclusions
conclusionsof
of this
this study
study
would
wouldnot
notchange
changeif
if the
theorganic
organiccarbon
carbondates
dateswere
wereexcluded.
excluded.
The
benthic and
and planktonic
planktonic ages
ages of
of >5000
>5000
The reservoir-corrected
reservoir-corrected
benthic
'4C
years were
were converted
converted to
to calendar
age (Table
3) using
•4Cyears
calendar
age
(Table3)
usingthe
the
nonlinear
relationship
of
Bard
et
al.
[1992]:
nonlinearrelationshipof Bard et al. [ 1992]:
calendar
age =-5.85
= -5.85 x
x 10
(conventional
'4C
calendar
age
10'6
(conventional
t4Cage)2
age)2
++ 1.39
'4C
- 1807.
1.39(convential
(convential
t•Cage)
age)1807.
(1)
ages in
The
'4C age'
refers to
to •4C
'4C ages
The term
term"conventional
"conventional•4C
age" refers
in
radiocarbon
years which
which have
have been
radiocarbonyears
beenreservoir
reservoircorrected.
corrected. Data
Data
used
to construct
construct the
the non-linear
non-linear relationship
relationship of
of Bard
et ci.
usedto
Bard et
al.
[1992]
by Bard
et al.
ci. [1993].
[1992] are
are published
publishedby
Bardet
[1993]. Bard
Bardet
et ci.
al. [1992]
[1992]
also
present a linear
linear relationship
relationship for
alsopresent
foruse
usewith
with'4C
•C dates
damsfrom
from9
to
between these
these two
to 18
18 ka.
ka. Differences
Differencesbetween
two relationships
relationships(linear
(linear
minus
nonlinear)
range
from
5
to
360
years.
minusnonlinear) range from 5 to 360 years. The
The differences
differences
between
the two
two equations
equations are
arethus
thus comparable
comparable to
to the
the 2a
betweenthe
2o errors
errors
of
factors
of our
ourdates.
dams.Likewise,
Likewise,calendar
calendarcorrection
correction
factorsfrom
fromequation
equation
(1)
of <5000
<5000 •C
'4C years
years are
areclose
closeto
to the
the precision
precision of
(1) for
forages
agesof
of the
the
AMS-'4C
dates.We
Wedid
didnot
notattempt
attempt any
any correction
correction factors
for
AMS-•4Cdates.
factors
for
these
young dates.
dates. E.
E. Bard
Bard (personal
communication,
theserelatively
relativelyyoung
(personalcommunication,
1996) considers
considers equation
equation (1)appropriate
(1) appropriate for
1996)
for samples
samplesbetween
between
22,000 years,
years, and
and thus
•C ages
agesof
of 10,000
10,000and
and22,000
thuswell
wellconstrained
constrained
for
correction of
of our
our LOM
for calendar
calendarcorrection
LGM samples.
samples.
Stable
Stable Isotopic
Isotopic Measurements
Measurements
Oxygen (•JtsO,)
(8"O,) and
were
Oxygen
andcarbon
carbon(8'3C,)
(•J•3C.)stable
stableisotopes
isotopeswere
measured
at
Oregon
State
University using
measured
at Oregon State University
usingaaFinnigan
FinniganMATMAT251
stable isotope
isotope mass
with an
251 stable
massspectrometer,
spectrometer,equipped
equippedwith
an
Autoprep
Systems
automated
carbonate
preparation
AutoprepSystemsautomatedcarbonatepreparationdevice.
device.
Each
sample consisted
consistedof
of 12
12 G.
G. hulloides
bulloides shells
shells (300(300- to
to 355Eachsample
355tni size)
the LOM
horizon in
in 10
10 sediment
!,tm
size)collected
collectedfrom
from the
LGM horizon
sedimentcores.
cores.
Isotopic
data use
use the
isotopic delta
delta notation
notation (õ),
(6), in
in per
per
Isotopicdata
thestandard
standard
isotopic
sell
relative to
the Pee
scale.
mil (%)
(9'00)relative
to the
PeeDee
Deebelemnite
belemnite(PDB)
(PDB)scale.
Calibration
to PDB
PDB was
Calibrationto
wasdone
donethrough
throughthe
theNBS-19
NBS-19and
andNBS-20
NBS-20
standards
Institute
Standards and
standards of
of the National
National
Institute
of Standards
and
Technology.
External
precision
estimates
for
6180
and
6'3C,
Technology. Externalprecisionestimatesfor õt80 and õ•3C,
based
on replicate
of local
local calcite
are _+0.08
±0.08
basedon
replicateanalyses
analysesof
calcitestandards,
standards,
are
and
respectively.
and±0.04%o,
:k0.04%o,
respectively.
Regional
salinity (5)
and the
the oxygen
oxygen isotopic
isotopic composition
Regionalsalinity
(S)and
composition
of
(6"O,,) are
are positively
[Craig
of water
water(•JtsOw)
positivelycorrelated
correlated
[Craigand
andGordon,
Gordon,
1965].
6hbO.
is aa function
function of
of both
both temperature
(T)and
1965].Because
Because
•JtaO,
is
temperature
(T) and
6"O,
lines
of
constant
6"O,
plotted
in
T-S
space
approximate
õ•Ow,linesof constant
õ•O, plottedin T-Sspace
approximate
lines
density.
linesof
of constant
constant
density. This
This relationship
relationshipholds
holdsover
oversmall
small
spatial
spatialscales
scaleswhere
whereit
it is
is safe
safeto
toassume
assumethat
that the
theregional
regional
unity - 3180
slope
and
are
We
salinity
•J•aO,•
slope
andintercept
intercept
areconstant.
constant.
Wethus
thususe
use
the
slope
of
3'O,
along
the
42°N
transect
as
a
crude
measure
of
theslopeof •JtsO,
alongthe42øNtransect
asa cn•e measure
of
the
LOM
density
gradient.
This
gradient
yields
an
estimate
of
theLGM densitygradient. This gradientyieldsan estimateof
surface water
water flow
flow direction
direction and
magnitude, assuming
surface
and magnitude,
assuming
geostrophy.
geostrophy.
195
195
ORTIZ
ET AL.:
AL.: GLACIAL
GLACIAL CALIFORNIA
CALIFORNIA CURRENT
CURRENT AT
AT 42øN
42°N
ORTIZ ET
Table 3.
dates for
for the Multitiacers
Table
3. AMS-14C
AMS-•nC dates
Multitracers Cores
Raw
Raw
Sample
Sample
Core
Core
W8709A-8TC
W8709A-8TC
W8709A-STC
W8709A-8TC
W8709A-STC
W8709A-8TC
W8709A-STC
W8709A-8TC
W8709A-8TC
W8709A-8PC
W8709A-SPC
W8709A-8PC
W8709A-SPC
W8709A-8PC
W8709A-8PC
W8709A-SPC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-I3PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-I3PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8709A-13PC
W8809A-21GC
W8809A-31GC
W8809A-3 IGC
W8809A-31GC
W8809A-31GC
W8809A-31GC
W8809A-3IGC
W8809A-31GC
W8809A-29GC
W8809A-29GC
W8809A-29GC
W8809A-29GC
W8809A-29GC
W8809A-53GC
W8809A-53GC
W8809A-53GC
W8809A-53GC
W8909A-57GC
W8909A-57GC
W8909A-570C
W8909A-57GC
W8909A-57GC
W8909A-57GC
AMS-C,'
AMS?C?
Depth.'
Depth,a
cm
cm
Material
Material
Source
Source
27-28
27-28
77-78
77-78
125-126
125-126
120-130
120-130
150-160
150-160
20-25
50-55
50-55
80-85
80-85
111-116
111-116
25-30
95-100
95-100
125-130
125-130
125-130
125-130
195-200
195-200
195-200
195-200
220-225
220-225
220-225
220-225
270-275
300-305
300-305
300-305
300-305
330-335
330-335
390-395
400-405
400-405
400-405
400-405
175-176
175-176
bulk
bulkCorg
Corg
bulk
bulkCorg
Cor•
bulk
bulkCorg
Corg
planktics
planktics
planktics
planktics
planktics
planktics
plankucs
planktics
planktics
planktics
planktics
planktics
planktics
planktics
mixed
mixedbenthics
benthics
mixed
mixedbenthics
benthics
planktics
planktics
mixed
mixedbenthics
benthics
planktics
planktics
mixed
mixedbenthics
benthics
planktics
planktics
planktics
planktics
mixed
mixedbenthics
benthics
planktics
planktics
planklics
planktics
planktics
planktics
mixed
mixedbenthics
benthics
planktics
planktics
G.
G. btdloides
bulloides
G. bulloides
hulloides
G.
G. bulloides
bulloides
G.
G. bulloides
hulloides
G.
G. bulloides
hulloides
G. hulloides
bulloides
G.
G. bulloides
bulloides
bulloides
G. bulloides
bulloides
G. builoides
G. bulloides
builoides
bulloides
G. hulloides
bulloides
G. hulloides
bulloides
G. hulloides
G. bulloides
bu!!oids
G.
Lyle et
etal.
al. [1992]
[1992]
Lyle et
cial.
L¾1e
al.119921
[1992]
cial.
Lyle et
al. [1992]
[1992]
cial.
Lyle et
al.119921
[1992]
Lyle et
etal.
Lyle
al.119921
[1992]
Lyle et
eioj.
al.119921
[1992]
Lyle et
ci al. [1992]
Lyle
[1992]
Lyle ci
aL 119921
L¾1e
eta/.
[19921
Lyle et
ci al. [1992]
[1992]
Gardner
Gardneret
et al
al.[this
[thisissue]
issue]
Gardner
Gardnercial.
et al.Ithis
[thisissue]
issue]
Gardner
Gardner etal.
et al. Ithis
[thisissue]
issuel
Gardner
Gardneretal.
et al.[this
[thisissue]
issue]
Gardner
Gardneretal.
et al. [this
[thisissuel
issue]
Gardner
Gardneretal.
et al.[this
[thisissue]
issue]
Gardner
Gardnerci
et al. [this
[thisissuel
issue]
Gardner
Gardnercial.
et al.[this
[thisissue]
issue]
Lyle et
cial.
L¾1e
al.[19921
[1992]
Gardner
Gardnercial.
et al.[this
[thisissue]
issue]
Gardner
Gardnerci
et al. Ithis
[thisissue]
issue]
ci al. [1992]
Lyle et
[1992]
Lyle ci
L¾1e
et al.
al. 119921
[1992]
Gardner
Gardnerci
et al.
al. [this
[thisissue]
issue]
Gardner
Gardner cial.
et al. [this
[thisissuel
issue]
this study
this
study
this
thisstudy
study
this study
this
study
this
thisstudy
study
this study
this
study
this
thisstudy
study
this study
this
study
this
thisstudy
study
this
thisstudy
study
this
thisstudy
study
this
thisstudy
study
this
thisstudy
study
this
thisstudy
study
this
thisstudy
study
5-6
12-13
12-13
39-40
65-66
160-161
160-161
220-22
1
220-221
232-233
140-141
140-141
170-171
170-171
200-201
200-201
14-15
20-2
1
20-21
58-59
58-59
ka
ka
6.94
6.94
10.44
10.44
15.30
15.30
12.28
12.28
15.85
15.85
15.76
15.76
18.49
18.49
20.92
21.16
21.16
7.00
7.00
11.01
11.01
11.51
11.51
9.96
9.96
14.63
14.63
13.43
13.43
15.86
15.86
14.04
14.04
15.27
15.27
18.49
18.49
16.87
16.87
18.37
18.37
19.82
24.05
24.05
21.96
20.92
16.10
16.10
16.54
16.54
3137
31.37
36.01
36.01
20.72
43.35
43.35
>45.60
>45.60
13.43
13.43
15.03
15.03
18.13
18.13
15.64
15.64
15.75
15.75
43.65
43.65
Raw
Raw
AMS-'4C
AMS-•nC
Error, ka
Error,
ka
0.11
0.11
0.13
0.13
0.21
0.21
0.25
0.25
0.29
0.29
0.40
0.28
0.28
0.38
0.38
0.61
0.61
0.23
0.23
0.36
0.36
0.33
0.33
0.23
0.23
0.39
0.39
0.19
0.19
0.50
0.50
0.28
0.28
0.22
0.38
0.38
0.27
0.27
0.27
0.27
0.61
1.53
1.53
0.49
0.49
0.16
0.16
0.17
0.17
0.10
0.10
0.50
1.26
1.26
0.14
2.37
2.37
N/A
N/A
0.11
0.11
0.80
0.11
0.11
0.80
0.90
0.90
1.16
1.16
Reservoir
Reservoir
Corrected
Corrected
Age,d
Age,d ka
2.64
2.64
6.14
11.00
11.00
11.56
11.56
15.13
15.13
15.04
15.04
17.77
17.77
20.20
20.20
20.44
20.44
6.28
8.63
8.63
9.14
9.14
9.24
9.24
12.25
12.25
12.71
12.71
13.48
13.48
13.32
13.32
14.55
14.55
16.12
16.12
16.15
16.15
17.65
17.65
19.10
19.10
21.67
21.67
2124
21.24
20.20
20.20
15.38
15.38
15.82
15.82
30.65
35.29
20.00
42.63
42.63
>44.88
12.71
12.71
14.31
14.31
17.41
17.41
14.92
15.03
15.03
42.93
42.93
Calendar
Calendar
Age,
Age,
ka
ka
2.64
2.64
6.51
6.51
12.78
12.78
13.48
13.48
17.88
17.88
17.78
17.78
21.05
21.05
23.88
24.16
24.16
6.69
9.76
9.76
10.40
10.40
1034
10.54
14.34
14.34
14.91
14.91
15.87
15.87
15.67
15.67
17.18
17.18
19.07
19.07
19.12
19.12
20.90
20.90
22.61
25.57
25.57
25.08
23.89
23.89
18.19
18.19
18.72
18.72
35.30
39.96
39.96
23.66
23.66
46.82
46.82
>48.80
>48.80
14.92
14.92
16.89
16.89
20.62
20.62
17.63
17.63
17.77
17.77
47.09
47.09
aaW8709A-8PC
overpenetrated
by
value
must
be
totothe
depth
listed
here
for
from
W8709A-8PC
overpenetrated
by140
140an
cm[Lyle
[Lyleci
etal.,
al.,1992].
1992].This
This
value
must
beadded
added
thetabulated
tabulated
depth
listed
here
forsamples
samples
from
W8709A-8PC
true
W8809A-29GC
and
W8709A-8PCto
to determine
determine
tmedepth
depthbelow
belowseafloor.
seafloor.
W8809A-29GCdouble
doublecored
coredby
by135
135cm
cmbased
basedon
onvisual
visualinspection
inspection
andAMS
AMSdating
datingresults,
results,
135
cm must
must be
be subtracted
subtracted from
fran the
values
tabulated
here
to determine
true depth
depth below
below sea
seafloor.
135
cm
the
values
tabulated
here
to
determine
tme
floor.
b Raw data from Lyle cial. [1992] were originally published in reservoir corrected form. Revised calendar corrections for these samples are
bRawdata
from
Lyleetal.[1992]
were
originally
published
inreservoir
corrected
form.Revised
calendar
corrections
forthese
samples
are
based
themethods
methodsdescribed
describedininthe
thetext.
text. Dates
Datesfrom
fromGardner
Gardner et
etal.
obtained from
from J.V.
J.V. Gardner
Gardnerprior
priorto
topublication.
publication. Values
Values
basedcxi
on the
al. [this
[thisissue]
issue]were
wereobtained
presented
here are
are averages
of two
two consecutive
consecutive 2.5
2.5 cm
cm samples.
samples. The
errors for
for each
each sample
are listed
listed in
in the
the table.
table.
presented
here
averages
of
Thesum
sumof
of the
theindividual
individualerrors
sampleare
CCalculated
using the
the Libby
libby half-life
for
'4C.
cCalculated
using
half-life
for
•4C.
d The planktic and mixed benthic dates were reservoir corrected as described in the text. Following Lyle cial. [1992], the bulk Corg dates were
dTheplanktic
and
mixed
benthic
dates
were
reservoir
corrected
asdescribed
inthetext.Following
Lyle
etal.[1992],
thebulk
Corg
dates
were
offset
corrected
planktic
dates.
offsetby
by 4.3
4.3ka
karelative
relativeto
tothe
thereservoir
reservoir
corrected
planktic
dates.
We estimate
estimatethe
theoxygen
oxygenisotopic
isotopic composition
composition of
of calcite
calcite in
in
We
equilibrium
withthe
thewater
water
column
(0) using
TT and
equilibrium
with
column
(8•gO,)
using
and8'O,,
8•gO,as
as
inputs
equationof
of Epstein
Epstein et
et al.
inputs to
to the
thepaleotemperature
paleotemperature
equation
al.
