Male Antarctic fur seal pups foraged significantly farther from their birth site at South Georgia than female pups. Over the course of winter, both male and female pups' locations shifted eastward and moved farther from the continental shelf, possibly to exploit different prey in upper water columns. The study tracked 10 pups (5 males in 2001, 5 females in 2002) using satellite tags to analyze their at-sea distribution in relation to sex and environmental conditions between years.

1. ORIGINAL PAPER
N.L. Warren Æ P.N. Trathan Æ J. Forcada Æ A. Fleming
M.J. Jessopp
Distribution of post-weaning Antarctic fur seal Arctocephalus gazella
pups at South Georgia
Received: 27 January 2005 / Revised: 8 June 2005 / Accepted: 13 June 2005
Ó Springer-Verlag 2005
Abstract Potentially some of the biggest gaps in our
knowledge about the ecology of Antarctic fur seals
(Arctocephalus gazella) relate to juvenile animals. We
investigated the at-sea distribution of five male and five
female fur seal pups post-weaning. The study was car-
ried out at Bird Island, South Georgia during two suc-
cessive winters using satellite-linked platform
transmitter terminals (PTTs). Our results are analysed in
relation to pup sex and the physical environment and
productivity of those 2 years, as well as in the context of
our present knowledge of where post-breeding females
and males forage. The available physical and biological
data during both of the winters of this study suggest that
both years were not unusual. We report marked differ-
ences between the sexes with male pups foraging sig-
nificantly further away from land and their birth site
than do females. The pups foraged in areas to the East
of Bird Island seldom reported as foraging areas for the
adult population. Also as winter progressed they showed
a more oceanic distribution leaving the continental shelf,
possibly to exploit a different prey source that was more
readily available in the upper water column.
Introduction
The Antarctic fur seal (Arctocephalus gazella) popula-
tion at South Georgia has recovered from the brink of
extinction over the course of the twentieth century.
Initial indications of recovery started with the discovery
of a few small, isolated breeding colonies in the 1930s;
these had increased to an estimated population of over
1.5 million by the early 1990s (Boyd 1993). Today, the
population is thought to be in excess of 3 million (Bar-
low and Croxall 2002).
A recent estimate of food consumption by Antarctic
fur seals at South Georgia, assuming a diet mainly of
krill (Reid and Arnould 1996), suggests that this popu-
lation consumes approximately 3.84 million tonnes of
krill annually (Boyd 2002a), based on the 1991 popula-
tion estimates. This removal of krill from the South
Georgia region potentially brings fur seals into direct
competition with other species and with man. Compet-
itive interactions with sympatric species are thought to
be increasingly important and certainly are not negligi-
ble, especially for other krill specialists such as macaroni
penguins (Barlow and Croxall 2002). Similarly, interac-
tions between fishermen and seals, either through com-
petition for resources or through incidental mortality,
are increasingly recognised as an important issue in
ecosystem management; both entanglement in fishing
gear (Arnould and Croxall 1995) and by-catch (Hooper
et al. 2004) are now known to occur in South Georgia
waters.
Consequently, as the population of Antarctic fur
seals continues to expand and as interactions with other
marine predators and with man intensify, it is increas-
ingly important to obtain information about the diet,
feeding behaviour and foraging areas of these top pre-
dators. In the Southern Ocean, such information is
considered to be critical to the management process
(Agnew 1997); this is because Southern Ocean fisheries,
including that for Antarctic krill (a major constituent of
the diet of Antarctic fur seal), are managed using eco-
system-based methods (http://www.ccamlr.org/pu/e/
pubs/am/toc.htm; CCAMLR 2002).
Many studies have investigated the at-sea distribution
of Antarctic fur seals throughout their complete cir-
cumpolar range (e.g. Staniland et al. 2004; Boyd et al.
2002, 1998 in the Southern Atlantic; Bonadonna et al.
N.L. Warren Æ P.N. Trathan (&) Æ J. Forcada Æ A. Fleming
M.J. Jessopp
British Antarctic Survey, Natural Environment Research Council,
Madingley Road, Cambridge, CB3 0ET UK
E-mail: pnt@bas.ac.uk
Tel.: +44-1223-221602
Fax: +44-1223-221259
Present address: M.J. Jessopp
Department of Zoology, Ecology and Plant Science, University
College Cork, Lee Maltings, Cork, Ireland
Polar Biol (2005)
DOI 10.1007/s00300-005-0037-x

2. 2001; Guinet et al. 2001 in the Indian Ocean; Robinson
et al. 2002 in the Pacific). However, most studies have
concentrated on breeding females and very little work
has been carried out on males or on other demographic
categories.
