I AD-A261 538WHOI-92-36

4A

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A Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds):

Physical Oceanography Moored Array Component

by

Carol A. Alessi1 ' ,,

Steven J. Lentz' -

Robert C. BeardsleycBelmiro M. Castro2 r

W. Rockwell Geyer' .

'Woods Hole Oceanographic InstitutionWoods Hole, Massachusetts 02543

Instituto Oceanografico Universidade Sao PauloSao Paulo, Brasil

September 1992

Technical Report

Funding was provided by the National Science Foundation through Grant Nos.OCE 88-12917 and OCE 91-15712.

Approved for public release; distribution unlimited.

93-04230Iti! l~ lC'I'• • N

WHOI-92-36

A Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds):

Physical Oceanography Moored Array Component

by

Carol A. Alessi'Steven J. Lentz'

Robert C. Beardsley'Belmiro M. Castro2

W. Rockwell Geyer'

'Woods Hole Oceanographic InstitutionWoods Hole, Massachusetts 02543

21nstituto Oceanografico Universidade Sao PauloSao Paulo, Brasil

September 1992

Technical Report

Funding was provided by the National Science Foundation through Grant Nos.OCE 88-12917 and OCE 91-15712.

Reproduction in whole or in part is permitted for any purpose of theUnited States Government. This report should be cited as:

Woods Hole Oceanog. Inst. Tech. Rept., WHOI-92-36.

Approved for publication; distribution unlimited.

Approved f rDD ibu n:

IeJames Luyten, C airmanD-- epartment of Physical Oceanography

Table of Contents

L ist of T ables ....................................................................

List of Figures ................................................................... v

List of Appendix Tables and Figures ............................................. vii

A bstract ......................................................................... ix

1. Introduction ................................................................. 1

2. The M oored Array ........................................................... 4

2.1 Moored Array Location and Timing ..................................... 4

2.2 M ooring Design ........................................................ 7

2.3 Instrumentation ............................................... 132.4 Deploym ent Strategy .................................................... 15

2.5 Mootiag Recovery and Data Return ................................ 18

2.6 Data Processing Methods ............................................... 22

3. Description of Data Presentation ............................................. 23

4. Acknowledgments ........................................................... 28

5. R eferences ................................................................... 29

6. D ata Presentation ........................................................... 31

Appendix: Evaluation of the AmasSeds M3 Current Meter Data .................. 79

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List of Tables

1. Sediment and Water Discharge for the 10 Rivers with Greatest Sediment Discharge 2

2. Principal Participants and Scientific Components .................................... 3

3. Summary of Moored Sensors ......................................................... 17

4. Statistics of Hourly Averaged Data - Entire Time Period, For: ...................... 24

Cross-Isobath and Along-Isobath Velocity ............................................ 24W ater Tem perature ................................................................. 24

C onductivity ........................................................................ 24

Salinity ............................................................................. 24

Air Tem perature .................................................................... 25

Cross-Isobath and Along-Isobath Wind .............................................. 25

Cross-Shelf and Alongshore W ind Stress ............................................. 25

P ressure ............................................................................. 25Scalar Speed ........................................................................ 25

5. Statistics of Hourly Averaged Data - Common Time Period, For: ................... 26

Cross-Isobath and Along-Isobath Velocity ............................................ 26W ater Temperature ................................................................ 26

Conductivity ........................................................................ 26

Salinity ............................................................................. 26

Cross-Isobath and Along-Isobath Wind .............................................. 27

Cross-Shelf and Alongshore Wind Stress ............................................. 27

P ressure ............................................................................. 27Scalar Speed ........................................................................ 27

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List of Figures

Figure 1. Bathymetric chart of the Amazon shelf and slope showing the 5locations of the three AmasSeds mooring sites. Also shown arethe locations of the three-element STACS moored array.

Figure 2. Cross-section of the shelf with the bottom profile and instrument . . . 6locations.

Figure 3. Timeline of the primary physical processes affecting the Amazon . . . 8shelf.

Figure 4. Schematics of the AmasSeds moorings.... 9

Figure 5. Relative positions for the surface and subsurface moorings at M1 . . . 12and M2.

Figure 6. Schematic of the dual-rotor VACM ... 14

Figure 7. InterOcean S4 and the IOUSP SD2000 current meter. . . . 16

Figure 8. Data return from the AmasSeds moored array. 19

Figure 9. Time series of the hourly-averaged M2 and ECMWF wind records 21for 23 days.

Figure 10. Time series of the hourly-averaged air temperature, M2 and ... 34ECMWF wind records for the entire time period.

Figures 11-16. Composite (stacked) plots of the PL64 low-pass filtered currents. . . . 36

Figures 17-20. Composite (stacked) plots of the hourly averaged current corn- ... 48ponents.

Figures 21-22. Composite (overlay) plots of the PL64 low-pass filtered water tern- . . . 56perature and salinity time series records.

Figures 23-29. Composite (stacked) plots of the hourly averaged individual water .

temperature, salinity and conductivity time series records.

Figure 30. Hourly-averaged and PL64 low-pass filtered time series of the two . . . 74speed records from the dual rotor VACM.

Figure 31. Time series of the hourly-averaged barometric pressure record ... 76

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vii

List of Appendix Tables

Al. Unidirectional Velocity Profiles Used as Input into Mooring Dynamics Model ......... 82'

A2. Variable Parameters for the Mooring Dynamics Model ............................... 82

List of Appendix Figures

Al. Times series of S4 speed and S4 lip .................................................. 80

A2. Observed and predicted S4 dip plotted as a function of S4 speed ..................... 83

A3. Time series of S4 corrected speed and the difference between the top SD2000 speed

and the S4 corrected speed .......................................................... 86

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ix

I Abstract

A Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds) is a cooperativeresearch program by geological, chemical, physical, and biological oceanographers fromBrazil and the United States to study sedimentary processes occurring over the continentalshelf near the mouth of the Amazon River. The physical oceanography component ofAmasSeds included a moored array deployed on the continental shelf approximately 300 kmnorthwest of the Amazon River mouth near 3.5"N. The moored array consisted of a cross-shelf transect of three mooring sites located on the 18-m, 65-m, and 103-m isobaths.The moored array was deployed for approximately 4 months, from early February, 1990 tomid-June, 1990, obtaining time series measurements of current, temperature, conductivity,and wind. This report describes the physical oceanography moored array component andprovides a statistical and graphical summary of the moored observations.

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1. Introduction

A Multidisciplinary Amazon Shelf SEDiment SLudy (AmasSeds) is a coopera-tive research program being conducted by geological, chemical, physical, and biologicaloceanographers from Brazil and the United States. The AmasSeds program was designedto study the continental shelf near the mouth of the Amazon River with emphasis on themajor sedimentary processes. The Amazon River annually discharges into the AtlanticOcean over six trillion cubic meters of f-esh water, a billion tons of sediment, and nearly abillion tons of dissolved material (Table 1). On a global basis, these totals represent 181of the fresh water (Oltman, 1968), 10% of the fluvial sediment (Meade et al., 1985), and8% of the dissolved solids (Gibbs, 1972) entering the oceans from rivers. The AmasSedsprogram was designed to investigate the processes influencing the dispersal and ultimatefate of these constituents as they flow out onto the North Brazil continental shelf.

There are five research components comprising AmasSeds: (1) Physical Oceanogra-phy, (2) Sediment Transport, (3) Turbidity Effects on Geochemistry, (4) Diagenetic/iAuthi-genetic Processes, and (5) Sedimentology and Stratigraphy. The principal investigators andresearch topics of each group are listed in Table 2. A detailed description of the AmasSedsresearch program, its development, and scientific objectives were presented in Eos by theAmasSeds Research Group (1990). A brief description of past research on the Amazonshelf and preliminary results from each of the five research components were presented ata special session at the 1990 AGU Fall Meeting and in the April, 1991 issue of Oceanog-raphy. The physical oceanographic results (including some results from the moored arraymeasurements) were presented in Oceanography by Geyer et al. (1991).

The Physical Oceanography component of AmasSeds was designed: to characterizethe temporal and spatial variability of the Amazon River plume as it flows northwestwardover the Amazon shelf; to determine the processes influencing the plume dynamics, in-cluding mixing between the plume and the surrounding ocean water; and to investigatephysical processes influencing the sediment distribution over the shelf, including bottomstress. To address these objectives, the physical oceanography field work included:

* Long-term moored measurements of wind, current, temp "rature, and conductivityto determine tidal and low-frequency variability in the shelf flow field, stratification.surface wind stress, and bottom stress;

e A series of four regional hydrographic (CTD) and acoustic Doppler current profiler(ADCP) surveys to measure the spatial distributions of temperature, salinity, density,turbidity and currents over the Amazon shelf during the four stages (falling, low,rising, and high) of tVie river discharge cycle;

2~

Table 1: Discharge of sediment and water for the ten riverswith greatest sediment discharge

(from Milliman and Meade, 1983; Meade et aL, 1985)

Sediment Water IDischarge Discharge

River (106 tons/yr) (km 3/yr)

Ganges/Brah maputra 1670 971Amazon 1200 6300Huangho (Yellow) 1080 49Changjiang (Yangtze) 478 900Irrawaddy 285 428Magdalena 220 237Mississippi 210 580Orinoco 210 1100Hungho (Red) 160 123 3Hekong 160 470

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Table 2: List of participants and research topics in the five scientific components of ArnasSeds

Physical Oceanography

R. C. Beardsley WHOI Structure and dynamics of large-scale density front.W. R. Geyer WHOI Circulation processes.

S. J. Lentz WtIOI Bottom stress: forcing variables and implications for sediment transport.

J. H. Trowbridge WHOIL. B. Miranda IOUSPB. A. Castro IOUSP

Sediment Transport

R. W. Sternberg UW Physical processes responsible for sediment resuspension and deposition.D. A. Cacchione USGS Sediment transport rates.D. E. Drake USGS Characteristics of flocs and discrete particles in suspension.K, Kranck BIOG. Dias UFF

Turbidity Effects on Geochemistry

D. J. DeMaster NCSU Release of uranium from sediments and scavenging of particle-reactive species.W. J. Showers NCSU Exchange between the seabed and water column based on radium- 22 8 and radium- 22

4 tracers.W. S. Moore USC Relationship of silicate and carbon uptake rates to surface turbidity and chlorophyll.B. A. McKee LUMCD. M. Nelson OSUW. 0. Smith UT

Diagenetic/Authigenic Processes

R. C. Aller SUNY Early diagenesis dominated by iron (Fe) and managanese oxides.J. Y. Aller SUNY Formation of Fe carbonates and clay minerals.J. E. Mackin SUNY Benthos distribution and effects of biological versus physical mixing.N. E. Blair NCSUB. Knoppers UFFS. R. Patchineelam UFF

Sedimentology and Stratigraphy

C. A. Nittrouer SUNY Strata formation and emplacement of sedimentary characteristics.S. A. Kuehl USC Importance of nearshore and intertidal accretion.

