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Goddard Space Flight Center

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NIMBUS 7 CZCS

.... C OASTA L ZO N E

C(:_LO R SCAN NER IMAG ERY

for Select,£d Coastal Regions
NIMBUS-7 CZCS

COASTAL ZONE

COLOR SCANNER IMAGERY

for Selected Coastal Regions

North America - Europe

South America - Africa - Antarctica

Level II Photographic Product

N/ A

Goddard Space Flight Center

Prepared under the direction of

Dr. Warren A. Hovis, Chairman

CZCS, Nimbus Experiment Team

Edmund F. Szajna, Sensor Manager

Space and Earth Sciences Directorate

Walter A. Bohan

The Walter A. Bohan Company
Prepared for

National Aeronautics and Space Administration

Goddard Space Flight Center

Space and Earth Sciences Directorate

Greenbelt, MD 20771

by

THE WALTER A. BOHAN COMPANY

2026 OAKTON STREET, PARK RIDGE, ILLINOIS 60068

APPLIED RESEARCH IN SATELLITE METEOROLOGY AND OCEANOGRAPHY

under contract No. NAS 5-29079
CGLgR

Contents

Foreword ........................................................... v

Introduction ....................................................... vii

The Nimbus-7 Coastal Zone Color Scanner (CZCS) ................... ix

The Coastal Zone Color Scanner

Atmospheric Correction Algorithm ............................... xiii

List of Contributors .............................................. xvii

Members of the Nimbus Experiment Team (NET)

for the Coastal Zone Color Scanner (CZCS) ...................... xix

Section 1

Gulf of AlaskaAleutian IslandsBering Sea ....................... 1

1A Gulf of AlaskaAleutian Islands ................................... 3

The Alaskan Stream and Gulf of Alaska Circulation

1B Gulf of AlaskaSoutheast Bering Sea .............................. 7

Sea Surface Turbidity

Section 2

Pacific North American Coast .................................... 11

2A North America West Coast ...................................... 13

Seasonal Development of Coastal Upwelling

2B Vancouver Island ............................................... 21

Coastal Productivity and Dynamic Patterns

2C Northern California/Cape Mendocino ............................. 25

The California Current--A Comparison of False-Color

CZCS Pigment and Thermal Infrared Imagery

2D Central California/Monterey Bay ................................. 29

The California Current Upwelling System

Section 3

Atlantic North American Coast ................................... 33

3A Carolina Capes/Sargasso Sea ..................................... 35

Slope Water/Tidal Mixing/Gulf Stream Meanders and Rings

3B Cape Hatteras/Cape Cod ........................................ 41

Gulf Stream Eddies--Circulation Features

3C Cape Hatteras/Gulf of Maine .................................... 45

Phytoplankton Distribution in Early Spring

3D Cape Hatteras/Sargasso Sea ..................................... 49

The Gulf Stream--A Distinct Ocean Color Front

3E New England Seamount Chain ................................... 53

Effects of the New England Seamount Chain

on Gulf Stream Surface Flow

3F New England Coast ............................................. 57

Enhancement of Phytoplankton Growth by Tidal Mixing

Section 4

Gulf of Mexico/Caribbean Sea ................................... 61

4A Florida West CoastCentral Gulf of Mexico ....................... 63

The Loop Current--Augmentation of Primary Production

4B Gulf of Mexico/Cuba ........................................... 67

The Loop Current/Mesoscale Eddies

111
Section 5

Western European Basin .......................................... 73

5A Celtic SeaBay of Biscay ........................................ 75

Phytoplankton (Coccolithophores)

Section 6

Atlantic South American Coast ................................... 79

6A Amazon River .................................................. 81

The Amazon River Outfall

Section 7

South Africa 85

7A South Africa West Coast ........................................ 87

The Benguela Current Coastal Upwelling

7B South Africa South Coast ....................................... 91

The Agulhas Current--Surface Temperature,

Eddies, Water Content

Section 8

Antarctica .......................................................... 95

8A Drake Passage/Western Scotia Sea ............................... 97

The Polar Front/Cold-Core Rings--Effects on

Abundance and Distribution of Phytoplankton

iv
Foreword

We are presently in an era when new scientific information flows in at a

rate that threatens to overwhelm the student in what, for lack of

constructive processing, is degraded to useless noise. It is important to

assure ourselves from time to time that oceanography retains its rightful

place in the forefront of earth science because the ocean is the only readily

accessible sample for study of the behavior of an extensive liquid on a

whirling globe. To retain its unique place among the welter of spectacular

competing discoveries which relate to assemblages of a range of scale from

the smallest particles to the immense galaxies of outer space and to their

degree of sophistication from mundane to exotic, it will be necessary to

provide and nourish a literature that has sufficient substance to stimulate

the imagination of the keenest scientific minds.

Perusal of this collection of papers will reassure the thoughtful reader

that, at this milestone, oceanography, far from slipping into humdrum

obsolescence, remains vital and is still at the cutting edge of scientific

revelation of the cosmos around us. By way of examples, one can single

out the application of ocean acoustic tomography that realizes a new

three-dimensional representation of the deep sea, and remote sensing that

effects the synchronous charting of extensive areas of the superficial layers

of the ocean from the vantage point of space satellites. This latter ability

frees the perception of the student from the constriction inherent in

anecdotal point-to-point sampling that in the past has been forged by the

narrow field of view available from traditional shipboard observation.

Many descriptions in earlier oceanographic texts, because they are derived

from observations widely differing in times and methods, result in

incongruities. As a result of today's enlarged and refined facilities, smallscale and evanescent events, as well as the interrelations of patterns

separated in space and time now emerge so that, little by little, the

complexity of the world seas is unfolding. Many areas that until recently

belonged to the "mare incognita" are now part of the immediate coherent

cognizance of oceanographers. Thanks in part to this integration of

perception, the progress of the science is assured. The outlook is indeed

promising.

Gifford C. Ewing

v
ORIGINAL PAGE IS

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Introduction

Global observations from earth-orbiting satellites began in the 1960's

with imagers utilizing vidicons for cloud imagery to study the dynamic

motions for meteorological purposes. Oceans were observed, but only the

brightest features such as river plumes were observable with these early

sensors. Even then it was obvious that satellites presented an opportunity

to study the vast areas of the oceans in a manner and timeframe impossible

with ships or aircraft, since an area of 250,000 square miles could be

observed in one minute. Development of improved optical sensors

paralleled an increase in interest by oceanographers in studying oceans

from space. Ship and aircraft ocean color measurements showed that

ocean color could be related to water content in a meaningful way, and

that the effects of interference by atmospheric backscatter of sunlight

could be overcome. These developments led to an opportunity in the early

1970's where scientific interest, sensor technology, availability of a nearideal spacecraft, and recognition of the potential benefits by NASA gave

birth to the Coastal Zone Color Scanner (CZCS) program.

The CZCS sensor utilizes scanning techniques developed for

meteorological and earth resources purposes modified to add a tilt

capability to avoid glint, and with spectral bands and dynamic ranges

optimized for ocean color. Details of the sensor characteristics are given

by Hovis et al. (1980). A scheme to remove the interfering effects of the

atmosphere, Rayleigh and aerosol backscatter, was developed by

members of the CZCS Nimbus Experiment Team (NET) Gordon et al.

(1980) and Gordon et al. (1983). This atmospheric correction scheme is the

most unique element of the CZCS program, and makes possible the results

shown in this atlas.

The atlas is intended to provide interpretations of CZCS products from

the viewpoints of a wide range of oceanographic scientists as an

introduction for those not already familiar with the potential of space for

such information gathering. Experience has shown that each scientist who

examines a CZCS product sees something unique based on his own

experience. It is the goal of the atlas and the CZCS NET to introduce these

products to the widest possible spectrum of users and assist them in

acquiring and interpreting the data. To that end, the data is deposited in a

public archive, the Satellite Data Services Division of NOAA, NESDIS,

with no restriction on its dissemination except the modest cost of

reproduction. A list of the NET members and the address of the archive is

found on page xix.

PRECEDING PAGE BLANK NOT FILIM'%_

Warren A. Hovis, Chairman

CZCS, Nimbus Experiment Team

_A|[ V I.... INTENT!ON_Lb¥ BLANll

References

Gordon, H. R., D. K. Clark, J. L. Mueller, and W. A. Hovis, 1980: Phytoplankton

pigments from the Nimbus-7 Coastal Zone Color Scanner: Comparisons with surface

measurements. Science, 210, 63-66.

Gordon, H. R., D. K. Clark, J. W. Brown, O. B. Brown, R. H. Evans, and W. W.

Broenkow, 1983: Phytoplankton pigment concentrations in the Middle Atlantic Bight:

Comparison of ship determinations and CZCS estimates. Applied Optics, 22, 20 36.

Hovis, W. A., D. K. Clark, F. Anderson, R. W. Austin, W. H. Wilson, E. T. Baker, D. Ball,

H. R. Gordon, J. L. Mueller, S. Z. E1-Sayed, B. Sturm, R. C. Wrigley, and C. S.

Yentsch, 1980:Nimbus-7 Coastal Zone Color Scanner: System description and initial

imagery. Science, 210, 60 63.

_____ ..... vii
The Nimbus-7 Coastal Zone Color Scanner

(CZCS)

The Coastal Zone Color Scanner (CZCS) is the first spacecraft

instrument devoted to the measurement of ocean color. Although

instruments on other satellites have sensed ocean color, their spectral

bands, spatial resolution, and dynamic range were optimized for

geographical or meteorological use. In the CZCS, every parameter is

optimized for use over water to the exclusion of any other type of sensing.

The signal-to-noise ratios in the spectral channels sensing reflected solar

radiance are higher than those required in the past. These ratios need to be

high because the ocean is such a poor reflecting surface that the majority of

the signal seen by the reflected energy channels at spacecraft altitudes is

backscattered solar radiation from the atmosphere rather than reflected

solar energy from the ocean.