Several studies on the foraging distribution of marine
mammals have observed marked differences between
sexes (Boyd et al. 1998; Stewart 1997; Kovacs et al.
1990, Hindell et al. 1991; LeBoeuf et al. 1993; Stewart
and DeLong 1993) and age classes (Merrick and Loug-
hin 1997; McConnell et al. 2002) of pinnipeds. These
studies highlight that conclusions about feeding behav-
iour and foraging distribution could potentially be
biased if intra-specific differences are ignored. The
importance of gaining a better understanding of fur seal
distribution across different age classes and sexes is
therefore essential.
Potentially one of the biggest gaps in our knowledge
is that for juvenile animals. Very little is known about
juveniles after they leave their birth site until they return
to breed as 3-year olds (females) or 7-year olds (males).
Consequently, in this study, we investigated the at-sea
distribution of Antarctic fur seal pups in the period
immediately after they were weaned. The study was
carried out at Bird Island, South Georgia during two
successive winters using satellite-linked platform trans-
mitter terminals (PTTs). Our results are analysed in
relation to the sex of the pup and the physical environ-
ment (bathymetry, sea surface temperature) and a
measure of primary productivity (SeaWiFS), as well as
in the context of our present knowledge of where post-
breeding females forage.
Materials and methods
Experimental design
Platform transmitter terminal are expensive both in
terms of the cost of the instruments and their operations
(Boyd 2002b). Our experimental design was therefore a
compromise between sample size and our intended
protocol. Consequently to reduce variability associated
with gender and inter-annual environmental differences
we deployed tags on one gender only in each of our
study years, but were careful to monitor environmental
conditions in both years.
The study period extended from April until early
September 2001 for males and from April to late
December 2002 for females. When comparing the male
and female distributions, we have only considered the
months in which data were available for both sexes, thus
the period of interest ranged from the start of April until
the end of August in both years.
Deployments
The study was carried out from Freshwater Beach, Bird
Island, South Georgia (54°00¢S; 38°02¢W). Prior to
weaning and departure from the breeding beaches
(Doidge et al. 1986), five male and five female pups were
chosen randomly in April 2001 and 2002, respectively.
The pups were caught using a well-established restrain-
ing method (Boyd et al. 1998). Weight measurements
were collected and each individual was given a unique
identification marker with numbered tags (Dalton Sup-
plies, Henley-on-Thames, UK). The 180 g satellite-
linked platform transmitter terminals (PTTs; Model ST
À18 25% duty cycled; Telonics, USA, packaged by
Sirtrack, New Zealand) were deployed to the fur of each
study animal in the mid-dorsal region between the
scapulae using epoxy glue (Boyd et al. 1998). Total de-
vice mass always represented less than 1.5% of the fur
seal body mass. The animals were subsequently released.
No handling interval lasted more than 30 min
Data handling
The resulting Argos uplinks and locations were filtered
to remove potentially unreliable records. Locations
determined by two or fewer uplinks were removed (all
B and Z Classes). The remaining uplinks (Classes 3, 2, 1,
0 and A) were deemed to be reliable (Vincent et al. 2002)
and were further filtered by identifying fixes that would
require an unrealistic rate of travel. The ‘maximum
speed parameter’ in the filter was set to 2.0 m sÀ1
(Boyd
1996). The data were then plotted and analysed using
ESRI ArcMap 8.3. The point distributions were trans-
formed into density estimates using Kernel-based
methods.
Using the coordinates of two points, the distance
between these two were calculated using the great circle
arc which is the shortest distance between two points on
a spherical surface (Maling 1992).
Environment
The physical environment probably drives a large pro-
portion of the observed biological variability at South
Georgia (Trathan et al. 2005); we thus compared the
differences between the two study years in terms of Sea
Surface Temperatures (SST). We also compared the
biological environment during the two years in terms of
surface chlorophyll-a. These two environmental vari-
ables were used to describe the conditions that the fur
seals were experiencing during both years. Data outputs
from these analyses include monthly SST grids in units
of degrees Celsius (°C) with an approximate spatial
resolution of 4 km.
