856
0735
OF
)CEANOGRAPHY
Temperature Sections along the
C-line Over the Shelf off Cabo
News, Peru from Moored Current
Meters, 18 March-10 May 1977 and
CTD Observations, 5 March-18 May
1977
by
K. H. Brink
W. E. Gilbert
A. Huyer
OREGON
STATE
Reference 79-2
CUEA Technical Report 49
January 1979
Office for the International Decade
of Ocean Exploration
National So lance Foundation
OCE 78-03380
OCE 78-03381
/,,School of Oceanography
Oregon State University ,
--torvallis, Oregon 97331
Temperature Sections along the C-line
Over the Shelf off Cabo Nazca, Peru
from Moored Current Meters, 18 March-10 May 1977
and CTD Observations, 5 March-15 May 1977
by
K. H. Brink
W. E. Gilbert
A. Huyer
Reference 79-2
(CUEA Technical 'Report 49)
January 1979
Office for the International Decade of Ocean Exploration
National Science Foundation
OCE 78-03380 and 78-03381
TABLE OF CONTENTS
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THE OBSERVATIONS .
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METHOD OF PREPARATION AND PRESENTATION
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INTRODUCTION .
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9
THE TEMPERATURE SECTIONS .
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10
ACKNOWLEDGMENTS
REFERENCES
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List of
Figures and Tables
Page
Figure 1.
Sigma-t vs. temperature for the upper 300 m of CTD stations
2
over the shelf and upper slope, during MELVILLE Legs 1, 2 and
4, and ISELIN Legs 2 and 4 (stations 3-8, 13-29, 48-53,
57-61, 87-93, 120-125, 154-159, 162-167, 204-209, 230-235,
266-271, 323-328,-344-349, 386-391 and 802-809).
Figure 2.
Location of main hydrographic line, called the "C-line" and
3
current meter moorings along it, during the MAM 77 phase of
JOINT-II.
Figure 3.
5
Distributions of the mean and standard deviations of the low
passed temperature time series from the current meter array,
18 March to 10 May 1977.
Table 1.
Summary of positions, water depths and current meter depths
3
for instrument arrays along the C-line during the MAM 77
phase of JOINT-II.
Table 2.
Dates of hydrographic sections along the C-line, showing ship,
leg, C/STD operating institution, and the page of the
temperature distribution.
6
1
INTRODUCTION
Over the continental shelf at 15°S off Peru, sigma-t is a well-defined
function of temperature (Figure 1) and hence temperature alone may be used
to monitor the changes in stratification, to test the thermal wind equation,
and to monitor the hydrographic response to wind events.
In this report we
present vertical-offshore distributions of temperature over the continental
shelf and upper slope along a single line as measured by repeated hydrographic
sections and a moored current meter array.
THE OBSERVATIONS
The observations were made during the third intensive phase (MAM 77)
of the JOINT-II program conducted by the Coastal Upwelling Ecosystems
Analysis (CUEA) Program to study coastal upwelling off Peru.
The most
frequent and intensive observations were made along the C-line, which
intersects the Peru coast at 15°02'S (Figure 2).
Current meter moorings were deployed along the C-line beginning on
4 March 1977, and the array was completed on 16 March; recovery of the
array began on 11 May and was completed on 14 May 1977.
The array (Table 1)
consisted of five subsurface moorings (Lobivia, Lagarta, Ironwood, Mila,
and Agave) installed by Oregon State University (Enfield, Smith and Huyer,
1978), and two surface moorings (PS and PSS) installed by Pacific Marine
Environmental Laboratory, NOAA (Halpern, 1978).
The current meters sampled
temperature at intervals of 15 or 20 minutes; the temperature sensors are
believed to be accurate within ±0.05°C.
The original time series were
filtered to reduce high frequency noise and decimated to hourly values.
The hourly data were again filtered to suppress tidal oscillations and
2
27.0
26.5
25.51
25.01
24.5
10.0
12.0
14.0
16.0
18.0
20.0
TEMPERATURE (C)
Figure 1.
Sigma-t vs. temperature for the upper 300 m of CTD stations
over the shelf and upper slope, during MELVILLE Legs 1, 2
and 4, and ISELIN Legs 2 and 4 (stations 3-8, 13-29, 48-53,
57-61, 87-93, 120-125, 154-159, 162-167, 204-209, 230-235,
266-271, 323-328, 344-349, 386-391 and 802-809).
3
Table 1.