The CZCS is a conventional multi-channel scanning radiometer

utilizing a rotating plane mirror at a 45 degree angle to the optic axis of a

Cassegrain telescope. The rotating mirror scans 360 degrees, however,

only 80 degrees of data centered on the spacecraft nadir is collected for

ocean color measurements. During the rest of the scan, the instrument

acquires a view of deep space and of internal instrument sources for

calibration of the various channels. Spatial resolution, at spacecraft nadir,

is 825 × 825 meters with some degradation at the edges of the scan swath.

The useful swath width from a spacecraft altitude of 955 km is 1600 km.

oRECEDING PAGE BLANK NOT FILMED

p_ _/III ,,,, ,...i i|ON_,_kl,_ BLANK

ix
The CZCS has six spectral bands, five sensing backscattered solar

radiance and one sensing emitted thermal radiance. Table 1 shows the

center wavelengths, the spectral bandwidths, and the minimum signal-tonoise ratio specified for the instrument at the most sensitive gain setting;

that is, the gain setting that would be used for the darkest targets. The first

four channels were selected to cover specific absorption bands and the socalled hinge point. These channels are meant to look at water only and

saturate when the field of view is over land surfaces and clouds. The

spectral response of Channels 1 through 5 is illustrated in Figure 1.

Table 1. CZCS Performance Parameters.

Performance

Parameters 1 2

Scientific Observation Chlorophyll Chlorophyll

Absorption Correlation

Center Wavelength 0.443 0.520

X Micrometers (blue) (green)

Spectral Bandwidth 0.433 - 0.510 -

AX Micrometers 0.453 0.530

Instantaneous Field

of View (1FOV)

Channels

3 4

Yellow Chlorophyll

Stuff Absorption

0.550 0.670

(yellow) (red)

0540 - 0.660 -

0.560 0.680

0.865 x 0865 Milliradians

(0.825 x 0.825 km at sea level)

5 6

Surface Surface

Vegetation Temperature

0.750 11,5

(far red) (infrared)

0.700 -- 10.5 -

0.800 12.5

Co-registration

at NADIR <0.15 Milliradians

Accuracy of Viewing

Position Information <2.0 Mil[iradians

at NADIR

Signal to Noise >150 >140 >125 >100

P, atio (min.) at at at at at

Radiance Input 5.4I 3.50 2.86 1.34

N< (mW/cm 2 • STER • /lm)

Consecutive

Scan Overlap 25%

>100 NE-FD of

at 0.220°K at

10.8 270°K

Modulation Transfer t at 150 knl target size, 0.35 rain. at 0.825 km target size

Function (MTF)

Figure 1. CZCS Spectral Response for Channels 1-5.

10

9

8

7

6

5

4

3

2

1

0

/

I S (nm, 7AVELEN?TH

420 460 500 540 580 620 660 700 740 780 820

Channel 5 has the same spectral response as Channel 6 of the Landsat

multi-spectral scanner series. The gain of Channel 5 is fixed and set to

produce the same percentage of maximum signal over land targets as the

Landsat Channel 6. However, the actual radiance for saturation is higher

since the Nimbus-7 spacecraft crosses the Equator at high noon whereas

Landsat crosses the Equator at 9:30 a.m. local time.

The CZCS Channel 6 (10.5 to 12.5 #m) measures equivalent blackbody

temperature as seen by the sensor with a moist equivalent temperature

difference of less than 0.35 ° K at 270 ° K. Atmospheric interference with

this channel, principally from weak water vapor absorption in the 10.5 to

X
12.5 /zm region, can produce measurement errors of several degrees.

Temperature gradients, however, should be seen quite well because of the

extremely low moist equivalent temperature difference of this sensor.

Channel 6 senses equivalent blackbody temperature with the same spatial

resolution as the other channels and is co-registered with those channel s.

All channels of the CZCS instrument operate simultaneously. During

daytime operations all six channels provide useful information. If the

sensor operates at night, only data from Channel 6 is usable.

The CZCS has considerable flexibility built-in to accommodate a wide

range of conditions. The first four spectral bands, for instance, have four

separate gains that change, on command, to accommodate the range of

sun angles observed during the complete orbit and throughout the various

seasons. The gains are changed to utilize the best dynamic range possible

without saturating over-water targets. Normally, the gain used in the first

four channels is determined by the solar elevation angle of the target to be

acquired. When a special circumstance is expected, such as a particularly

bright material in the water, the gain can be changed to accommodate the

special circumstances.

In addition to gain change, the CZCS scan mirror can be tilted from

nadir to look either forward or behind the spacecraft line of flight. It can

tilt in two degree increments, up to twenty degrees in either direction. This

feature was built into the instrument to avoid the glint caused by capillary

waves on the ocean that would obscure any scattering from below the

surface. The angle of tilt of the scan mirror is determined by the solar

elevation angle. It is normally tilted to avoid sunglint and would only be

commanded to look into the glint for a special sunglint study.

Since Nimbus-7 orbits from south to north in daylight, the scan mirror

is positioned to look behind the satellite when the spacecraft is south of the

subsolar point and ahead of the spacecraft when it is north of the subsolar

point. Tilt and gain setting information is transmitted with the CZCS data

and is part of the data product records.

To improve the instrument response to ocean color, a DC offset can be

inserted into the on-board processing of the radiance measured in the first

four bands. In the DC offset mode, the entire digital capability of the onboard digitizer is utilized to cover approximately the top 30 percent of the

signal which contains modulation due to change in ocean color. Since the

knowledge of the exact amount of the offset eliminated in the on-board

processing is always known, it can be reinserted where needed for

processing on the ground.

The sensor is turned on in sufficient time prior to collection of data to

allow for instrument warm-up and for the sensor to stabilize. Since all

channels are calibrated continuously during flight, any effect of turn-on

transient should be noticed immediately.

The most important aspect to be understood about the CZCS operation

is that data acquisition is limited, due to spacecraft power constraints, to

approximately two hours per day. Because of this operational limit, data

must be taken in carefully preselected locations. Minimum on-off data

taking time is a two-minute segment. Frequently, longer segments are

taken--up to a maximum of ten minutes of continuous data.

The CZCS data is transmitted from the spacecraft to ground receiving

stations at a rate of 800 kb either in real time or in playback of the tape

recorder. Whenever possible the data is recorded in real time. However,

when a satellite is out of the range of tracking stations, the data is recorded

on an on-board tape recorder. These tapes contain both radiometric

information from the imagery and CZCS housekeeping information.

xi
The Coastal Zone Color Scanner

Atmospheric Correction Algorithm

Warren A. Hovis, Chairman

CZCS Nimbus Experiment Team

Structure that can be clearly seen in the water in the Level II data

product from the Coastal Zone Color Scanner (CZCS) is quite frequently

not obvious in the Level I data product where only an approximate

Rayleigh correction for the atmosphere is carried out to increase contrast.

A scene from 10 June 1979, off the East Coast, is shown in both the Level !

and Level II products (pages xiv and xv), illustrating the power of the

atmospheric correction algorithm. The difficulty in estimating what the

final product will look like before applying the complete atmospheric

correction technique is obvious.

PRECEDING PAGE BLANK NOT _ILMED

_J_ll_ _/_,11,,INIEIwTiONALLYBLANI_ xiii
OR{GrNAZ PAOZ

.OE POOR QUALITY

86H +

+

Nimbus-7. Orbit 3171. 10 June 1979. CZCS Level I Images.
An Example of the Coastal Zone Color Scanner

Atmospheric Correction Algorithm Capability

A number of observers utilizing CZCS data have been confused by the

fact that structure in the water that can be seen quite clearly on one day,

may not be so clearly identifiable on images taken on successive days. One

problem is that when the area in question is directly, or nearly directly,

below the subsatellite track, the sensor is viewing the area through the

minimum atmosphere. The same area may be visible several days after, but

the atmospheric attenuation will increase as the path length increases since

the scanner can scan out to 40 degrees either side of the spacecraft nadir. In

some cases, scenes are not selected for Level II processing because of an

apparent lack of information in the Level I data. The Level I image on this

page is the only Level I image shown in this atlas; however, Level I images

constitute the major archive from which scenes are selected for Level II

processing. Potential investigators should understand the characteristics

of the Level I data.

The technique for processing the Level I data to remove the atmospheric

effect has been described extensively by Gordon (1978 and 1981a), and

Gordon et al. (1979), and is used by NASA in the production of all of the

Level II imagery. The Level I image shown on this page appears to contain

very little ocean content information along the East Coast, which is

obscured by a light aerosol band extending from the area of the mouth of

Chesapeake Bay, over Cape Cod, and into the Gulf of Maine. This scene

would probably have not been selected for Level II processing except that

there was a ship operating in the area outside of the light aerosol bank

along the East Coast during the validation phase of the CZCS program,

and it was desirable to produce the Level II for that area of the image that

appeared to be clear. The Level II image (opposite page), presented in the

conventional Level II format, shows the amount of detail that can be

extracted from the Level I data after application of the atmospheric

algorithm. Very little evidence of the light aerosol bank is seen at all, and

considerable structures are seen in the water in both pigment and diffuse

attenuation coefficient imagery. This case should be kept in mind before

rejecting any of the Level I imagery for conversion to Level II when the

scene is of great interest and yet appears to show little detail in Level I.

Unless the Level I data is saturated, in which case no correction will be

successful, there is the potential of extracting information such as that

shown in this remarkable case.

References

Gordon, H. R., 1978: Removal of atmospheric effects from satellite imagery of the oceans.

Applied Optics, 17, 1631-1636.

, 198 la: a preliminary assessment of the Nimbus-7 CZCS atmospheric correction

algorithm in a horizontally inhomogeneous atmosphere. In Oceanography from Space,

edited by J. F. R. Gower, Plenum Press, New York, 257--266.

Gordon, a. R., J. L. Mueller, and R. C. Wrigley, 1979: Atmospheric correction of

Nimbus-7 Coastal Zone Color Scanner imagery, Presented at IFAORS Workshop on

Interpretation of Remotely Sensed Data, Williamsburg, VA, May 23--25 (also in

Remote Sensing of Oceans and Atmospheres, edited by a. Deepak, Academic Press,

New York, 1980).

xiv
ORIGINAl; PAGE IS

OF POOR QUALITY

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Nimbus-7. Orbit 3171. 10 June 1979. CZCS Level II Images.