J. M. Pine USC Seismic character of preserved strata.A. G. Figueiredo UFFL. E. Faria UFPA

Notes:

C. A. Nittrouer and D. J. DeMa.ster were responsible for overall project administration,

BIO: Bedford Institute of Oceanography UFPA: Universidade Federal do ParnIOUSP: Institute of Oceanography, University of Sao Paolo, Brazil USC: University of Soith CarolinaLUMC: Louisiana University Marine Consortium USGS: U.S. Geological Survey, Menlo Park, CA

NCSU: North Carolina State University UT: University of TennesseeOSU: Oregon State University UW: University of Washington

SUNY: State University of New York, Stony Brook WHOI: Woods Hole Oceanographic Institution

UFF: Universidade Federal Fluminense

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"* Short-term, high-resolution measurements of the small-scale circulation, and mixingprocesses in the frontal zone between the Amazon River plume and the more saline

ocean water;

"* Lagrangian observations of near-surface circulation using satellite-tracked drifters;

"* Synoptic observations of the near-surface suspended sediment distribution throughsatellite imagery. 3

Technical reports presenting the edited hydrographic data have been publishedby Limeburner and Beardsley (1989, 1991a,b) and Limeburner et al. (1992). This re-port focuses on the long-term moored array component. The moored array component isdescribed in Section 2, which includes a description of the site and the moored array, asummary of the instrumentation, the data return, and the data processing procedures. A Idescription of the data presentation, and statistical summaries of the moored data are givenin Section 3. Time-series plots of unfiltered (hourly averages) and low-pass filtered datafor each instrument are presented in Section 6. Time series plots of the following variablesare presented: wind, air temperature, barometric pressure, current, water temperature,conductivity, and salinity (derived from temperature and conductivity measurements). 3

2. The Moored Array 32.1 Moored Array Location and Timing I

Primary objectives of the physical oceanography component of AmasSeds wereto characterize the temporal variability of current, temperature, and salinity over the INorth Brazil shelf and to relate that variability to likely forcing such as the Amazon Riverdischarge, the North Brazil Current (NBC), and the local wind stress. To address theseobjectives, a three-element moored array of wind, current, temperature, and conductivitysensors was deployed on an open-shelf transect perpendicular to the shelf topography. Thelocation of the moored array is shown in Figure 1 along with the SubTropical Atlantic IClimate Study (STACS) moored array discussed in the next paragraph.

The AmasSeds moored array was deployed about 300 km northwest of the river Imouth, across the region of highest sediment accumulation defined by Kuehl et al. (19S6).The shelf is about 230-km wide in the vicinity of the moored array (Figure 2). From thecoast to the 20-m isobath (125 km offshore), the bottom is nearly flat (slope Iti '). W-The bottom then drops more steeply (slope t 10-') between the 20-m isObath ail(I theshelfbreak. Mooring sites were located over the flat inner shelf on the 18-m isobath (des-

ignated Ml), over the steeper portion of the mid-shelf near the 65-m isobath (designated

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I520w sic 500 490 480 470 460

604 - ____L ___

0

I 50 AmzSCo*Ae.apb

r ~~~40 _______

1 33

IMIM

00.

Figure 1: Bathymetric chart of the Amazon shelf and slope showing the locations of thetwo AmasSeds mooring sites deployed by WHOI(e), the joint WHOI/IOUSP mooring siteI ~(4), and the three-element STAGS moored array(.

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MI,. I0

10

20 M433

30

40 150

'~0C

70 AmasSeds A rray80 ~VACUWI

90 o Inverted VAC'C.go * Dual Rotor VACM/C

I OUSP CurrentMeterAInfet~cean S4 Current Meter100 .. oo.Wind speed and direction

110 '~ Surface BuoyI11 Subs urface Buoy

, 2 oo 25 75 100 125 ,50 175 200 225

Ohshore Distance (km)

IFigure 2: Cross-section of the shelf at the open-shelf transect showing the bottom profile

and instument locations for the AmasSeds moored array. The wavewrider deployed at M1 5is not shown, and was never recovered.

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M2), and near the shelf break on the 103-m isobath (designated M3). The MI and M2moorings bracketed the region of high net sediment accumulation. At the moored array,hydrographic surveys indicated that the Amazon plume was typically 5-10 m thick andusually extended offshore from the coast beyond the M2 mooring. The M3 mooring wasdeployed with joint Brazil/US support to provide a link between the AmasSeds array andthe STACS moored array which was deployed across the NBC (Figure 1) to study itsvelocity structure and transport variability (Johns et al., 1990).

The AmasSeds moored array was deployed for a period of four months, from earlyFebruary, 1990 to mid-June, 1990. The timing was chosen to span the period of risingAmazon discharge (Figure 3) when maximum sediment discharge was assumed to occur.During this period, transport of the NBC was near its minimum and the wind stress wasdecreasing from its seasonal maximum in February (Figure 3). The STACS moored arraywas deployed for a period of seven months, from February 1, 1990 to September 25, 1990.The period of AmasSeds and STACS moored array data overlap extended from February 9,1990 to June 18, 1990.

2.2 Mooring Design

A total of six moorings were designed and fabricated at WHOI for the AmasSedsmoored array component, three surface and three subsurface moorings. Strong tidal andsubtidal :urrents, shallow water, large tidal depth variations, unstable bottom characteris-tics, intensive coastal fishing activity, and scarce background data resulted in a challengingmooring design problem. Surface currents were expected to reach a maximum of nearly5 knots (2.5 m/s). The final designs shown in Figure 4 used a pair of surface and subsurfacemoorings at Ml and M2 and a subsurface mooring at M3. All the moorings supportedcurrent meters spanning the water column. In addition, the M2 mooring also supported awind recorder, and a waverider was deployed at MI. The relative positions of the surfaceand subsurface moorings at mooring sites M1 and M2 as well as the waverider deployedat M1 are shown in Figure 5. Also shown in Figure 5 is the position of the instrumentedbottom tripod, GEOPROBE. The tripod was deployed by USGS to study sediment trans-port and the physical processes (using current measurements at four levels) influencingsediment dynamics (Oceanography, 4, 21-26).

The MI and M2 subsurface moorings were short enough that only chain was usedbetween moorirg components. A ground chain to a secondary anchor with a small surfacemarker buoy was used as a two-stage recovery method. If the surface marker buoy haddisappeared, the chain on the bottom could have been used as a target for a grapplingtrawl recovery. The M3 mooring was deployed with an acoustic release at the shelf breakwhere there was relatively little fishing activity.

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mean monthly wind stress 3regionna'l " -- .coastline ".';.

orientation ", .NBC

retroflexion

3 300 NBC 30E p

(D % 20

2001a

10Amazonnw%. 1 ~

C z

o minimum

E0< 0 L 0

J F M A M J J A S 0 N 0

Moored Array Componenxt1990

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Figure 3: Timeline showing the moored array deployment period in the context of the

seasonal cycle. The peak wind stress occurring in February is about 1.1 dyn cm-2 (Picaut

et al., 1985). The flow of the North Brazil Current (NBC) (Philander and Pacanowski,1986) is given in Sverdrups ( x 10 M3s s-1 ). The current flows northwestward along the

coast, but retroflects eastward during part of the year. (Modified from Nittrouer et al., 51991.)

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TCRCID BUOY W/ SURLYN FOAMIVER. LIGHT AND ARGUS BEACON IARKER BUOY

SURLYN FOAmiARKER BUOY

3M 3/8' CHAIN

I IM 3/4" 'HAIN

3M INVERTED VACM W/CONDUCTIVITY

2M 1/'• CHAIN

750 L3 DEPRESSOR WEIGHT 15M 3/8' 153 3/8rCHAIN CHAIN

41' SPKERE

33M 3J4' CHAIN !M 3/8* CHAIN

351'1 34"CHAINCHAIN VACM ',d/C3NI)UCT :%:-ý

15M 3/4' 2M 3/8' CHAIN1000 LB 45M 3/8" 500 LB CHAIN 500 LB (VET 12. 1300 LB 'WET WT)ANCHOR CHAIN ANCHOR ANCH13R ANCHOR W/PLY•W=:Z

45" 4 3/8' CHAIN SASE

;-.v•-- .. - -: /j- • / /-- - -

AMASSEDS MOORING MI

Figure 4: Schematics of the AmasSeds moorings.

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VATt IROI MTEMPERATURE MAKXER BUOY SURLYN FOAM

s N 3/8 ' MARXER BUJOY.

Im WATER TEMPERATURE /CONDUCTIVI TY CHAIN 5M 3/8' CHAIN

114 3/4' CHAIN

-3.M

"INVERTED VACM V/CONDUCTIVITYT I

25M 1/2' CHAIN50M 3/0' WIRE ROPE

VACM V/CONDUCTIVITY

32M 504 318,WIRE ROPE

20M 1/2' CHAIN I4N VACM V/CONDUCTIVITY 41' SPHERE

54M42M4 1/2* CHAL;.750 LB DEPRESSOR WEIGHT

1M 3/8" CHAIN

62M VANE AND ROTORDUAL ROTOR INVERTED 1,ACM

50M 3/4' CHAIN4 /C'NDUCTIVITY

201 3/' CAIN6414 SPEED ONLY'20M 3/4" 20M 3/4 C14AIN IM 3/8' CHAIN

2300 LB 1251M 3/8' 500 LB CHAIN 500 Li (WET 1200 LB ( JET W.)UANCHOR ANCHOR NCHOR WT.) ANCHOR ANCHOR W/PLYYTWD

f j 8514 3/1' CHAIN BASE

OM DEPTH ' "I ..' " -// /- IAMASSEDS MOORING M2 3

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Figure 4 (cont.) I

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44' ALUMINUM SPHERE

2M 3/8' CHAIN

30M IOUSP CURRENT METER1.5M 3/8' CHAIN

32M S4 CURRENT METER

27.5M 3/8' WIRE ROPEW/FAIRING

61M IOUSP CURRENT METER

28M 3/8' WIRE ROPEW/FAIRING

28' STEEL SPHERE

IM 3/8' CHAIN

93M IOUSP CURRENT METERIM 3/8' CHAIN

iDACS RELEASE

IM 3/8' CHAIN

3M 3/4' NYLON

2.4M 1/2' CHAIN

3400 LB MACE ANCHOR

103M

AMASSEDS MOO]IRING M3

Figure 4 (cont.)

12 .3

WaveniderI

N INN

Toroid

Subsurface buoy 02mMI

A GEOPROBE3

4 ~NI

Subsurface buoy 0. mM21

Figure 5: Relative positions of the surface and subsurface moorings at MI (upper panel) and %M2

(lower panel). The GEOPROBE is identified by (A), surface guard buoys (*~), subsurface buoys(O~waverider ([B), and instrumented toroid buoys ()

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The M1 and M2 surface current meter moorings were by far the most difficult todesign, prepare, and deploy. The antiquated toroid buoys which were available requiredextensive repair and modification, including fabrication of new rigid bridles and towersfor lights and meteorological instruments. Both toroids were foam-filled in the center anddecked-over which increased the total buoyancy and reduced the drag. The M1 mooringwas designed for a water depth of 20 m, supported only one current meter, and had a750-pound depressor weight directly below the current meter to reduce the vertical tilt ofthe current meter. The M2 mooring was designed for a water depth of 60 m, supportedthree current meters, and a compromise depressor weight of 750 pounds was used below thebottom current meter. A larger depressor weight would have reduced the tilt of the lowercurrent meters significantly but would have risked sinking the surface buoy in the case ofextreme currents. Both M1 and M2 surface moorings were set with chain ground lines tosmaller secondary buoy moorings to provide a backup recovery method. In addition, bothtoroids were deployed with lights, radar reflectors, and WHOI-built ARGOS transmittersto monitor their positions in near-real time.