Summary of positions, water depths and current meter
depths for instrument arrays along the C-line during
the MAM 77 phase of JOINT-II.
Position
Station
PSS
Agave
PS
Mila-5
Ironwood
Lobivia
Lagarta
15°03.4'S
15°04.0'S
15°06.8'S
75°27.0'W
75°27.8'W
75°30.2W
15°06.0'S
15°09.9'S
15°11.5'S
15°10.0'S
75°30.8'W
75°32.9'W
75°34.3'W
75°36.0'W
Water
Depth (m)
75
86
121
121
205
580
620
Current Meter Depths (m)
4.5,8,12,16
26,46,67,77
2.5,4.6,8.1,12,16,20,24
19,39,59,80,100,115
24,44,63,105,155,180
58,83,183,283
92,115,214,512
15°S
15°30'
Figure 2.
Location of main hydrographic line, called the "C-line"
and current meter moorings along it, during the MAM 77
phase of JOINT-II.
4
decimated to a six-hourly interval; these low-passed time series have
been presented in the report by Brink, Smith and Halpern (1978).
The
common period for the low-passed time series extends from 18 March to
10 May 1977.
The distributions of the mean and the standard deviation
calculated for the common period is shown in Figure 3.
In this report,
the low-passed temperature time series have been used to plot the
vertical-offshore temperature distribution for each day within this
common period.
Hydrographic sections along the C-line were made primarily by two
different groups--the group studying physical frontal dynamics headed
by C. N. K. Mooers and J. Van Leer, and the mesoscale hydrography group
headed by L. I. Codispoti and A. Huyer.
Fourteen sections along the C-line were made by the frontal group,
between 17 and 30 March 1977, during Leg 1 of the R/V ISELIN.
These
observations were made with a 9040 Plessey CSTD system operated by the
University of Miami's Rosenstiel School of Marine and Atmospheric
Science (RSMAS).
As yet, a data report containing these observations has not
been completed; the temperature data was provided to us in the form of
isotherm depths (W. Johnson and C. N. K. Mooers, personal communication).
Over the shelf, each CSTD cast extended to within a few meters of the
bottom.
Nineteen hydrographic sections (Table 2) were made along the C-line
between 5 March and 15 May 1977 by the mesoscale hydrography group.
These observations were made during Legs 1 and 2 of the R/V MELVILLE
(3-9 March and 12-30 March 1977), Leg 2 of the R/V ISELIN (4-23 April
1977), Leg 4 of the MELVILLE (4-27 May 1977), and Leg 4 of the ISELIN
(10-20 May 1977), and the data have been presented in a data report
5
X0.31
20
I
I
I
10
DISTANCE FROM SHORE (km)
Figure 3.
Distributions of the mean and standard deviations of
the low passed temperature time series from the current
meter array, 18 March to 10 May 1977.
6
Table 2.
Dates of hydrographic sections along the C-line,
showing ship, leg, C/STD operating institution,
and the page of the temperature distribution.
CTD
Date
Ship
5 Mar 77
6 Mar 77
7 Mar 77
16 Mar 77
16 Mar 77
17 Mar 77
18 Mar 77
19 Mar 77
19 Mar 77
20 Mar 77
21 Mar 77
22 Mar 77
22 Mar 77
23 Mar 77
24 Mar 77
24-25 Mar 77
25 Mar 77
26 Mar 77
27 Mar 77
27 Mar 77
28 Mar 77
29 Mar 77
30 Mar 77
9 Apr 77
12 Apr 77
16 Apr 77
19 Apr 77
21 Apr 77
Melville
Melville
Melville
Melville
Melville
Iselin
Iselin
Iselin
Melville
Iselin
Iselin
Melville
Iselin
Iselin
Iselin
Melville
Iselin
Iselin
Iselin
Melville
Iselin
Iselin
Iselin
Iselin
Iselin
Iselin
Iselin
Iselin
Melville
Melville
Melville
Iselin
Melville
5 May 77
9 May 77
13 May 77
15 May 77
16 May 77
Leg
Operator
Page
I
I
OSU
RSMAS
RSMAS
RSMAS
I
OSU
RSMAS
I
RSMAS
I
RSMAS
I
OSU
RSMAS
10
10
12
14
14
16
16
18
18
20
20
22
22
24
24
26
26
28
30
30
32
I
I
RSMAS
RSMAS
32
34
I
I
I
II
II
OSU
OSU
OSU
OSU
I
OSU
RSMAS
I
I
RSMAS
RSMAS
I
OSU
RSMAS
I
RSMAS
II
II
I
II
II
II
II
II
II
II
IV
IV
IV
IV
IV
OSU
OSU
OSU
OSU
OSU
OSU
OSU
OSU
OSU
OSU
44
46
50
54
56
70
74
76
76
78
7
(Huyer et al., 1978).