XV
List of Contributors

Mark R. Abbott

Jet Propulsion Laboratory

California Institute of Technology

4800 Oak Grove Drive

Pasadena, CA 91106

and

Scripps Institution of Oceanography

University of California, San Diego

La Jolia, CA 92093

Frank P. Anderson

National Research Institute for Oceanology

Council for Scientific and Industrial Research

P.O. Box 320

Stellenbosch 7600

South Africa

Edward T. Baker

Pacific Marine Environmental Laboratory/NOAA

7600 Sand Point Way, N.E.

Seattle, WA 98115

Robert L. Bernstein

Scripps Institution of Oceanography

University of California, San Diego

La Jolla, CA 92093

William W. Broenkow

Moss Landing Marine Laboratory

P.O. Box 223

Moss Landing, CA 95039

Ken L. Denman

Institute of Ocean Sciences

P.O. Box 6000

9860 West Saanich Road

Sidney, B.C. V8L 4B2

Canada

Sayed Z. El-Sayed

Department of Oceanography

Texas A&M University

College Station, TX 77843

James F. R. Gower

Institute of Ocean Sciences

P.O. Box 6000

9860 West Saanich Road

Sidney, B.C. V8L 4B2

Canada

Eileen E. Hofmann

Department of Oceanography

Texas A&M University

College Station, TX 77843

Patrick M. Holligan

Marine Biological Association

Citadel Hill

Plymouth PL1 2PB

United Kingdom

PAGE _/_VI INTENTIONALLY BLANK

Takashi Ichiye

Department of Oceanography

Texas A&M University

College Station, TX 77843

Donald B. Olson

Rosenstiel School of Marine and

Atmospheric Science

University of Miami

4600 Rickenbacker Causeway

Miami, FL 33149

Thomas C. Royer

Institute of Marine Science

University of Alaska

Fairbanks, AK 99701

Eckart H. Schumann

Department of Oceanography

University of Port Elizabeth

P.O. Box 1600

Port Elizabeth 6000

South Africa

L. Vere Shannon

Sea Fisheries Research Institute

Private Bag X2

Rogge Bay 8012

Cape Town

South Africa

Charles C. Trees

Department of Oceanography

Texas A&M University

College Station, TX 77843

Michel Viollier

Station d'Oc6anologie et de Biologie Marine

Place Georges Teissier

F-29211 Roscoff

France

Robert C. Wrigley

Ames Research Center/NASA

Mail Stop 242-4

Moffett Field, CA 94035

Charles S. Yentsch

Bigelow Laboratory of Ocean Sciences

McKown Point

West Boothbay Harbor, ME 04574

_EDING PAGE BLANK NOT FIL_

xvii
Members of the Nimbus Experiment Team (NET)

for the Coastal Zone Color Scanner (CZCS)

Dr. Warren A. Hovis, Chairman

CZCS, Nimbus Experiment Team

Dr. Frank P. Anderson

National Research Institute for Oceanology

Council for Scientific & Industrial Research

P.O. Box 320, Stellenbosch 7600

South Africa

202-362-8805 (South African Embassy

in Washington, D.C.)

Dr. John Apel

Applied Physics Laboratory

The Johns Hopkins University

Laurel, MD 20707

301-953-5038

Mr. Roswell W. Austin

Visibility Laboratory P003

Scripps Institution of Oceanography

University of California, San Diego

La Jolla, CA 92093

619-294-3680

Dr. Edward T. Baker

Pacific Marine Environmental Laboratory/NOAA

NOAA Building Number 32

7600 Sand Point Way, N.E.

Seattle, WA 98115

FTS8-446-6251

Mr. Dennis K. Clark

NOAA/NESDIS

Oceanic Sciences Branch

Suitland Professional Center

Room 310

Washington, D.C. 20"233

301-763-4244

Dr. Sayed Z. EI-Sayed

Texas A&M University

Department of Oceanography

College Station, TX 77843

409-845-2134

Dr. Howard R. Gordon

Physics Department

University of Miami

P.O. Box 248046

Coral Gables, FL 33124

305-284-2323

Dr. James L. Mueller

U.S. Naval Post Graduate School

Department of Oceanography

Monterey, CA 93940

408-646-3266

Dr. Boris Sturm

Commisione delle Comunita Europee

2102 Centro Euratom di Ispra

Ispra, Italy

(0332) 780131/780271

Mr. Robert C. Wrigley

Ames Research Center/NASA

Mail Stop 242-4

Moffett Field, CA 94035

415-694-6060

Mr. Charles S. Yentsch

Director of Research

Bigelow Laboratory of Ocean Sciences

McKown Point

West Boothbay Harbor, ME 04574

207-633-2173

CZCS Archive

Mr. Carroll A. Hood

NOAA/NESDIS

Satellite Data Services Division

World Weather Building

Room 100

Washington, D.C. 20233

301-763-8111

PRFA)EDING PAGEI BLANK NOT FILMED

PAGL_INTENftOi¢_qLt_ _t_ xix
Section l

Gulf of Alaska/Aleutian Islands/Bering Sea

1A Gulf of Alaska/Aleutian Islands

The Alaskan Stream and Gulf of Alaska Circulation

Gower and Royer ............................................... 3

1B Gulf of AlaskaSoutheast Bering Sea

Sea Surface Turbidity

Baker .......................................................... 7
1A Gulf of Alaska/Aleutian Islands

James F. R. Gower

Institute of Ocean Sciences

Sidney, B.C., Canada

and

Thomas C. Royer

Institute of Marine Science

University of Alaska

Fairbanks, Alaska

The relatively fresh surface water of the Gulf of Alaska converges into

the Alaska Current and then flows out into the Pacific via the Alaskan

Stream, a narrow boundary current that follows the continental slope

along the southeast side of the Aleutian Island chain.

The following two CZCS images present rare glimpses of the flow

pattern in the Gulf of Alaska. They show the convergent flow of water into

the Alaska Current and Alaskan Stream; the movement of the stream

along the continental shelf breakoff, the Alaska Peninsula, and the

Aleutian Island arc; and the onset of eddy formation south of Unalaska

Island.

Areas of high productivity are shown by the high pigment

concentrations on the continental shelf near Kodiak Island. Flow features

close to the coast, in and to the east of Cook Inlet, are traced out by

patterns of river and glacial silt introduced by the high run-off

characteristic of the region.

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5 -

N

ORBIT c47=nq _..__o., 10JIJLTq............ ";""-:(-UU, FI TI:_-:, 2210i-!Fi ':]t"iT GAIN 1-4=2 THF.'.E::.-I:HOLf-I OFF TILT ANGLE (_! I('_]

GRID CENTER DATA" 22F_4.93_GHT 5":l''"----I_L"I 16T'L----"TN::.]:l__lNEL --;'(5AZ 152 ROLL --i--!'£ PITCH --iZ.1"i-1"r"AN _Zl,2

+ 2 +

I I I I I I I I I I I I

5

9

N

1T6N ....................... i + ! 2 +

F'I GHENT

t i

15_rN

PIGHENT IN HILLIGRaii&...'HETERS_3

0 .06 .08 .12 .19 .2T •39 .ST .83 i ..>8 2. ii 3.46 5.69 9.35 11.98 25.25 .32.0

ALGORITHI'tS: 01 00 00 00 00 02 01 00 .80 00

56T SCAN LINES PROCE:SSED 0 :SCANLINES HI:S::S:ING

CIF' 'v'ER CRT NC, I-iF'S 'v'ER :S:F'EE:.# FRAME #

V810528 ZEst6::.01- 'v'8.;O5,.J1 FTgZO"K_. ZGO4620£A

4-2. Nimbus-7. Orbit 3589. 10 July 1979. CZCS Pigment Image.

: FOLboaT .Ftt_iil_
O_ _{_R QUALITY

The Alaskan Stream and Gulf of Alaska Circulation

July and September 1979

The waters of the northern Gulf of Alaska contain very large acrossshelf gradients of salinity caused by the high influx of fresh water along the

British Columbia and Alaska coasts. This influx alters the vertical density

gradients, resulting in contrast in surface temperature and phytoplankton

concentration. Near the coasts the suspended sediments brought in by the

fresh water also result in strong but smaller scale ocean color differences.

Persistent cloud cover in this area makes successful satellite imaging a

rare event. For thermal infrared images the horizontal temperature

contrasts are low, usually covering a range of 1 ° to 2 ° C, making it difficult

to trace ocean features. The CZCS ocean color (pigment) images, by

contrast, show dramatic flow features traced by the varying

phytoplankton concentrations in the stratified Gulf of Alaska water.

The CZCS pigment image on 10 July (4-2) covers a small strip of the

northeast Pacific Ocean along the southern edge of the Aleutian Island

chain (4-1). The image shows the surface ocean color structure associated

with the Alaskan Stream in terms of pigment level variations in the range

of 0.4 to 1.0 mg m -3. Some of the Aleutian Islands appear as black areas in

the image; others are covered by clouds and cannot be identified.

However, most of the southeastern coasts of the Aleutian Island chain in

the right half of the image are cloud-free.

The Alaskan Stream is the major current by which water leaves the Gulf

of Alaska. It flows westward as a narrow jet along the continental slope,

between 200 m and 2,000 m (4-1). The stream structure visible in the image

(4-2) confirms the narrow (60 km) width deduced by Royer (1981) from

hydrographic observations, and shows the start of a recirculating eddy

near the bottom center of the image, south of Unalaska Island. Such

recirculation, in which Gulf of Alaska water mixes into the Pacific Ocean,

has been deduced to occur within a range of longitudes as discussed by

Thomson (1972). The position of this eddy is at the start of this range and

near the position for the start of recirculation reported by Wright (1981),

for March 1980. Eddies of this type are of great interest and were, for

example, the subject of a 30-day cruise in 1981. Such images, if taken

immediately before and during such a cruise, would be very valuable both

for the planning of the cruise and for the subsequent data analysis.