[1953]. For
use SST
surface salinity
salinity
[1953].
Formodem
modemconditions
conditionswe
we use
SST and
andsurface
from
Levitus [1982]
[1982]as
asthe
theinputs.
inputs. Conversion
Conversion of
of salinity
salinity to
from Levitus
to
the northeast
relationship of
of Zahn
Zahn et
et al.
•5•80.uses
usesthe
northeastPacific
Pacificrelationship
al.
[1991 a]:
[1991a]:
- 14.01
%.
8"0,, = 0.405(salinity)
0.405(salinity)
14.019'oo.
(2)
(2)
To
To estimate
estimatethe
the relative
relative magnitude
magnitudeof
of the
theLGM
LGM SST
SST and
and
surface
salinity changes
recordedin
in 8•80.,
8"O, we
(1) an
surface
salinity
changes
recorded
weassume
assume
(1)
an
LGM ice
ice volume
volume •80
6O effect
relative
values
effectof
of+1.3%
+1.39'oo
relativeto
topresent
present
values
slope
[e.g.,
1989;
[e.g.,Fairbanks,
Fairbanks,
1989;Mix,
Mix, 1987],
1987],(2)
(2)aasalinity-8'5O
salinity-8•sO.
slope
the
same
as
at
present,
and
(3)
a
constant
depth
habitat
for
the same as at present, and (3) a constantdepthhabitat for G.
G.
bulloides
sites at
at present
present [Ortiz
et al.
al. 1995].
bulloides((0O-30
30 m
m in
in these
thesesites
[Ortiz et
1995].
The third
third assumption
assumptionis
is the
the weakest.
weakest. In
The
In the
theGulf
Gulf of
of Alaska,
Alaska, G.
G.
bulloides
and 150
m [Miles,
Zahn et
bulloides resides
residesbetween
between 100
100 and
150 m
[Miles, 1973;
1973; Zahn
et
al.
depth range
range is
is within
al. 1991a].
1991a]. This
This depth
within the
themain
mainpycnocline,
pycnocline,
below
the base
base of
of the
below the
the mixed
mixed layer
layer and
andabove
abovethe
the North
North Pacific
Pacific
halocline.
to Zahn
Zahn et
et al.
halocline. According
Accordingto
al. [1991a],
[1991a], this
thissubsurface
subsurface
habitat
makes the
the •O
8"O of
G.
up
habitatmakes
oflate
lateholocene
holocene
G.bu!!oides
bulloides
uptoto1%o
19'oo
enriched
relative
to
seasonally
weighted
surface
water
8O
enriched
relativeto seasonally
weighted
surface
water•O, for
for
the
of Alaska.
Alaska. IfIf the
the relationship
relationship to
to the
the pycnocline
is
the Gulf
Gulf of
pycnocline is
functional,
functional, aa shift
shift to
to aasimilar
similardepth
depthhabitat
habitatduring
duringthe
the1.GM
LGM
196
196
AL.: GLACIAL
GLACIAL CALIFORNIA CURRENT AT
AT 42øN
42°N
ORTIZ ET AL.'
could result
result in
in aa •so
8"O offset
offsetof
ofup
upto
to 1%oo
1% during
during the
the LGM.
could
LGM. Thus
Thus
any
downward
shift
of
the
depth
habitat
of
G.
bulloides
toward
anydownward
shiftof thedepthhabitatof G. bulloides
toward
The
x and
andyy components
of wind
wind stress
stress(()• are
defined
as:
The x
components
of
) are
defined
as:
(4a)
'r
(4a)
=PCaIUIU,
the
or
in
salinity
thepycnocline,
pycnocline,
ordecrease
decrease
in the
theregional
regional
salinity-slope
result in
of
slopeat
atthe
theLGM,
LGM,would
wouldresult
in an
anoverestimate
overestimate
ofLGM
LGM and
cooling
based
on
8O,.
cooling
based
on•0,.
(4b)
=PC,fr1Y,
y =
ey
calF,
(4b)
The
gradient, measured
in LGM
G. bulloides
bulloides
The offshore
offshore813C
6nC gradient,
measured
in
LGM G.
(6'3C,)
is
compared
with
equilibrium
calcite
values
shells,
shells,is compared
with equilibrium
calcitevalues
the
wind
stress
components
in
per
where
where•x and
and5ryare
are
the
wind
stress
components
indynes
dynes
per
predicted
from water
column &'3C
measurementson
on dissolved
dissolved
are
the
products
of
the
x
or y
'
and
predicted
from
watercolumn
6•C measurements
square
centimeter,
and
square
centimeter,
and
lala
and
I•
are
the
products
of
the
x
or
inorganic carbon
carbon in
in the
the same
sametransect
transect [Ortiz
[Ortizetetal.
al. 1996].
1996]. The
inorganic
The component
of wind
speed and
and velocity
velocity [Bakun
componentof
wind speed
[Bakunand
and Nelson,
Nelson,
with dissolved
dissolved nitrate,
nitrate,
watercolumn
8'3C0
watercolumn
6nCmcare
arewell
wellcorrelated
correlated
with
1991].
field corresponds
correspondsto
toaa level
level about
about 40
40 m
1991]. The
The model
modelwind
wind field
m
and
thus we
we consider
consider the
the isotopic
isotopic data
data to
to be
be aa good
good proxy
proxy for
andthus
for
above
sea
level.
Use
of
a
constant
logarithmic
scaling
factor
abovesealevel. Use of a constantlogarithmicscalingfactorto
to
upper
ocean nutrient
nutrient gradients
gradients in
in this
from 40
40 m
m to
to "standard"
"standard" 10-m
10-m winds
winds typically
typically used
for
upperocean
thisregion.
region. We
We emphasize
emphasize convert
convertfrom
usedfor
gradients
because absolute
absolute $•C
8"C values
values are
are affected
affectedby
by (1)
(1) the
calculations would
decreaseour
ourwind
windstress
stress estimates
estimates by
such calculations
would decrease
by
gradients
because
the such
We hold
[CM
decrease
relativetotothe
theHolocene
Holoceneocean
ocean (about(about 10-15% [Stull,
[Stull, 19881.
1988]. We
hold air
air density
density (p)
(p) and
and the
the
LGM&'3CDIC
6nCmcdecrease
relative
g cm
cm'-aand
dimensionless
drag coefficient
(Cd
8'3CIJC
O.4%o;
Cwry and
and Crowley
[1987]),
dimensionless
drag
coefficient
(Cd)) at
at22
22xx iO
10-3g
and1.3
1.3
0.4%0;Curry
Crowley
[1987]),(2)
(2) the
themodern
modem
decrease
due
CO2
the upper
upper ocean
x iO
[Nelson,
1977;
Bakun
and
1991].
decrease
dueto
toinput
inputof
ofanthropogenic
anthropogenic
CO2 into
intothe
ocean x
10'3respectively
respectively
[Nelson,
1977;
Bakun
andNelson,
Nelson,
1991].
along-shore
(-0.6±O.2%c
thisregion
region [Ortiz
[Ortizetet al.
al. 1996]),
1996]), and
To
To calculate
calculateoffshore
offshoreEkman
Ekmantransport,
transport, the
the along-shore
(-0.6-!-0.2%o
ininthis
and(3)
(3) the
the
coastal wind
wind stress
stress was
wasobtained
obtainedfrom
fromthe
the uu and
andvvcomponents,
components,
potential
for
in
potential
for8'3C
6nCdisequilibria
disequilibria
inG.
G.bulloides.
bulloides.For
Forequation
equation coastal
then
to 0.6
0.6°ø by
and
by the
theninterpolated
interpolated
to
by 0.6°
0.6øresolution,
resolution,
anddivided
dividedby
the
(3),
carbon isotopic
isotopic disequilibrium
disequilibriumin
in the
the $nC,
8'3C, of
of
(3),we
wemodel
modelthe
thecarbon
Coriolis
parameter,
f.
G.
G. bulloides
bulloides as
as aafunction
functionofofcalcification
calcificationtemperature,
temperature,T,,
T c, Coriolisparameter,f.
Wind stress
stress curl,
curl, the
the second
Wind
secondwind
wind variable
variable we
we studied,
studied, is
is
following
following Ortiz
Ortiz er
et al.
al. [1996]:
[1996]:
defined
defined as:
as:
= •nC,
ö'3C, +
+
813Ce
8•C, =
2.0crc'6•v•ø
(3)
(3)
We
use the
the LGM
modem analog
analog SST
We use
LGM modem
SSTvalues
valuesderived
derivedfrom
fromthe
the
foraminiferal faunas
faunas to
foraminiferal
to estimate
estimateT,.
T•.
(ac)
cur1C=1,--
(5)
We
windstress
stresscurl
curlon
on the
the model
model grid
grid using
We calculated
calculated wind
using aa
centered,
centered, finite
finite difference
difference scheme:
scheme:
Simulating
Simulating Wind-Driven
Wind-Driven Upwelling
Upwelling
Upwelling,
injects nutrients
Upwelling,which
whichinjects
nutrientsinto
intothe
theupper
upperocean
oceanand
and
thus
supports
biological
productivity,
is
driven
by
the
winds in
thussupports
biologicalproductivity,
is drivenby thewinds
in
First, along-shore
two
ways in
in this
boundary
setting.
twoways
thiseastern
eastern
boundary
setting. First,
along-shore
winds
from the
the north
winds from
north drive
driveoffshore
offshoreEkman
Ekmantransport.
transport.Coastal
Coastal
Active coastal
coastal
upwelling
the
upwellingreplaces
replaces
thewater
watermoved
movedoffshore.
offshore. Active
upwelling
is
limited
to
about
50
km
offshore,
mostly
over
upwellingis limitedto about50 km offshore,mostlyoverthe
the
continental
shelf, but
but its
continentalshell
its effects
effectscan
canextend
extendfarther
farther offshore
offshore as
as
coastal
seaward. Second,
divergence of
of
coastalnutrients
nutrientsare
areadvected
advectedseaward.
Second,divergence
winds
(wind stress
stress curl)
curl)drives
drivesupwelling
upwellingininthe
theopen
openocean.
ocean. In
winds(wind
In
the
positive
curl
thenorthern
northernhemisphere,
hemisphere,
positive(cyclonic)
(cyclonic)wind
windstress
stress
curl
induces
oceanic upwelling,
inducesoceanic
upwelling,whereas
whereasnegative
negative(anticyclonic)
(anticyclonic)
wind-stress
wind-stresscurl
curl results
resultsin
indownwelling.
downwelling. These
Thesemechanisms
mechanisms
often
reinforceeach
eachother
otherbut
butare
arenot
notstrictly
strictly linked.
linked. Changes
often reinforce
Changes
- 1r(i+1,j)r"(i 1,j)1 1'(i,j--1)_'(i,j_ 1)]
iL
curl•=[*Y(i+l,J)-*•(i-l,
1 (6)
curFr
=[
iL
(6)
that
curl'
based
on
and •5 at
thatapproximates
approximates
curlyat
atgrid
gridlocation
location
based
on• and
at
four
neighboring grid
points separated
four neighboring
grid points
separatedby
by distances
distancesb.Lx
ALx and
and
the
ALy
of 120
1977].
ALyof
120km
km[Nelson,
[Nelson,
1977]. We
Wedid
didnot
notemploy
employ
the
overlapping-grid
overlapping-gridmethod
methodof
of Bakun
Bakunand
andNelson
Nelson[1991]
[1991]because
because
un]ike
unlike their
their irregularly
irregularlyspaced
spacedobservations,
observations,our
ourmodel
modelwind
wind
fields
relatively smooth
60-km
fields are
arerelatively
smoothon
onaaregularly
regularlyspaced
spaced
60-kmgrid.
grid.
Our
wind stress
stresscurl
curlestimates
estimateswere
wereinterpolated
interpolatedto
to0.6
0.6°
by 0.6
0.6°ø
Our wind
ø by
resolution
for
graphic
presentation
using
the
nearest
neighbor
resolutionfor graphicpresentationusing the nearestneighbor
method,
yielding resolution
resolution similar
similar to
to the
method,yielding
the seasonal
seasonalmaps
mapsof
of
Bakun
Bakun and
and Nelson
Nelson [1991].
[ 1991].
in
in one
onemechanism
mechanismcan
canbe
bedecoupled
decoupledfrom
fromthe
theother.
other.
these two
To isolate
isolate these
two effects
effects of
of coastal
coastal and
and open-ocean
open-ocean
upwelling
calculated Ekman
Ekmantransport
transport and
and wind
wind stress
upwellingwe
wecalculated
stresscurl
curl
using
wind
fields
from
the
National
Center
for
Atmospheric
usingwind fieldsfrom the NationalCenterfor Atmospheric
model
climate model
Research
(NCAR) atmospheric
Research (NCAR)
atmospheric regional
regional climate
(RegCM). The
of the
the RegCM
RegCM used
usedhere
herehas
has 13
13 vertical
vertical
(RegCM).
Theversion
versionof
levels and
and 60-1cm
60-km grid
grid spacing
spacing over
over aa 3000
3000 x
x 3000
levels
3000 km
kmdomain
domain
centered
16°W (i.e.,
(i.e.,the
the comers
corners of the
centeredat
at 38°N,
38øN,1116øW
themodel
modeldomain
domain
are
NW=49.6°N, 137.3øW;
137.3°W; NE=49.6°N,
94.6°W; SW=23.9°N,
are NW--49.6øN,
NE--49.6øN, 94.6øW;
SW=23.9øN,
130.1°W; SE=23.9°N,
130.1øW;
SE=23.9øN,101.9°W).
101.9øW). Model
Model wind
wind fields
fields from
from
Hostetler
et al.
for 60
Hostetleret
al. [1994]
[1994] were
were sampled
sampledfor
60 days
daysto
tocalculate
calculate
offshore
offshore Ekman
Elcmantransport
transportand
andwind
windstress
stress curl.
curl. Perpetual
Perpetual
January
and July
July simulations
simulations were
wererun
runusing
using control
control (0
(0 ka)
ka) and
Januaryand
and
[GM
LGM (18
(18 ka)
ka)boundary
boundaryconditions
conditionsderived
derivedfrom
from the
the coarse
coarse
resolution
general circulation
circulation model
model (GCM)
(GCM)runs
runs of
of
resolutionCOHMAP
COHMAPgeneral
Kutzbach
and Guetter
Kutzbach and
Guetter [1986].
[ 1986].
Results
Results
Comparison of
of Modern
Comparison
Modern and
and Glacial
Glacial Foraminlferal
Foramlnlferal
Faunas
Faunas
Modem
Modern and
and LGM
LGM foraminiferal
foraminiferal percentage
percentagedata
data appear
appearin
in
Table
4, and
and the
the abundances
abundances of
of dominant
dominant species
Table4,
speciesare
areillustrated
illustrated
in Figure
Left-coiling N.
3a) and
in
Figure 3.
3. Left-coiling
N. pachyderma
pachyderma(Figure
(Figure 3a)
and G.
G.
bulloides
(Figure
3d)
dominate
the
LGM
fauna,
accounting
for
bulloides(Figure3d)dominate the LGM fauna,accountingfor
>70% of
of the
at
This
>70%
the foraminifera
foraminifera
at each
each site.
site.
This combination
combination
resembles
the modern
subpolar fauna
faunaofof the
the Gulf
resemblesthe
modern subpolar
Gulf of
of Alaska
Alaska
[Sautter
and Thunell,
Thuneil, 1989].
1989]. High
percentages of
of these
these species
species
[Sautterand
High percentages
occur in
inour
ourLGM
[GMtransect
transect as
as far
far west
west as
as 130°W,
some 650
650 km
occur
130øW, some
km
offshore. In
left-coiling N.
offshore.
In contrast,
contrast, left-coiling
N. pachyderma
pachydermaand
and G.
G.
ORTIZ
ET AL.:
AL.: GLACIAL
GLACIAL CALIFORNIA
CURRENT AT
AT 42øN
42°N
ORTIZ ET
CALIFORNIA
CURRENT
197
0 00 N 00 %0 000
0ooeodd
q
bulloides
uncommon at
at 42øN,
42°N, accounting
accountingfor
for only
only
bulloidesare
are presently
presentlyuncommon
about
10%
of
the
fauna
west
of
128°W.
Modem
percentages
rise
about10% of the faunawestof 128øW.Modempercentages
rise
to
to about
about40%
40% of
of the
thefauna
faunaat
at126°W
126øW(300
(300km
kmoffshore).
offshore).