A Datawell waverider was deployed at Ml to obtain measurements of the surface

gravity wave spectrum. Since the waverider buoy has very little buoyancy and, would notsurvive or remain on the surface in the high current conditions expected at M1 if deployedin the standard way, a special mooring was designed and successfully tested in VineyardSound, an area where the currents reached 2.8 knots (1.4 m/s).

2.3 Instrumentation

Current, temperature, and conductivity measurements on the MI. and M2 moor-ings were made using WHOI Vector-Averaging Current Meters (VACMs). To measurein-situ conductivity, each VACM was equipped with a SeaBird conductivity cell mountedto the instrument case. The near surface VACMs at M1 and M2 were deployed invertedjust below the rigid toroid bridle so that the current sensors were located at a depth of3 m. This was done to increase the likelihood that the sensors would be in the thin surfaceplume of low- salinity water which the hydrographic surveys revealed was typically 5 to10 m thick near the moored array transect. The VACM on the M2 subsurface mooringwas modified so that it had two rotors, one on either end of the case (Figure 6), in anI effort to estimate bottom stress from the velocity shear. The VACMs were prepared inthe standard way with 0.125-inch-diameter Kennametal 801 (a tungsten/titanium carbide)pivot/delrin block bearings. To reduce biofouling, the VACMs were completely coated withTributyl-Tin anti-fouling paint before deployment. In addition, the conductivity cells weredeployed with anti-fouling sleeves inserted in both ends of each cell. The VACMs were setto record data every 7.5 minutes.

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Rotor0.5 m 1

Vane

SeaBirdConductivitySensor

1.2m 3. MDual-rotor

VACMat 62 mr

O.5m Rotor

Figure 6: Schematic of the dual-rotor VACM de-lyd on the subsurface mooring at M2. 5II

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Wind speed and direction were measured at 3.5 m above the surface on the mid-shelf M2 mooring using a standard WHOI Vector Averagin6 Wind Recorder (VAWR)mounted on the toroid buoy (Dean and Beardsley, 1988). The VAWR also recorded watertemperature and conductivity data from sensors mounted at 1 m depth on the mooringbridle of the buoy. The VAWR was set to record P",erage data every 7.5 minutes.

The M3 subsurface mooring supported three SD2000 current meters built in Nor-way by Sensordata and one WHOI InterOcean S4 current meter. The SD2000 current me-ter is similar to an Aanderaa current meter but smaller and more lightly built (Figure 7).The vertical strength member of the SD2000 was found to be inadequate to survive thenormal mooring tension. Stainless steel cages were designed and fabricated at WHOI topass the mooring tension around the current meter while minimizing its flow disturbanceand allow the current meter to orient itself freely into the flow. The SD2000 instrumentsused a solid-state memory to store four-minute burst samples of vector-averaged currentspeed, direction, and temperature data every tw- V_,urs. The SD2000 had been purchasedby IOUSP as an inexpensive lightweight cui rent meter suitable for use in shallow coastalwaters. Because its performance on a subsurface mooring in a strong western bouhdarycurrent was untested, an S4 current meter was deployed about 2.75 m below the uppermostSD2000 to provide some redundancy ind data for an instrument comparison. The S4 wasone in routine use at WHOI and was configured to measure and record current speed,direction and pressure every 20 minutes. A summary of the moored ilnstiumentat;on andsensors deployed during AmasSeds and other descriptive information is given in Table 3.

2.4 Deployment Strategy

Due to the short M1 and M2 moorings, double anchor design, and high currents,the M1 and M2 surface and subsurface moorings were deployed from the R/V Iselin whileshe was anchored. Once the desired location was reached and the ship anchored, theinstrumented section of the mooring was deployed over the side and off the stern. Thenas the main anchor was being lowered on the groundline, the ship took in anchor chain sothat the groundline was stretched out on the bottom into the current and the main andsecondary anchors were separated as much as possible. Then the secondary surface markerbuoy was released and the deployment completed. This approach worked reasonably well,although it placed great strain on the ship's anchor windlass. The M1 waverider mooringand the M3 subsurface mooring were deployed anchor labt from a freely floating ship. Acombination of SatNav and GPS was used for navigation.

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Figure 7: Inter~cean S4 and the IOUSP SD2000 current meter.I

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Table 3: Station information and sensors deployed during AmasSeds

Station Water Location Instrument Sensor Record Data Record(Mooring Depth N/W Sensor Depth Rate Source Length

Type) (W) Type (m) (min) (days)

MI. 18 03004.51' VACM(I) 3.0 75 WH1O! 102(Surface) 50018.80' WT 3.0 7.5 128

CD 3.0 7.5 128

M1 18 03004.47' VACM 16.0 7.5 WHOI 128(Subsurface) 50018.80' WT 16.0 7.5 128

CD 16.0 7.5 128

M2 65 03023.12' VAWR -3.5 7.5 WHOI 23(Surface) 49056.23' AT -3.5 7.5 41

WT 1.0 7.5 65CD 1.0 7.5 65

VACM(I) 3.0 7.5 WHO[ 65WT 3.0 7.5 65CD 3.0 7.5 65

VACM 32.0 7.5 WHOI 65WT 32.0 7.5 65CD 32.0 7.5 65

VACM 54.0 7.5 WHOI 65WT 54.0 7.5 65CD 54.0 7.5 65

M2 65 03023.02' VACM(D) 62.0 7.5 WHOI 128(Subsurface) 49056.48' WT 62.0 7.5 128

CD 62.0 7.5 128PR 62.0 7.5 128SD 62.0 7.5 128SD 64.0 7.5 128

I M3 103 04004.29' BCM 30-0 120.0 IOUSP 128(Subsurface) 49037.35' WT 30.0 120.0 IOUSP 128

S4 32.0 20.0 WHOI 128PR 32.0 20.0 WHOI 128

BCM 61.0 120.0 IOUSP 0WT 61.0 120.0 IOUSP 128

BCM 93.0 120.0 IOUSP 128WT 93.0 120.0 IOUSP 128

PR: Pressure CD: Conductivity AT: Air Temperature WT: Water TemperatureSD: Scalar Speed S4: Inter-Ocean S4 Curretnt MeterBCM: Current Meters made id Norway by Sensordata, deployed by IOUSPVACM: Vector Averaging Current MeterVACM(I)I Inverted Vector Averaging Current MeterVACM(D): Inverted Vector Averaging Current Meter with Dual Rotors

VAWR: Vector Averaging Wind RecorderIOUSP: Institute of Oceanography, University of Sao PaoloWHOI: Woods Hole Oceanographic Institution

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2.5 Mooring Recovery and Data Return

The data return from the AmasSeds moored array is summarized in Figure 8. Anumber of mooring and instrument failures occurred during the mooring deployment whichcontributed to loss of data. An overview of these problems is given below. A completedata return resulted in about 128 days of data (Table 3).

The AmasSeds moored array was deployed on Leg 1 (February 8-12, 1990) ofAmasSeds Cruise 2 and mostly recovered on Leg 5 (June 16-25, 1990) of Cruise 3. Allmooring work was done from the R/V Iselin, which was based in Belem, Brazil duringboth Cruises 2 and 3. Cruise 2 contained a total of five legs over the period February 8-March 30. Cruise 3 contained five legs over the period May 1-June 25. One advantage ofthis ship schedule was that the Iselin usually visited the MI and M2 mooring sites at least 3once every leg and the surface moorings could be located and visually inspected. Withina few weeks of deployment, the M2 ARGOS transmitter stopped. On Leg 3 of Cruise 2,the transmitter package was taken to the ship and found to have a cracked housing and Iwater inside. A new transmitter was assembled with existing and some new parts andremounted on the M2 toroid. Since it was unclear if this new transmitter would work, aDraper Lab low-cost drifter (LCD) surface buoy which contained an ARGOS transmitterwas also mounted to the tower. Several LCDs were onboard to be deployed as part of theregional scale hydrographic/acoustic Doppler current profiler survey. A LCD surface buoy 3was also mounted on the M1 surface buoy as backup.

Only the toroid and the subsurface mooring marker buoy were found at the surface 3when recovery operations started at the MI site in mid-June, 1990. The surface currentwas initially slack so that the ship was able to recover the subsurface mooring markerbuoy first within 20 minutes without anchoring. The main anchor had about two feet of 3mud on top, indicating its depth of burial. The toroid and rest of the MI mooring wassuccessfully recovered through the ship's A-frame. Chain was present beneath the missingtoroid marker buoy, suggesting it was stolen. The vertical chains of both the surface Iand subsurface moorings had pieces of gill nets wrapped around them, indicating a highintensity of fishing. 3

The M1 3 m VACM was missing its rotor when it was recovered. Subsequentexamination of the current data suggests the rotor failed abruptly on May 22 (101 daysafter deployment). The cage showed indications of the rotor rubbing or bouncing aroundfor a period of time before the rotor broke up and its pieces flushed from the cage.

The rotor on the VACM at 16 m depth on the M1 subsurface mooring was out ofits pivot when recovered. The rotor speed observations from this sensor did not reveal anobvious time when the sensor failed so all the data is presented in this report. However, thecurrent speeds show a trend suggesting a gradual degradation of the speed data starting in

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19

FEB MAR APR MAY JUN10 20 10 20 30 10 20 30 10 20 30 10

till ! 111111.1111111111 llllll I I II I III t lll Ill ii II I I 1 11 1 i lt I lI i tl t[I|tItill tl i t 11111111 1itit mi mi t il i It i l ulllt~ 1111111tt

MI 3m

MI 16m

M2 Meteorological

M2 1m

M2 3m

AmasSeds Data ReturnI M2 32m-- Current or Wind

M2 Temperature and Conductivity

---------------------- Temperature only

PressureM2 62m

M3 30m

M3 32m

M3 61m

M3 93m

10 20 10 20 30 10 20 30 10 20 30 10

FEB MAR APR MAY JUN

Figure 8: Data r- lurn from the AmasSeds moored array.

20 1I

mid-April. This is most likely due to the heavy growth of barnacles found over the lowerpart of this instrument, including the rotor, when it was recovered. Why this one VACM Iexperienced so much biofouling is unclear, since the other current meters were relativelyclean when recovered.