The CZCS pigment image on 6 September (5-2), shows turbulent

patterns traced out by varying phytoplankton pigment concentrations

over a large area of the Gulf of Alaska. The patterns are distorted by the

convergent flow of the surface water into the Alaska Current. It is this

current which moves across the middle of the image from right to left

following the 2,000-m contour on the shelf break (5-1), and converges into

the Alaskan Stream to the west. The indicated pigment levels and the flow

pattern on the left side of the image are very similar to those in 4-2, which

shows the same area two months earlier.

A solid cloud layer covers the far left side of the image, and there are

cloud bands and cloud lines across the right side (compare with 5-1).

Patches of clouds confuse the coastline, especially near the upper right

corner. Streaks of thinner clouds are not perfectly masked to black north

of the Alaska Peninsula in this example, and some of the more linear light

features in the center of the image are of atmospheric origin.

Light tones in the upper right area of image 5-2 indicate the areas of high

chlorophyll content on the continental shelf southwest and northeast of

Kodiak Island and near Middleton Island. Shoals in those areas cause

vertical mixing, allowing nutrient-rich water to be brought to the surface.

4 _LI)OUT : FR_I_4t]_
13I_GINAL PAGE IS

1TON + 2 + I_+N

- I I /

164N + 2 +

cloud

patches

142N

5-1. Locator Map for 5-2.

ITON

ORBIT 84390 86SEPT9 211850 TO 212058 GHT GAIN 1-4=3 THRESHOLD OFF TILT ANGLE 0.0

GRID CENTER DATA: 211951 GMT 55.GBN 155.82N SUN EL 39 AZ IGO ROLL -0.0 PITCH 0.0 YAW 0.4

+ 2 + 144N

PIGMENT IN HILLIGRAHS./METERS_7

0 .OG .08 .12 .19 .2T .39 .ST

ALGORITHMS: 02 Ol Ol 00 00 Og 02 00 00 00

96g SCAN LINES F'ROCESSED T SCAN LINES HISSING

PIGMENT

•83 i .28 2 .ii 3.46 5.69 9.35 ii .98 2S .25 32.0

CIP VER CRT NO DPS VER SPEC. # FRAME #

V ZE712341 V821015 FTg20+O ZG312311

5-2. Nimbus-7. Orbit 4390. 6 September 1979. CZCS Pigment Image. (M-Middleton Is., K-Kayak Is.)
The resulting high productivity supports the valuable fisheries of the area.

The patchiness illustrated here is, in general, similar to the variations in

benthic marine populations.

Patterns resulting from flow of water from these areas into the westward

Alaska Current along the shelf break can also be identified in the image.

Off Kodiak Island, the flow is converging from a broader eastern

boundary current into the swift (speeds >1 m s-l), narrow, western

boundary current of the Alaskan Stream (Royer, 1981). Further

convergence is apparent as the flow continues to the southwest.

Because of the high coastal runoff to the east of Kodiak Island, gray

tones in the image near this coast will be affected by river and glacial silt as

well as by phytoplankton pigment concentrations. Features of the

nearshore circulation are thus made visible on the image.

The narrow Alaska Coastal Current (<20 km wide) can be seen adjacent

to Kayak Island as a lighter tone due to large silt loads from glaciers

(Malaspina Glacier and others). At the southwest tip of the island the flow

bifurcates. A portion joins the Alaska Current, flowing westward along

the shelf break, while the rest flows into a cyclonic pattern behind the

island (arrows, 5-1). This nearshore flow is joined by the silt-laden Copper

River water (white) and flows westward into Prince William Sound where

additional, less silty water enters to cover the Copper River water. This

nearshore circulation has been identified by satellite-tracked drifting

buoys (Royer et aL, 1979). The nearshore water of the Alaska Coastal

Current leaves Prince William Sound and brings nutrient-rich water to the

shelf fisheries east of Kodiak Island. From the image, it can be seen that

part of the coastal current enters Cook Inlet through the Kennedy

Entrance. Within Cook Inlet, light tones are caused by the high silt

concentrations from the Susitna and Mastanuska Rivers. There is little

evidence of the Alaska Coastal Current to the west of Kodiak Island since

the fresh water influx is small.

References

Royer, T. C., 1981: Baroclinic transport in the Gulf of Alaska. Parts I and II. J. Marine

Res., 39, 239 266.

Royer, Y. C., D. V. Hansen, and D. J. Pashinski, 1979: Coastal flow in the northern Gulf of

Alaska as observed by dynamic topography and satellite-tracked drogued drift buoys.

J. Phys. Oceanogr., 9, 785-801.

Thomson, R. E., 1972: On the Alaskan Stream. J. Phys. Oceanogr., 2, 363-371.

Wright, C., 1981: Observations of the Alaskan Stream during 1980. NOAA Technical

Memorandum ERL PMEL-23.

5
1B Gulf of Alaska/Southeast Bering Sea

Edward T. Baker

Pacific Marine Environmental Laboratory/NOAA

Seattle, Washington

Circulation in the northeast Gulf of Alaska is dominated by the eastern

and northern limbs of the North Pacific subarctic gyre. The broad and

sluggish eastern limb narrows, deepens, and accelerates near the head of

the gulf, turning westward to flow south of Kodiak Island and the Alaska

Peninsula as the Alaskan Stream.

In the southeastern Bering Sea, circulation patterns and hydrographic

domains are bathymetrically controlled. A hydrographic front

approximately coincident with the 50-m isobath separates well-mixed and

turbid inshore water from stratified, less turbid offshore water.

t_RECED[NG PAG_ _LANK NOT F_

PAGE 6 INTENTIONALLY
Sea Surface Turbidity

September 1979

The northeastern Gulf of Alaska is bordered by mountainous coastline

containing numerous glaciers, rivers, and streams which deliver large

quantities of suspended material to the gulf during the summer when

maximum discharge occurs. A CZCS image of the diffuse attenuation

coefficient of the area from late summer (9-2) illustrates various processes

that transport this coastally derived material offshore. (The diffuse

attenuation coefficient image is used instead of the pigment image due to

the preponderance of inorganic material in Alaskan coastal waters.) The

image also illustrates what appear to be streamlines of the Alaska Current,

the northern portion of the subarctic gyre that sweeps through the gulf

with peak surface speeds of 100 cm s-L

Inspection of the CZCS image of the Alaskan coast in the region around

Kayak Island (see locator map 9-1) reveals a prominent plume of turbid

coastal water deflected offshore in an anticyclonic gyre created by

impingement of the Alaska Current on Kayak Island. Similar offshore

transport of suspended particles occurs on the south side of Montague

Island, although in this image clouds obscure much of that area. These

coastal processes provide large quantities of material to the Alaska

Current for westward transport.

West of Montague Island, the continental shelf widens and forces the

northern border of the Alaska Current southward. West of Kodiak Island,

the broad sweep of the Alaska Current in the eastern gulf coalesces into a

relatively narrow, fast-flowing current, with sharply defined borders,

called the Alaskan Stream. Although no synchronous hydrographic data

is available for this image, historical observations suggest that the sharp

ocean color gradient (dashed line-G) may indicate the southern limit of the

Alaska Current/Alaskan Stream.

The CZCS image of the westward flowing Alaska Current/Alaskan

Stream presents markedly different flow characteristics than eastward

flowing boundary currents such as the Gulf Stream or the Kuroshio.

Streamlines of the Alaskan currents (not shown) are relatively organized

and show little indication of the multiple meanders and extensive eddy

formation observed in the Gulf Stream. Theoretical considerations based

on vorticity conservation predict multiple wavelike features in the flow

pattern of prograde flows (depth decreases to the left looking downstream)

such as the Gulf Stream but not in retrograde flows (depth decreases to the

right looking downstream) such as the Alaskan currents; CZCS imagery

of these two current systems support those predictions.

In the southeastern Bering Sea, a change in the degree of vertical

mixing, occurring at roughly the 50-m isobath (9-1), controls the areal

distribution of both hydrographic properties and suspended particles.

Inshore of the 50-m isobath, the water column is typically well-mixed and

alongshore distribution of local sediment sources produces high turbidity

levels and sharp offshore gradients. In the CZCS image, the-diffuse

attenuation coefficient decreases abruptly seaward of this frontal zone,

particularly along the Alaska Peninsula. Unlike the coast of the Gulf of

Alaska, water flow on the north shore of the Alaska Peninsula is tidally

dominated and mean flow is very weak. Offshore transport of suspended

particles by advection rarely occurs. Loss of suspended particles from the

nearshore zone is largely by seaward diffusion; therefore, offshore

gradients are steep.
ORIGINAL PAGE _

OF POOR QUALITY

1TON + 2 + 144N

Bering Sea • Inlet

9-1. Locator Map for 9-2.