000do
C
Two
and
Two more
more subpolar
subpolarspecies,
species,Globigerina
Globigerinaquinqueloba
quinqueloba
and
Globigerinita
roughly equal
equal
Globigerinita glutinata,
glutinata, were
were found
found at
at roughly
percentages
in both
data sets.
sets. Another,
percentagesin
both the
themodern
modemand
and LGM
LGM data
Another,
al. 19961
the deep-dwelling
Globorotalia scitula
et al.
the
deep-dwelling Globorotalia
scitula [Ortiz
[Ortiz et
1996]
in
000000000 N
o 0 e ooooooooo•
coo 00000
Oj
o.o.o.
oooc:5c•c5c5c•c5c5c5c:5c5
decreased
in abundance
abundanceininthe
the LGM
LGMsamples
samplesrelative
relative to
to the
decre• in
the
modem
modemones
ones(Figure
(Figure3).
3).
Transitional
at
Transitionaltaxa,
taxa,including
includingN.
N. dutertrei,
dutertrei,decreased
decreased
at LGM
LGM
relative
Peak abundance
relativeto
to present
presentin
in the
the cores
coresnear
nearthe
thecoast.
coast. Peak
abundance
of right-coiling
right-coilingN.
N. pachyderma
pachyderma (30%)
(30%)isis similar
similar in
in the
of
the modem
modem
and LGM
LGMassemblages
assemblages (Figure
(Figure3h)
3h) but
but moved
moved offshore
offshore during
and
during
the 1GM
expense of
species
the
LGM at
at the
the expense
of modem
modemsubtropical
subtropical species
(Orbulina
ruber) (Figure
3).
(Orbulinaurnversa
universaand
andGlobigerinoides
Globigerinoides
ruber)
(Figure3).
- Cfl 0% In
0 ' 0"
In
00
en
In 0%
N 00- %O %0
-.000
In
N
0000000000-0
.O
0000000000000
The
planktonic foraminiferal
The LGM
LGM planktonic
foraminiferal fauna
fauna at
at 42°N
42øN records
records
expansion of
expansion
of subpolar
subpolarconditions
conditions as
as far
far west
west as
as130°W,
130øW,
trending to
to transitional
transitional waters
trending
waters offshore.
offshore. These
These data
data are
are
consistent with
consistent
with ice-age
ice-age cooling
cooling across
acrossthe
the entire
entire transect.
transect.
000000
0000 000000 In N
en
Similar to
to the
Similar
the modem
modem distribution,
distribution, the
the LGM
LGM fauna
fauna associated
associated
with cooler
cooler water
occurrednear
near the
the coast,
coast, while
with
water occurred
while the
the wannerwarmer-
000000000000 N
000000000000
o.o.o.o.o.o.
ooooooddddddd
waterLGM
LGMfauna
faunawas
wasfound
foundoffshore.
offshore. Some
Some of
of the
the decrease
decrease in
in
water
0. universa
O.
universaand
andG.
G.ruber
ruberobserved
observedcould
couldreflect
reflect greater
greater
dissolution in
in LGM
LGM sediment
sediment samples
samples than
than in
in modem
dissolution
modemsediment
sediment
trap samples.
samples. IfIf so,
the
trap
so,our
ourresults
resultswould
wouldoverestimate
overestimate
the extent
extentof
of
ice-age
cooling
far
offshore.
ice-agecooling far offshore.
oooooo•
--00 In 00 N 000% 0%
0% 0
00 N - en 00-
Modern Analog
Modern
Analog Sea
Sea Surface
Surface Temperatures
Temperatures
0.
in the
O. universa
universa and
and G.
G. ruber
ruber drive
drive the
the anomalous
anomalous warmth
warmth in
the
offshore
estimate
[Ortiz
and
Mix,
this
issue].
These
species
offshoreestimate[Ortiz and M/x, thisissue]. These speciesare
are
a
en en en
'0
0 In In
N
en
en N en
N
N N N 000% In
InN
rare in
in N.
N. Pacific
core tops
midlatitudes, probably
probably because
rare
Pacificcore
topsfrom
from midlatitudes,
because
Because the
they
they are
are highly
highly sensitive
sensitive to
to dissolution.
dissolution. Because
the
N
en N -
OCnO%%C
0 en N en
The
modem analog
analog SST
The modem
SST estimates
estimatesderived
derivedfrom
from the
themodem
modem
sediment trap
trap faunas
faunas track
trackatlas
atlasvalues
valuesatatthe
thecoastal
coastalsites
sites but
but
sediment
overestimateSST
SSTat
atthe
thesite
sitefarthest
farthestoffshore.
offshore. The
of
overestimate
The presence
presenceof
N 000 N '000 '0
-
000000000000
In
000000Cc1
calibration
data set
set is
is composed
of partially
calibration data
composedof
partially dissolved
dissolvedcore
core
tops,
this
"no-analog"
bias
shows
up
in
the
well-preserved
tops, this "no-analog" bias shows up in the well-preserved
sediment
trapsamples.
samples.We
Weexpect
expectthat
thatthis
thisbias
bias isis not
not aa
sedimenttrap
00
problem
problemfor
for the
theLGM
LGM samples.
samples.
%O N %0 en co N In
'0 N '00
In N N 0 '0 N
NNenNen---.
00 Ifl N in
The best
best modern
analogs for
The
modern analogs
for the
theLOM
LGM California
California Current
Current
foraminifera
are from
from core
core top
top sediments
sediments in
in the
the Gulf
of Alaska,
foraminiferaare
Gulf of
Alaska,
although some
some analog
analog samples
from similar
similar latitudes
latitudes in
in
although
samplescome
comefrom
the
the North
North Atlantic.
Atlantic. The
Thedissimilarity
dissimilaritycoefficients
coefficientsfor
foreach
eachcore
core
were small
small (well
(wellbelow
belowthe
theempirical
empiricalcutoff
cutoffofof0.2),
0.2),so
so the
the
were
analogs
are
excellent
(Fable
5).
analogsare excellent(Table 5).
At the
the LGM,
the annual
At
LGM, the
annualaverage
averagemodem
modem analog
analog SST
SST was
was
3.3°±1.5°C cooler
cooler than
than modem
modern atlas
atlas SST
SST at
at 42øN
42°N (Table
(Table 5,
5,
3.3ø+1.5øC
Figure
4).
SST
remained
coolest
near
the
coast
and
increased
Figure4). SST remainedcoolest near the coast and increased
offshore. The
offshore thermal
thermal gradient
gradient was
was similar
similar to
to
offshore.
TheLOM
LDM offshore
today's (about
0.3°C // degree
degree longitude).
longitude). Given
Given the
the 1.5°C
error
today's
(about0.3'12
1.5øC error
of the
of
the method,
method,there
therewas
wasno
nostatistically
statisticallysignificant
significantstructure
structureto
to
N 00 -.00 '
0%
N In In 00 In
%0 en %0
qqqe0000In.00
00000000
In
000000000000
00 00 00 00 00 00N 0
0000-00000
N In'0
0000d
I
dddd4ddddd4•N
e.i
ooqoo.00%cN'o.-.o.c
00000ed..o
the LGM
the transect.
transect.
LGM - modern
modern SST
SST difference
difference across the
Oxygen
Isotopes and
and Sea
Oxygen Isotopes
Sea Surface
Surface Temperatures
Temperatures
The 8•O
&O of
at
LGM was
washigher
highernear
nearthe
thecoast
coast
The
ofG.
G.bulloides
bulloides
atthe
theLGM
and
lower
offshore
(Figure
5,
Table
5).
This
gradient
agrees
and lower offshore(Figure5, Table 5). This gradientagrees
with
gradients implied
implied by
by the
the glacial
glacial
with the
the sense
senseof
of temperature
temperaturegradients
I
'0
N - N N - NNN
o
1
-:
of the
the oxygen
fauna.
fauna. Predictions
Predictionsof
oxygen isotopic
isotopic composition
compositionof
of
equilibrium
calcite,8•O,,
8'O,, based
on modern
equilibrium
calcite,
basedon
modernatlas
atlasSST
SSTand
and
0000
1-'
000000
.0 '
ORTIZ
AT 42
42°N
ORTIZ ET
ET AL.:
AL.: GLACIAL
GLACIAL CALIFORNIA
CALIFORNIA CURRENT
CURRENT AT
ON
198
o 80
80 a N. pachyderma L
60
•O
20 bG.
glutinata •
I n0
.
'•10
<
0'•?:•.
10
< 5 ••
20
20
.
I
.
• 'm,
x
20
<
<
....
.2.-' ß,-'-•
00 ß
. ø,i-..i.i.
• 20
ß, ß, . • ß < 05
0 -r'-•
-.
10
j••'
5
5
•
.
°:
<10<
10
0
0
ßr- i ß, ß• ß
\
•
15
i G. ruber
I•=10
'
10
Oq.....
0
134 132
134
132 130
130 128
128 126
126 124
124
134
134 132
132 130
130 128
128 126
126 124
124
Longitude (°W)
Longitude
(øW)
Longitude
Longitude(°W)
(øW)
-- -- -m°- --
10
' -=,
0 -• '--7:•=:'n
134 132
132 130
134
130 128
128 126
126 124
124
hh N.
N.pachydermaR
pachyderma
R
2O-
',
20
20
40 -
gr(7.quinqueloba
qiwLuva
g
30
20
20
10
0
134
134 132
132 130
130 128
128 126
126 124
124
134
134 132
132 130
130 128
128 126
126 124
124
o
50
50
øø40
40 f O.universa
10
40
40:
,
134
134 132
132 130
130 128
128 126
126 124
124
134
134 132
132 130
130 128
128 126
126 124
124
d G. bulloides
o 60: d
G.hulloides o
ø 15 eG.scitula
20
, '
, ß, ß • Oqav. , ß, ß• ß •' 0Oq
o 80
80
•
C N. dutetrei
15
• 10
5
5
134
134 132
132 130
130 128
128 126
126 124
124
'I
20
20
Modern sediment
trap
Modem
sediment
trapfaunas
faunas
ß
<
5
5
•
0Oß.=•-=¾-• -'r =
134
134 132
132 130
130 128
128 126
126 124
124
Longitude (°W)
Longitude
(øW)
Last
Last Glacial
Glacial Maximum
Maximum fossil
fossil faunas
faunas
Figure
species percentages
across the
Figure 3.
3. Planktic
Planktic foraminifera
foraminifera species
percentagesacross
the transect
transectat
at 42°N:
42øN: (a)
(a) left
left coiling
coiling N.
N.
pacizyderma, Co)G.
(b) G. glistinata,
N. d.uertrei,
(d) G.
G. bulloides,
bulloides, (e)
(e) G.
G. scitula,
scitula, (f)
(f) O.
0. universa,
pachyderma,
glutinata, (c)
(c) N.
dutertrei, (d)
universa, (g)
(g) G.
G.
quinqueloba,
(h) rightright- coiling
and
quinqueloba,(h)
coilingN.
N. pachyderma
pachyderma
and(i)
(i) G.
G. ruber.
ruber. Solid
Solid squares
squaresdenote
denoteLGM
LGM horizon.
horizon. Open
Open
squares
denote modem
modem sediment
sedimenttrap
trap data
data based
based on
on flux-weighted
flux-weighted averages
averages of
of seasonal
seasonal data
squaresdenote
datareported
reportedby
by Ortiz
Ortiz
and
and Mix
M/x [19921.
[19921.
Assuming
all of
of the
salinities,
-0.09% 610
Assumingall
the observed
observedgradients
gradientsin
in 6180
8"0 arose
arosefrom
from
salinities,yield
yieldaazonal
zonalgradient
gradientin
in 8'°O
8•'0,ofof-0.09%o
8"0 I/
temperature, the
the associated
associated offshore
degree
longitude (r•=0.79,
(r2=0.79,n=10)
n=10) at
at these
degreelongitude
thesesites.
sites. A similar
similar temperature,
offshorethermal
thermalgradient
gradientwould
wouldbe
be
longitude.
gradient
calculatedfrom
fromthe
theLGM
LGMsamples
samples
was
-0.13%8•aO
6O // 0.50
0.5ø to
to 0.6
0.6 °C
ø(2/ /degree
degree
longitude. This
This is
is about
abouttwice
twice the
the
gradientcalculated
was
-0.13%o
temperature gradient
gradientat
at present,
present, and
and twice
twice that
that estimated
degree
longitude (r2--0.72,
(r2=0.72,n=10).
n=10). The
The offshore
offshoreslope
slope of
of the
estimatedfrom
from
degreelongitude
the temperature
the
LGM
fauna
(+0.3
°C
I
°
longitude).
Possible
LGM
denser
water
(colder and/or
and/or saltier)
saltier) near
explanations
LGM 8"O
8•'Odata
datasuggests
suggests
denser
water(colder
near theLGM fauna(+0.3 ø(2/ olongitude). Possibleexplanations
could
LGM salinity
salinity gradient
gradient was
was steeper
steeper than
than the
the
dense water
couldbe
be that
that(1)
(1) the
the LGM
the
the coast
coastrelative
relative to
to less
less dense
water offshore,
offshore, implying
implying
southward
geostrophic
flow
as
at
present.
modem
one,
(2)
the
LGM
salinity/8'8O
slope
was
steeper
than
southwardgeostrophicflow as at present.
modem
one,(2) theLGM salinity/8•80,,
slopewassteeper
than
Table 5.
G. bulloides
355 gm)
tm) Stable
Across
Table
5. LGM
LGM Modem
ModemAnalog
AnalogMethod
MethodSST
SSTand
andLGM
LGM G.
bulloides(300(300- 355
StableIsotope
IsotopeMeasurements
Measurements
Acrossthe
the
Muhitracers Transe•t
Transect
Multi,racers
Cove
Core
Name
Name
6706-2
6706-2
W8709A-13PC
W8709A-13PC
W8809A-530C
W8809A-53GC
W8809A-21GC
W8809A-21GC
W8709A-O8PC
W8709A-08PC
W8809A-29GC
W8809A-29Cd2
W8809A-31GC
W8809A-3
IGC
W8909A-57GC
W8909A-57GC
W8709A-01BC
W8709A-01BC
W8909A-48GC
W8909A-48GC
Sample
Depth,
Sample
Depth, Longitude,
Longitude,
an
cm
259-260
259-260
275-276
275-276
168-169
168-169
140-141
140-141
22-23
22-23
156-157
156-157
15-16
15-16
22-23
22-23
21-22
21-22
17-18
øW
Mean
LGM
Mean
LGM
SSTaa
Dissimilarity
DissimilaritySST
124.94
124.94
125.75
125.75
126.26
126.26
126.91
126.91
127.68
127.68
129.00
129.00
130.01
130.62
130.62
131.96
131.96
132.67
132.67
0.06
0.06
0.07
0.07
0.05
0.05
0.09
0.09
0.05
0.05
0.06
0.06
0.10
0.10
0.05
0.05
0.09
0.09
0.09
0.09
9.0
9.0
10.0
9.8
9.8
8.8
9.3
9.3
9.8
9.8
10.6
9.8
11.8
11.8
Modem
Modem LaMLGM-Present
Present &80,
8180,
SST
SST1'
SST
b
SSTChange
Change %OPDB
%0PDB
11.8
12.3
12.6
12.9
13.3
13.8
14.1
14.2
14.4
14.5
aBai,i foiaminifezal
faimas
using
thethe
modem
analog
method,
associated
errors
are
°C.
aBa•,d
onforaminife•
faunas
using
modem
analog
method,
associated
errors
are±1.5
:kl.5øC.
1'lnterpoheed
to core
re locations
locatsons from
fran Levitus
[19821.
bInterpolated
to
Levitus
[1982].
-2.8
-2.3
-2.3
-2.8
-2.8
-4.1
-4.0
-4.0
-4.0
-3.5
-4.4
-2.6
-2.7
-Z7
2.79
2.97
2.97
3.16
3.16
2.70
2.70
2.81
2.28
2.67
2.52
2.19
1.82
&3C,
813C,
%oPDB
%0
PDB
-0.03
-0.27
-0.27
0.20
0.20
0.07
0.07
-0.06
-0.06
0.07
0.07
-0.09
-0.09
037
0.37
0.82
0.82
0.87
0.87
ORTIZ
AL.: GLACIAL
CURRENT AT
AT 42øN
42°N
ORTIZ ET
ET AL.'
GLACIAL CALIFORNIA
CALIFORNIA
CURRENT
Carbon Isotopes
Carbon
Isotopes and
and Nutrient
Nutrient Gradients
Gradients
22
4Modem
(sediment
trap)
foraminifera
o• 18
•
14-•
.-
12
In the
In
the absence
absenceof
of active
activeupwelling,
upwelling,modem
modemsurface
surfacewaters
waters
(offset
to
the
LGM
mean)
yield
8'3C0
predictions
near
(offsetto the LGM mean)yield •nC, predictions
near2.5%o
2.59'0o
with small
with
small variation
variation across
acrossthe
the transect
transect(Figure
(Figure 6).