During most of these sections, temperature observa-
tions were made with a Geodyne conductivity-temperature-depth system
operated by Oregon State University; data were normally obtained at least
The
once every two or three meters as the instrument was being lowered.
accuracy of the CTD temperature sensor is believed to be ±0.02°C.
During
MELVILLE Leg 4, the CTD system was sometimes inoperable; for these
occasions, we used the temperature data from Niskin bottle cast to obtain
the temperature distributions.
METHOD OF PREPARATION AND PRESENTATION
The sections were prepared on a standard scale of 25 m and 2 km per
cm; this scale is well suited to distributions of properties over the
continental shelf and upper slope.
300 m are shown:
Only the inshore 30 km and the upper
these limits include all but one instrument of the
current meter array.
Temperature was contoured at intervals of 1°C;
additional dashed contours are shown for half-degree isotherms.
There were three distinct data sources, and the sections have been
prepared somewhat differently for each.
For the sections from the current
meter data, daily values of the low passed temperature were plotted at
the current meter locations; these distributions were then contoured by
hand; interpolating approximately linearly and smoothing by hand.
The
locations of the current meters on the subsurface arrays are shown as
dots; those on the surface moorings are shown as vertical bars, since
these current meters were very closely spaced in the vertical.
Throughout
this report, the sections from the current meters are shown on the righthand pages.
The temperature distributions based on hydrographic.sections are
shown on the left-hand pages.
available.
We used CTD or CSTD data whenever they were
For the sections using bottle casts (5 May and 13 May), we
have shown dots to indicate the sample depths; the data were plotted at
the actual sample depth, and the fields contoured by hand.
N
When CTD
data were available, we plotted the actual isotherm depths observed at
each station, and connected these depths from station to station,
smoothing
the isotherms by hand.
For the CTD data obtained with the Oregon State CTD system (Table 2),
we had access to the entire data set.
For these sections, we have shown
the bottom of each CTD cast by an inverted "T".
We have also shown
isothermal layers as vertical solid lines, whenever the CTD temperature
remained constant within ±0.01°C for at least 5 m.
For the CSTD data from ISELIN Leg 1, obtained from the RSMAS CSTD
system, only tabulated isotherm depths were available.
For this reason,
we have not indicated isothermal layers on these sections.
On these
sections, each CSTD cast over the shelf extended to a few meters of the
bottom and the lower limit of each cast is not shown explicitly.
These
sections are distinguished in the body of the report by the RSMAS
acronym in the lower right corner.
The bottom profile for the current meter sections was drawn by
connecting the known mooring depths by a smooth line.
For the hydrographic
sections, we plotted the bottom depths of all CTD stations except those
from ISELIN Leg 1 as a function of distance from shore, and drew a smooth
line such that most, but not all, of the points were above the bottom.
This same bottom profile was used in preparing all of the sections from ISELIN
Leg 1.
9
ACKNOWLEDGMENTS
We thank Chris Mooers and Walter Johnson of the University of Delaware
for providing us with the CSTD data from ISELIN Leg 1 so it could be
included in this
report.
from the moored current
Bob Smith and Dave Halpern provided the data
meters.
Marcia Benad
assisted in preparing the
temperature sections from hydrographic data. Preparation of the report
was supported by the Office for the International Decade of Ocean
Exploration under Grants OCE 78-03380
and OCE 78-03381.
This is a
contribution to the Coastal Upwelling Ecosystems Analysis Program.
REFERENCES
1978. A compendium of time
K. H., R. L. Smith and D. Halpern.
series measurements from moored instrumentation during the MAM 77
Brink,
phase of JOINT-II. School of Oceanography, Oregon State University,
72 pp.
CUEA Technical Report 45, Ref. 78-17.
Enfield, D. B., R. L. Smith and A. Huyer. 1978. A compilation of observations from moored current meters. Vol. XII, Winds, currents and
temperature over the continental shelf and slope of Peru during
JOINT II, March 1976 - May 1977. Oregon State University, School of
Data Report 70. Reference 78-4.