ORBIT 04_90 06SEPT9 211850 TO 212050 GMT GAIN 1-4=3 THRESHOLD OFF TILT ANGLE 0.0

GRID CENTER DATA: 211951 GHT 55.68N 155.82N SUN EL 39 AZ 160 ROLL -0.0 PITCH 0.0 YAH 0.4

ITON + 2 4 144N

I ! I | I I I

5

o

N i i i , i i ..... i i i i i i

164N + 2 + 142N

DIFFUSE ATTENUATION COEFFICIENT

DIFFUSE ATTENUATION COEFFICIENT IN HETERS_-I

e @28 .OS4 .e41: ,eSe ,_61. @75 ,e9£ , 112 ,_....... zv • _._T _ .8e4 ._o4_q.... 304 .3T1 .453 .500

ALGORITHHS: 02 01 01 00 00 03 02 00 00 00 CIP VER CRT NO DPS VER SPEC, # FRAHE #

963 SCAN LINES PROCESSED T SCAN LINES HISSING V ZE312341 V821015 FT32040 ZG312341

9-2. Nimbus-7. Orbit 4390. 6 September 1979. CZCS Diffuse Attenuation Coefficient Image.
Section 2

Pacific North American Coast

2A North America West Coast

Coastal Upwelling

Bernstein ...................................................... 13

2B Vancouver Island

Coastal Productivity and Dynamic Patterns

Gower and Denman ............................................ 21

2C Northern California/Cape Mendocino

The California Current--A Comparison of False-Color

CZCS Pigment and Thermal Infrared Imagery

Abbott ........................................................ 25

2D Central CaliforniaMonterey Bay

The California Current Upwelling System

Wrigley and Broenkow ......................................... 29

PRECEDING PACE _LANK NOT FrLMED

II
2A North America West Coast

Robert L. Bernstein

Scripps Institution of Oceanography

University of California, San Diego

La Jolla, California

When coastal winds change from wintertime westerly or southwesterly

to summertime northerly along the North American west coast, surface

water is driven southward and offshore. Cooler, nutrient-rich waters

underneath are brought to the surface, creating conditions favorable for

phytoplankton growth. Thus during summer, cool, green water (high

chlorophyll pigment levels) is clearly detected by sensors operating in the

blue-green and thermal infrared portions of the spectrum. The earliest

seasonal development of upwelling occurs in the spring along Baja

California, and peaks later as one proceeds north toward Vancouver

Island. The process usually reaches its maximum amplitude in July along

the central and northern California coast.

?RECEDING PAGE BLANK NOT FILMED

• mI_DiNG PAGE BL_K NOT :PILMED

eAB.E ],:'_'-- iNIENTION_ALI-¥ BLANK

13
Seasonal Development of Coastal Upwelling

March-July 19 79

The seasonal development of coastal upwelling is clearly indicated by

the following sequence of images, which show chlorophyll pigment levels

derived from CZCS data. Along the Pacific Coast of Baja California, on

17 March (14-1), only modest development is observed, compared with

subsequent images 15-1 and 15-2, one and two months later, respectively.

Also observed is the persistent cyclonic rotation just off Punta Eugenia

which is well-known from numerous hydrographic surveys. Cyclonic

eddies tend to spin-up there, eventually detaching and drifting westward at

a rate of about 4 to 5 km day -_. The isolated patch of high pigment about

300 km west of Punta Eugenia (15-2), may be the indication of an eddy

apparently having been spun-up along the coast two months earlier. Also

in the image several other southwestward-directed jets of high pigment

water (light tones) are observed which exhibit cyclonic turning. Such jets

and eddies are a recurring phenomenon all along the west coast during the

upwelling period. They tend to appear in the same locations, in association

with configurations of the coastline, offshore bathymetry, and wind which

combine to favor intense upwelling.

Proceeding north to southern California, a comparison of images 16-1,

16-2, and 17-1 shows the steady development of upwelling (light tones,

high pigment levels) between early April and July of 1979. Note that by

July (17-1), Point Conception has become a center for strong persistent

upwelling. Even more dramatic is the shift from winter to summer

conditions along northern California (18-1 and 18-2). The CZCS image

for July (18-2) shows the development of offshore jets, and a cyclonic eddy

is observed between Cape Mendocino and Point Arena. Such eddies occur

regularly at this location during the summer, from where they translate

southward at a rate of 5 to 10 km day -_

Further north along the Oregon, Washington, and Vancouver Island

coastlines (19-1 and 19-2), similar upwelling development is observed

between March and July 1979. Of interest in the March image (19-1)is the

small amount of upwelling-induced, high-pigment water close to the coast,

probably induced quite temporarily by north or northeasterly winds which

created the cloud-free conditions to permit a view of the surface. The

upwelled water acts as a tracer, allowing visualization of the northward

current along the coastal region. This northward flow, known as the

Davidson Current, appears at the surface only during winter, but is

actually present at greater depths throughout the year.

14
_R:I:GINALPAGEI8

___2_X QUALITY

ORBIT 01998 1TMART9 191235 TO 191405 GMT GAIN i-4=2 THRESHOLD OFF TILT ANGLE 16.0

GRID CENTER DATA: 191320 GMT 2T.25N 115.3TN SUN EL G1 AZ 161 ROLL -0.1 PITCH -.0..0 YAN 0.3

12TN + i + 106N

I I I I I I I I I I I I I I I I I I I I I I

.3

-2

N

N

124N

PIGMENT IN HILLIGR_S..._METERS_3

8 .06 ,08 .12 .19 .2T

i i I I I I I

i + 10÷N

PIGHENT

•39 .ST .83 1.28 2.11 3.46 5.69 9 ..35 11.98 25.25 32.0

ALGORITHHS: 01 00 00 _0 _ 82 _i 00 80 _

T£T SCAN LINES PROCESSED 0 "/-" .o._.HN F."..x LINES HI::.-;:f;ING

CIP VER CRT NO DPS VER SPEC. # FRAME #

'v' ZE2:24TS1 ",/U20401 FT32_40 ZG2.?47sll

14-1. Nimbus-7. Orbit 1998. 17 March 1979. CZCS Pigment Image.
....._ili iiiii!

123H 99H

120W ....

ALGORITHMS: 01 00 00 00 00 OZ 01 00 00 00

9T0 SCAN LINES PROCESSED 0 SCAN LINES HISSING

i _.... ......... ........

PIGMENT

98N

CIP VER CRT NO DPS VER SPEC. # FRAME #

i ....

V801005 ZE92501- V820208 FT32040 ....ZGO92502

PIGMENT IN HILLIGRAMS.,,'METERS_:3

0 .06 .08 .iZ • 19 .2T .39 .ST .83 i .28 £ .II 3.46 5 .G9 9 -35 ii -98 ,--5.25 32 .i9

ALGORITHMS: 01 00. 00 00. 00 02 01 00 00 00

970 SCAN LINES PROCESSED 0 SCAN LINES HISSING

CIP VER CRT NO DF'q: VER :I-I:F'EC. # FF.'.AME:1t:

V ZETG891- ',,,,,",E',2_-!4_._1FT32i-!40 Zq9TG8i-._Z

15-2. Nimbus-7. Orbit 2772. 12 May 1979. CZCS Pigment Image.

15
134N

ORBIT 0224T 04APRT9 193211 TO 193411 GMT GAIN 1-4=1 THRESHOLD OFF TILT ANGLE 20.0

GRID CENTER DATA: 193312 GMT 31.43N 121.1gN SUN EL 63 AZ 161 ROLL -0.1 PITCH -0.2 YAN 0.3

i +

igiW + i +

PIGMENT

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

9T0 SCAN LINES PROCESSED 0 SCAN LINES MISSING

lION

109N

CIP VER CRT NO DPS VER SPEC. # FRAME #

V800TIO ZE05501- V820501 FTg2040 ZG005502

16-1. Nimbus-7. Orbit 2247. 4 April 1979. CZCS Pigment Image.

128N

ORBIT 02TT2 12MA'fT9 190940 TO i'31140 ISMT GAIN 1-4=i THRESHOLD OFF TILT ANGLE 20.0

GRID CENTER DATA: 191041 GHT TT.84N II6.OIN SUN EL Tg AZ 155 ROLL -0.1 PITCH -0.0 YAN 0.4

+ 2 +

I I I I I I I ................... I I I

106N

126_ +

PIGMENT IN MILLIGRAMS/METERS_S

0 .06 .08 .12 .19 .2T .39 .5T

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

9T0 SCAN LINES PROCESSED 0 SCAN LINES MISSING

2 + 104N

PIGMENT

• 83 i .28 2 .ii 3.46 5.69 9.35 ii .98 25.25 32.0

CIP VER CRT NO DPS VER SPEC. # FRAME #

V ZET6891- V820401 FTg2040 ZGgTG80g

16-2. Nimbus-7. Orbit 2772. 12 May 1979. CZCS Pigment Image.

16

¢N_*-_GiN__LP A GE I8
o F POOR Qu

ORBIT 83PiT is! 88JULT9 193953 TO 194153 GHT GAIN i-4=1 THRESHOLD OFF TILT ANGLE 20.0

GRID CENTER DATA: 194053 GNT 33.85N 123.54N :]:UN EL T!5 AZ 141 ROLL -0.2 PITCH 0.2 YAW 0.3

13TW + 1 112N

134N ÷ 1 + ll/N

PIGHENT

PIGMENT IN HILLIGRA[,_!-2..-.-HETEF_EI:_3 ..... ........... ............................

0 .06 ,L-!',] .12 .19 .27 .39 .57 ,83 1.28 2.11 3.46 5.69 9.35 11.98 25.25 32,8

ALGORITHM:I:: i-_1 I[_,-! 0,_! L-![]! 0_!! 02 01 i-%1 ,-!IZ};-!I:_ CIP VER CRT NO DPS VER SPEC. # FRAHE #

9TiZ! SCAN LINES PROCESSED i-I :':;CAN LINES; [IISSING V8i-lOTlfl ZE45101- V82_-_501 FT32i-_40 ZG045101

17-1. Nimbus-7. Orbit 3560. 8 July 1979. CZCS Pigment Image.

17
..... ?,!!ii£1_ iiii!i,iiiii i?:iiiiii!iiii_iSi,_yi

134N

ORBIT 02081 23MART9 192229 TO 192429 @MT GAIN 1-4=i THRESHOLD OFF TILT ANGLE 18.0

GRID CENTER DATA: 192329 @MT 41.00N 121.13N SUN EL 49 AZ 162 ROLL -0.1 PITCH -0.0 YAN 0.3

+ 2 +

i

110N

130N + 2 +

PIGMENT

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

9T0 SCAN LINES PROCESSED $$$ SCAN LINES MISSING

108N

CIP VER CRT NO DPS VER SPEC. # FRAME #

V8104£I ZE49482- V820208 FT32040 Z@849404

18-1. Nimbus-7. Orbit 2081. 23 March 1979. CZCS Pigment Image.