6). Active
Active
upwelling
upwelling brings
bringsnutrient-rich
nutrient-richwaters
watersfrom
fromaround
around70
70 m
m depth
depth
to
the
surface
(Figure
6).
This
reduces
surface
813C0
to
to thesurface
(Figure6). Thisreduces
surface•nCc to values
values
near
8'3C,
atatlOOm
nearthose
thoseat
at100
100m
m at
atthe
thesame
samesite.
site.The
Themodem
modem
fi•aCc
100m
increases
offshore
by
about
19k.
This
shift
reflects
shoaling
of
increasesoffshoreby about 19'0o.This shift reflectsshoalingof
the
nutricline in
in response
to southward
geostrophic flow
the nutric]ine
responseto
southwardgeostrophic
flow and
and
local
localwind
windforcing.
forcing.
The
8'3C of LGM G.
G. bulk>ides
bulloides range
range from
from -0.279k
near
The/5•C
-0.279'0o
nearthe
the
"......
m 16-1.
Levitus
SST
"""'"- T
.__
I• 108
LGM
fomminff'
era
coast
near
coast to
to 0.879k
0.879'0o
near132.5°W
132.5øW (Figure
(Figure 6,
6, Table
Table 5).
5). After
After
LGM radiolaria
6
'
134
I
132
'
I
130
'
I
128
'
I
126
199
'
124
Longitude
(°W)
Longitude
(øW)
disequilibrium
effects are
are estimated
estimated and
and removed
removed (equation
disequilibriumeffects
(equation3),
3),
the
mean
613C
of
G.
bulloides
approximates
water
column
8'3C,
themean/5•Cof G. bulk>ides
approximates
watercolumn/SnC,
derived
from
ofofwater
column
8'3CDIC corrected
corrected for
derived
frommeasurements
measurements
water
column/5•3Cmc
for
the
813CD1C
decrease
andthe
themean
mean ocean's
ocean's
theanthropogenic
anthropogenic
•5•Cmcdecrease
and
glacial-interglacial
613C01
shift. The
The offshore
gradient
in
glacial-interglacial
•SnCmc
shift.
offshore
gradient
in 8'3C
•SnC
FIgure
across the
the transect.
transect. Modem
Figure 4.
4. Temperature
Temperaturegradients
gradientsacross
Modem
thermal
gradient (open
(open circles)
circles) is
is from
fromLevitus
Levitus[1982].
[1982]. Modem
Modem
thermalgradient
analog
SST estimates
estimates based
based on
on the
the sediment
(open remains, suggesting large offshore nutrient gradients as at
analogSST
sedimenttrap
trap faunas
faunas(open
remains, suggesting large offshore nutrient gradients as at
squares)
are from
from Ortiz
Ortiz and
and Mix
Mix [this
squares)are
[this issue].
issue]. Solid
Solid squares
squares present. Westward translation of the LGM 8'3C, gradient
present. Westwardtranslationof the LGM •5•aC,gradient
denote
modem analog
analog SST
estimates based
based on
denote modem
SST estimates
on glacial-age
glacial-age
results
from ~126øW
126°W and
-128°W are
Pisias
results from
and-128øW
are from
from Sabin
Sabin and
and Pisias
relative
westward
relativeto
to the
thepresent
presentgradient
gradientsuggests
suggests
westwardtranslation
translationof
of
the
nutrient
coupled to
the associated
associated
nutrient gradients,
gradients, perhaps
perhaps coupled
to an
an
increase
increasein
in net
netupwelling
upwellingas
asfar
farwest
westas
as130°W.
130øW.
[1996]. Radiolarian
estimate at
at ~130øW
130°W isisfrom
[1996].
RadiolarianSST
SST estimate
fromthis
thisstudy.
study.
Error
bars are _+1.5øC
±1.5°C for
and radiolarian
Error bars
for both foraminiferal
foraminiferal and
radiolarian SST
SST
estimates.
estimates.
Shell
Rates and
Shell Accumulation
Accumulation
Rates
and Foraminlieral
Foraminiferal
Productivity
Productivity
foraminiferal
transfer function
foraminiferal fauna
fauna. . Imbrie-Kipp
Imbrie-Kipp transfer
function SST
SST
estimates
estimates are
are based
based on
on LOM
LGM radiolarian
radiolarian faunas.
faunas. Radiolarian
Radiolarian
the modem
modern slope,
slope, or
or (3)
the
(3) G.
G. bulloides
bulloideslived
lived deeper
deeperin
in the
thewater
water
column nearer
nearer the
the coast
column
coastduring
duringthe
theLGM.
LGM.
The
8h10of
ofLGM
LGMG.
G.hulloides
builoidesisishigher
higherby
by~39'0o
-3% than
The/5•'O
thanmodem
modem
After
accounting
8"O,
predicted
for
the
sea
surface
(Figure
5).
/5•'O,predicted
for theseasurface
(Figure5). Afteraccounting
for
.3%oice
icevolume
volumeeffect
effect
meanocean
ocean/5•sOw,we
8O,we can
foraa 11.39'0o
ononmean
can
estimate an
an upper
upper limit
limit for
for the
temperature change
change across
across
estimate
the LGM
LGM temperature
The
rates of
of left-coiling
and
The accumulation
accumulation
rates
left-coilingN.
N. pachyderma
pachyderma
andG.
G.
bulloides
bulloidesshells
shellsnear
near126°W
126øWare
aremuch
muchgreater
greaterat
at the
theLGM
LGM than
than
in
traps (Figure
7). This
This cannot
cannot be
be an
in the
themodem
modemsediment
sedimenttraps
(Figure 7).
an
artifact
the
artifactof
of dissolution,
dissolution,because
because
theLGM
LGM sediment
sedimentsamples
samplesare
are
-1
Modem
5180efromLevitus
[1982]
the
assumingthe
the slope
slope of
of the
the regional
regional salinity/8'8O
thetransect,
transect,
assuming
salinity//5•*Ow
relationship
unchanged, and
andG.
G. bulloides
bulloides calcified
calcified in
in the
the
relationshipwas
wasunchanged,
mixed
layer(its
(its present
present habitat
habitat at
at these
mixed layer
thesesites
sitesas
asrecorded
recordedby
by
the
MOCNESS
plankton tows).
M•S
plankton
tows). This
This estimate
estimate suggests
suggests the
magnitude of
of the
the •LOMcooling
cooling at
at these
these sites
sites could
have been
magnitude
could have
been
•o
we have
40..
6°C at
at most.
4ø- 6øC
most. For
For comparison,
comparison, we
have plotted
plotted the
the
foraminiferal
modem analog
SST estimates
estimates as
foraminiferalmodem
analogLGM
LGM SST
as equivalent
equivalent
8'10, predictions
using
assumptions
(Figure
5).
/5•O,
predictions
usingthe
thesame
same
assumptions
(Figure
5).
A
4°-6°C
cooling
based
on
the
oxygen
isotope
data
is at
at the
A 4ø-6øCcooling basedon the oxygen isotope data is
the
upper
statistical
limit
of
the
3.3°±l.5°C
cooling
estimated
by
u•
statisticallimit of the 3.3ø+1.5øCcoolingestimatedby
the
modem analog
analog faunal
faunalmethod.
method. However,
is likely
likely some
the modem
However, itit is
some
of
of this
thisapparent
apparent4°-6°C
4ø-6øCcooling
cooling reflects
reflectslocal
local increases
increasesin
in
salinity
upwelling, or
or aa change
salinitydriven
drivenby
by stronger
strongerice-age
ice-ageupwelling,
changeof
of
the depth
depth habitat
habitatof
ofG.
G.bulloides.
bulloides. For
the
For example,
example,the
the deviations
deviations
between
expressed
between the
the modern
modemanalog
analogpaleotemperatures
paleotemperatures
expressedas
as
and
the
G.
bulloides
8180
measurements
can
be
minimized
•so, andtheG. bulloides
•so measurements
canbeminimized
a residual
yielding a
in aaleast
sense,
in
leastsquares
squares
sense, yielding
residualof
ofO.09%o
0.099'0o
(approximately
our8•O
60 machine
precision)
using aa 8•so
8"O offset
offset
(approximately
our
machine
precision)
using
than the
of -O.75±0.05%o. This
of-0.75:k0.059•.
This offset
offset is
is smaller
smaller than
the 1%
19'0ooffset
offset
relative to
waters attributed
attributedtoto modern
modem G.
G. bulk>ides
bulloides in
in
relative
to surface
surface waters
the
Gulf of
of Alaska
Alaska due
due to
to aa depth
depthhabitat
habitatnear
near100
lOOm
[Zahnetetal.
the Gulf
m [Zahn
al.
1991a].
Thus,
while
G.
bulloides
8"O
helps
to
constrain
the
1991a]. Thus,while bulk>ides
15•sO
helpsto constrainthe
zonal
thermal gradient
gradient it
zonalthermal
it does
doesnot
notprovide
provideaaunique
uniquemeasure
measureof
of
the
the absolute
absolutetemperature
temperaturechange.
change.
• Ice
Volume
•
LGM
E -4øC
MAT
'•
SST
.
4
136
136
ß 1111
I ' I ' I ' I ' I ' • '
LGM•sO fromG.hulloides
Coast
134
124
124
132
132
130
130
128
126
126
122
Longitude (°W)
Longitude
(øW)
Figure
Oxygen
isotopic
composition
(6O) of
Figure 5.
$.
Oxygen isotopic composition(•O)
of G.
G.
bulloides from
from LGM
LGM sediments
sediments across
acrossthe
the Multitracers
Multitracers transect.
transect.
bulloides
Shown for
for comparison
comparison are
equilibrium calcite
calcite /5•O
6"O for
Shown
areequilibrium
for modem
modem
waters
squares). The
data
waters(open
(opensquares).
TheG.
G. bulloides
bulk>ides
dataare
areconsistent
consistentwith
with
a 4•-6øC
4'-6°C cooling
cooling assuming
of +1.39k,
a
assuming(1)
(1) an
anice
icevolume
volumeeffect
effectof
+1.39'oo,
(2) the
the modem
modern $S- /5•O
8180slope
slopeof
of +0.41
+0.41 also
also applies
the
(2)
appliesduring
duringthe
glacial,
(3) aa mixed
glacial,and
and(3)
mixedlayer
layerdepth
depthhabitat.
habitat. The
The foraminiferal
foraminiferal
modem
analog SST
estimates (open
(open circles)
modemanalog
SST estimates
circles)suggest
suggestaa2°-4°C
2ø-4øC
cooling.
cooling.
ORTIZ
AL.:ßGLACIAL
CURRENT AT
AT 42øN
42°N
ORTIZ ET
ET AL
GLACIAL CALIFORNIA
CALIFORNIA
CURRENT
200
200
4
3-
Modem fi13C
13Cce(O
Modem
Modern Modem
(0m)
m)
513
I
'3Ce
Ce
-r
I
Post
Post
Upwelling
Upwelling
(1OOm
(100
m)%
• ..........
.*.
....................
•.
•
Active
....
'""'-... '"'""•N
x ,/'"Active
Upwelling
"--....
ß
Upwelhng
fluxes
appears robust.
robust. Because
species are
heterotrophic,
fluxesappears
Becausethese
thesespecies
areheterotrophic,
they
theyare
aresensitive
sensitiveto
to food
foodsupply
supplyand
andthus
thusto
to productivity
productivity(Orfiz
(Ortiz
et
rates of
et al.
aL 1996).
1996).We
We interpret
interpretthe
thehigher
higherLGM
LGM accumulation
accumulation
rates
of
these
to higher
thesespecies
speciesas
as due
dueto
higher productivity
productivityof
of the
theheterotropic
heterotropic
foraminifera.
This isis consistent
consistent with
foraminifera. This
with the
the carbon
carbonisotopic
isotopic
evidence
for westward
westwardexpansion
expansion of
of nutrient
evidencefor
nutrient supplies
suppliesnoted
noted
above.
above.
Ekman Transport
Ekman
Transport and
and Coastal
CoastalUpwelling
Upwelling
The
by the
The seasonal
seasonaloffshore
offshore Ekman
Ekman transport
transport simulated
simulatedby
the
RegCM
for modem
modern boundary
boundary conditions
conditions captures
captures the
the basic
basic
RegCM for
Physiological offset
ffset
0Coast
Coast
LGM G. bulloides
hulloides
LGM
structure
and magnitude
magnitude of
of the
the coastal
coastal upwelling
upwelling seasonal
seasonal cycle
structureand
cycle
in
the California
California Current
Consistent with
in the
Current(Figure
(Figure 8).
8).
Consistent
with
observations [Huyer,
observations
[Huyer, 1983],
1983], north
northof
of 40°N,
40øN,coastal
coastalupwelling
upwelling
is
is seasonal,
seasonal,strong
strong in
in July
July but
butabsent
absent(or
(ordownwelling)
downwelling)in
in
January. Between
40°N, coastal
coastal upwelling
upwelling persists
persists
January.
Between30°N,
30øN, and
and40øN,
throughout
the year,
year, but
but is
is strongest
strongest in
in summer.
summer. South
of 30°N
throughoutthe
Southof
30øN
Longitude
Longitude(°W)
(øW)
both
both observations
observationsand
and the
the model
modelrecord
recordroughly
roughly constant
constant
coastal upwelling throughout the year.
Figure 6.
6.
Carbon
of G.
Figure
Carbonisotopic
isotopic composition
composition(8'3C)
(õnC) of
G. coastalupwelling throughoutthe year.
North of
of 45°N,
offshore Ekman
transport
North
45øN, modelmodel-simulated
simulatedoffshore
Ekmantransport
bulloides from
from glacial
glacial sediments
sediments across
acrossthe
the 42øN
42°Ntransect.
transect. The
bulloides
The
exceeds
This
feature
exceeds observed
observed values
values for
for both
both seasons. This
feature
magnitude
of
the
carbon
isotopic
disequilibrium
(physiological
magnitudeof the carbonisotopicdisequilibrium(physiological
effects at
at the
the northern
of the
offset,
is estimated
using equation
equation 3.
3. probably
probablyreflects
reflectsedge
edgeeffects
northernboundary
boundaryof
the
offset,A8'3C,,)
ASnC,_,)
in G.
G. bulloides
bulloides
is
estimated
using
Modem
8'3C
values
at
42°N
based
on
measurements
from
Ortiz
model
domain.
Peaks
in
observed
offshore
transport
between
Modem•nC, valuesat42øNbasedon measurements
fromOrtiz modeldomain. Peaksin observedoffshoretransportbetween
at
plotted for
after being
being offset
offset for
for the
the 35°N
and 40øN
40°N are
aredisplaced
displacedsouthward
southwardby
bythe
themodel
modelby
by 1ø-2
1-2°ø
et al.
al. [1996]
[1996] are
are plotted
for reference
referenceafter
35øNand
glacial
8C01 shift
-0.4%o and
the anthropogenic
shift ofof - latitude.
This most
most likely
glacial•nCmc
shiftofof-0.4%0
andthe
anthropogenic
shift
latitude.This
likely reflects
reflectsdifficulty
difficultydefming
definingcoastline
coastline
0.6%o.
0.6%o.
shape
shapeprecisely
preciselyin
in the
thegridded
griddedmodel.
model.
Simulated
offshore
Ekman
transport at
at the
SimulatedoffshoreEkmantransport
theLGM
LGM was
waslower
lowerin
in
both
seasons than
than itit is
is at
at present
present (Figure
(Figure8).
8). North
North of
of 42øN
42°N the
the
both seasons
more dissolved
dissolvedthan
thanthe
themodem
modemsediment
sedimenttrap
trapsamples.
samples. Given
predicts coastal
coastal downwelling
downwelling in
in both
Major
more
Given model
modelpredicts
bothseasons.
seasons. Major
potential errors
errors in
in sediment
rates associated
associated with
with reductions
in
summer
upwelling
occur
north
of 40øN,
40°N, and
and winter
winter
potential
sedimentaccumulation
accumulationrates
reductionsin summerupwellingoccurnorthof
timescale
uncertainties, we
we hesitate
hesitate to
to interpret
interpret structure
in the
occursas
as far
far south
south as
as 33°N.
timescaleuncertainties,
structurein
the downwelling
downwelling occurs
33øN. South
South of
of 33°N,
33øN,
decreasing offshore
offshore accumulation
accumulation rates.
rates. Given
Given the
the consistency
changesin
in coastal
coastal upwelling
upwelling are
are relatively
relatively small,
decreasing
consistency predicted
predictedchanges
small,
of the
to modem
probably
within the
the range
range of
of model
model uncertainties.
uncertainties. The
of
the result,
result, however,
however, the
the net
net increase
increase relative
relative to
modem
probablywithin
The overall
overall
-1
-1
,
136
1 36
124
ß134
I ' 132
I ' 130
I ' 128
I ' 1126
• 6 ' 124
I ' 122
134
132
128
122
15000
15000
10000
10000-
4
5000
5000
--0---O--
0
134
134
15000
130
130
132
128
128
126
126
S
•
150001
' • ' •
B G. bulloides
Modern
Modern
(sediment traps)
(sediment
traps)
124
124
LGM
LGM
10000
10000
5000
5000
0
134
134
-
132
132
130
130
128
128
126
126
124
124
Longitude (°W)
Longitude
(øW)
Figure
Figure 7.