Oceanography, Corvallis, Oregon.
343 pp.
JOINT-II near-surface circulation studies:
Halpern, D.
1978.
Report 1. CUEA SYNAPSE Synapse No. 2, pp. 2-12.
Progress
Huyer, A., W. E. Gilbert, R. Schramm, and D. Barstow. 1978. CTD observations off the coast of Peru, R/V MELVILLE, 4 March - 22 May 1977,
and R/V COLUMBUS ISELIN, 5 April - 19 May 1977. School of Oceanography,
Oregon State University, Data Report 71, Reference 78-18. 409 pp.
10
6
7
6
4
5
1T_L-t'5I
I
3
-4
100
.1--
.000
-o
/4
/3
.
2130 Z, 4 - 0230 Z, 5 Mar 77
300
23
21
''
13
16
18
/5
I
j
100
/4
22002, 5-09002,6 Mar 77
/2
I
30
I
" 1300
I'
i
20
I
10
DISTANCE FROM SHORE (km)
I
0
12
27
29
25 24
Ole
/6 =
100
/2
30
10
20
DISTANCE FROM SHORE (km)
J300
0
14
57
58
60
59
61
100
1730 Z - 2200 Z
-1
30
//
,
16 Mar 77
J300
1'
20
IO
DISTANCE FROM SHORE (km)
0
16
/9 21 /8
19
24
23
T 1
/6
/5
100
/4
N
/3
0900-1400 Z, 18 Mar 77
I
30
I
I'
RSMAS
I
20
I
I
10
0/STANCE FROM SHORE (km)
300
I
0
17
La Lo
I
PS
PSS
M
A
20
10
0/STANCE FROM SHORE (km)
300
0
18
26
27
25
28
29
30
r,
/8
i
/6 =
/5
100
/4
-/3
0930-15002, 19 Mar 77
/2
RSMAS - 300
30
20
10
DISTANCE FROM SHORE (km)
0
19
La Lo
I
PS
PSS
M
A
10
20
DISTANCE FROM SHORE (km)
300
0
20
/9
/2
30
42
'
44
48
46
RSMAS
20
10
DISTANCE FROM SHORE (km)
300
0
21
300
10
20
DISTANCE FROM SHORE (km)
300
0
22
120
124
123
121
125
100
300
/8 51
57
55
53
r ' /r
/5
N
/4
F**' /3
0830-1530 2, 22 Mar 77
//
I
30
I
I
RSMAS -300
I
20
I
I
10
DISTANCE FROM SHORE (kin)
1
1
0
23
PSS
A
PS
M
a L
i i i -'
.
'/5
=-- /4
.
/3
11
0000 Z, 22 Mar 77
/O
20
-300
10
DISTANCE FROM SHORE (km)
0
24
58 20
60
69
73
71
/8
17
.01
I-_--
67
64
62
77
75
/6
/5
100
/4
/2
.
0600-1500 Z, 24 Mar. 77
RSMAS
I
30
I
1
20
10
DISTANCE FROM SHORE (km)
j0300
25
300
PS
La Lo
M
PSS
A
10
20
DISTANCE FROM SHORE (km)
300
0
26
159
91
157
158
156
99
97
95
93
154
155
0
100
f ..
30
RSMAS
20
10
DISTANCE FROM SHORE (km)
- 300
0
27
10
20
DISTANCE FROM SHORE (km)
0
28
113
117
115
119
121
/7
100
/4
/2
.0900-1600 7,26 Mar 77
RSMAS
30
20
10
DISTANCE FROM SHORE (km)
300
0
29
PS
PSS
M
A
-1200
-4300
10
20
DISTANCE FROM SHORE (km)
30
125
123
127
129
131
I
167
/9
165
166
162
163
164
100
12302-20002, 27 Mar 77
I
30
I
I
10
20
DISTANCE FROM SHORE (km)
J300
1
0
31
PS
La Lo
I
M
PSS
A
10
20
DISTANCE FROM SHORE (km)
-
300
0
32
20
150
146
154
152
100
RSMAS
/9
174
171
300
178
176
/5
I00
I--
.0230- 1000 Z, 29 Mar 77
RSMAS
30
20
10
DISTANCE FROM SHORE (km)
300
0
33
La Lo
I
PS
Pss
M
A
20
t0
DISTANCE FROM SHORE (km)
300
0
34
-4100
RSMAS
30
20
10
DISTANCE FROM SHORE (km)
J300
0
35
10
20
DISTANCE FROM SHORE (km)
37
PS
PSS
M
A
-1200
I
I
I
PSS
A
PS
M
aL
-f300
Zoo
20
10
0/STANCE FROM SHORE (km)
300
0
39
200
300
20
10
DISTANCE FROM SHORE (km)
0
41
a L
PS
PSS
M
A
200
300
PS
-1200
1300
20
10
DISTANCE FROM SHORE (km)
0
43
300
10
20
D/S TANCE FROM SHORE (km)
0
44
209/7 208
207
206
205
/2
1200 2 -2200 2, 9 Apr 77
1
30
I
10
20
DISTANCE FROM SHORE (km)
1300
0
45
PS
La Lo
M
I
PS
La Lo
I
M
PSS
A
PSS
A
100
300
10
20
D/STANCE FROM SHORE (km)
0
46
230
231
232 233
235
100
/.?