ORBIT 0.3629 13.JlJLT__ 1 93 103 TO 193303 GHT GAIN 1-4=I THRESHOLD OFF TILT ANGLE 20.0

GF'ID CENTER DATA: i qT"- _.._o._- _ @MT 3T .52N 122.26N SUN EL TZ AZ 14T ROLL 0.0 PITCH 0.Z YAM 0.3

136N + 1 + 11IN

I I I I ! I I I I ! _ ! I I I I I I I I I I I I I I

133N + 1 + 109N

PIGMENT

PIGMENT IN MILLIGRAMS/METERS_3

0 .06 .08 .12 .19 .2T .39 .ST .83 1.28 2.11 3-_6 5.69 9.35 11.98 25.25 32.0

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

9T0 SCAN LINES PROCESSED 0 SCAN LINES MISSING

CIP VER CRT NO DPS VER SPEC. # FRAME #

V800TIO ZE18801- V820501 FT320÷0 ZGOI880ZA

18-2. Nimbus-7. Orbit 3629. 13 July 1979. CZCS Pigment Image.

18

OP, IG_N.&Z,, PAGE iS
1 TC I95T£5 GI'IT GAIN 1-4=3 THRE:.-;:HCIL]-' _-"FF TILT ANGLE

GRID CENTER DATA: I95G_5 GHT 42 AZ i61 E'.,:-:ILL l.:_!.l] PITCH -l-!. 1 ","AN it_..! .4

142N +:: IZIN

:_.3'_q.N ........ + ................. ............... i .... + i S-I.,I

F'I GHENT

ALGOF.'.ITHH:.-;: • i-!l i-!@ lr..!l.:.!i-!i-! i-!i-! i4:..-. i-!l @i-! i-!i-! i-.E!

9T@ :.]:IZ:AN LINE:?;: PE'.I211Z:E:!-U;:ED l..-! 8:IZ:AN LINE:S: t"II:._:;::.:;:IN,:]

IZ:IF' 'vIER I]:RT NI[") ]-IF':'.E;:'VER :.-;:F'EIZ:I # FRAHE #

",,,"1,-',1@57.8 ZE4T41EI, I - 1',,,'ll,-I,2i-._2_.:l',E', FT32i]!4@ ZG',Ell4T4i]!3

19-1. Nimbus-7. Orbit 2026. 19 March 1979. CZCS Pigment Image.

CIRBIT @3643 14...TI_ILT9 195313 T(-) 195513 ,:]hiT GAIN 1-'t=1 THRE:.-;:HI:-:ILf-I -IFF TILT ANI:-:4LE 2i..).i-!

GRIf-I I-:ENTER ]"IATA-" 1'954-13 ,:-;["iT 4',-',.65N 131.23-.J :.-I:LIN EL 61 AZ 15Z E'.I:-:,LL -@.Z F'ITI-:H @.l ","AN @.3

1 4',31...l + 2 + 1 1 6N

19-2. Nimbus-7. Orbit 3643. 14 July 1979. CZCS Pigment Image.

021G_N_ 2AGE _S

19
2B Vancouver Island

James F. R. Gower

and

Ken L. Denman

Institute of Ocean Sciences

Sidney, B.C., Canada

The prevailing northwest wind that blows along the Canadian west

coast in the summer months causes upwelling of nutrient-rich water onto

the continental shelf off Vancouver Island. The resulting primary

production leads to high chlorophyll pigment levels in surface water near

the coast. This productivity is important to the local fisheries, especially

the commercially valuable salmon industry. The pigment-rich water also

traces out dynamic patterns of surface flow, particularly those that result

in movement of shelf water offshore to deeper water.

?RECEDING PAGE BLAI_I_ b_OT FILMED

21
Coastal Productivity and Dynamic Patterns

July 1979

Persistent cloud cover seriously hinders regular monitoring of the

Vancouver Island region, but occasional cloud-free images show the

variety of features that occur. The CZCS image on 14 July (22-2) shows the

waters around Vancouver Island, B.C., Canada, on a clear day during the

summer period when coastal upwelling leads to high productivity on the

continental shelf. This image is remarkable in the clarity with which the

resulting pigmented water has traced out interesting features of the coastal

dynamics. The locator map (22-1) provides ocean features and bottom

contours at 200- and 2,000-m depths for comparison. It should be noted

that most of the features visible in the image have very low temperature

contrast with the surrounding water, so that thermal infrared images will

often not record them.

The waters on the continental shelf and in the straits of Georgia and

Juan de Fuca show high pigment levels (>5 mg m-3), although apparent

values in the image will be increased by silt from coastal runoff. This

increase is especially evident at the mouth of the Fraser River (see

enlargement, 23-1), whose plume can be faintly seen in the image. Isolated

brighter areas in Queen Charlotte Sound, north of Vancouver Island,

correspond roughly to the positions of shoals S. The fresher surface water

from this sound flows southward F down the west coast of Vancouver

Island where it is entrained in the cyclonic eddy El. CZCS imagery for the

next two days (not shown) indicate that the eddy remained stationary

(<3 km translational motion per day) while rotational velocities of

20 km day -1 (20 cm s -1) are implied by displacement of surface features.

The apparent center of the eddy is located at 49 ° 32"+1" N and

127 ° 33"+2" W. The diameter of the eddy is about 20 km, but

counterclockwise rotation can be seen over an area at least twice this large.

Thomson (1984) has studied an eddy at this same location that was

observed in September 1980 in hydrographic data, but which was not

present in July of that year. He suggests that the position of the eddy is

ultimately related to bottom topography, and that its formation is

triggered by baroclinic instability due to the vertical shear between the

opposing southward surface flow and the northward subsurface flow in

the California Undercurrent along the continental slope. In the present

case, the eddy may have formed from the horizontal shear between the

temporary northward flow of shelf water, caused by the strong wind

reversal that occurred a few days earlier, and the southward flow further

offshore.

The increasing width of the band of pigmented water (>2 mgm -3) to the

southeast of this eddy corresponds to the widening continental shelf (see

200-m contour, 23-1). Presence of a second eddy E2 (23-1), on the shelf off

the mouth of the Strait of Juan de Fuca, can be traced by the motion of

features between successive days. This eddy appears to be a regular feature

of the summer circulation (Freeland and Denman, 1982). At its center,

water is brought up to the surface from the California Undercurrent

through a branch of the Juan de Fuca Canyon.

A clearly visible hammerhead feature H is moving to the west at about

20 km day -1. The length of the head of this feature is increasing at a rate

that, on 14 July, implies an age of about five days. Its starting location, at

the edge of the continental shelf near the boundary of the eddy E2, has a

similar pigment concentration. The narrow trail of high-pigment water to

the east of this feature appears to trace out its path over this time period,

although rotation of the eddy E2 has moved this trail to the south and

lengthened it.

The starting date of 9 July deduced for the feature H corresponds to a

22
O_ £OOR ,q_J_;.:.:l _Y.

14',-',N + 2 + 116N

nearly solid cloud

Charlotte

Legend:

El, E2: eddies

F: fresh water

H: hammerhead feature

S: shoal area

B.C. CANADA

Fraser R. plume!

Strait of

Juan de

WASHINGTON

142H + 2 + i 16N

22-1. Locator Map for 22-2 and 23-1.

14 8 H

i

116N

1

N

142H

F'IGHENT I N I"1ILL IGRAH:L--;..,"HETEP/.-;_.:':[.

@ •i..-!i.;:- • 0',-', • 12 • 19 • 2T • 39 •57

ALGOF.'.ITHN::.-;= @i i-!@ i._.-.!i-!i-!i-! i-!i-! i-!:--. 01 i..--!i.-..! @i-! i-!i-!

q.i_'q :.-;I-:AN LINE:f; F'F.'.0CE:£:f;E]-I i-! :£F:AN LINE::.--; NI::.-;::.-;ING

22-2. Nimbus-7. Orbit 3643. 14 July 1979. CZCS Pigment Image.
strong break in the northwest wind regime in which the coastal upwelling,

which had continued since April, was briefly replaced by downwelling. It

seems probable that the launch of this feature to the west may be related to

this wind event.

Other fainter features are visible further offshore in the clearer, less

pigmented water. Velocities here are 8-10 km day -1 to the southwest.

.................. _:_2_._Z _,

The areas of high chlorophyll pigments (light tones in 23-1) indicate

areas of high summer planktonic production which imply potential food

sources for young salmon. These salmon are known to feed in the area

during summer months on their journey to the open ocean where they

spend their adult life. The areas adjacent to the eddy E2 also support a

large adult salmon fishing industry. The information on surface dynamics

is extremely valuable in showing the water movements which cause and

modify the distribution of these food sources. This example demonstrates

how the CZCS imagery can provide this information where the absence of

strong temperature contrasts makes infrared imagery of little value.

References

Freeland, H. J., and K. L. Denman, 1982" A topographically-controlled upwelling center

off Vancouver Island. J. Marine Res., 40, 1069 1093.

Thomson, R. E., 1984" A cyclonic eddy over the continental margin of Vancouver Island:

Evidence for dynamic instability. Submitted to the J. Phys. Oceanogr.

23-1. Enlarged View. Nimbus-7. Orbit 3643. 14 July 1979' CZCS Pigment Image with depth contours.

23
2C Northern California/Cape Mendocino

Mark R. Abbott

Jet Propulsion Laboratory

California Institute of Technology

Pasadena, California

and

Scripps Institution of Oceanography

University of California, San Diego

La Jolla, California

The California Current System was originally thought to be a broad,

slow-moving, southward current. However, it is apparent from CZCS

imagery that this idea is far too simple. Rather, the California Current is

more like a series of eddies and jets with a net southward drift. The jets

themselves are interesting features in that they are associated with the

larger promontories in the coastline. Velocities in these jets range from 50

to 100 cm s -l, and they often extend several hundred kilometers away from

the coast. Thus, the jets could be an efficient mechanism for the exchange

of high chlorophyll productive nearshore waters with poorer productive

offshore waters.