The SeaWiFS-derived estimates of surface chloro-
phyll-a concentration were obtained from the Goddard
Distributed Active Archive Centre using the standard
OC4v4 chlorophyll algorithm, described by O’Reilly
et al. (2001). The grids were in units of mg mÀ3
and had
an approximate spatial resolution of 9 km.
The area for the analysis of the SST and SeaWiFS
around South Georgia was set as 49–57° South and

3. 20–44° West to incorporate the overall distribution of
the fur seals during both winters.
Data used to trace the Antarctic polar front and the
Southern Antarctic circumpolar current, one of the fast
moving jets of the Antarctic Circumpolar Currents were
taken from Moore et al. (1999), Orsi et al. (1995) and
Trathan et al. (1997).
To determine the extent of the differences between
years for these oceanographic variables, we analysed
differences between the means of each month and year
by regression analysis. The same method was used for
both the SeaWiFS and SST data.
Five different models were fitted to the data using
Splus (Mathsoft Inc. Cambridge MA, USA):
– A simple linear model where SeaWiFS or SST are a
function of month, year and the interaction of month
on year.
– The same model without the interaction of month on
year.
– Two linear models with separate intercept.
– Two linear models with a separate intercept and a
quadratic relationship
– A simple linear model with a quadratic relationship.
These five models were compared using a model-
order selection criterion based on parsimony, where
more complicated models are penalised for the inclusion
of additional parameters, named the Akaike Informa-
tion Criteria (AIC); the model with the lowest AIC was
chosen.
Results
Oceanography
There was no significant difference between years for
the SST values around South Georgia (Fig 1a,
t3,6=1.71, P= 0.13; À1.7°C to +10°C). Both years,
Fig. 1 a Mean values and linear
regression analysis (with 95%
confidence levels) of Sea
Surface Temperature around
South Georgia from April until
August (the empty squares
representing Winter 2002,
whereas the full squares Winter
2001). b Mean values and linear
regression analysis (with 95%
confidence levels) of SeaWiFS
around South Georgia from
April until August (the empty
squares representing Winter
2002, whereas the full squares
Winter 2001)

4. showed a linear decline in sea temperatures as winter
progressed.
A significant difference between years for the SeaW-
iFS was recorded (Fig 1b, F3,6= 12.04, P= 0.006) and
this was to the 10À2
mg mÀ3
level; an amount we did not
consider to be biologically significant, knowing that the
difference between a productive and unproductive area
in summer around South Georgia ranges from 15–
20 mg mÀ3
to <0.3 mg mÀ3
, respectively (Korb et al.
2004). Winter productivity also declined over our study
area from April to August.
We thus assumed that both winters did not differ
greatly in terms of productivity and temperature and
therefore the weaned seals experienced similar environ-
mental conditions.
Tracking duration and overview of movements
Male and female post-weaning pups in our study sample
were not significantly different in weight (t-test5= 2.57,
P= 0.11; Table 1).
Between 4 April and 31 August, a total of 532 loca-
tions were received (‘Males’= 414, ‘Females’= 118).
Over this period the mean tracking duration was
120 days for males (86–140 days) and 80 days for fe-
males (24–141 days). Two of the PTTs deployed on fe-
males stopped uplinking within 2 months of
deployment, resulting in fewer locations.
Throughout the entire study period all animals re-
mained south of the Antarctic Polar Front (Fig. 2a, b).
The main focus of uplinks for both genders was centred
around Bird Island and the northwest continental shelf.
They showed similar range in terms of latitude, from 51°
to 55°S, but differed in longitudes, females going further
west (range from 42° to 32°W), whereas males foraged
further east (range from 40° to 24°W). If we encompass
their overall distribution within a rectangular box which
includes the furthest locations to the north, east, south
and west the male area covered 500,000 km2
and the
female 360,000 km2
, thus the male area was approxi-
mately 39% larger than the region used by females.
These areas overlapped over 220,000 km2
representing
61% and 43% of the total female and male areas,
respectively.
The furthest distance recorded from the natal site was
approximately 900 km for male pups and 400 km for
females or 750 km and 300 km from the nearest point
on South Georgia. In all months apart from April, when
most individuals were still within the vicinity of Bird
Island (Fig. 3), there was a significant difference between
sexes in their range (Table 2, P<0.01) with males re-
corded further away from their birth site than females
(Fig. 3).