1200
0800 z -1530 z, 12 Apr 77
1
1
30
10
20
DISTANCE FROM SHORE (km)
1300
0
47
La Lo
I
20
PS
PSS
M
A
10
DISTANCE FROM SHORE (km)
300
0
49
200
300
10
20
DISTANCE FROM SHORE (km)
0
50
266
267
270
269
268
271
100
'1400Z-2300Z, 16 Apr 77
I
30
20
I
F
10
DISTANCE FROM SHORE (km)
1300
0
51
La Lo
I
PS
M
PSS
A
10
20
D/STANCE FROM SHORE (km)
0
53
PS
PSS
M
A
-1200
-4300
La Lo
I
20
PS
PSS
M
A
10
DISTANCE FROM SHORE (km)
54
I
326
325
324
323
327
16
100
'l- /2
I
30
I
I-
I
I
I
1
IO
20
DISTANCE FROM SHORE (km)
J300
0
55
300
PSS
A
PS
La Lo
I
M
200
20
10
DISTANCE FROM SHORE (km)
300
0
56
349
/7 348
347
346
345
/6
I
I
344
I
/5
too
awl
/4
/3
2130 Z, 20 - 0600 Z, 21 Apr 77
30
10
20
DISTANCE FROM SHORE (km)
300
0
57
PSS
A
PS
a L
20
10
DISTANCE FROM SHORE (km)
0
59
N
PS
a L
M
PSS
A
20
10
D/S TANCE FROM SHORE (km)
0
61
20
10
DISTANCE FROM SHORE (km)
0
63
PS
PSS
M
A
PS
PSS
A
M
a Lo
A--/5
100
/4
L3
200
11
/2
h//
0000 Z, 28 Apr 77
.
I.
20
i
1
10
DISTANCE FROM SHORE (km)
1300
0
E
65
a L
La Lo
I
PS
PSS
M
A
PS
PSS
M
'A
200
300
10
20
D/S TANCE FROM SHORE (km)
0
67
200
300
La Lo
I
PS
PSS
M
A
300
20
10
DISTANCE FROM SHORE (km)
0
69
La Lo
La Lo
I
I
PS
PSS
M
A
PS
PSS
M
A
20
10
0/STANCE FROM SHORE (km)
300
0
70
367
365
366
364
363
/6'
- /5
100
' 01302-10002, 5 May77
//1:.
.,
I
30
.
10
20
DISTANCE FROM SHORE (km)
J300
0
71
PS
La Lo
I
M
PSS
A
20
10
DIS TANCE FROM SHORE (km)
0
73
PS
a Lo
I
M
=
PSS
A
PS
La Lo
I
PSS
A
M
200
20
10
DISTANCE FROM SHORE (km)
300
0
74
386
30
387
388
389
390
10
20
DISTANCE FROM SHORE (km)
391
75
PSS
A
PS
a Lo
M
I
.
4
/6
9
11
11
11
11
11
/5
-1
11
11
0000 7-, 9 May 77
/2
i
1
PS
La Lo
I
M
I
300
PSS
A
10
20
DISTANCE FROM SHORE (km)
300
0
76
809
807 808 806
804
803 /7 802
-1100
10002,14-01002, 15 May 77
J300
30
10
20
DISTANCE FROM SHORE (kin)
0
78
428
429
433
430
431
I
i
i
.
0300 2 -1230 2, 16 May 77
/2
l
30
1
I
20
I
1
I
10
DISTANCE FROM SHORE (km)
J300
0