PltlilOl_DINO ,PAC,B BL_NK _0_ __

_A_E__ INTENTIONALLY BLANI_

25
The California Current--

A Comparison of False-Color CZCS Pigment

and Thermal Infrared Imagery

July 1981

The CZCS image (27-1) and AVHRR image (27-2) were obtained on

7 July and 8 July, respectively. These images of the West Coast were made

during the presence of an unusually strong high pressure center in the

Pacific Northwest coupled with a low pressure center off the coast of

southern California. The result was strong northerly winds along the coast

with sustained speeds of 15 m s-1 near Cape Mendocino.

The images reveal several features typical of eastern boundary currents.

Such currents are typically areas of high productivity and, hence, high

biomass. They are also areas of upwelling, although there is some question

as to whether this is classic wind-driven coastal upwelling or a larger scale

process forced by the curl of the wind stress.

The near-time coincidence of these images reveals significant large-scale

similarities between near-surface pigment (27-1) and sea surface

temperature distributions (27-2). In general, colder water is associated

with higher pigment concentrations, although one can detect numerous

areas that differ from this. For example, a comparison of the two images

indicates that the upwelling areas near Cape Mendocino have very low

temperatures and low pigment concentrations. This is consistent with the

combination of upwelling of very deep, clear water to the surface and the

delay time in the phytoplankton response to this nutrient-rich water.

Finally, the CZCS pigment image (27-1) shows some of the limitations

of the current CZCS algorithms. In particular, some of the high pigment

concentrations near San Francisco Bay and near the mouth of the

Columbia River are a result of high sediment concentrations, not

phytoplankton concentrations.

26
_ i _ _iii_i_!i_i_i_i_iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii

_R P__OT'__?t .C'R.APH

27-1. Nimbus-7. Orbit 1348. 7 July 1981.

CZCS False-Color Pigment Image.

27-2. NOAA-6. AVHRR. 8 July 1981.

False-Color Sea Surface Temperature Image.

27
2D Central California/Monterey Bay

Robert C. Wrigley

Ames Research Center/NASA

Moffett Field, California

and

William W. Broenkow

Moss Landing Marine Laboratory

Moss Landing, California

The California Current is an eastern boundary current characterized by

half-knot southerly drift, punctuated by mesoscale eddies and coastal jets.

Coastal upwelling occurs along the central California coast, usually

during the spring and summer (March through July) due to Ekman

divergence caused by persistent northwesterly winds. A transition period

(August through October) of weaker winds marks the end of the strongest

coastal upwelling. Between November and February the occurrence of

periodic southerly winds causes a surface convergence along the coast and

promotes northerly surface flow within 50 km of shore (the Davidson

Current or California Countercurrent).

_22c2D_a eAG_ BLaN_ _OT _mM_._

29
The California Current Upwelling System

May, July, and September 1979

Three CZCS pigment images (30-1, 31-1, and 31-2) are shown for the

California Current System between Cape Mendocino and San Diego. All

three images show that highest pigment concentrations are confined to

within 200 km of shore (about the distance from Pt. Reyes to Pt. Sur). This

agrees with the observation that the main axis of the California Current

lies about 300 km offshore along central California (Hickey, 1979).

Although many of the eddies and meanders shown in these images are

transient features of the California Current, a persistent cyclonic

geostrophic eddy (E, 31-1) has been observed south of San Francisco

(Broenkow and Smethie, 1978; Hickey, 1979). Apparent shoreward flow

of lower pigment waters (L, streaks of darker tones) from the "'San

Francisco Eddy" is shown in the 13 July (31-1) and 6 September (31-2)

images, and some indication of lower pigment waters (L, faint dark tones)

intruding into Monterey Bay are shown in the 13 May image (30-1). The

location of this eddy is apparently due to local change in the wind stress

curl (Hickey, 1979) and perhaps to the abrupt bathymetric break at

Monterey Bay (Broenkow and Smethie, 1978).

Coastal jets extending normal to the coastline are frequently observed in

the California Current. A prominent jet (C J1) in the 13 May image (30-1)

may have resulted from counterrotating eddies as suggested by Mooers

and Robinson (1984). A similar, but larger such feature (C J2) is shown in

the 6 September image (31-2) at about the same latitude, but further

offshore. High pigment levels along the coast south of Pt. Conception in

the 13 May image (30-1) seem to spawn several small (50 km) filaments

(arrows) between Santa Cruz Island and San Diego. In addition, the large

arcuate feature 150 km west of Pt. Conception in the image showed high

radiances in the 443, 520, and 550 nm bands relative to surrounding

waters. Viewed in false-color CZCS imagery (not shown) this feature

appeared white, suggesting it was not caused entirely by phytoplankton

absorption. Since the feature was not sampled from ships, its origin

remains something of a mystery, but it is suspected to be due to

Coccolithophorids, which are algae with calcium carbonate shells.

Several upwelling loci are found along the central California coast: the

area from Cape Mendocino to Pt. Reyes, from Pescadero Pt. to Monterey

Bay, and from the Big Sur coast south of Monterey Bay to Pt. Conception.

The 13 May image (30-1) shows high pigment levels in coastal waters just

north of Pt. Conception, an apparent lack of high-pigment waters along

the Big Sur coast, and higher levels in and north of Monterey Bay. A ship

station in the center of Monterey Bay on this date showed a chlorophyll

concentration of 8.7 mg m-3; a 2.5 mg m -3 chlorophyll concentration was

measured in the pigment-poor tongue extending into the Bay. The 3×3

pixel averages of CZCS data at these locations showed 2.1 and 1.1 mg m -3,

respectively. The 13 July image (31-1) is partially obscured by clouds

trailing southwest from Cape Mendocino where thermal infrared imagery

(not shown) indicated coolest surface waters and intense upwelling. It is

interesting that the CZCS data indicate that highest pigment

concentrations were located 50 to 100 km offshore except along the Pt. Sur

upwelling area. Incipient upwelling may occur with a rapid offshore

transport of plankton-rich coastal waters which are replaced by cool, lowchlorophyll waters. As phytoplankton production proceeds, the waters

warm and become colored.

Ship data at two stations in Monterey Bay just before satellite overpass

on 13 July (31-1) indicated chlorophyll concentrations of 6.9 and

11.7 mg m -3, respectively, both of which are indicative of highly productive

water. CZCS data at these locations gave values of 2.4 and 4.5 mg m -3,

respectively. Wrigley and Klooster (1983) compared surface truth data

30
obtained by Moss Landing Marine Laboratories with the CZCS data and

found that the CZCS values consistently underestimate pigment

concentrations in the areas where pigment levels are greater than 3 mg m -3.

They attribute the discrepancy to excessive atmospheric correction caused

by phytoplankton reflectance in the 670-nm band. The small black areas

between San Francisco and Monterey Bays (31-1) and south of Big Sur

(31-2) are image processing artifacts where the water-leaving radiances at

443, 520, and 550 nm were reduced to zero by the atmospheric correction

algorithm. The condition, caused by pigment levels beyond the limits of

the normal CZCS correction scheme, often occurs in images along the

central California coast in the 443-nm band, but is rarely found in all three

bands.

.......... i.............. _:::::::iii iiiiiii!i %_%_::: _.._...... _:i:_,,_

References

Broenkow, W. W., and W. M. Smethie, Jr., 1978: Surface circulation and replacement of

water in Monterey Bay. Estuarine and Coastal Marine Science,6, 583-603.

Hickey, B. M., 1979: California Current System: Hypotheses and Facts. Progress in

Oceanography, 8, 191-279.

Mooers, C. N. K., and A. R. Robinson, 1984: Turbulent jets and eddies in the California

Current and inferred cross-shore transport. Science, 223, 51-53.

Wrigley, R. C., and S. A. Klooster, 1983: Coastal Zone Color Scanner data of rich

coastal waters. In: Digest, International Geoscience and Remote Sensing Symposium,

31 August-2 September 1983, San Francisco, CA.

134N

ORBIT 02786

GRID CENTER DATA:

13HAYT9 192845 TO 193045 GHT

192946 GHT 35.11N 121.12N

+

GAIN 1-4=1 THRESHOLD OFF TILT ANGLE 20.0

SUN EL T2 AZ 156 ROLL -0.1 PITCH -0.0 YAW -0.0

1 + ll8W

131N +

PIGMENT IN HILLIGRAMS/METERS_3

0 .06 ,08 .12 .19 .2T .39 .ST

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

9T0 SCAN LINES PROCESSED 0 SCAN LINES HISSING

1

PIGMENT

IISN

i!iiii_151 /

5.69 9.35 ii .98 25.25 32.0

CIP VER CRT NO DPS VER SPEC. # FRAHE #

V800615 ZE05801- V820501 FT32040 ZG005803

30-1. Nimbus-7. Orbit 2786. 13 May 1979. CZCS Pigment Image.
ORBIT 0._c9 IgJULT9 193103 TO 193303 GMT GAIN i-4=i THRESHOLD OFF TILT ANGLE 20.0

GRID CENTER DATA: 193203 GMT gT.52N 122.26N SUN EL T2 AZ 14T ROLL 0.0 PITCH 0.2 YAM 0.3

136N + 1 + 111N

13 W | I ! ! ! t + I ! ! ! ! ! I _ ! ! ! ! ! I ! ! | !i + 109N

P I GHENT

ALGORITHMS:: 01 00 00 O0 00 02 Ol 00 00 00 CiP VER CRT NO DPS VER SPEC. # FRAME #

9T0 SCAN LINES PROCESSED 0 SCAN LINES MISSING V800T10 ZE18801- V820501 FT32040 ZG018802A

31-1. Nimbus-7. Orbit 3629. 13 July 1979. CZCS Pigment Image. ORIGINAL PAGE IS

OF POOR QUALITY

ORBIT 04389 06SEPT9 192805 TO 193005 GMT GAIN 1-4=1 THRESHOLD OFF TILT ANGLE 14.0

GRID CENTER DATA: 192906 GMT 35.80N 121.09N SUN EL 60 AZ 163 ROLL -0.0 PITI3H 0.1 'IAN i3.3

133W + 1 + lllW

i _10N 130W + 1 +

P IGHENT

PIGMENT IN MILLIGRAM$/METER$_g ....... ......