Over the course of the winter, the mean locations also
moved eastwards; the majority of uplinks were west of
Bird Island in April and shifted eastwards thereafter
(Fig. 4 a, b, Table 2). Similarly, fewer locations were
within the 200 m or 500 m isobaths of the South
Georgia Continental shelf as winter progressed (Fig. 4c)
Table1Deploymentandtrackingcharacteristicsof10fursealpupsintheirrespectiveyears.TheoverlappingperiodofApriltoAugustwaschosenforthecomparativestudybetween
theoppositesexes
TagsSexWeight
(kg)
Satellite
tag
Date
Deployed
Dateof
firstuplink
Dateof
lastuplink
Number
ofdays
uplinking
Numberof
uplinks
Number
ofuplinks-
ApriltoAugust
Maximum
distancefrom
birthsite
Apr-Aug(km)
Daterecovered
W6758M17.9152704/04/200104/04/200129/06/2001865353758Notrecovered
W6757M16.1153104/04/200106/04/200124/08/20011406363614Notrecovered
W6761M17.7154304/04/200104/04/200104/08/20011227979231Notrecovered
W6759M17.33020104/04/200107/04/200105/09/2001151110106903Notrecovered
W6760M17.23020204/04/200104/04/200127/07/2001114113113658Notrecovered
W6579F15.82380106/04/200210/04/200209/06/2002602424301Notrecovered
W6577F18.42380706/04/200207/04/200225/12/2002262802026527/12/2002
W6578F152381206/04/200216/04/200224/11/20022229053407Notrecovered
W6576F13.52381306/04/200210/04/200221/05/2002411111252Notrecovered
W6580F15.22381406/04/200206/04/200230/04/2002241010258Notrecovered

5. with the fur seals foraging away from the continental
shelf into deeper waters.
Discussion
Recent evidence suggests that large-scale physical pro-
cesses rather than local factors govern much of the
observed variability in the northern Scotia Sea around
South Georgia (Trathan and Murphy 2002; Trathan
et al. 2003; 2005) and that such physical variability has
profound consequences for some of the major biological
components in the marine ecosystem (Trathan et al.
2003, 2005; Atkinson et al. 2004; Jessopp et al. 2004;
Forcada et al. 2005). The forcing factors governing
much of this physical variability originate outside the
Scotia Sea. Thus, anomalies in the physical environment
at South Georgia, particularly anomalies in SST corre-
late well with El Nin˜ o processes in the western Pacific
Fig. 2 Distribution of female (a) and male (b) fur seal pups (A.
gazella) during their first winter at sea. Hatched area representing
the extent of overlap

6. (Trathan and Murphy 2002) with the Pacific leading
South Georgia by 2–3 years.
Based on the correlation between the western Pacific
and South Georgia, SST in both areas can be used to
determine whether the 2 years of this study were
anomalous. Based on this relationship, and the results
presented above (Fig. 1a), it is evident that all SST
values between May and August in both years (2001,
2002) were between the respective 20% and 80%
quantiles of recorded values at South Georgia (1988–
2004). Similarly, no major La Nin˜ a/El Nin˜ o events were
recorded in the Pacific in the 3-year period prior to this
study, again supporting the suggestion that both years of
the study were not unusually anomalous in terms of
their temperature (Trathan and Murphy 2002).
Similarly, the levels of winter standing crop (chloro-
phyll-a) were very low in both years, and though they
differed from each other by approximately 0.1 mg mÀ3
,
the difference is unlikely to have been biologically sig-
nificant, given the very large differences observed be-
tween eutrophic and oligotrophic areas during the
summer months (Korb and Whitehouse 2004). The
summer bloom evident in the region (Korb and White-
house 2004) declines to a minimum over the winter
months of April to August. For the period 1999 to 2004
the range of average winter values varied between
Fig. 3 Monthly representation
of the satellite tag uplinks in
relation to their distance from
South Georgia (including Bird
Island)

7. 0.206 mg mÀ3
(during 2004) and 0.446 mg mÀ3
(during
2000) with a mean of 0.268 mg mÀ3
(standard devia-
tion=0.085); both study years fell within one standard
deviation of the average winter value. This again sup-
ports the suggestion that both years of this study were
not unusual in terms of their productivity.