The special waverider mooring deployed at M1 was never recovered. The waveriderbuoy was observed to be floating at the surface in very strong currents whenever the Iselinpassed the M1 site shortly into the deployment period so that that aspect of the mooring Idesign seemed to be successful. Whether the mooring failed or the surface buoy was stolenor cut free, is not known. 3

The most significant problem affecting data return was the failure of the M2 surfacemooring. ARGOS positioning data revealed that the M2 surface buoy began driftingon April 16, 1990 (65 days after deployment). The buoy was tracked and subsequentlyrecovered off Suriname on April 29, 1990 aboard the R/V Iselin during its transit fromMiami to Belem to start AmasSeds Cruise 3. Examination of the surface buoy revealedthat the mooring failed at a shackle 1 m below the toroid bridle and above the firstcurrent meter. The rest of the M2 surface mooring, including all the current meters, wasrecovered on June 22, 1990 by dragging during the scheduled mooring recovery leg (the Isurface marker buoy was then missing and presumed stolen). The main anchor had at least1.5 feet of mud on top, indicating depth of burial. The shackle linking the two sections ofthe mooring was not recovered so the specific cause of the mooring failure is not known.One likely candidate based on past experience in high current conditions is that the nuton the shackle worked loose and wore through the cotter pin. If the nut is not tightenedenough prior to deployment, strumming of the mooring line can cause the nut to back offand vibrate enough to quickly wear out the shackle pin and cotter pin. Pieces of ropefound attached to the M2 toroid (see next paragraph) and elongated chain links found in 3the M2 groundline also suggest that at some point prior to recovery, a fishing boat or boatshooked onto this mooring.

The M2 VAWR rotor and vane assembly were found broken off during a visit bythe Iselin to the mooring site in early March. At the same time, a large rope was foundtied off around the toroid tower and one leg of the tower was bent, suggesting that the Itower had been 'lassoed' and used to tie up fishing boats. Consequently, the wind velocitydata series was only 23 days long, ending on March 5. Because of this short wind record,ECMWF (European Centre for Medium-Range Weather Forecasts) winds were acquiredto supplement the moored wind observations. A comparison of the winds at M2 and theECMWF winds is shown in Figure 9. The VAWR air temperature sensor returned 41 daysof data through March 22, and the VAWR water temperature and conductivity sensorsreturned full data records.

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AmasSeds M2 and ECMWF Winds (m/s)

M2 (solid). ECMWF (dash)

0.: II

3.I 3II I I I I

F

Cross-Shelf

10 11 12 13 14 15 16 17 18 19 20'21 22 23 24 25 26 27 26 1 2 3 4 5

1.

3. --~

0. U IL

II

-3. F

ýI. sh r . .

10 1 1 1 141516 7 1 1 202122 23 24 25 26 27 28 1 2 3 4 5

Figure 9: Time series of the hourly-averaged M2 and ECMWF wind records for 23 days.

22 3i

Attempts to recover the M2 subsurface mooring during the AmasSeds recoverycruise were unsuccessful. Its surface marker buoy was missing and even though the moor- Iing had been deployed with good positioning data, extensive dragging did not hook themooring. Fortunately, a Brazilian fisherman subsequently recovered this mooring on Au-gust 12, 1990 and the one VACM was returned to WHOI on May 8, 1991. The elongated Ichain links in the M2 surface mooring groundline and the extensive but unsuccessful drag-ging suggest that the M2 subsurface mooring was moved by fishing activity prior to theAmasSeds recovery leg. Due to the expulsion of foreign fishing vessels from French Guinea Iwaters during the spring of 1990, a large fleet of Brazilian and Korean shrimpers werefishing in the M2 area in late spring. During the June recovery leg, at least 10 trawlers 3were in sight at any time while the Iselin was working at M2.

The M3 subsurface mooring was recovered without incident. About half of the 3wire rope fairing was still intact. The current meters showed little biofouling and allinstruments returned full data records except the 61 m SD2000 which returned no currentdata. The SD2000 current meters were in good mechanical condition including the rotors iand bearings except the 61 m instrument which had a loose mounting shaft and the stainlesssteel mounting frame of the 30-m instrument which was twisted about 450 (this may haveoccurred during recovery).

It should be noted that the accurate determination of mean water depth at thethree mooring sites was made quite difficult in this experiment by the combination of large Isurface tides, variations in the surface plume, variable bottom composition and bearing

strength, and the presence of fluid muds and shifting sediment over the inner and mid-si 'f.The water depth and instrument depths listed in Tables 3-5 represent best estimates basedon a variety of inputs which include the ship's PDR data corrected for local sound speed,the moored pressure data, and the mooring configurations. The instantaneous water depth 3can vary from the mean by at least ± 1.4 in, the maximum surface tide amplitude at theshelf break (Flagg and McDowell, 1981).

2.6 Data Processing Methods

Data from the M1 and M2 instruments (VAWR, VACMs) were recorded internallyon standard magnetic cassette tapes and transcribed onto 9-track tapes at WHOI. The 3data were then converted to scientific units and edited using the standard current meterprocessing system developed at WHOI (Tarbell et aL, 1988). This included a carefulcheck of the timebase, truncation to remove launch and retrieval transients, the removalof erroneous data cycles, and interpolation to fill any resulting gaps in the data.

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For the M3 mooring initial decoding of the S4 current meter data was done atWHOI by R. Geyer, and final editing of the IOUSP Sensordata SD2000 current meterswas done by B. Castro during a visit to WHOI in 1991. The M3 time series were truncatedto a common time period and corrected for magnetic variation. An evaluation of the effectsof mooring tilt on the S4 current observations and comparison of the S4 at 32 m and theSD2000 at 30 m are given in the Appendix. Time series of the hourly-averaged S4 pressureat 32 m, which were used in the calculation to correct for dip, is shown in Figure Al.

For all vector and scalar variables that were sampled at intervals less than onehour, hourly values were formed by vector or scalar averaging (computed using a runningmean), centering time on the hour (e.g., the value assigned to 1200 is an average of datacollected between 1130 and 1230). Hourly averaged data for the SD2000 current meterswere formed by linear interpolation between the samples recorded every two hours.

The current and wind vectors were rotated into an along-shelf coordinate systemoriented 450 counterclockwise with respect to true north so that the along-shelf componentis positive towards 315'T and the cross-shelf component is positive towards 45°T. This isalso the coordinate system used in the STACS data set (Johns et al., 1990). Note thatisobath orientations are roughly 325°T at the Ml mooring, 315'T at the M2 mooring and310°T at the M3 mooring. The mean flow within the Amazon plume (3 m depth on theM1 and M2 moorings) is toward 320°T.

I Salinities were estimated from the SeaBird temperature and conductivity observa-tions using the SeaBird software.

I For examining low-frequency (subtidal) variability, the hourly data were filteredusing the PL64 filter. The filter is symmetric with a total of 129 weights applied to thehourly time-series. The PL64 filter has a half-power point of 38 hours. A summary of thePL64 filter, including the generating function, was given by Beardsley, Limeburner, andRosenfeld (1985).

3. Description of Data Presentation

The data are presented in the form of time series plots. Each plot covers the timeperiod between February 9, 1990 and June 22, 1990. The PL64 low-pass filtered vectorplots are subsampled every six hours. For display purposes all plots are shown on twopages, side by side, with the time axis on each page spanning 66.5 days. For each variablepresented, the vertical scales are generally the same but the ranges vary. The exception issalinity, where the vertical scale for M2 varies.I

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Table 4: Hourly-Averaged Statistics - Entire Time Period

Water Start Time Stop Time Sensor StdSta Depth (y m d/hm) (y m d/hm) Duration Depth Mean Dev Max Min

(m) GMT GMT (Days) (m)

Cross-Isobath Velocity (cm/a) 3M1 18 900209/1300 900522/0500 102 3.0 5.12 101.52 202.52 -201.84M1 18 900209/1600 900617/1600 128 16.0 -0.52 76.61 185.13 -192.59

M2 65 900210/0100 900416/1100 65 3.0 7.47 34.92 118.75 -89.18 3M2 65 900210/0100 900416/1100 65 32.0 -6.01 35.17 73.10 -81.42M2 65 900210/0100 900416/1100 65 54.0 -2.84 41.29 80.09 -79.37M2 65 900209/2300 900618/1100 128 62.0 -6.99 33.57 77.63 -75.39

M3 103 900210/0800 900618/1200 128 30.0 8.03 22.60 92.48 -71.28M3 103 900210/0800 900618/1200 128 32.0 -0.32 25.62 71.72 -78.97M3 103 900210/0800 900618/1200 128 93.0 -4.02 18.84 66.76 -60.82

Along-Isobath Velocity (cm/s)

M1 18 900209/1300 900522/0500 102 3.0 41.38 40.86 135.14 -90.90M1 18 900209/1600 900617/1600 128 16.0 6.42 19.58 89.23 -50.18 UM2 65 900210/0100 900416/1100 65 3.0 73.64 40.64 183.82 -33.88M2 65 900210/0100 900416/1100 65 32.0 45.76 14.39 85.69 9.70M2 65 900210/0100 900416/1100 65 54.0 15.58 8.13 37.82 -6.92M2 65 900209/2300 900618/1100 128 62.0 10.53 11.85 47.31 -23.04 3M3 103 900210/0800 90G618/1200 128 30.0 78.82 28.40 213.71 -3.70M3 103 900210/0800 900618/1200 128 32.0 83.59 26.96 146.64 -7.48M3 103 900210/0800 900618/1200 128 93.0 17.55 11.65 72.09 -25.57

Water Temperature (OC)

M1 18 900209/1600 900617/1600 128 3.0 27.91 0.58 29.47 26.71MI 18 900209/1600 900617/1600 128 16,0 27.27 0,33 28.40 26.56

M2 65 900210/0100 900416/0900 65 10 27.62 0.50 29.21 26.63M2 65 900210/0100 900416/0100 65 3.0 27.62 0.48 29.20 26.66M2 65 900210/0100 900416/1100 65 32.0 26.85 0.38 27.69 25.31M2 65 900210/0100 900416/1100 65 54.0 26.04 0.98 27.48 23.89

M2 65 900209/2300 900811/1000 128 62.0 26.42 1.09 27.70 23.69

M3 103 900210/0800 900618/1200 128 30.0 28.31 0.52 29.76 26.89M3 103 900210/0800 900618/1200 128 61.0 27.50 0.54 28.63 24.68M3 103 900210/0800 900618/1200 128 93.0 24.34 2.09 28.13 17.78

Conductivity (s/m)

MI 18 900209/1600 900617/1600 128 3.0 3.31 0.78 5.24 1.35MI 18 900209/1600 900617/1600 128 16.0 5.03 0.49 5.66 2.97

M2 65 900210/0100 900416/0900 65 1.0 4.21 0.93 5.74 1.89M2 65 900210/0100 900416/1100 65 3.0 4.40 0.85 5.74 2.11M2 65 900210/0100 900416/1100 65 32.0 5.67 0.04 5.77 5.49 UM2 65 900210/0100 900416/1100 65 54.0 5.59 0.10 5.75 5.36

M2 65 900209/2300 900618/1100 128 62.0 5.55 0.10 5.72 5.30

Salinity (psu)

MI 18 900209/1600 900617/1600 128 3.0 19.56 5.13 32.71 7.28

M1 18 900209/1600 900617/1600 128 16.0 31.43 3.49 35.87 17.34

M2 65 900210/0100 900416/0900 65 1.0 25.69 6.41 36.34 10.76 IM2 65 900210/0100 900416/1100 65 3.0 26.92 -5.86 36.34 11.89M2 65 900210/0100 900416/1100 65 32.0 36.23 0.09 36.41 34.95M2 65 900210/0100 900416/1100 65 54.0 36.24 0.03 36.35 36.15M2 65 900209/2300 900618/1100 128 62.0 36.00 0.13 36.24 35.54