7.
Shell
ratesfor
for(a)
(a) left-coiling
left-coilingN.
N. pachyderma
pachydermaand
and (b)
(b) G.
G. bulloides,
Shell accumulation
accumulation
rates
bulloides,two
two
heterotrophic
planktonic foraminifera.
foraminifera. Modem
from annually
annually average
average sediment
sediment trap
trap flux
flux at
at
heterotrophic
planktonic
Modemrates
ratesare
arederived
derivedfrom
the
LGM shell
shell accumulations
accumulationsare
arefrom
fromthe
the 10
10 cores
cores across
the three
threesediment-trap
sediment-trapmooring
mooringsites.
sites. LGM
acrossthe
the 42°N
42øN
transect.
transect.
ORTIZ
CALIFORNIA
CURRENT AT
AT 42øN
42°N
ORTIZ ET
ET AL.:
AL.: GLACIAL
GLACIAL
CALIFORNIA
CURRENT
201
201
negative curl
boundary,
negative
curl simulated
simulatedalong
along the
the southern
southern
boundary,are
are
unrealistic.
The
modern
July
simulation
also
indicates
unrealistic. The modern July simulation also indicateslocal
local
zones of
(negative
zones
of intense
intenseconvergence
convergence
(negativecurl)
curl)near
nearthe
theupwelling
upwelling
150150
front at
and 32øN.
32°N. These
features are
arenot
not present
present in
in the
front
at 38°N
38øNand
Thesefeatures
the
maps of
of Bakun
and
Nelson
11991].
Given
these
apparent
maps
Bakun
and
Nelson
[1991].
Given
these
apparent
100100
weaknesses in
in the
the model
simulations, we
only interpret
weaknesses
modelsimulations,
we only
interpretbroad
broad
features, and
and rely
rely on
on difference
maps between
modern and
and iceicefeatures,
differencemaps
betweenmodem
5050
age
The hope
hope is
is that
that model
modelbiases
biasescommon
commonin
in both
both
ageconditions.
conditions.The
runs would
wouldtend
tendtotocancel,
cancel,minimizing
minimizingthe
thenet
net bias
bias in
in the
runs
the
difference
maps.
difference
maps.
0 ..................................................................
•,,
... • •...•...•
..._-._.._-...2.,,,•..-'•,,.
The LGM
wind stress
stress curl
suggest enhanced
The
LGM wind
curlsimulations
simulations suggest
enhanced
positive curl
curl in
in offshore
offshore regions
regions for
for both
both the
January
and
July
Downwelling
simulation
positive
the
January
andJuly
-50
simulations
(Figures
9b
and
9e).
LGM-minus-modem
difference
simulations(Figures and
LGM-minus-moderndifference
48
'
' ';6' ' '4'0' ' '4'4' ' '48
maps conf'um
confirm that
that ice-age
ice-age curl
curl was
wasmore
morepositive
positive offshore
offshore in
in
maps
100
both January
Upwelling
B: January
both
Januaryand
andJuly.
July.In
In the
theLGM
LGMJanuary
Januarysimulation,
simulation,curl
curl
200
200
Upwelling
A:Jul•
-- • ,. sMiømduel7t
io
n
;
o
0
'
U
.
.
.
!
.
.
decreasednear
nearthe
the coast
coast north
north of
Thus, on
decreased
of 33°N.
33øN. Thus,
on an
an annual
annual
50
average
basis, the
the model
averagebasis,
modelsimulations
simulationssuggest
suggestaa net
netwestward
westward
translation of
of curl-driven
upwelling offshore
offshore between
translation
curl-drivenupwelling
between30°N
30øNand
and
42°N during
during the
the LGM,
at
42øN
LGM, relative
relativeto
to conditions
conditions
at present.
present.
0
',
,',
Discussion
Discussion
-50
LGM
"-.
-100
150
Downwelling
I
The
The Glacial
Glacial Temperature
Temperature Decrease
Decrease
\
Simulation"X
,
28
28
40
44
36
32 ' ' '3•'
3•2
' '20'
' '24
48
48
Latitude
Latitude (°N)
(øN)
Our
results suggest
suggest that
SST
Ourresults
thatthe
themean
meanannual
annual
SSTat
at42°N
42øNduring
during
the
3.3°±1.5°Ccooler
coolerthan
thanpresent.
present. This
theLGM
LGM was
was3.3ø:1:1.5øC
Thistemperature
temperature
estimate
is consistent
with
faunal
estimateis
consistent
withthe
theradiolarian
radiolarian
faunaltemperature
temperature
estimates
of Moore
Moore [1973]
[1973] and
andMoore
Mooreet
et al.
al. [1980]
estimatesof
[1980] in
in three
three
cores near
et al.
cores
near our
our locations.
locations. Similarly,
Similarly, Prahi
Prahl et
al. [1995]
compared temperature
temperature estimates
estimates based
based on
and radiolarian
radiolarian
compared
onUk37
Uk•?and
faunal
estimates in
in one
here
faunalestimates
onecore
corestudied
studied
here(W8709A-8PC)
(W8709A-8PC)and
and
inferred an LGM
LGMtemperature
temperaturedecrease
decreaseof
of4.0ø+1.5øC,
4.0°±1 .5°C,similar
similar to
inferred
our
our estimate.
estimate.
The
between these
methods is
somewhat
The agreement
agreement between
these methods
is somewhat
surprising. Measurements
ofofthe
Uk37
index in
in sediment
traps
surprising.
Measurements
the
Uk3?
index
sediment
trapsat
at
the
same
sites
used
here
yielded
an
annual
temperature
of
the samesites usedhere yieldedan annual temperature
of
reduction in
in coastal
coastal upwelling
upwelling at
at the
the LGM
is associated
reduction
LGM is
associatedwith
with
1O.6°±1.1°C
withno
no significant
significant offshore
offshore gradient
gradient [Prahi
10.6ø+1.1øC
with
[Prahlet
et al.
southward
translation of
of atmospheric
southwardtranslation
atmosphericpressure
pressuresystems
systemsand
and
1993]. This
estimate
is
significantly
cooler than
the
12°-15°C
1993].
This
estimate
is
significantly
cooler
than
the
12
ø15øC
associated
winds,
which
is
driven
in
the
model
by
large
associatedwinds, which is driven in the model by large
annual
mean SST
SST at
at these
these sites.
Prymnesiophyte
algae
which
annual
mean
sites.
Prymnesiophyte
algae
which
northern
hemisphere
ice
sheets
and
lower
sea
surface
northern hemisphere ice sheets and lower sea surface
generate the
the alicenone
alkenone signal
signal bloom
generate
bloomin
in the
thespring
springand
andsummer
summer
temperatures.
temperatures.
and
reside within
within the
the thermocline,
thennocline, rather
rather than
than at
at the sea
and reside
seasurface
surface
[Prahi
et al.
1993].
In
contrast,
the
radiolarian
transfer
[Prahl
et
al.
1993].
In
contrast,
radiolarian
transfer
Wind
Wind Stress
Stress Curl
Curl and
andOpen-Ocean
Open-OceanUpwelIing
Upwelling
function generates
generates temperatures
temperaturesbased
basedon
on the
the calibration
calibration of
function
of
Bakun and
and Nelson
Nelson [1991]
[1991] report
report modern
modem seasonal
seasonal variations
variations Holocene
Holocene faun_as
faunas against
against mean
annual
sea
surface
temperature.
Bakun
meanannualseasurface
temperature.
in
stress curl
curlover
overthe
theCalifornia
CaliforniaCurrent.
Current. In
According to
toPrahl
Prahi et
a al.
different
in wind
wind stress
In winter,
winter, west
west
According
al. [1995],
[1995],these
thesetwo
twoseemingly
seemingly
different
of
126°W
along
our
42°N
transect,
curl
is
negative,
produce similar
similar temperature
temperatureestimates
estimatesbecause
becausein
in the
the
of 126øWalong our 42øN transect,curl is negative, yielding
yielding methods
methodsproduce
downwelling
in the
the interior
gyre. In
North Pacific,
Pacific, mean
mean annual
annual SST
SST over
over the
the range
downwellingin
interiorof
of the
thesubtropical
sublxopical
gyre.
Insummer,
summer, North
range0°-15°C
0ø-15øCis
is
positive
curl drives
drives strong
strong upwelling
upwelling east
east of
of 128°W.
equivalent to
to the
at
positivecurl
128øW. South
Southof
of
equivalent
thesummer
summertemperature
temperature
at the
thepycnocline.
pycnocline.
40°N,
positive curl
curl near
near the
thecoast
coastpersists
persists throughout
throughout the
the year,
year,
Sabin
40øN, positive
Sabin and
and Pisias
Pisias [1996]
[1996] used
usedthe
thesame
sameradiolarian
radiolariantransfer
transfer
and
thus
offshore
upwelling
reinforces
year-round
coastal
function as
as Prahl
Prahi et
transect from
from 35°
and thus offshore upwelling reinforces year-round coastal function
et al. [1995]
[1995] in
in aa meridional
meridionalIxansect
35ø
upwelling
in this
this area.
area. The
to 55øN.
55°N. Their
included
two cores
upwellingin
TheRegCM
RegCM simulations
simulationsof
of wind
windstress
stress to
Theirtransect
transect
includedtwo
coresused
usedhere
here(W8709A(W8709Acurl
January (Figure
(Figure 9a)
9a) and
and July
July (Figure
8PC and
We supplement
supplement the
the two
curlfor
for modern
modernJanuary
(Figure9d)
9d) capture
capture 8PC
andW8709A-13PC).
W8709A-13PC).We
two published
published
these
In January,
curl is
is negative
LGMradiolarian
radiolarian temperature
temperatureestimates
estimates at
at 42øN
42°N with
with one
one from
thesebasic
basicfeatures.
features. In
January,simulated
simulatedcurl
negative LGM
from
offshore,
consistent with
observations. Positive
Positive curl
persists W8809A-3
1CC(radiolarian
(radiolariantaxonomy
taxonomy courtesy
courtesy of
of M.
M. Webber,
Webber,
offshore, consistent
with observations.
curl persists
W8809A-31GC
near
south of
of Oregon
The resulting
radiolarian SST
nearthe
thecoast
coastin
in both
bothseasonal
seasonalsimulations,
simulations,especially
especiallysouth
OregonState
StateUniversity).
University). The
resulting radiolarian
SST
about 40øN.
40°N.
about
estimates
cooling of
of 4.2°±1.5°C,
.5°C, and
estimatesyield
yield LGM
LGM cooling
4.2ø+1.5øC,4.4°±l
4.4ø+1.5øC,
and
The
model simulations
simulations are
are not
not perfect,
2.4°±1.5°C
in the
the three
three sites
sites relative
relative to
to modem
The model
perfect,however.
however. North
North of
of
2.4ø+1.5øCin
modernatlas
atlasvalues,
values,
47°N,
simulated curl
curlisis always
always positive,
positive, unlike
from the
estimate of
of
47øN, simulated
unlike observations.
observations. indistinguishable
indistinguishablefrom
the foraminiferal-based
foraminiferal-basedestimate
This
is
probably
an
edge
effect
near
the
northern
limit
of
the
3.3°±1.5
°C
cooling
in
this
region
(Figure
4).
This is probably an edgeeffect near the northernlimit of the
3.3ø+1.5øC coolingin thisregion(Figure4).
RegCM
of positive
The
3°-4°C cooling
cooling we
we estimate
estimate was
was roughly
roughly constant
constant across
RegCM domain.
domain. Similarly,
Similarly, edge
edge effects
effects of
positive curl
curl
The3ø-4øC
across
simulated
along the
the western
boundarysouth
south of
of 32°N,
estimate is
is smaller
the entire
entire east-west
east-west transect.
transect. Our estimate
smaller than the
simulated along
western boundary
32øN, and
and the
and simulated
simulated offshore
offshore Ekman
transport
FIgure
Figure 8.
8. Observed
Observedand
Ekmantransport
for
(a) Modern
Modern observations
observations for
for July
for the
theCalifornia
CaliforniaCurrent.
Current. (a)
July
compared
with
modern
and
LGM
July
simulations.
(b)
Modem
comparedwith modem and LGM July simulations. (b) Modern
observations
with modern
modern are
are based
based on
on
observationsfor
for January
Januarycompared
comparedwith
winds
NCAR RegCM
RegCM runs
runs of
of Hostetler
Hostetler et
etal.
windsfrom
from the
theNCAR
al.[1994].
[1994].
ORTIZ ET AL.: GLACIAL
GLACIAL CALIFORNIA
CALIFORNIA CURRENT
CURRENT AT
AT 42
42°N
ORTIZ
øN
202
50
o&njaivary
Modm.
n JanuaryQid
Cuff
on July
Modern
JulyCurl
Curl
Contours 1lO
dynes
(Contom
041
dyrman-3)
Contours 1041
lO dyne.
(ContOtl•
dyr• an-3)
,•n4)
45
-I,
-I
dl
-
3
45
((39
.'-' L.1'
ß•1 35
-14
t4
I
-2 -3
30
3°
3o
IL,
---
I
25
130
130
120
120
125
115
115
110
I10
125
125
130
50
120
115
I15
110
11o
LGM •ulyCurl
(Contom los dyrescm4)
45
,40
z• 4o
35
ß• 35
30
3o
25
130
120
120
125
125
115
115
110
110
Jainy
LGM -- Mon
Modexn
Jau•'y aid
Curl
Contoiis 1041
lO dyne.
(Contom
dyr• an-3)
e.14)
45
45
•
130
125
50
120
115
I10
LGM - ModernJulyCurl
(Contom 104 d•
,m14)
2%f'l
r_________' '
45
7i
40
4O
XII-.
\.1
'• 35
35
1
t..
30
3O
30
!:
25
';'" :
130
25
125
125
120
Lcngimdc q'W)
W)
l.m•itud•
115
115
110
I10
130
130
125
125
120
120
LUik
Loa•itud•('
q'W)
115
IlS
110
I10
FIgure
wind
curl
Current region.
region. Results
January,
Figure 9.
9. Simulated
Simulated
windstress
stress
curlfor
forthe
theCalifornia
CaliforniaCurrent
Resultsare
arefrom
from (a)
(a) modem
modemJanuary,
(b)
(c) glacial
glacial January-modem
January-modernJanuary,
January,(d)
(d)modem
modernJuly,
July, (e)
(e)glacial
glacial July,
July, and
(b) glacial
glacialJanuary,
January,(c)
and(I)
(f) glacial
glacialJulyJulymodem
July. Contours
are
wind
modemJuly.
Contours
arein
in 10°
104dynes
dynescm3.
cm4. Cyclonic
Cyclonic
windstress
stresscurl
curl(positive
(positivevalues,
values,solid
solidcontours)
contours)
drives oceanic
oceanic upwelling.
upwelling. Anticyclonic
Anticyclonic wind
wind stress
stress curl
curl (negative
contours) drives
drives oceanic
drives
(negativevalues,
values,dashed
dashedcontours)
oceanic
downwelling. The
The calculations
calculations are
are based
based on
on winds
winds from
from the
the NCAR
NCAR RegCM
RegCM runs
runs of
of Hostetler
Hostetler et
et al.
al. [[1994].
downwelling.
1994].
ORTIZ
CURRENT AT
AT 42øN
42°N
ORTIZ ET AL.: GLACIAL
GLACIAL CALIFORNIA
CALIFORNIA CURRENT
5°-1O°C
cooling suggested
suggested by
by Mortyn
from
6180
5ø-10øC
cooling
Mortynet
etal.
al.[1996]
[1996]
from
8•aO
Borderland
bulloides in the Southern California
of
of G.
G. bulloides
California
Borderland
sediments, but
but larger
larger than
than the
cooling
based
on
Uk37
sediments,
the1.5°C
1.5øC
cooling
based
onthe
the
U•
tanperature
Site 893
temperate index
inc!•x in
in ocean
oceandrilling
drillingprogram
program(ODP)
(ODP)Site
893
from
Basin [Herbert
et al.
from the
the Santa
Santa Barbara
Barbara Basin
[Herbert et
al. 1995].