Annual indices of pup production and pup survival
at birth (Forcada et al. 2005) for the breeding seasons
following the two winters of this study (summers of
2001–2002 and 2002–2003), were between the respective
20% and 80% quantiles of recorded values between
1988 to 2004. A second species, the gentoo penguin
(Pygoscelis papua), which is also an important predator
at South Georgia (Trathan et al. 2005), also showed a
similar response with indices of reproductive success
falling between the 20% and 80% quantiles of recorded
values (1988–2004). This again indicates that both sea-
sons were not unusually anomalous. Thus, the available
physical and biological data during both of the winters
of this study, together with the breeding performance of
fur seals (and other predators) following each winter
study period, suggests that both years were not unusual.
Some caution should be taken with the overall dis-
tribution and differences in areas between male and fe-
male pups as they could conceivably result from a
combination of individual preferences unrelated to
gender, given the relatively small sample sizes. The dif-
ferences in satellite tag performances were not thought
to be gender related since male and female weaned fur
seals of this study were not significantly different by
mass, the total device mass always represented less than
1.5% of the fur seal body mass and the first and last tags
to cease uplinking were both deployed on females. The
varying performances of the tags were thus attributed to
other factors such as battery performance or tags lost at
sea.
Our results show that throughout the whole of the
winter period during both years of this study, both male
and female post-weaning juvenile fur seals stayed south
of the Antarctic Polar Front (Trathan et al. 1997) and
within the waters of the Antarctic Circumpolar Current
(ACC) (Orsi et al. 1995). The main area of activity for
both genders was centred at Bird Island and to the
northwest of the South Georgia (Fig. 2a, b) in an area
previously reported to be important for adult female fur
seals during both winter and summer (Staniland et al.
2004; Boyd et al. 2002). This region was, however, most
used at the start of the winter with an easterly shift as
the season progressed. Within this western shelf region,
most uplinks were within the 500 m depth contour.
Previous studies have shown that the diving behav-
iour of adult female fur seals varies, depending upon
their foraging location (Staniland et al. 2004). Females
foraging over the continental shelf dive both deeper and
longer than those diving over oceanic waters beyond the
shelf break, with a considerably greater frequency of
dives <20 m in the oceanic waters (Median dive depth
Shelf= 40 m, Far Oceanic= 35 m n.s.) (Staniland et al.
2004; Staniland and Boyd 2003). This is most likely
Table2Foragingtripcharacteristicsofmaleandfemalefursealpupsduringthewinters2001and2002,respectively
AprilMayJuneJulyAugust
MalesFemalesMalesFemalesMalesFemalesMalesFemalesMalesFemales
Minimum
range(km)
12531471131120758
Maximum
range(km)
494258903301860350658407698349
Average
range(km)
121±137126±89329±295***152±70***359±233***208±114***460±186**306±137**604±85***257±104***
Average
latitude(°)
À54.22±0.77À53.40±0.63À53.88±0.49À53.47±0.73À53.62±0.77À53.35±1.01À52.85±0.81À52.35±0.81À53.69±0.44À53.21±0.92
Average
Longitude(°)
À37.22±2.27À37.87±1.84À33.51±4.97À37.76±2.06À32.76±3.5935.71±1.97À31.44±2.60À34.66±2.20À28.85±1.34À34.79±1.89
Numberof
uplinks
79449641103129612379
Number
ofPTTs
5554534232
(Valuesoftheaveragesaremean±s.d;averageswerecomparedusingt-teststheresultsofwhichwerenon-significantunlessindicatedotherwiseby*P<0.05,**P<0.01and***P<
0.001)

8. associated with the dietary items available in the water
column; indeed, Staniland et al. (2004) showed that fe-
males foraging over oceanic waters consumed a greater
proportion of fish, than did females over continental
shelf waters. Staniland and Boyd (2003) suggest that
females foraging over oceanic waters have a higher
efficiency in terms of the energy return per dive.