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Table 4: Hourly-Averaged Statistics - Entire Time Period

Water Start Time Stop Time Sensor StdSta Depth (y m d/hnm) (y m d/hm) Duration Depth Mean Dev Max Min

(m) GMT GMT (Days) (m)

Air Temperature (*C)

M2 65 9W0210/0100 900322/1900 41 -3.5 26.66 0.86 28.09 23.18

Cross-Isobath Wind (m/s)

M2 65 900210/0100 900305/0900 23 -3.5 -4.82 1.47 1.25 -7.88EW - 900209/0000 900618/2300 130 - -4.30 1.73 0.20 -8.28

Along-Isobath Wind (m/s)

M2 65 900210/0100 900305/0900 23 -3.5 0.45 2.00 5.96 -5.21EW - 900209/0000 900618/2300 130 - 0.86 1.65 4.52 -4.02

Cross-Shelf Wind Stress (dynes/cm2 )

M2 65 900210/0100 900305/0900 23 -3.5 -0.49 0.21 0.10 -1.34EW - 900209/0000 900618/2300 130 - -0.42 0.27 0.00 -1.27

Alongshore Wind Stress(dynes/cm 2 )

M2 65 -- 0210/0100 900305/0900 23 -3.5 0.04 0.21 0.85 -0.58EW - "i0209/0000 900618/2300 130 - 0.07 0.16 0.51 -0.53

Pressure (db)

M2 65 900209/2300 900618/1100 129 62.0 59.85 0.88 62.25 57.60

%13 103 900210/0800 900618/1200 128 32.0 34.97 1.96 43.99 30.30

Scalar Speed (cm/s)

M2 65 900209/2300 900618/2200 129 62.0 35.36 14.64 85.46 6.88M2 65 900209/2300 900618/2200 129 64.0 29.53 11.58 73.64 6.23

I Note: EW = European Centre for Medium-Range Weather Forecasts

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Table 5: Hourly-Averaged Statistics - Common Time Period 3Water Start Time Stop Time Sensor Std

Sta Depth (y m d/hm) (y m d/hm) Duration Depth Mean Dev Max Min

(M) GMT GMT (Days) (i)

Cross-Isobath Velocity (cm/u)

MI 18 900210/0800 900416/0900 65 3.0 3.09 107.27 202.52 -201.84M1 18 900210/0800 900416/0900 65 16.0 0.04 93.25 185.13 -192.59 IM2 65 900210/0800 900416/0900 65 3.0 7.41 34.90 118.75 -89.18M2 65 900210/0800 900416/0900 65 32.0 -5.98 35.12 73.10 -81.42M2 65 900210/0800 900416/0900 65 54.0 -2.84 41.20 80.09 -79.37 UM2 65 900210/0800 900416/0900 65 62.0 -4.62 35.31 82.07 -74.93

M3 103 900210/0800 900416/0900 65 30.0 8.77 19.11 77.28 -50.46M3 103 900210/0800 900416/0900 65 32.0 -0.14 29.14 75.00 -82.59 UM3 103 900210/0800 900416/0900 65 93.0 -4.77 19.07 66.76 -56.34

Along-Isobath Velocity (cm/s)

MI 18 900210/0800 900416/0900 65 3.0 38.21 45.18 135.14 -90.90 iMI 18 900210/0800 900416/0900 65 16.0 8.24 24.07 89.23 -43.52

M2 65 900210/0800 900416/0900 65 3.0 73.77 40.60 183.82 -33.88M2 65 900210/0800 900416/0900 65 32.0 45.68 14.30 83.15 9.70M2 65 900210/0800 900416/0900 65 54.0 15.56 8.13 37.82 -6.92M2 65 900210/0800 900416/0900 65 62.0 12.84 8.05 34.21 -7.73

M3 103 900210/0800 900416/0900 65 30.0 70.33 15.92 122.83 16.58M3 103 900210/0800 900416/0900 65 32.0 95.52 21.76 157.71 16.38M3 103 900210/0800 900416/0900 65 93.0 19.63 10.20 51.53 -2.67

Water Temperature (*C)

M1 18 900210/0800 90041F , 3 65 3.0 27.51 0.46 28.86 26.71MI 18 900210/0800 9004.. ;:,,O 65 16.0 27.10 0.27 28.10 26.56

M2 65 900210/0800 900416/0900 65 1.0 27.62 0.50 29.21 26.63M2 65 900210/0800 900416/0900 65 3.0 27.62 0.48 29.20 26.66 IM2 65 900210/0800 900416/0900 65 32.0 26.85 0.38 27.69 25.31

M2 65 900210/0800 900416/0900 65 54.0 26.04 0.98 27.48 23.89M2 65 900210/0800 900416/0900 65 62.0 25.99 1.03 27.49 23.89

M3 103 900210/0800 900416/0900 65 30.0 27.96 0.46 29.30 26.89M3 103 900210/0800 900416/0900 65 61.0 27.25 0.43 28.21 24,68M3 103 900210/0800 900416/0900 65 93.0 24.61 1.79 27.29 19.23

Conductivity (s/m)

M1 18 900210/0800 900416/0900 65 3.0 3.29 0,72 4.92 1.70MI 18 900210/0800 900416/0900 65 16.0 4.92 0.50 5.59 2.97

M2 65 900210/0800 900416/0900 65 1.0 4,21 0.93 5.74 1.89M2 65 900210/0800 900416/0900 65 3.0 4.40 0.85 5.74 2.11M2 65 900210/0800 900416/0900 65 32.0 5.67 0.04 5.77 5.49M2 65 900210/0800 900416/0900 65 54.0 5.59 0.10 5.75 5.36M? 65 900210/0800 900416/0900 65 62.0 5.56 0.10 5.72 5.35 U

Salinity (psu)

M1 18 900210/0800 900416/0900 65 3.0 19.58 4.82 30.74 9.30MI 18 900210/0800 900416/0900 65 16.0 30.73 3.56 35.31 17.34 IM2 65 900210/0800 900416/0900 65 1.0 25.66 6.40 36.34 10.76M2 65 900210/0800 900416/0900 65 3.0 26.90 5.85 36.34 11.89M2 65 900210/0800 900416/0900 65 32.0 36.23 0.09 36.41 34.95 IM2 65 900210/0800 900416/0900 65 54.0 36.24 0.03 36.35 36.18M2 65 900210/0800 900416/0900 65 62.0 36.09 0.07 36.23 35.93 I

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Table 5: Hourly-Averaged Statistics - Common Time Period (continued)

Water Start Time Stop Time Sensor StdSta Depth (y m d/hm) (y m d/hm) Duration Depth Mean Dev Max Min

(m) GMT GMT (Days) (m)

Pressure (db)

M2 65 900210/0800 900416/0900 65 62.0 60.17 0.87 62.25 58.02

M3 103 900210/0800 900416/0900 65 32.0 35.37 1,43 40.08 32.26

Scalar Speed (cm/s)M2 65 900210/0800 900416/0900 65 62.0 36.18 14.93 85.46 8.69M2 65 900210/0800 900416/0900 65 64.0 29.80 11.56 73.64 6.84

I Cross-Isobath Wind (m/s)

EW - 900210/0800 900416/0900 65 - -5.17 1.52 -0.73 -8.28

Along-Isobath Wind (m/s)

EW - 900210/0800 900416/0900 65 - 0.29 1.64 4.14 -4.02

Cross-Shelf Wind Stress (dynes/cm2 )

EW - 900210/0800 900416/0900 65 - -0.55 0.27 -0.02 -1.27

Alongshore Wind Stress(dynes/cm 2 )EW - 900210/0800 900416/0900 65 - 0.02 0.17 0.51 -0.53

Note: EW = European Centre for Medium-Range Weather Forecasts

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IThe basic statistics for the hourly averaged data covering the entire period for

each record are shown in Table 4. To facilitate comparisons, Table 5 shows the statistics 3for the common 65-day time period when most sensors worked, 0800 February 10 - 0900April 16, 1990 (GMT).

The hourly-averaged air temperature at M2 and the M2 and ECM WF winds areshown in Figure 10. Composite (stacked) plots of the PL64 low-pass filtered currentsare presented in Figures 11-16. The time-series for each instrument have bc.en stacked Uvertically on the same time base for easy comparison. Composite plots of the hourly-averaged current velocity components are shown in Figures 17-20. 3

Composite (overlay) plots of the PL64 low-pass filtered water temperature andsalinity records by mooring are presented in Figures 21 and 22. Composite (stacked)plots of the hourly-averaged individual water temperature, salinity, and conductivity time Iseries records are shown in Figures 23-29. Time series of the hourly-averaged and PL64low-pass filtered speed records from the dual rotor VACM are shown in Figure 30. Thehourly-averaged pressure record at M2 is shown in Figure 31.

4. Acknowledgments i

The authors would like to express their appreciation to the many individuals whohelped to make the AmasSeds moored array field program successful. In particular, wewould like to acknowledge Sean Kery, Peter Clay, and Dave Simoneau for their work in idesigning and fabricating the moorings, Scott Worrilow and Bryan Way for preparing anddebriefing the VAWR and VACMs and conductivity cells, and Susan Tarbell who read andedited the VAWR and VACM data. Dick Limeburner made several unscheduled visits to Ithe MI and M2 toroids, one to recover the broken M2 VAWR wind sensors and anotherto recover the failed ARGOS transmitter and mount the Draper Lab LCDs as backupARGOS transmitters. The deployment crew consisted of Dave Simoneau, Scott Worrilow,Pat O'Malley, John Trowbridge, Belmiro Castro, and Bob Beardsley. The recovery crewconsisted of Dave Simoneau, Scott Worrilow, Peter Clay, Belmiro Castro, Dick Limeburner, 5and Bob Beardsley. Additional help during the extensive dragging operations was given byGeorge Tate and Joanne Theade (USGS), and Dick Sternberg (University of Washington).We also want to acknowledge the fine job of ship handling done by the officers and crew Iof tne R/V Iselin during the moored array deployment and recovery operations.

George Tupper and Brian Racine did the mooring model calculations presented inthe Appendix, and Anne-Marie Michael helped prepare the final version of this report.

The U.S. component of the AmasSeds moored array field program was supported 3by NSF Grant OCE 88-12917. The Brazilian mooring work at M3 was supported by

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FAPESP grant 89/3508-4. The preparation and publication of this report is funded byNSF grant OCE 91-15712.

5. References

AmasSeds Research Group (1990). A Multidisciplinary Amazon Shelf SEDiment Study.Eos Transactions, American Geophysical Union, 71, 45, November 6, 1990.

Beardsley, R. C., R. Limeburner, and L. K. Rosenfeld, 1985. Introduction to CODE-2Moored Array and Large-Scale Data Report. Woods Hole Oceanographic InstitutionTechnical Report, WHOI-85-35, CODE Technical Report No. 38, 234 pp.