1995]. These
These
differences
may in
in part
part reflect
reflect regional
variations,
differencesmay
regionaltemperature
temperature
variations,
although
Morlyn
et
al.
[1996]
did
not
attempt
to
constrain
althoughMortyn et al. [1996] did not attemptto constrainthe
the
effect
of upwelling-related
upwelling-relatedsalinity
salinityvariations
variationson
on8•aO,
8'o, which
eff•t of
which
203
203
depleted
in nutrients
nutrients are
high in
depleted
in
arehigh
in 6"C01.
8•Cmc.The
TheLGM
LGMoffshore
offshore
gradient
of
6'3C
in
G.
bulloides
thus
implies
higher
gradient 8•C in
bulloidesthusimplieshighernutrient
nutrient
content near
near the
content
the coast
coast and lower
lower nutrient
nutrient content
content offshore.
offshore.
Zonal
Thermal
Gradients
and
Flow
Zonal
Thermal
Gradients
and Southward
Southward
Flow
The
gradient in
in G.
G. bulloides
bislloidesacross
across42øN
42°Nis
is steeper
steeper
TheLGM
LGM 6'3C
8•C gradient
than
the modern
modernwater
watercolumn
columngradient
gradientatatthe
thesea
seasurface.
surface. ItIt is
is
thanthe
similar to
to the
the modern
8'3C gradient
gradient at
at 100
m (Figure
6). The
similar
modem$'•C,
100 m
(Figure6).
The
offshore subsurface
enrichment trend
offshore
subsurface enrichment
Ixend in
in the
the modern
modern ocean
ocean
begins east
east of
of 128°W.
high
begins
128øW.In
Inthe
theLGM
LGMsamples,
samples,
high8'3C
$'•Cvalues
values
are
not encountered
east of
of l30°W.
are not
encountered
east
130øW.IfIfG.
G.bulloides
bulloidesoccupied
occupiedaa
surface habitat,
habitat, LGM
greatly enriched
surface
LGM surface
surfacewaters
waters were
were greatly
enrichedin
in
nutrients
relative to
to modem
modem ones
ones across
If
nutrients relative
across the
the entire
entire transect.
transect. If
At
42°N, LGM
LCM temperatures
temperaturesremained
remainedcoolest
coolestnear
nearthe
the coast
coast
At 42øN,
and
increasedoffshore.
offshore.This
Thispattern
patternisis similar
similar to
to the
and increased
the modern
modern
100 m
G. bulloides
G.
bulloides occupied
occupied aa depth
depth habitat
habitat closer
closer to
to 100
m
(consistent
Gulf of
of Alaska
(consistentwith
with its
its apparent
apparentmodern
modem Gulf
Alaska habitat),
habitat),
would
would likely
likely reduce
reduc• the
theamplitude
amplitudeof
of their
theirinferred
inferredcooling.
cooling.
zonal
and suggests
suggests that
that aa
zonal thermal
thermal gradient
gradient at
at this
this latitude
latitude and
southward
flowing California
California Current
Current was
was still
still present
southwardflowing
presentduring
during
the
LGM.
The
steeper
offshore
60
gradient
relative
the LGM. The steeperoffshore8•aOgradientrelativeto
to the
the
modem
water
column
8180,
gradient
at
42°N
may
suggest
aa
modernwatercolumn8•aO,gradientat 42øNmay suggest
stronger
density
gradient,
and
if
so,
geostrophy
would
require
strongerdensitygradient,andif so, geostrophywouldrequire
enhanced southward
this possibility
enhanced
southwardadvection.
advection. However,
However, this
possibility
should
be viewed
viewed with
withcaution
cautiondue
duetotouncertainties
uncertaintiesinin the
the slope
slope
shouldbe
of
of the
theLGM
LGM S-8"O
S-fi•aOrelationship
relationshipand
andforaminiferal
foraminiferaldepth
depth
habitats.
habitats.
Southward
flow at
at 42øN
42°N requires
requiresthat
that the
the LGM
LGM polar
polar front
Southwardflow
front
remained
north of
of our
our sites.
sites. Had
remained north
Had the
the Polar
Polar front
front shifted
shifted south
south of
of
our
locations,
local
wind
forcing
would
have
been
more
heavily
our locations,local wind forcingwouldhavebeenmore heavily
influenced by
by the
influenced
the cyclonic
cyclonicAleutian
Aleutianlow.
low. In
In response,
response, aa
poleward
boundary current
current of
of the
the subarctic
subarctic gyre
gyre
polewardflowing
flowing eastern
easternboundary
then offshore
waters were
in nutrients
nutrients down
down to
to -~lOOm,
then
offshore waters
were enriched
enriched in
100m,
and
coastal waters
waterscarried
carriedroughly
roughlythe
the same
samenutrient
nutrient content
content as
andcoastal
as
modem
In either
modem waters.
waters. In
either case,
case, 1GM
LGM nutrients
nutrients in
in offshore
offshore
regions
most likely
regionsof
of the
theCalifornia
California Current
Currentax
at 42°N
42øN were
were most
likely
slightly to
slightly
to greatly
greatly enhanced
enhancedrelative
relative to
to their
theirmodern
modernvalues.
values.
Variations
in [CM
Variations in
IfJM wind
wind forcing
forcing could
couldcause
causesuch
such aa nutrient
nutrient
change by
by (1)
enhancing coastal
change
(1)enhancing
coastalupwelling
upwelling due
due to
to greater
greater
offshore Ekman
offshore
Ekmantransport,
transport, (2)
(2) enhancing
enhancingoceanic
oceanicupwelling
upwelling
resulting
resulting from
from greater
greaterwind
wind stress
stress curl,
curl, or
or (3)
(3) enhancing
enhancing
southward flow
flow due
due to
to stronger
southward
strongerbasin
basinscale
scalewind
wind stress
sixesscurl.
curl.
We
discount
the
first
mechanism
because
the
RegCM
We discountthe first mechanismbecausethe RegCM results
results
suggest
in the
suggestthat
thatcoastal
coastalupwelling
upwellingnorth
northof
of35°N
35øNdecreased
decreased
in
the
California
Currentduring
duringthe
theLGM
LGM(Figure
(Figure8),
8), aa result
result which
which is
is
CaliforniaCurrent
consistent
rates of
of coastal
consistent with
with lower
lower accumulation
accumulation rates
coastal diatoms
diatoms
[Sancetta
et
al.
1992]
and
marine
organic
carbon
[Lyle
et al.
al.
[Sancettaet al. 1992] andmarine organic carbon [Lyle et
would
have replaced
replaced the
the California
California Current
Currentover
over our
our sites.
sites. 1992].
would have
RegCM simulations
simulations support
support the
1992]. RegCM
the second
secondmechanism,
mechanism,
Under
such conditions,
conditions, one
one would
expect to
to see
Undersuch
wouldexpect
seecold,
cold, nutrientnutrient- enhanced
LGM wind-stress
wind-stress curl
curl in
in the
Current
enhanced LGM
the California
California
Current
enriched water
walerthroughout
throughoutthe
the transect,
transect, with
with aa zonal
enriched
zonal thermal
thermal relative
This implies
relative to
to modem
modemconditions
conditions(Figure
(Figure9).
9). This
implies that
that
gradient
gradientreversed
reversedfrom
from that
thatobserved
observed(i.e.
(i.e.warmer
warmertemperatures
temperatures enhanced
oceanic upwelling
upwelling supplied
suppliednutrients
nutrients from
from below
below to
enhancedoceanic
to
near
This pattern,
nearthe
thecoast
coastwith
withaagradual
gradualoffshore
offshorecooling).
cooling). This
pattern, increase
increase the
the nutrient
nutrient content
content of
ofoffshore
offshoreLGM
LGM waters,
waters,decrease
decrease
which
is similar
which is
similar to
to the
themodern
modemwintertime
wintertime regime
regime at
at 42°N,
42øN, their
and
the
their6'3C
b'•C composition,
composition,
andindirectly
indirectlyproduce
produce
theobserved
observed
would
be associated
associated with
with offshore
offshore oceanic
oceanic upwelling
upwelling in
in the
would be
the
increase in
offshore accumulation
accumulation rates
rates of
increase
in offshore
of heterotrophic
heterotrophic
LOM
LGM subarctic
subarcticgyre.
gyre.
foraminiferal shells
shells by
by increasing
foraminiferal
increasingprey
preydensity.
density.
The
third potential
potential mechanism
for increasing
increasing the
the nutrient
The third
mechanismfor
nutrient
Enhanced
Glacial
Nutrient
Content
Enhanced
Glacial
Nutrient
Content
content
content of
of the
the LGM
LGM California
California Current
Current is
is enhanced
enhanced southward
southward
flow.
the
gradient
ofofLGM
flow.As
Asnoted
notedpreviously,
previously,
theoffshore
offshore
gradient
LGM6180
We observed a >1%o
6'3C enrichment
enrichment in LGM
>1%O 8'3C
LGM G. bulloides
bulloides
is
consistent
with
enhanced
southward
advection
during
is consistent with enhancedsouthwardadvection during the
the
shells
relative to
to those
those near
near the
the coast
coast(Figure
(Figure6).
6). This
shellsoffshore
offshorerelative
This
LGM.
GCM results
results of
of
LGM. The
Thecoarse
coarseresolution
resolutionatmospheric
atmosphericGCM
enrichment
does
not
appear
to
be
related
to
the
organisms
enrichmentdoes not appear to be related to the organism's Kutzbach and Guener [1986] suggest that North Pacific winds
Kutzbach
and
Guetter
[1986]
suggest
that
North
Pacific
winds
physiological
as
physiologicalcarbon
carbonisotopic
isotopicdisequilibrium
disequilibrium
aspredicted
predictedfor
for
were stronger and displaced southward at the LGM. These
temperawre
effects [Ortiz
et al.
1996]. Paleoceanographic
temperatureeffects
[Ortiz et
al. 1996].
Paleoceanographic were stronger and displacedsouthwardat the LGM. These
changes
increase the
the proportion
proportion of
of cold,
changescould
could increase
cold, nutrient-rich
nutrient-rich
factors
that could
in airfactors that
could cause the enrichment
enrichment include
include variations
variations in
airwater
flowing
from
the
LOM
North
Pacific
Current,into
into the
the
water
flowing
from
the
LGM
North
Pacific
Current,
sea
equilibration
state,
nutrient
content,
or
some
combination
seaequilibrationstate,nutrientcontent,or somecombination
equatorward
LGM
California
as
opposed
Current,
to
the
equatorward
LGM
California
Current,
as
opposed
to
the
of
of both
both effects.
effects. Local
Local equilibration
equilibration with
with the
theatmosphere
atmosphere
poleward LGM Alaskan Current. This would shift the character
seldom
reaches completion
completion in
waters
seldomreaches
insurface
surface
watersdue
dueto
to differences
differences polewardLGM AlaskanCurrent.This wouldshift the character
the LGM
LGM California
California Current
Current toward
toward more
more subarctic
subarctic conditions
conditions
in the time of contact with the atmosphere (order of months) of the
in the time of contact with the atmosphere(order of months)
relative to
to the
the time
time required
for isotopic
isotopic equilibration
relative
requiredfor
equilibration(order
(orderof
of
years to
to decades)
andcompeting
competing biological
biological carbon
carbon transports.
years
decades)and
transports.
and
result in
in the
the upward
upwardtilting
tilting of
of isopycnals,
andresult
isopycnals,aa geostrophic
geostrophic
readjustment
to enhanced
enhancedsouthward
southwardflow.
flow. A
readjustmentto
A similar
similar concept
concept
explains
years with
anomalous subarctic
subarctic zooplankton
zooplankton biomass
explains
years
with
anomalous
biomass
If 6'3C01
were fully
fully equilibrated
equilibrated with
with the
the atmosphere
atmosphere (holding
(holding
If
8•Cmcwere
in the
the modem
modern California
California Current
Current [Chelton,
[Chelton, 1982;
1982; Chelton
in
Chelton and
and
other
constant), itit would
follow aa slope
other effects
effectsconstant),
would follow
slope near
near -0.l4%
-0.14%o Davis,
Davis, 1982;
1982; Chelton
Chelton et
et al.
al. 1982].
1982].
be higher
higher
6"CDZC
I °Cso
sothat
that the
the 8•C•c in
•Cmc/øC
incolder
colderwater
waterwould
wouldbe
The net
net results
results of
of both
The
both the
the second
second and
and third
third mechanisms
mechanisms
than
thanin
in warmer
warmerwater
water[Kroopnick,
[Kroopnick,1974].
1974].In
In this
thiscase,
case,we
wewould
would would
be to
to cool
would be
cool the
the surface
surface waters
waters of
of the
the LGM
LGM California
California
expect
bulloides shells
shells closer
closer to
to the
6'3C
expectG. bulloides
thecoast
coastto
torecord
record
•C
Current
and increase
increase its
its nutrient
nutrient content.
content. These
Currentand
Thesechanges
changeswould
would
values
higherthan
thanthose
thoseoffshore.
offshore. This
This is
is not
not the
the case.
values+0.4%o
+0.4%ohigher
case. in
waters with
with lower
lower 5•C
6'3C values
values farther
farther offshore
in turn
turnproduce
produce
waters
offshore
A
of
6'3C
offshore is
A better
betterexplanation
explanation
of increasing
increasing
•C offshore
is that
thatsurface
surface and
the offshore
shell accumulation
accumulation rates of
and increase
increase
offshore
shell
of
waters rich
rich in
whereas
those
heterotrophic
foraminifera.
As
a
result,
we
cannot
definitively
in nutrients
nutrients are
arelow
lowininö'3CDIC,
•
8 Cmc, whereasthose heterotrophic
foraminifera.As a result, we cannotdefinitively
204
ORTIZ
AL.: GLACIAL
GLACIAL CALIFORNIA
CALIFORNIA CURRENT
CURRENT AT
AT 42øN
42°N
ORTIZ ET AL.:
distinguish
between
these mechanisms.
Mechanisms
2 and
distinguish
betweenthese
mechanisms.
Mechanisms
2
and33
are
however,
large-scale
are not
notentirely
entirelyindependent,
independent,
however,because
because
large-scale
curl provide
variations
variations in
in wind
windstress
stress curl
provide the
the forcing
forcing for
for the
the
Sverdrup
balance as
as well
well as
as for
upwelling
Sverdmpbalance
for local
localopen-ocean
open-ocean
upwelling
[Chelton,
[Chelton, 1981,
1981, 1982].
1982].
Community
Ecology of
of the
Community Ecology
the Glacial
Glacial California
California
Current
Current
The foraminiferal
foraminiferal fauna
fauna of
of the
the LGM
LGM California
California Current
Current at 42°N
42øN
is
is similar
similar to
to that
that of
ofthe
themodern
modern Gulf
Gulf of
of Alaska.
Alaska.
Does
Does the
the
ecologic
shift recorded
recorded by
by the
the foraminifera
foraminiferareflect
reflectthe
the plankton
plankton
ecologicshift
community
as
a
whole?
Perhaps.
communityas a whole? Perhaps.
Marine
rates in
Marine organic
organiccarbon
carbonaccumulation
accumulation
rates
in some
someof
of the
thesites
sites
at present,
studied
here were
lower during
studiedhere
were lower
during the
the LGM
LGM than
than at
present,
export [Lyle
et al.
al. 1992].
lower carbon
carbon export
suggesting
suggesting lower
[Lyle et
1992].
diatom indicators
indicators of
of
Chaetoceros spores,
Accumulation
rates
Accumulation
ratesof
of Chaetoceros
spores,diatom
the
coastal upwelling
upwelling ecosystem,
were
themodern
moderncoastal
ecosystem,
werealso
alsolow
low during
during
pollen assemblages
[Sancetta
et al.
al. 1992].
the LGM
the
•
[Sancellaet
1992]. Ice-age
Ice-age pollen
assemblages
were
dominated
by
pine
and
mountain
hemlock,
in contrast
contrast to
weredominatedby pine andmountainhemlock, in
to
the modem
modem assemblage
of
the
assemblage
of oak,
oak,redwood,
redwood,and
andalder
alder[Sancetta
[Sancellaet
et
and alder
alder at
at the
the LGM
suggests aa
al. 1992].
1992]. Loss
Loss of
of redwood
redwoodand
LGM suggests
reduced
supply due
due to
to loss
loss of
of summer
summer coastal
coastalfog.
fog. Fog
reducedmoisture
moisturesupply
Fog
over
relatively
warm
atmosphere
is
generated
by
is generatedby relatively warm atmosphereover colder
colder
all suggest
(upwelled)
oceanic waters.
(upwelled)oceanic
waters. These
Theseresults
results all
suggestlower
lower
coastal
coastalupwelling
upwellingduring
duringthe
theLGM.
LGM.