Post-weaning juveniles are approximately 50% of the
mass of adult females and only 14% of adult males;
consequently, such a difference in size and mass should
impact significantly upon their overall diving and for-
aging capacity (Wartzok 1991). McCafferty et al. (1998)
in their study on the diving behaviour of pups found no
significant differences in maximum dive depth between
genders. They further showed that prior to weaning, the
maximum-recorded depth range of pups (26 m) was
close to the range of depths to which adult females most
commonly dive whilst foraging (22 m). However,
McCafferty et al. (1998) revealed that such extensive
dives were uncommon and therefore, on body mass
alone, we would anticipate that post-weaning juveniles
would generally dive to depths that were less deep than
Fig. 4 Proportion of uplinks
east or west of Bird Island and
the longitudinal shift during
winter (a, b, c) Proportion of
uplinks within the 200 m and
500 m isobaths over the
continental shelf of South
Georgia

9. those of adult females. Thus, post-weaning juveniles
foraging over the shelf in an area intensively used by
other fur seals and higher predators would need to in-
crease their diving capacity rapidly and/or target dif-
ferent prey items.
After April, the majority of uplinks were to the east
of Bird Island and over deeper waters (Fig. 4). This ra-
pid move away from continental shelf waters is consis-
tent with post-weaning juveniles seals possibly targeting
a different prey source that was more readily available in
the upper water column. The reasons for this easterly
shift are unclear but could be partly associated with the
distribution of Antarctic krill, a major component in the
diet of adult fur seals and possibly in that of juveniles.
Although the distribution and biomass of krill has been
little studied during the winter, summer studies suggest
that there is a greater biomass of krill at the eastern end
of South Georgia, compared with the western end
(Brierley et al. 1998). Evidence from diet studies (from
Bird Island) (Reid 1995) together with information from
the fishing industry (Trathan et al. 1998; Reid et al.
2004), suggest that krill is present throughout the winter.
However, there is usually a decrease in the occurrence of
krill in the diet of fur seals during winter (Reid 1995). It
is not yet clear whether the shift in scat composition
between summer and winter recorded on Bird Island
(Reid and Arnould 1996; Reid 1995) reflects season
variability or the different sex ratio hauling out and
feeding around Bird Island during those times of year.
The fact that winter diet analysis (Reid 1995) mainly
represented adult and sub adult male Antarctic fur seals
and reported a greater consumption of shelf living fish
species such as Champsocephalus gunnari and Lepido-
notothen larseni as part of the diet, suggest yet again a
probable difference for the weaned pups foraging in
oceanic waters. Similarly, fishing vessels target krill
aggregations at greater depth over the course of the
winter (Reid et al. 2004), suggesting that krill may be-
come less accessible during some periods of the winter.
Only during the early stages of the breeding season,
do adult males and females Antarctic fur seals overlap
spatially; otherwise they show a geographic sexual seg-
regation (Boyd et al. 1998, Staniland 2005). Fur seals do
not recruit until age 3 (females) or 7 (males) and until
this age are superficially morphologically similar (al-
though some differences in body composition were no-
ted in Arnould et al. 1996, but not in Rutishauser et al.
2004), the juveniles of our study had a similar body mass
(P= 0.11, t-test 5= 2.57). A priori, and at least until
they recruit, both male and female post-weaning juve-
niles may be expected to show similar diving and for-
aging behaviour. Consistent with other marked
differences between the genders observed days after
birth, when male pups play-fight, a behaviour seldom
observed in females (Warren and Jessopp, personal
observation); the geographic separation observed be-
tween sexes and reported here, could suggest that gen-
der-specific behavioural differences in fact develop early
in life.
The performances of our satellite tags and the lack of
information about the distribution and biomass of krill
(or any other fur seal prey) during winter, does not allow
us to make firm conclusions about the reasons for our
observed results. However, we have shown that both the
physical and biological environments were similar be-
tween years as was the observed level of breeding success
each subsequent summer season. Consequently, based
on these multiple indicators, together with the known
sexual segregation of adults, we suggest that the ob-
served differences in our satellite uplinks could be the
result of early sexual segregation of fur seal juveniles.
Acknowledgements We wish to thank all staff of the British Ant-
arctic Survey research station on Bird Island for all their support
and help. Janet Silk for helping with ArcGIS. Keith Reid and Iain
Staniland for useful suggestions and two anonymous referees. We
thank the SeaWiFS Project (Project Code 970.2) and the Goddard
Earth Sciences Data and Information Services Centre / Distributed
Active Archive Centre (Project Code 902) for the production and
distribution of satellite data products and the Physical Oceanog-
raphy Distributed Active Archive Center (PO.DAAC) at the
NASA Jet Propulsion Laboratory, Pasadena, CA http://pod-
aac.jpl.nasa.gov for the distribution and production of the SST
data.
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