Dean, J. P., and R. C. Beardsley, 1988. A vector-averaging wind recorder (VAWR)system for surface meteorological measurements in CODE (Coastal Ocean DynamicsExperiment). Woods Hole Oceanographic Institution Technical Report WHOI-88-20,77 pp.

Flagg, C. N., and S. McDowell, 1981. Current and hydrographic measurements of theNorth Brazil coastal current between 2* and 7°N latitude. EG&G EnvironmenitalConsultants. Submitted to Esso Exploration, Inc., August.

Geyer, W. R., R. C. Beardsley, J. Candela, B. Castro, R. V. Legeckis, S. J. Lentz, R.Limeburner, L. Miranda, and J. H. 'rrowbridge, 1991. The physical oceanography ofthe Amazon outflow. Oceanograp-,' 4, 8-14.

Gibbs, R. J., 1972. Water chemistry of the Amazon River. Geochimica et CosmochimicaActa, 36, 1061-1066.

Johns, W. E., R. L. Molinari, and D. Wilson, 1990. International resew h activities inthe tropical Atlantic Ocean off northern Brazil. Eos, Transactions j, the AmericanGeophysical Union, 71, 43 (abstract).

Kuehl, S. A., D. J. DeMaster, and C. A. Nittrouer, 1986. Natuac of sediment accumulationon the Amazon continental shelf. Continental Shelf Research, 6, 209-225.

Limeburner, R., and R. C. Beardsley, 1989. CTD observations off northern Brazil dur-ing A Multidisciplinary Amazon Shelf SEDiment Study, AmasSeds, August, 1989.Woods Hole Oceanographic Institution Technical Report, WHOI-89-53, 134 pp.

Liineburner, R., and R. C. Beardsley, 1991a. CTD observations off northern Brazil duringA Multidisciplinary Am.•zon Shelf SEDiment Study, AmasSeds, February - March,1990. Woods Hole Oceanographic Institution Technical Report, WHOI-91-11, 344 pp.

30 3I

Limeburner, R., and R. C. Beardsley, 1991b. CTD observations off northern Brazil duringA Multidisciplinary Amazon Shelf SEDiment Study, AmasSeds, May - June 1990. IWoods Hole Oceanographic Institution Technical Report, WHOI-91-12, 344 pp.

Limeburner, R., I. D. Soares, J. Candela, and R. C. Beardsley, 1992. CTD observations 3on the North Brazil Shelf during A Multidisciplinary Amazon Shelf SEDiment Study(AMASSEDS), November 1991. Woods Hole Oceanographic Institution TechnicalReport, WHOI-92-27, 257 pp.

Meade, R. H., T. Dunne, J. E. Richey, U. De M. Sanots, and E. Salati, 1983. Storage andremobilization of suspended sediment in the lower Amazon River of Brazil. Science, U228, 488-490.

Milliman, J. D., and R. H. Meade, 1983. World-wide delivery of river sediment to the 5oceans. Journal of Geology, 91, 1-21.

Moller, D., 1976. A computer program for the design and static analysis :i single-point 3subsurface maooring systems: NOYFB. Woods Hole Oceanographic Institution Tech-nical Report, WHOI-76-59, 105 pp. I

Nittrouer, C. A. (Editor) 1991. Oceanography, The Oc(, 'tography Society, Vol. 4, No. 1,47 pp- i

Oltman, R. E., 1968. Reconnaissance investigations of the discharge and water quality ofthe Amazon River. U.S. Geological Survey, Circular 552, Washington, D.C., 16 pp.

Philander, S. G. H., and R. C. Pacanowski, 1986: The mass and heat budget in a modelof the tropicad Atlantic Ocean. Journal of Geophysical Research, 91, 14,212-14,220. g

Picaut, J., J. Servain, P. Lecompte, M. Seva, S. Lukas, and G. Rougier, 1985. ClimaticAtlas of the Tropical Atlantic Wind Stress and Sea Surface Temperatur,. 1964-19q79.Universit6 de Bretagne Occidentale, 467 pp.

Tarbell, S. A., A. Spencer, and E. T. Montgomery, 1988. The Buoy Group Data Process-ing System. Woods Hole Oceanographic Institution Technical Memorandum, WHO!-3-88, 207 pp. I

III

1 31

6. Data Presentation

!IIIII

32 1IUIIUIIIIIIIIIIIII

I 33

IIIIIIIIIIIIIIIIII

341

M2 and ECMWF' Winds (m/s)l10 . . . . .. . . .. . . .

M2 315*T Is up (PL64 Filter)3

ECMWF 31 5*T isu PL6 Filter)

io i0s02 30 101

10. I M2 Hourly-Averaged Cross-Shelf Component5.

-10 -......... . ...................I

10. ECMWF Cross-Shelf Component

0.-5. ...

10. - M2 Hourly-Averaged Alongshore Component3

-5. 3-10........ ... .. .. ..... .. . . . .... .. . . . .

10. ECMWF Alongshore Component5.0. U _ L t rtt

Hourly-Averaged Air Temperature at M42

10 2010 230 101FEB MAR APR

Figure 10I

35

M2 and ECMWF Winds (m/s)

5.fr40.

-5. M2 315°T Is up (PL64 Filter)10. .. .. .. . . . . . ...

' .ECMWF 315*T Is up (PL64 Filter)20 30 10 20 30 10 20

10 M2 Hourly-Averaged Cross-Shelf Component

I 5.-1. "................................ I..................

10. ECMWF Cross-Shelf Component5 . .

0.1-1. 20 30 120 30 1020

10 M2 Hourly-Averaged Alongshore Component

-1. ... ,...................... I...... ..10.10.*] ECMWF Alongshore Component,

-5.

20 30 10 20 30 10 20

Hourly-Averaged Air Temperature at M2

26.

.24. r..... ...... ........... .. I. ...20 30 10 20 30 10 20

APR MAY JUN

Figure 10 (cont.)

36I

PL64 Low-Pass Filtered Currents (cm/s) at M1 and M2

50. 325.

0. 11 milI-25.

-50.-

25 F 1l (1 6m)

-25. L.,% -

175.

150.

125. M2 (3m)

100.1

75,

7.M2 (32m)I I50.U

50.

-25. 5 2 255 1 15 2 25 35 10 5

FEB MAR APRm

Figure 1I I

37

IPL64 Low-Pass Filtered Currents (cm/s) at M1 and M2

75. M1 (3m)

50.I o25.

j0. fl-25.

-50.

25. m M1 (16m)

175.

150.

125. M2 (3m)

100.

75.

50.25.

0.

-25.

75. - M2 (32m)I o0.

I •° M2 (54m)'•0.

50, -I

I 50.

25. M2 (62m)

0.! mm..xQ --, i . . . . . . .,.. ......... . . . . - . ..... .................. .20 25 30 5 1 0 15 20 25 30 5 10 15 20

APR MAY JUN

Figure 11 (cont.)

38 .IIII

PL64 Low-Pass Filtered Currents (cm/s) at 13 i200.........................

175. M3 (30m). 3150.

125..

100.75.

50. 1

25.

150.

M3 (32m)125. 1100.

50.

25.15 20 25 5 0 15 20 25 30 5 10 15

FEB MAR APR

III

Figure 12 1

39

PL64 Low-Pass Filtered Currents (cm/s) at M3

200....................................

175. M3 (30m)150.

125. "

100.

75.50.

25.

150.

150 M3 (32m)125.

100. -

I75.50.

25.

0.

I•o. FM3 (93m) !I25. IILt b.a 1166 \tAI 19fIkk1IIall LmaI

L 20 25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

IIIII Figure 12 (cont.)

40 .II

PL64 Low-Pass Filtered Cross-Shelf Component (cm/s) at M1 and M2 I5 0 . . . . . . . . . . . . . . . .. t. ,. . . . .'. . . . . . . . ... ... . . . . . ..25. M1 (3m0.

-25. I

-50.

25. - M 1 (1165)

50.-25. 30o. o° A A A /•A r AAn02." V ,-V V-v V •v V V" -- v -605

-25. 3-50.

-25. I:M2 (32m)

2 5.) -M2(54) 1-25. - .. . v

25. IFM2 (62m)-2 .• ----- -. . ,, , . , .... ... . . , .

-2 . 10 1 5 ... 2 5 I0 ... 20. . 25 30 5' L6 .. L

FEB MAR APR

I

I

Figure 13 1

41

I PL64 Low-Pass Filtered Cross-Shelf Component (cm/s) at M1 and M250 . . . . . ... . . . . .... . . . ' ' ' , , , . .... . . . .. . . . . . ' '

(3m)

25".-M (16m)

0.

-25.

"l

50

I 2550.M2 (32m)

-25. L

25I M2 (54m)

-25.

I 25. M

0.

15 20 25 30 5 10 15 20 25 30 5 10 15 20APR MAY JUN

III

I Figure 13 (cont.)

42

I

III

PL64 Low-Pass Filtered Cross-Shelf Component (cm/s) at M3

75 M3 '(30m) .. . . ... . . .0.-

or I

-25.

o. --- --K _(• -,__,_ ___________

FEB MAR APR

IIIII

Figure 14 I

43

PL64 Low-Pass Filtered Cross-Shelf Component (cm/s) at M375. i " ;. { o • .. ......... . . .." "".. ..... ... " ........... . .

U' 5O.~M3 (30m)50.

0. '\V"V " -

-25.

20 25 30 5 10 15 20 25 30 5 10 1 5 200 APR MAY JUN

3Figure 14 (cont.)

44 .PL64 Low-Pass Filtered Atongshelf Component (cm/s) at M1 and M42

50.

25.1

0. 1-25.[-,

175. i M 1 (3m)I

125. ~

175. -

75

25.

-25.

-50.3

10. M2 (32m)a

50.1

25. 1-25.

So M2 (54m)I

25.1'0.I

-25.FEB MA P

M2 (62m

Figure 15

45

PL64 Low-Pass Filtered Alongshelf Component (cm/s) at M1 and M2100. . . . . . . . . . . . . . . . . .

7 5 . M 3 m

50. -

25.

0.

-25.

-50.

25. -M1 (16m)

-25.

175.

150. M2 (3m)

125.

100.

75.

50.

25.

0.

-25.

--50.

100.M2 (32m)

75.

50.

25.

0.

-25.

505 M2 (54m)

25.

0.-25.

20 25 . 0 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

Figure 15 (cont.)

46 .

I

PL64 Low-Pass Filtered Alongshelf Component (cm/s) at M3

175..............

ISO. M3 (30m)

125. !

100.

75. !50. -

25.

-25. g

-50.

150.2,.0"- M3 (32m)

12. 1

100.

75. I

50.-

25. !

0.

-25.5-25.50. - M

.10 15 20 25 5 10 15 20 25 30 5 10 15

FEB MAR APR

FII

Figure 16 I

I 47

PL64 Low-Pass Filtered Alongshelf Component (cm/s) ot M3I175. .. ... ... .ISO. M3 (3Cm)125.

100.I75.

0.I -2-5.-50.

15 'M3 (32m)

100.I75.50.

25.

0.I -25.

. 3 (93m I20 25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

Figure 16 (cont.)