Reduction
of coastal
coastal upwelling,
upwelling, coupled
coupled with
with our
our evidence
evidence for
for
Reductionof
higher
nutrient
content
and
foraminiferal
shell
fluxes
along
higher nutrientcontent and foraminiferalshell fluxes along
an
most
most of
of the
the42°N
42øNtransect
transectduring
duringthe
theLGM,
LGM, suggest
suggest an
ecosystem
similar to
to that
ecosystemsimilar
that of
of the
themodern
modernGulf
Gulf of
of Alaska.
Alaska.The
The
high-nutrient, highCurrent is
modern
California Current
modern California
is aa high-nutrient,
highThe
chlorophyll,
high-export
ecosystem.
chlorophyll, high-export ecosystem. The dominant
dominantprimary
primary
et al.
producers
in this
this environment
producersin
environmentare
arelarge
largediatoms
diatoms[Hood
[Hood et
al.
1990].
that
graze on
on
1990]. These
Thesediatoms,
diatoms,and
andthe
themacrozooplankton
macrozooplankton
that graze
them,
export
a
relatively
large
fraction
of
the
total
biological
them,export a relatively large fractionof the total biological
In contrast,
contrast,
productivity as
as fecal
productivity
fecalpellets
pelletsand
andsinking
sinkingparticltu.
particles. In
the Gulf
Gulf of
of Alaska
is aa high-nutrient,
the
Alaska is
high-nutrient,low-chlorophyll,
low-chlorophyll,lowlowof aa
export system.
export
system.An
An active
activemicrobial
microbial loop,
loop, composed
composedof
variety
of
small
autotrophs
and
heterotrophs,
makes
recycling
varietyof small autotrophsandheterotrophs,makesrecycling
more efficient
efficient here
here than
than in
in the
more
the California
California Current
Current [Miller
[Miller et
et al.
al.
1991]. In
In such
such systems,
systems, aa smaller
1991].
smallerfraction
fraction of
of organic
organicmatter
matter
flowing
CaliforniaCurrent
Currentwas
wasstill
still present
present at
the
flowing California
at 42°N
42øNduring
duringthe
LGM,
and
that
the
polar
front
must
have
remained
north
of
this
LGM, andthat thepolarfront musthave remainednorth of this
latitude band.
latitude
band.
Cooling
Cooling was
waslikely
likely aa response
response to
to stronger
stronger open-ocean
open-ocean
upwelling
advection
upwellingand
andsouthward
southward
advectiondriven
drivenby
by higher
higherwind
windstress
stress
curl.
Coastal
upwelling
decreased
at
42°N
during
the
LGM.
curl. Coastalupwellingdecreased
at 42øN duringthe LGM.
LGM
watersof
ofthe
theCalifornia
California Current
Current were
wererelatively
relatively high
high in
LGM waters
in
nutrients offshore
offshore (based
(basedon
on carbon
carbon isotope
isotope data)
nutrients
data) and
and low
low in
in
biomass
due to
(based
biomassdue
to more
more intense
intensegrazing
grazingby
by microorganisms
microorganisms
(based
on
reduced
organic
carbon
accumulation
rates
and
increases
on reducedorganic carbonaccumulationrates andincreasesin
in
This suggests
heterotrophic
heterotrophicplankton).
plankton). This
suggeststhat
thatduring
duringthe
theLGM
LGM
the
of the
the plankton
planktoncommunity
communityof
thenorthern
northernCalifornia
CaliforniaCurrent
Currentwas
was
similar
to the
of the
similar to
the modern
modernplankton
plankton community
community of
the Gulf
Gulf of
of
Alaska.
Alaska.
Acknowledgmenta.
the captain
captain and
and crew
crew of
Acknowledgments.We
We thank
thankthe
of RN
R/V Wecoma.
Wecoma.
I.
Gardner
(USGS)
kindly
provided
unpublished
'4C
dates.
M. Webber
J. Gardner(USGS)kindlyprovided
unpublished
•nCdates.M.
Webber
and
from
andL.
L. Welling
Welling assisted
assistedwith
with the
the radiolanan
radiolariandata.
data.Comments
Comments
fromN.
N.
Plains,
P. Wheeler,
Wheeler,M.
M.Abbott,
Abbott,L.L Welling,
Welling, and
and reviews
reviews from
Pisias,P.
from J.
J.Gardner,
Gardner,
D.
reviewer
Funding
was
D. Anderson,
Anderson,and
andan
ananonymous
anonymous
reviewerwere
werehelpful.
helpful.
Funding
was
from
a
NASA
Graduate
student
fellowship
and
from
NSF.
Curation
of
froma NASA Graduatestudentfellowshipand from NSF. Curation
of
materials
materialsat
at OSU
OSU was
wasfunded
fundedby
byNSF.
NSF. This
This is
is Larnont-Doherty
Lamont-DohertyEarth
Earth
Observatoiy
contribution
5599.
Observatory
contribution
5599.
References
References
Bakun,
A., and
and C.S.
CS. Nelson,
The seasonal
cycle of
Bakun,A.,
Nelson,The
seasonalcycle
of wind-stress
wind-stresscurl
cud in
in
subtropical
eastern boundary
boundasycurrent
current regions,
regions,J.
I. Phys.
Phys. Oceanogr.,
subtropical
eastern
Oceanogr.,21,
21,
1815-1834,
1815-1834, 1991.
1991.
Bard,
E., M.
M. Arnold,
Arnold, and
Bard, E.,
and B.
B. Hamelin,
Hamelin, Present
Presentstatus
statusof
of the
the radiocarbon
radiocarbon
calibration
for the
the Late
Late Pleistocene
Pleistocene (IPC4
(IPC4 abstracts
abstracts and
calibrationfor
andsupplementary
supplementary
materials).
materials).GEOMAR
GEOMARReport
Report15,
15, 52-53,
52-53,1992.
1992.
Bard, E.,
B., M.
34.Arnold,
Arnold,R.G.
R.G.Fairbanks,
Fairbanks,and
andB.
B. Hamlin,
Hamlin,23øTh-23nu
230Th-2U and
Bard,
and'4C
•nC
ages
by mass
on
Radiocarbon, 35,
agesobtained
obtainedby
massspectrometsy
spectrometry
oncorals,
corals,Radiocarbon,
35, 191191199,
199, 1993.
1993.
Barnard,
variability
off
Barnard,A.H.,
A.H., Seasonal
Seasonal
variabilityof
of zooplankton
zooplankton
off the
theCalifornia
Califomia
coastr
A box
box model
model approach,
approach, M.A.
M.A. thesis,
thesis, 91
91 pp.,
pp., Oregon
coast:A
OregonState
StateUniv.,
Univ.,
Corvallis,
Corvallis,1994.
1994.
Be, A.W.H.,
A.W.H., An
An ecological,
ecological, zoogeographic,
zoogeographic, and
and taxonomic
taxononuc review
review of
of
B6,
recent
Micropaleontology,
vol.
recentplanktonic
planktonicforaminifera,
foraminifera,in
inOceanic
Oceanic
Micropaleontology,
vol.1,1,
edited
San
editedby
by A.T.S.
A.T.S.Ramsey,
Ramsey,pp.
pp.1-100,
1-100,Academic,
Academic,
SanDiego,
Diego,Calif.,
Cald.,
1977.
1977.
Chekctn,
D.B., Intemnmml
Interannual variability
variability of
of the
the California
California Current
Chelton,D.B.,
Current-- Physical
Physical
factors,
XXII, 34-48,
factors,Calif.
Calif.Coop.
Coop.Fish.
Fish.Invest.
Invest.Rep.
Rep.XXII,
34-48,1981.
1981.
Qiehosi,
response of
of the
the California
Current to
to forcing
forcing
Chelton,D.B.,
D.B., Large-scale
Large-scale
response
CaliforniaCurrent
XXIII, 130-148,
by
the wind
wind stre•s
stress cud,
cud, Calif.
Calif Coop.
by the
Coop.Fish.
Fish. Rep.
Rep.XXIII,
130-148,1982.
1982.
(iehon,
D.B.,
Chelton,
D.B.,and
andRE.
R.E.Davis,
Davis,Monthly
Monthlymean
meansea-level
sea-levelvariability
variabilityalong
along
sinks
sinks to
to the
the seafloor.
seafloor.
The
decrease in
in export
export productivity
The decrease
productivityof
of the
theLGM
LGM California
California
the
coast of
of North
North America,
America, J.
I. Phys.
the West
west coast
Phys.Oceanogr.,
Oceanogr.,12,
12,757-784,
757-784,
Current
at
42°N
is
ultimately
linked
to
changes
inthe
the physical
physical
Currentat 42øN is ultimatelylinked to changesin
1982.
1982.
environment. However,
these physical
physical changes
changesdid
did not
not simply
simply
environment.
However,these
Chekon,
D.B., P.A.
P.A. Bemal,
Bemal,and
andJ.A.
l.A. McGowan,
McGowan, Large-scale
Large-scale interannual
Chelton,D.B.,
interannual
cause the
cause
the biological
biological interactions
interactions of
of the
themodem
modemoceanic
oceanic
physical
and biological
biological interaction
interactionin
inthe
the California
California Current,
Current, J.
I. Marine
physicaland
Marine
community to
to run
Res.,
community
run more
moreslowly.
slowly. Rather,
Rather,the
the physical
physicalchanges
changes
Res.,40, 1095-1125,
1095-1125,1982.
1982.
variations
in
appear
to have
have resulted
resulted in
in the
the replacement
replacementof
of the
the high-export
high-export Craig,
Craig, IL,
H., and
andLI.
L.I.Gordon,
Gordon,Deuterium
Deuteriumand
andoxygen-l8
oxygen-18
variations
inthe
the
appearto
ocean
in
in
oceanand
andmarine
marineatmosphere,
atmosphere,
in Stable
StableIsotopes
Isotopes
inOceanographic
Oceanographic
flux,
modern coastal
coastal upwelling
upwelling community
community with
with aa low-export
flux, modern
low-export
SPOLETO Conference
on Nuclear
Nuclear
Studies
Studiesand
andPaleotemperatures,Third
Paleotemperatures,Third
SPOLETO
Conference
on
flux, subarctic,
flux,
subarctic,open-ocean
open-oceanupwelling
upwellingcommunity.
community.
Geology,
by E.Tiongionrn,
pp.
Cons. Naz.
Naz. Ric.
Geology,edited
editedby
E.Tiongiorini,
pp.9-130,
9-130, Cons.
Ric. Lab.
Lab.
GeoL
Nucl., Pisa,
Geol.Nucl.,
Pisa,Italy,
Italy,1965.
1965.
Conclusions
Conclusions
Foraminiferal
species and
Foraminiferalspecies
andisotopic
isotopic data
data from
from 10
10 sediment
sediment
cores
decrease
coressuggest
suggestthe
themagnitude
magnitudeof
of the
theLGM
LGMtemperature
temperature
decrease
330
across
acrossthe
theCalifornia
CaliforniaCurrent
Currentat
at42°N
42øNduring
duringthe
theLCM
LGMwas
was3.3 ø
±1.5°C. The
The cooling
cooling was
roughly constant
constant across
the entire
+1.5øC.
was roughly
acrossthe
entire
Temperatures
remained
coolest
near
the
coast and
transect.
transect. Temperatures
remainedcoolestnear the coast
and
increased offshore,
offshore, similar
similar to
to the
the modern
average zonal
zonal
increased
modern annual
annual average
thermal
gradient. These
that
thermalgradient.
Thesefindings
findingssuggest
suggest
thatthe
theequatorward
equatorward
Curly,
W.B., and
and T.J.
Ti. Crowley,
Atlantic
Curry,W.B.,
Crowley,The
The8'3C
8nCof
ofequatorial
equatorial
Atlanticsurface
surface
waters:
for Ice
Ice Age
levels, Paleoceanography,
Paleoceanography, 2,
2,
waters:Implications
Implications
for
AgepCO2
pCO2 levels,
489-517, 1987.
1987.
Epstein, S.,
S., R.
R Buchsbausn,
H.A. Lowenstam,
Lowenstam, and
and H.C.
H.C. Urey,
Epstein,
Buchsbaum,H.A.
Urey, Revised
Revised
carbonatewater
temperature
scale,.
Geol.
carbonatewaterisotopic
isotopic
temperature
scale,.
Geol.Soc.
Soc.Am.
Am.Bull.,
Bull.,64,
64,
1315-1326,
1315-1326,1953.
1953.
Fairbanks, R.G.,
R.G., A
sea level
Fairb•s,
A 17,000-year
17,000-yearglacio-eustatic
glacio-eustatic sea
level record:
record:
Influence
meltingrates
rates on
on the
Influence of
of glacial
glacial melting
the Younger
YoungerDryas
Dryasevent
eventand
and
deep-ocean
circulation, Nature,
Nature, 342,637-642,
342.637-642, 1989.
deep-ocean
circulation,
1989.
Faure, G.,
G., Principles
Principles of
Isotope Geology,
Faure,
of Isotope
Geology,2nd
2nded.,
ed.,464
464pp.,
pp.,John
JohnWiley,
Wiley,
New
New York,
York, 1977.
1977.
ORTIZ
ET AL.:
AL.: GLACIAL
CALIFORNIA CURRENT
CURRENT AT
AT 42øN
42°N
ORTIZ ET
GLACIAL CALIFORNIA
205
205
Gardner,
sedimentation
beneath
Gardner,I.,
J.,W.
W. Dean,
Dean,and
andP.P.Darinell,
Dannell,Biogemc
Biogenic
sedimentation
beneath
the California
the past
the
California Current
Current System
System for
for the
past 30
30 ka
ka and
and
itspaleoceanographic significance,
significance, Paleoceanography,
Paleoceanography, this
this issue.
issue.
itspal•ographic
Hemleben,
C., M.
M. Spindler,
Hemleben,C.,
Spindler,and
and OR.
O.R.Anderson
Anderson(Eds.),
(Eds.),Modern
Modern
Planktonic
Foraminjfera,
363
New
Planktonic
Foraminifera,
363pp.,
pp.,Springer-Verlag,
Springer-Verlag,
NewYork,
York,1988.
1988.
Herbert,
seaHerbert, T.D.,
T.D., M.
M. Yasuda,
Yasuda,and
andC.
C.Burnett,
Bumeli,Glacial-interglacial
Glacial-interglacial
seasurface
surfacetemperature
temperaturerecord
recordinferred
inferred from
from alkenone
alkenoneunsaturation
unsaturation
indices,
Site 893,
Santa Barbara
Barbara Basin,
Basin, Proc.
Proc. Ocean
Ocean Drill
Drill Program,
Program, Sci.
indices,Site
893, Santa
Sci.
Results,
Re,suits,146, 257-264,
257-264,1995.
1995.
Hood,
R.R, MR.
and P.M.
P.M. Kosro,
Kosro, Surface
Surface patterns
Hood,R.R.,
M.R.Abbott,
Abbott,A.
A. Huyer,
Huyer,and
patternsin
in
temperature,
flow, phytoplankton
biomass,
in
temperature,
flow,
phytoplankton
biomass,and
andspecies
speciescomposition
composition
in
the
Res,
the coastal
coastaltransition
transitionzone
zoneoff
off northern
northernCalifornia,
California,I.
J.Geophys.
Geophys.
Res,95,
95,
Miocene,
by C.P.
C.P. Summerhayes,
Summethayes,W.L
W.L Prell,
Miocene, edited
editedby
Prell, and
and K.C.
K.C. Emeis,
Emeis,
Ceo!.
Spec. Publ.
Pbl. 64,
Geol. Soc.
Soc.Spec.
64,London,
London,197-213,
197-213,1992.
1992.
Ortiz,
J.D., and
and A.C.
AC. Mix,
of
Ortiz,I.D.,
Mix, Comparison
Comparison
of Imbrie-Kipp
Imbrie-Kipptransfer
transferfunction
function
and
estimates using
using sediment
sediment trap
trap and
and core
andmodern
modemanalogtemperature
analogtemperature
estimates
core
top
faunas, Paleoceanography,
Paleoceanography, this
topforaminiferal
foramimf'
eralfaunas,
thisissue.
issue.
Ortiz,
control
of
Ortiz,J.D.,
J.D.,A.C.
A.C. Mix,
Mix, and
andR.W.
R.W.Collier,
Collier,Environmental
Environmental
control
ofliving
living
symbiotic
and asymliotic
planktonic
foraminifera in
in the
symbioticand
asymbiotic
planktonicforaminifera
theCalifornia
Califomia
18081-18094, 1990.
Hostetler,
G.T. Bates,
Bates, and
and P.J.
PJ. Bartlein,
Hostetler,S.W.,
S.W., F.
F. Giorgi,
Giorgi,G.T.
Banlein,Lake-atmosphere
Lake-atmosphere
Bonneville and
feedbacks
with paleolakes
feedbacks associated
associatedwith
palcolakes Bonneville
and Lahontan,
Lahontan,
Science,
263,665-668,
Science,263,
665-668, 1994.
1994.
Huyer,
Prog.
Huyer, A.,
A., Coastal
Coastalupwelling
upwellingin
in the
theCalifornia
CaliforniaCurrent
Currentsystem,
system,
Prog.
Oceonogr.,
Oceanogr.,12,
12, 1434-1450,
1434-1450,1983.
1983.
Karlin,
Karlin, R.,
R., M.
M. Lyle,
Lyle, and
andR.
R. Zahn,
Zahn,Carbonate
Carbonatevariations
variationsin
in the
thenortheast
northeast
Pacific
Paleoceanography,
7,7,43-62,
Pacificduring
duringthe
thelate
lateQuaternary,
Quaternary,
Paleoceanography,
43-62,1992.
1992.
Kipp,
past
sea-surface
Kipp, N.G.,
N.G., New
New transfer
transferfunction
functionfor
forestimating
estimating
past sea-surface
conditions
from seaof
forammiferal
conditionsfrom
sea-bed
beddistributions
distributions
ofplanktonic
planktonic
foraminiferal
assemblages
in the
theNorth
North Atlantic,
Atlantic, in
in Investigations
Investigationsof
of late
late quaternary
quatemary
assemblages
in
by K.K.
paleoceanograpliy and
paleoceanography
and paleontology,
paleontology,edited
edited by
K.K. Turekian,
Turekian,
Memo,Geol. Soc.,
Memo,Geol.
Soc.,Am.,
Am., 145, 3-41, 1976.
1976.
Kroopnick,
between
'3C
waters
and
Kr•nick, P.,
P.,Correlations
Correlations
between
•3Cand
andECO2
•CO2in
insurface
surface
waters
and
atmospheric CO2,
CO2.Earth
Earth and
and Planet.
Planet. Sci.
Sci. Lett.
Leit. 22,
22,397-403,
atmospheric
397-403,1974.
1974.
Kutzbach,
I., and
orbital
Kutzbach, J.,
and PJ.
P.I.Guetter,
Guetter,The
Theinfluence
influence of
of changing
changing orbital
parameters
and
on climatic
for
parameters
andsurface
surfaceboundasy
boundaryconditions
conditions
on
climaticsimulations
simulations
for
the past
past 18,000
16, 1726-1759,
the
18,000years,
years,I.
J.Atmos.
Atmos.Sci.,
Sci.,16,
1726-1759,1986.
1986.
Levitus, S.,
S., Climatological
Climatological atlas
atlas of
of the
the world
world ocean,
ocean, NOAA
NOAAProf.
Prof. Pap.
Pap. 13,
Levitus,
13,
173
pp., U.S.
U.S. Govt.
Govt. Print.
Print Off.,
D.C.,
173pp.,
Off.,Washington,
Washington,
D.C., 1982.
1982.
Lyle,
J. Dymond,
Dymond, R.
R. Collier,
Collier, N.
N. Pisias,
Pisias, and
and E.
E. Suess,
Lyle,M.,
M., R.
R. Zahn,
Zahn,F.
F. PraM,
Prahl,I.
Sums,
Paleoproductivity and
and carbon
carbon burial
burial across
acrossthe
the California
California Current:
Current: The
The
Palcoproductivity
Muhitracers transect,
transect, 42øN,
42"N, Paleoceanography,
Paleoceanography, 7,
7,251-272,
Multitracers
251-272,1992.
1992.
Miles,
planktonic foraminifera
foraminifera in
in the
Pacific
Miles, G.A.,
G.A., Living
Living planktonic
thenortheast
northeast
Pacific
Ocean, M.A.
M.A. thesis,
thesis, 131pp.,
l3lpp., Univ.
Ocean,
Univ.of
ofOregon,
Oregon,Eugene,
Eugene,1973.
1973.
Miller,
B.W. Frost,
Frost,B.
B.Booth,
Booth,P.A.
P.A.Wheeler,
Wheeler,M.R.
MR Landry,
and N.
N.
Miller, C.B.,
C.B., B.W.
Landry, and
Welschineyer, Ecological
Ecologicalprocesses
processesin
in the
the subarctic
Welschmeyer,
subarcticPacific:
Pacific:Iron
Iron
limitation cannot
cannot be
be the
the whole
whole story,
stosy, Oceanography,
Oceanography,4,
4,71-78,
limitation
71-78, 1991.
1991.
Mix, A.C.,
A.C., The
The oxygen-isotope
oxygen-isotoperecord
record of
of glaciation,
in North
Mix,
glaciation,in
North America
America
and Adjacent
Oceans During
Dwing the
Deglaciation, The
The Geology
and
AdjacentOceans
the Lest
l.ast Deglaciation,
Geologyof
of
North America.
North
America,vol.
vol. K-3,
K-3, edited
editedby
by W.F.
W.F. Ruddiman,
Ruddiman,and
and H.E.
H.E. Wrig)it
Wright
Jr., pp.
Geol. Soc.
Soc. clam.,
of Am., Boulder,
Boulder, Colo.,
Cob., 1987.
Jr.,
pp.111-135.
111-135,Geol.
1987.
Moore, T.C.,
Late Pleistocene-Holocene
oceanographic changes
changes in
Moore,
T.C., Late
Pleistocene-Holocene
oceanographic
in the
the
northeastern Pacific,
northeastern
Pacific,Qunt.
Quat.Res.,
Res.,3,
3, 229-266,
229-266,1973.
1973.
GEOSECS
Atlantic, Pacific,
Pacf1c, and
Shore
based
GEOSECSAtlantic,
andIndian
IndianOcean
OceanExpeditions,
Expeditions,
Shorebased
Data
GEOSECS
AtlasSer.,
Ser., vol.
vol.7,
7, 200
200 pp.,
pp., U.S.
Data and
andGraphics,
Graphics,
GEOSECSAtlas
U.S. Gov.
Gov.
Print.
D.C.,
Print.Off.,
Off., Washington,
Washington,
D.C.,1987.
1987.
Parker,
F., Planktonic
in Pacific
Parker, F.,
Planktonicforaminiferal
foraminiferal species
speciesin
Pacific sediments,
sediments,
Micropaleontology,
8,
Micropaleontology,
8, 219-254,
219-254,1962.
1962.
Pralil,
RB. Collier,
Prahl,F.G,
F.G, R.B.
Collier,J.
I. Dymond,
Dymond,M.
M. Lyle,
Lyle, and
andM.A.
M.A. Sparrow,
Sparrow,A
A
biomarker
perspective on
on pryrnnesiophyte
prymnesiophyteproductivity
productivity in
in the
the northeast
northeast
biomarkerperspective
Pacific
Deep Sea
Sea Res.
Res. Part
Part 1,40,
PacificOcean,
Ocean,Deep
1, 40,2061-2076,
2061-2076,1993.
1993.
PraM,
F.G.,N.G.
N.G.Pisias,
Pisias,A.L
A.L Sabin
Sabin and
and M.
M. Sparrow,
of sea
Prahl,F.G.,
Sparrow,Assessment
Assessment
of
sea
surface
at 42°N
over
surfacetemperature
temperature
at
42øNin
in the
theCalifornia
CaliforniaCurrent
CurrentSystem
System
overthe
the
last
Paleoceanography, 10,
last30,000
30,000years,
years,Paleoceanography,
10,763-773,
763-773,1995.
1995.
Sabin,
A.L, and
change
Sabin,A.L.,
andN.G.
N.G. Pisias,
Pisias,Sea
Seasurface
surfacetemperature
temperature
changein
in the
the
northeast
Pacific
to
northeast
PacificOcean
Oceanfor
forthe
thepast
past20,000
20,000years
yearsand
andits
itsrelationship
relationship
to
climatic
in the
of North
North America,
America, Quat.
Qua:. Res,
climaticchange
changein
the Pacific
PacificNorthwest
Northwestof
Res,
46,48-61,
46,
48-61, 1996.
1996.
Sancetta,
C., M.
M. Lyle,
Lyle,LL Heusser,
Sancetta,C.,
Heusser,R.
R. Zahn,
Zahn, and
andJ.P.
I.P. Bradbuiy,
Bradbury,LateLateGlacial
Glacial to
to Holocene
Holocenechanges
changesin
in the
thewinds,
winds,upwelling
upwellingand
andseasonal
seasonal
production
Quat.
productionof
of the
thenorthern
northernCalifornia
CaliforniaCurrent
CurrentSystem,
System,
Quat.Res.,
Res.,38,
38,
359-370,
359-370, 1992.
1992.
Sautter,
L, and
succession
of
Sautter,L,
andR.
R.Thunell,
Thunell,Seasonal
Seasonal
succession
of the
theplanktonic
planktonic
foraminifera:
Resultsfrom
from aa four
sediment
foraminifera:Results
four year
yeartime-series
time-series
sedimenttrap
trap
experiment i•the
in the northem
northern Pacific,
Pacific,J.
I. Foraminiferal
Foraminferal Res.,
19,
experiment
Res.,
19,253-267,
253-267,
1989.
1989.
Spigai,
JJ., Marine
Marine geology
of the
Spigai,I.J.,
geology of
thecontinental
continentalmargin
margin off
off southern
southern
Oregon, Ph.D.
214
State
1971.
Oregon,
Ph.D.thesis,
thesis,
214pp.,
pp.,Oregon
Oregon
StateUniv.,
Univ.,Corvallis,
Corvallis,
1971.
Moore,
T.C.,LH.
LH. Burkle,
Buikle, K.
K. Geitmauer,
Moore, T.C.,
Geitznauer,B.
B. Luz,
Luz, A.
A. Molina-Cmz,
Molina-Cmz, J.H.
I.H.
Robertson,H.
H. Sachs,
Sachs, C.
C Sancetta,
and C
Robertson,
Sancetta,J.
I. Thiede,
Thiede, P.
P. Thompson,
Thompson,and
C.
Wenkam,
The reconatniction
of sea
in
Wenkaro, The
reconstruction
of
seasurface
surfacetemperatures
temperatures
in the
the
Current,
10,
Current,Paleoceanography,
Paleoceanography,
10,987-1009,
987-1009,1995
1995
Ortiz,
J.D., A.
C. Mix,
Mix, W.
W. Rugh,
Rugh, J.
I. M.
M. Watkins,
Watkins, and
andR.
R. W.
W. Collier,
Ortiz,J.D.,
A. C.
Collier,DeepDeepdwelling
foraminifera
dwellingplanktonic
planktonic
foraminiferaof
of the
theNE
NE Pacific
Pacificrecord
recordintermediate
intermediate
water
Geochim.
Ada, 22,4509-4523,
waterproperties,
properties,
Geochim.Cosmochim.
Cosmochim.
Acta,
22,4509-4523,1996.
1996.
Ostlund,
H.G.,H.
H. Craig,
Craig, W.S.
W.S. Broecker,
Broecker, and
and D.
(Eds.),
(•stlund,
H.G.,
D. Spencer
Spencer
(Eds.),
Stuiver,
M., and
and H.A.
H.A. Polach,
Polach, Reporting
Reportingof
of inc
'4C data:
Stuiver,M.,
data:A
A discussion,
discussion,
Radiocarbon,
Radiocarbon,19,355-363,
19, 355-363,1971.
1971.
Slull,
RB., An
An Introduction
to Boundary
Layer Meteorology,
666 pp.,
pp.,
Stall,R.B.,
Introduction
to
BoundaryLayer
Meteorology,
666
Mass., 1988.
Norwell, Mass.,
Zahn, R.,
and A.C.
A.C. Mix,
Mix, Water
Water mass
Zahn,
R., T.F.
T.F. Pedersen,
Pedersen,B.D.
B.D. Bornhold,
Bornhold,and
mass
conversion
in the
the glacial
conversion
in
glacialsubarctic
subarcticPacific
Pacific(54°N,
(54øN,148°W):
148øW):Physical
Physical
constraints
the benthicstable isotope
cons•ts and
and the
benthic- planktonic
planktonicstable
isotope record,
record,
Paleoceanography, 6,
Paleoceanography,
6, 543-560,
543-560,1991a.
1991a.
Zaire, R.,
R,A.
N.G.
Blaise, and
and R.
Zahn,
A.Rushdi,
Rushdi,
N.G.Pisias,
Pisias,B.D.
B.D. Bomhold,
Bornhold,B. Blaise,
R. Karlin,
Karlin,
Carbonate
depositionand
andbenthie
benthic•5•C
6'3C in
in the
Pacific:
Carbonatedepos'aion
thesubarctic
subarcticPacific:
Implications
for changes
changes of
of the
system,
during
Implications
for
theoceanic
oceaniccarbonate
carbonate
system,
duringthe
the
past 750,000
Earth Planet.
lb.
past
750,000years,
years,Earth
Planet.Sci.
Sci.Let:.,
Lett.,103,
103,116-132,
116-132,199
1991b.
Pacific
5,
PacificOcean
Ocean18,000
18,000B.P.,
B.P., Marine
MarineMicropaleontol.,
Micropaleontol.,
5, 215-247,
215-247,1980.
1980.
Modyn,
R.C. Thunell,
Thunell,D.
D. Anderson,
Anderson,L.D.
LD. Stott,
Stou, and
and I.J. Le,
La, Sea
Mort)n, P.G.,
P.G., R.C.
Sea
surface
changes
in
California
Borderlands
surfacetemperature
temperature
changes
in the
thesouthern
southern
California
Borderlands
during
the last
cycle,
11,
duringthe
lastglacial-interglacial
glacial-interglacial
cycle,Paleoceanography,
Paleoceanography,
11, 415415430,
430, 1996.
1996.
Nelson,
Nelson, CS.,
C.S., Wind
Wind stress
stressand
andwind-stress
wind-stresscurl
cud over
overthe
theCalifornia
California
U.S. Dept.
Current,
Current, NOAA
NOAA Tech.
Tech. Rep.
Rep. NMFS
NMFS SSRF-7l4,
SSRF-714, U.S.
Dept. of
of
S.
U.S. Geological
Geological Survey
Protection
S. Hostetler,
Hostetler,U.S.
Surveyat
atU.S.
U.S.Environmental
Environmental
Protection
Administration,
Corvallis,
OR
97330.
(email:
steve@sage.cgd.ucar.edu)
Administration,
Corvallis,OR 97330.(email:steve•0sage.
cgd.ucar.
edu)
M.
Lawrence
Livermore,
M. Kashgarian,
Kashgarian,
LawrenceLivermore
LivermoreNational
NationalLaboratory,
Laboratory,
Livermore,
CA
CA 92717.
92717.(email:
(email:kashgarian®LLNL.GOV)
kashgarian@LLNL.GOV)
A.C.
Mix,
Sciences,
Oregon
A.C. Mix, College
Collegeof
of Oceanic
Oceanicand
andAtmospheric
Atmospheric
Sciences,
OregonState
State
University.
Corvallis,
OR
97331-5503.
(email:
amix@oce.orsat.edu)
University,
Conrailis,
OR97331-550.3.
(email:amix@oce.orsat.
edu)
J.D.
Earth
of
I.D. Ortiz,
Ortiz,Lamont-Doherty
Lamont-Doherty
EarthObservatory
Observatory
of Columbia
ColumbiaUniversity,
University,
Palisades,
NY 10964.
(email:jortiz•ldeo.columbia.edu)
jortifl)ldeo.columbia.edu)
Palisades,
NY
10964.(email:
Commerce,
87
Commerce,
87 pp.,
pp.,1977.
1977.
Ortiz, J.D.,
Planktic foraminifers
fosaminifers of
of the California Current
I.D., Planktic
Current at
at 42°N:
42øN:Last
Last
Gla&l
Maximum
Unpublished
Ph.D.
Oregon
Glacial
Maximumand
andPresent,
Present,
Unpublished
Ph.D.Dissertation,
Dissertation,
Oregon
State
219
StateUniversity,
University,
219pp.,
pp.,1995.
1995.
Oniz, J.D.,
and
succession
Ortiz,
I.D., and
andA.C.
A.C. Mix,
Mix, The
Thespatial
spatialdistnbution
distribution
andseasonal
seasonal
succession
(Received November
November 29,
29, 1995;
revised September
September 30,
30, 1996;
of
1995;revised
1996;
of planktonic
plankt•c foriminifera
foraminifera in
in the
theCalifornia
CaliforniaCurrent
Currentoff
off Oregon,
Oregon, (Received
September 1987-1988,
in Upwelling
ssystems: evolution
evolutionsince
since the
the early
early
accepted October
October 3,
3, 1996)
September
1987-1988,in
Upwellingssysterns:
accepted
1996)