48 .Hourly-Averaged Cross-Shelf Component (cm/s) at M1 and M2

250. .. . . . . .. . . w l

150. 1100.

50.10.

-50.

-100.

-150.

-200.

150.

100.

50.10.

-50. -il-100.

-150.

1200. [L 23m

100. -M2 (34m)

50. 1 ,1 1 1 1

-50. 1-100.L

iQO M2 (32m)50.

0.[-50.

FEB. MAR APRm)Figu. 1

49

Hourly-Averaged Cross-Shelf Component (cm/s) at M1 and M2I 250.

200. - Ml (3m)

150. -

100.

50.

0.

-50.

-100. -

-150.

-200.

200. - M1 (16m)1oo. -50.

0.

-50.100.

-150.

-2oo.100.M2 (3m)

So. -0.

-50. •

-1oo.- 2(3m100.100. M2 (32m)

I 50.

I

F 10.

-_100.oL100. -M2 (54m)

50.

0.

-50.

100. M2 (62m)

50.-

-50.- 1 0 0 . , 55182

APR MAY Figure 17 (cont.)JU

503

Hourly-Averaged Cross-Shelf Component (cm/s) at M3

-50.

-100.1

100.I

50.

00. 1~~ Ifl 11111111911111111Jl I-50.w

il11M11111

-10.

-50.

20 111 25 5l 1- 1 0 a5 202-05A0FE MARN-NNN APRWRANN I

.* I-50. I

Figure 181

I 51

I Hourly-Averaged Cross-Shelf Component (cm/u) at M3

I -50...

-_100.

100.

50.10111.

0.

-100.10. M3 (93m)

I 0. 20 25 30 510 15.0.2 30 .. . .5, 10.. 15, 20,

APR MAY JUN

I Figure 18 (cont.)

Hourly-Averaged Alongshelf Component (cm/s) at M1 and M2

150.100.

50.a0. f l-I

-50.

-100.

-150.

100.

50.0. U111111MAA11hII ~khlfl .Jl

-50.

-200. 3200 M2 (3m)

150.-

100.-

50.30.

-50. 3

.M2 (32m)

50.

0.

-M2 (54m)I50.

0.

FE MAR APRm)

Figure 193

Hourly-Averaged Alorigshelf Component (cm/s) at M1 and M2

100.

50.

0.

-50.

-l00.

- 150.1100.

50.

-50.-

-lao.

200.

IO ,M2 (3m)

100.-

5o.-

0.

j-50.. M2 (32m)

100.

50.

.M2 (54m)

50.L

-50.

10.

20 25 30 *5. .10 15 20 25' 30 5 10 15 20APR MAY JUN

Figure 19 (cont.)

54 .

Hourly-Averaged Alongshelf Component (cm/s) ot k433

200.

150. 1100.

50. 1wA110.

M3 (32m)I

150.

00.

-50.

00.I

50.U1001.20 5 30 5 10 1

.E MAR APRm1

Figure.. 20 15 3 1,''

I5

200

200.

j 150.

100.

50.

0. ri -50.

20.M3 (93m)150.

I 10050.ki

ý50. 1 i . . . . .

20 25 30 5 j 5 20 25 30 5 10 15 20APR MAY JUN

Figure 20 (cont.)

561

PL64 Low-Pass Filtered Water Temperature (*C) at Ml

2.3 m... .......

26.j . . .. ... . .~, . . . . . . . . .. ...... a.10 15 20 25 5 10 15 20 25 30 5 10 15

FEB MAR APR1

30PL64 Low-Pass Filtered Water Temperature (*C) at M2

28. iM3m

24. 4

62mI

.10 15 20 25 5 0 15 2 5 30 5 10 155FEB MAR APR

PL64 Low-Pass Filtered Water Temperature (*C) at M3

28.30m

61mI26.

24.93

22.1

5oi si i 5 10 15 20 25 30 5 10 151

FEB MAR APR

Figure 21I

PL64 Low-Pass Filtered Water Temperature (*C) at M1

I 28. 6

20 25 30 5 ¶0 15 20 25 30 5 10 15 203APR MAY JUN

3 PL64 Low-Pass Filtered Water Temperature (0 )at M230. ..............................................

I 28. 62m

I 26.

I 24.

20 25 30 S. . 10 . 19 20 O . .25 . ..30, 5 10 15 . .20

APR MAY JUN

PL64 Low-Pass Filtered Water Temperature (*C) at M43

I 30

28. -61M

5 93m26.

24.

I 22.

L2. 20 25 30 5 '160 '1 20. 251 30....10..5.20

APR MAY JUN

I Figure 21 (cont.)

58 1II

PL64 Low-Pass Filtered Salinity (psu) at M140.................................... ...... .................. 335.

25. 3m !

2o. 115.

10. 3

t10 15 20 25 5 10 15 20 25 30 5 10 15 I

FEB MAR APR

PL64 Low-Pass Filtered Salinity (psu) at M240.........

62m54m

3m30. -I

25. 120. 515.

10.

10 15 20 25 5 10 15 20 25 30 5 10 15

FEB MAR APR g

IFigure 22 I

59

PL64 Low-Pass Filtered Salinity (psu) at M140 . .......... ..................... ..

35.

30. 16m

25. 3m

20.

15.

10.

.. ............................................25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

PL64 Low-Pass Filtered Salinity (psu) at M240. ................ ............................ ... ..............

35. 62m

30.

25.

20.

15.

20 25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

Figure 22 (cont.)

60 .

Hourly-Averaged Water Temperature (0C) at M1

32. rr.............1V....... II FTT.......................................

M1 3m330.

28.1

26. 130.

.Ml 16m

20. 25 10 15 2 25 30 5 10 1

FEB MAR APR

Figure 2

j 26.

I0

1 30.16

28. -l 16m

20 25j~ j 30 ..5. .10' 15 20 25 30 5' 10' 15' 20'

APR MAY JUN

Fiue2Icn.

621

Hourly-Averaged Water Temperature (*C) at M23

28. 126. 130.

25 M3

26. 130.

.M2 32m3

28.

26.

26.

24.

22. 128.

26.

24.

22. 10 15, 20... 25 1 I . 0..2 . 0 5. 0 1

FEB MAR APR

Figure 24

63

Hourly-Averaged Water Temperature (0 C) at M2

30 . . .I . ., ... ..... . ......... ... . ... .... I

M2 Im

28.

26. L30.

2[M2 3mS~28.

26.30. M2 32m

28.F

26.

24. -28.

M2 54m

26.

24.

2022.52 228.-

26.

S 24. -

22 . . . . . .. . . .2 5 -. . ,'. . . . . . . . . . . . I., . . . . . .,.. . . . ., j225 30 5 1 0 w5 20 25 5 10. .Ii ..20*

APR MAY JUN

Figure 24 (cont.)

641

Hourly-Averaged Water Temperature (0C) at M3

32, ............. ......................................

h43 30m

30..

28.3

26:-

M3 61 m

28. 126. 124.-30. 3

.M3 93m

28. 326. 324. 122.

20.

i-1810 159 20. 25 5. .106 15620 25 305. .10. .15-

FEB MAR APR

Figure 253

I 65

Hourly-Averaged Water Temperature (*C) at M3

IM3 30m

30.

28.-

26.

30.-

M3 613M

28.

26.

24.-

223.

20.

20 - 25 30 5 10 15 20 25 3 5. 10.15L20

APR MAY JUN

I ~Figure 25 (cont..)

66£ °° II

I

IHourly-Averaged Salinity (psu) at M1

25. 320.

15. -10.

5.40. i35.

30. 325.20.. M 1 16m" I

5 10 15 20 25 30 5 10 15

FEB MAR APR 3

IiSII

Figure 26I

67

I

i

Hourly-Averaged Salinity (psu) at M135. M

3 . . .

30.

25.

20.

15.'10.

40.-

35.

30.

25.20. FM1 16m

15. . .. . .. . . . .20 25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

I

Figure 26 (cont.)

681

Hourly-Averaged Salinity (psu) ot M2

40 ................... ............. ...............................

35. 130.

2. M2320.

15.

10.140.

35. 330.

25.

20.

10.

36.50

36.25 336.00

.35.5 - 2 3235.50

35.25 335.00

36.501

36.25

36.00 335.50

35.25 135.00r

36.50 336.25

36.00 335.75

25~i i 30 5 1'0 153

FEB MAR APR

Figure 271

69

Hourly-Averaged Salinity (psu) at M2

40. ............... ... ......................................

1 35.

30.. M2 1m

25..

20.

I 10.15

40.-I ~35.

30. M2 3m25.

20.

15.

10.

36.50

36.25

36.00

35.75 M2 32m

35.50

I 35.25

35.00

I 36.50 -

36.25

I 36.00 .

5 M2 54m

35.25

35.00 -

36.50 .

36.25 "

36.00

35.7535.50 '

20 25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

Figure 27 (cont.)

703

I

IHourly-Averaged Conductivity (s/m) at Ml 3

4.3. 1

2. 31. 16.-

5.3

4. 1

M1 16m

2.10 15 20 25 5 10 15 20 25 30 5 10 15 3FEB MAR APR

FIII

Figure 28 1

71

Hourly-Averaged Conductivity (s/m) at MI

5. Ml 3m

Ii

* 2.

6.

* 4.

M1 16m

20 25 30 5 10 15 20 25 30 5 10 15 20APR MAY JUN

i Figure 28 (cont.)

7/_1

Hourly-Averaged Conductivity (s/rn) at M2

5. 121

3.

2.1

6. 35. 3

4. M2 33.

2.16.00

. M2 32m5.75

5.5 0

5.25L6.00

.M2 54m

5.75 -1......

5.50

5.256.00

.M2 62m

5.75 15.50

5 .2 5 . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . . . . . . .

10 15 20 2 5 10 15 20 25 30 5 10 15'FEB MAR APR3

Figure 29

Hourly-Averaged Conductivity, (s/m) at M2

5.

4. M2 im

3.

2.

6. -

5.

4. M2 3m

3.

2.

6.00

. M2 32m

5.75

5.50

5.256.00-

M2 54m

5.75

5.50

5.256.00

M2 62m

5.75

5.505 .5 ..... .. .... .....20 25 30 5 10 15 20 25 30 5 10 15 20

2 APR MAY JUNFigure 29 (cont.)

741

80. Hourly-Averaged Speed (cm/s) at M2 (62m)

60.1

40.

20.3

01 15 2 25 5 10 1 0 25 30 5' 10' 15 3FEB MAR APR

Hourly-Averaged Speed (cm/s) at M2 (64m)

60.

40. 120.3

10.- 15 20 5 5 10 15 2Ch 25 30 5 10 15 3FEB MAR APR

PL64 Low-Pass Filtered Speed (cm/s) at M2 (62m -solid) and M2 (64m - dash)80.............................................................

60.

40.I

20. -

.1 5 2 5 5 10 1 0 25 30 5' 10 15

FEB MAR APRI

Figure 230

1. 75

I Hourly-Averaged Speed (cm/s) at M2 (62m)

60.

40.

I 20.

0. 20 25 30 10 15 20 25 30 5 10 6 . 15 . ..20'IAPR MAY JUN

IHourly-Averaged Speed (cm/s) at M2 (64m)80.

40.

I 20.

0. 20 25 30 5 10 1 0 25 30 5 10 15 20

A*P'R MAY JUN

I PL64 Low-Pass Filtered Speed (cm/s) at M2 (62m -solid) and M2 (64m - dash)80 ..............................................

1 60.

IJI 20.

2 25 3 5 1520 25 30 5 10 5 20IAPR MAY JUN

I Figure 30 (cont.)

76 3II

Hourly-Averaged Pressure (db) at M2 (62m)57.

158. I59.

60. I61. U

62. 163.1 15 20 25 5 10 15 20 25 30 10 15 1

FEB MAR APR

I3I

IIIII

FJigure 31 3

77

Hourly-Averaged Pressure (db) at M2 (62m)

59.

60.

61. -

62.

63 . . . . . . . . . . .... . . . . . . .. . . . , . . . . . . . . . . . . ..20 25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

IIIIIiII

I Figure 31~ (cont.)

78 3I

IIIUIIIIIIIUIIII

79

IAppendix: Evaluation of the AmasSeds M3 Current Meter Data

I The AmasSeds M3 mooring supported four current meters. There was a WHOI S4current meter measuring speed, direction, and pressure deployed at a static (no mooring

Sdip) depth of 32 m, then three identical Norwegian-built SD2000 current meters deployedat static depths of 30, 61, and 93 m. Mean water depth at the M3 site was approximately103 m. Each SD2000 measured speed, direction and temperature. Two problems with theM3 current meter data are examined below, the impact of mooring tilt on the S4 currentmeasurements and differences in observed currents between the top SD2000 and the S4which were separated by 2.75 mi in the vertical. The S4 current sensors have a cosineresponse in the vertical, thus the recorded S4 speed is equal to the true horizontal speedmultiplied by the cosine of the instrument tilt. This effect can be corrected if an empiricalrelationship between mooring dip and instrument tilt can be established. The SD2000was mounted to its support cage with a universal joint so that the current meter housingwould stay aligned horizontally into the flow independent of the vertical orientation of its

I support rod.

The S4 measured pressure which gives a record of the dip of the M3 mooring in theI strong tidal and NBC flows. Based on this pressure time series during the first 80 days of

deployment when both current meters seemed to function normally (this will be discussedlater), the mean S4 pressure when the S4 speed was less than 60 cm/s (and the mooringis assumed to be upright or close to upright) was subtracted from the original pressuretime series to give the instantaneous dip time series (Figure A1) which shows both thehigh-frequency pressure fluctuations caused by the tides and a larger subtidal variationdue to the subtidal current fluctuations. The maximum surface tide amplitude at M3 isabout 1.4 m based on Flagg and McDowell (1981).

I Using the S4 (32 m) and bottom SD2000 (93 in) current data, simple representa-tive unidirectional velocity profiles were constructed (Table Al) and used as input into astatic mooring dynamics model (Moller, 1976) to develop empirical relationships betweenS4 dip, tilt, and speed for four sets of model drag coefficients (Table A2). Models A-Ddiffer only in the drag coefficient used for the vertical mooring line components (wire rope,

Schain, and nylon) and what percentage of the wire rope was faired. The model results forS4 dip versus speed are shown in Figure A2 superimposed on the S4 data. The close agree-ment between the model A predicted dip and the observed dip suggests that model A isthe most realistic of the four models considered. Model A features a large drag coefficient(cd = 2.6) recently found to be optimal in mooring studies conducted at Bedford Instituteof Oceanography (G. Tupper, persoaal communication). Why this large drag coefficientproduced the most realistic predictions when the M3 wire rope was deployed with fairingis a mystery. Using model A to determine a simple empirical relationship between 54 di1

and tilt, the S4 speed measurement can then be corrected for tilt using the relationships:

I!

1 0(S4 Dip (m)) vs. S4 Speed (cm/s)160..........

140.

120.

100. 380.o ,60.

40. I

0.

-20.

F40.- 5 ... 10 .I 20 25 30 5 1 1FEB MAR APR!

Figure Al: Time series of S4 speed (cm/s) (upper trace) and S4 dip (decimeters) (lowertrace) for entire deployment period.

II

8081

10"(S4 Dip (in)) vs. S4 Speed (cm/s)

160.

40.

I 20.

0.

-20.

20 25 30 5 10 15 20 25 30 5 10 15 20

APR MAY JUN

IIII Figure Al: (cont.)

I

Table Al

Unidirectional Velocity Profiles Used as Input Into Mooring Dynamics 3Model. These profiles were chosen to bracket speeds measured with S4

(32 m) and bottom SD2000 (93 m) in 103 m water depth. For simplicity,model water depth is 100 m.

Profile Speed at Depth Type of INumber 0 m 30 m 100 M Profile

1 0 0 0 No Current I2 86 60 0 Linear3 143 100 0 Linear4 200 140 0 Linear5 60 60 0 Constant/Linear6 100 100 0 Constant/Linear7 140 140 0 Constant/Linear8 60 60 60 Constant/Linear9 100 100 60 Constant/Linear

10 140 140 60 Constant/Linear

11 117 100 60 Linear 312 174 140 60 Linear

U

Table A2 5Variable Parameters for the Mooring Dynamics Model

Model CD Fairing i

A 2.6 None 5B 1.3 None

C 1.3 50%

D 1.3 100% IIII

83

7

6 - _

6 r//

I ...

4 S4Sped/(m/l

A

2-2

-1 0 2 10 4 10 60 80 10'0 120 140 16'0

S4 Speed (cm/s)

Figure A2: Observed and predicted S4 dip plotted as a function of S4 speed. The observeddata were sorted into speed bins and the means and standard deviations of the dip andspeed in each bin computed and plotted. For each model, the results for the set of velocity

profiles (listed in Table Al) have been least-squares fitted with a simple polynomial which

is plotted here with the label A through D.I

IIII

I

84 I

IIIUUIIIIIUIIIIIII

I 85

I 1-dpm/6mif dip < 0,

Cos (tilt)

1 - dip (m)/168 m if dip > 0,

s, = s/cos (tilt) ,

where s, is the corrected speed and s the observed speed. During the first 80 days ofthe S4 time series, the mean and maximum dip and tilt were 2 and 6 m and 8 and 16*,respectively. The mean and maximum correction in speed were 1.3% and 4%.

A comparison of the corrected S4 and top SD2000 current time series (Figure A3)shows a significant difference in speed, with the corrected S4 speed (Ss4) reading greaterthan the SD2000 speed (SSDM2oo) for the first 80 days and then reading less for the final36 days. Linear regression analysis during these two time periods gives

SSD2000 = -11.1 + 0.895 * SS4

(first 80 days, correlation coef. = .921),

SSD2000 = 2.6 + 1.264 * SS 4

(last 36 days, correlation coef. = .885).

To understand individual instrument performance better, the S4 and top SD2000current time series were demodulated with a M2 signal using one day non-overlappingwindows. The semidiurnal tidal currents are aligned primarily in the cross-shelf direction,so demodulation of the cross-shelf current component with M2 determines the daily ampli-tude and phase of the semnidiurnal constituents. The results show the expected spring/neapcycle, but with the maximum amplitudes of the S4 decreasing from about 48-55 cm/s dur-ing the first 80 days to roughly 35-40 cm/s during the rest of the record. The SD2000also exhibited a clear spring/neap cycle during the first 80 days with maximum amplitudesof 28-46 cm/s, but the later behavior was much more erratic with larger maximum am-plitudes ranging up to 58 cm/s. The S4 maximum daily total current variance (roughlytwice the semidiurnal kinetic energy) dropped from about 1600-2000 (cm/s)2 during thefirst 80 days to roughly 600-1000 (cm/s)2 during the rest of the record. Since tidal theorydoes not predict such a large and rapid decrease in semnidiurnal energy, we conclude thatthe significant (order 30-40%) decrease in S4 current speed after the first 80 days is in-strumental. In a similar sense, we also conclude that the increase in SD2000 current speedafter the first 80 days is instrumental. There is no clear way to correct either time seriesso the data presented here contain these instrumental errors.

II

86

IIIII

Speed (cm/s) at 32m I150. -v-M

100.

50.

0. I

-50.Speed Difference (cm/s, 0m-32m),10 15 20 25 5 10 15 20 25 30 5 o 1 1S

FEB MAR APR

III

Figure A3: Time series of S4 corrected speed (upper line) and the difference between thetop SD2000 speed and the S4 corrected speed for the entire deployment period (lower line). 3

II

87

150 Sp eed (c m/s) at' 32m

100 .i

-50.

-5 . Speed Difference (Cm / s) (30m - .32m ). ... . . .20 25 30 5 10 is 20 2 30 5 10 is 20

APR MAY JUN

Figure A3 (cont.)

I DOCUMENT LIBRARY

March 11. 1991

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50272-101

REPORT DOCUMENTATION I 1. REPORT NO. 2, 3. Recipient's Accession No.

PAGE WHOI-92-364. Title and Subtitle S. Report Date

A Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds): Physical Oceanography September 1992

Moored Array Component

7. Author(s) 8. Performing Organization Rept. No.Carol A. Alessi. Steven J. Lentz. Robert C. Beardsley, Belmiro M. Castro and W. Rockwell Geyer WHO[ 92-36

9. Performing Organization Name and Address 10. Project/Task/Work Unit No,

The Woods Hole Oceanographic Institution i. Contrict(C) or Grant(G) No.Woods Hole, Massachusetts 02543 (C) (XO ,88-1 2917,(XE91-15712

(G)

12. Sponsoring Organization Name and Address 13. Type of Report A Period Covered

Funding was provided by the National Science Foundation. Technical Report14.

15. Supplementary Notes

This report should be cited as: Woods Hole (Geanog. Inst. Tech. Rept., W1101-92-36.

16. Abstract (Limit: 200 words)

A Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds) is a coopcrative research progrun by geological. chemic;d.physical, and biological oceanographers from Brazil and the United States to study seditnenutay processes occurring over thecontinental shelf near the mouth of the Amazon River. The physical oceanography component of AmasSeds, included a mooredarray deployed on the continental shelf approximately 300kin northwest of the Amazon River mouth ncar 3.5`N, The mtoorcd arrayconsisted of a cross-shelf transect of three mooring sites located on the 18-m, 65-m, and 103-mn isobaths. The moored array was,deployed for approximately 4 months, from early February, 1990 to mid-June. 1990, obtaining time series ma.,suremctnts of current.temperature, conductivity, and wind This report describes the physical oceanography moored array component and provides' astatistical and graphical summary of the moored observations.

17. Document Analysis a. Descriptors

I. moored oceanographic observations2. Amazon River/ North Brazil Continental Shelf3. AmasSeds (A Multidisciplinary Amazon Shelf SEDiment Study)

b. ldentifiers/Open-Ended Terms

c. COSATI Fleld/Group

18. Availability Statement 19. Security Class (This Report) 21. No. of Pages

Approved for publication; distribution unlimited. UNCLASSIFIEI) 10020. Security Class (This Page) 22. Price

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