0 .06 .08 .12 .19 .2T .39 .5T .83 1.28 2 .ii 3 ._r6 5.69 9.35 ii .98 25_25 32 .iZ_

ALGORITHMS: 02 01 01 00 00 03 02 00 00 O0

9TO SCAN LINES PROCESSED 0 SCAN LINES MISSING

C IP VER CRT NO DPS VER SPEC. # FRAME #

V800TIO ZE18901- V820821 FT32040 ZGOI89i-_2

31-2. Nimbus-7. Orbit 4389. 6 September 1979. CZCS Pigment Image.

31
Section 3

Atlantic North American Coast

3A Carolina Capes/Sargasso Sea

Slope Water/Tidal Mixing/Gulf Stream

Meanders and Rings

Olson .......................................................... 35

3B Cape Hatteras/Cape Cod

Gulf Stream Eddies--Circulation Features

Yentsch ....................................................... 41

3C Cape Hatteras/Gulf of Maine

Phytoplankton Distribution in Early Spring

Yentsch ....................................................... 45

3D Cape Hatteras/Sargasso Sea

The Gulf Stream--A Distinct Ocean Color Front

Yentsch ....................................................... 49

3E New England Seamount Chain

Effects of the New England Seamount Chain

on Gulf Stream Surface Flow

Gower ........................................................ 53

3F New England Coast

Enhancement of Phytoplankton Growth by Tidal Mixing

Yentsch ....................................................... 57

P]_J_I_)IIqG PAGE BLANK NOT EILMED

33
3A Carolina Capes/Sargasso Sea

Donald B. Olson

Rosenstiel School of Marine and Atmospheric Science

University of Miami

Miami, Florida

Five CZCS pigment images of the northwestern Sargasso Sea and the

North American slope and shelf are described. The pigment field shows

the rapid change in optical characteristics across the Gulf Stream.

Mesoscale features dominate the interior of the major water mass

provinces. A large warm-core ring appears as a low-pigment feature in the

slope water, and a number of cold-core rings can be seen in the Sargasso

Sea. These are regions with elevated pigment and are the centers of largescale advective features. Portions of the shelf region are low in pigment in

these particular images, in contrast to normal conditions. This, in

comparison with other years, implies large interannual variability in the

phytoplankton standing crops in these regions. Subscale plumes

associated with capes are also seen along the Carolina coast.

The CZCS images cover the area from the Carolina capes out to the

region between the Sargasso Sea and Scotian Shelf in a two-week period in

the mid to late spring of 1979. Since many of the features in the pigment

distributions are found in several of the images, the discussions included

with each of the images are relevant to the others. A mercator projection

depiction (35-1) identifies important features in the images in relation to

various landmarks. The reader is encouraged to compare the images in

order to obtain a better feeling for the temporal changes in the regions

covered.

GEORGES

ENTRAINMENT INTO

GULF STREAM CORE RIN

SLOPE

CHESAPEAKE

BAY

CAPE

_" AXIS OF NEW ENGLAND

COLD CORE RINGS SEAMOUNTS

CHARLESTON )_JJ"

SARGASSO SEA

OFF CAPES

80 ° 75 ° 70 ° 65 °

35-1. Mercator Projection Depiction. North Atlantic Coast Waters.

PAGe.- 3 oNauuY

PRECEDING PAGE BLANK NOT FILME_

35
Slope Water/Tidal Mixing/

Gulf Stream Meanders and Rings

April-may 1979

21 April

The CZCS pigment image (36-1) reveals a complex set of plumes (light

tones nearly perpendicular to coastline) associated with the Carolina

capes. These are superimposed upon a generally enhanced pigment

concentration within 10 to 30 km of the coast. This concentration is the

result of higher primary productivity caused by the introduction of

nutrients by river runoff and vertical mixing due to tidal stresses in the

shallow waters. The winds are also conducive to upwelling along this coast

although this is probably of minor significance, except in summer and fall.

The plumes associated with the capes might be explained as a combination

of simple offshore advection of high pigment water and an upwelling

response as the flow rounds the capes. Similar plumes are observed in

many regions of the world in relation to equatorward flow around capes

(Arthur, 1965; Brink et aL, 1983). The image also shows an entrainment of

a filament (narrow, white-tone band) of inshore high-pigment water into

the Gulf Stream at Cape Hatteras. This feature is about 10 km in width

suggesting low cross-scale mixing along its nearly 300-km length.

Entrainment of shelf water into the northern edge of the stream seems to

be a common occurrence at Cape Hatteras. Features similar to this

filament are reported by Ford and Miller (1952), and Fisher (1972), based

on the presence of low salinity shelf water along the edge of the stream.

In addition, the image also contains a cold-core, cyclonic ring which

seems to be advecting a streamer of low-chlorophyll fluid out of the Gulf

Stream. The ring is manifest as a high-pigment region in the Sargasso Sea.

The lowest pigment concentrations are not associated with the Sargasso

waters around the ring in the image, but rather with the Gulf Stream core.

A patch of this low-chlorophyll fluid appears to the west of the ring and

may indicate the advection of waters by the cyclonic ring out of the stream

core and into the Sargasso Sea.

2 May

The CZCS pigment image off the East Coast (37-1) gives a reasonable

coverage of the Gulf Stream between Cape Hatteras and the New England

Seamounts. In this image, the Gulf Stream appears as an abrupt reduction

in pigment concentration (A-B) as one proceeds from north to south. As

in the 21 April image (36-1), the stream core exhibits consistently lower

values of pigment concentration compared to the slope water to the north

and the Sargasso Sea to the south.

To the south, in the northern Sargasso Sea (37-1), there is an

approximately 30-km area of high pigment. This small, nearly circular

feature is probably associated with the core of a cyclonic ring. High

chlorophyll concentrations in cold-core ring centers in fall and spring are

described by Wiebe et al. (1976). They found carbon-14 measured

productivity in a ring during spring to be nearly double that in the

surrounding Sargasso Sea. This is attributed to enhanced nutrient levels as

compared to the Sargasso Sea and higher light penetration than that

found in the slope waters. The scale of the feature in this image is

somewhat less than the radius of the velocity maximum in a typical

cyclonic ring, suggesting that the high-pigment zone is associated with

increased productivity in a small region near the ring center or on the edge

of the ring in response to some asymmetry forced on the ring.

The structure of the meanders in the Gulf Stream and the warm-core

rings in the North American slope water is discussed below in relationship

to the images (37-2, 38-1, and 38-2). Structures of interest in this set of

images include the complicated patterns present in the slope water as

36 _ POOR QUAL|T_I_
manifest north of the Gulf Stream meander, just downstream of Cape

Hatteras •(37-1). Further east there is a large, warm-core ring and a large

(nearly 200 km), elongated filament of high-pigment water that appears to

the south of the eddy in each of the images.

3 May

This East Coast CZCS pigment image (37-2) shows features similar to

those along the Carolina capes (36-1) and Gulf Stream extension (37-1,

38-1, and 38-2). The higher pigment values associated with the capes (37-2)

are apparent. Note that the large-scale meander pattern in the Gulf Stream

is essentially the same as in the other images in this set. The details of the

pattern to the east of the warm-core ring are worth further comment in

relation to the time of this image and those on 7 and 8 May (38-1 and 38-2).

To the east of the warm-core ring (37-2) is a cyclonic (counterclockwise)

hook or streamer of low-pigment water. This feature and its time evolution

(38-1 and 38-2) suggest a cyclonic circulation of scale comparable to the

ring. Features such as these may imply a pairing of vortices which may be

of considerable importn.nce to the dynamics of regions, which are

characterized by strong non-linear eddies such as western boundary

current exte lsions.

continued

81N

ORBI T 02480

GRID CENTER DATA•

I I I

GAIN i-4=£ THRESHOLD OFF TILT AN,:]LE F:.@

:.-;:UNEL 6T AZ 16@ P...,:-)LL-0.1 PITi-:H-0.@ ',"AN-0.0

1 +

I I ! I I I

62H

2

9-

N

T8N I I I I / I I I I 1

P II:]HENT

I+ I I I I

• _ i_IZiii

3

2

-N

I

60N

5.69 9.35 i i .98 25.25 32.0

DF'::.-I:'I,/'ER :!]PEE:, # FRAI"tE #

'v'82@I:Z@',-', FT320'_0 ZG0._r0_r@l

36-1. Nimbus-7. Orbit 2480. 21 April 1979. CZCS Pigment Image.
ORBIT 02632 02MAYT9 160343 TO 160543 GMT GAIN i-4=1 THRESHOLD OFF TILT ANGLE 18.0

GRID CENTER DATA: 160443 GMT 36.18N OTO.13N SUN EL 68 AZ 159 ROLL 0.0 PITCH 0.1 YAW 0.5

82W + 2 + 60N

N

8eN ..... ........ ......... + ........................ + ............ ssN

PIGMENT

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00 :;PEC. # FRAME #

970 SCAN LINES PROCESSED 0 SCAN LINES MISSING V ZE2059TI V820401 FT32040 ZG2059TI

37-1. Nimbus-7. Orbit 2632. 2 May 1979. CZCS Pigment Image. O_JG_ZAL PACERS

OE POOR QUAJLITy

ORBIT 02646 03MAYT9 162242 TO 162442 GMT GAIN 1-4=I THRESHOLD OFF TILT ANGLE 20.0

GRID CENTER DATA: 162342 GMT 3T.65N OTS.2TN SUN EL 6T AZ 159 ROLL 0.1 PITCH -0.1 YAW 0.3

88W + 2 + 6414

1614 I I ............ I ......... + I : ...... I ........... ............2 | I .................. t: +

PIGMENT

.......

!

6214

PIGMENT IN MILLIGRAMS/METERS_3 ....... ............

0 .06 .08 .12 .19 .2T .39 .ST .83 1.28 2.11 3.46 5.69 9.35 11.98 25.25 32.0

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

970 SCAN LINES PROCESSED 0 SCAN LINES MISSING

CIP VER CRT NO DPS VER SPEC. # FRAME #

V ZE205981 V820401 FT32040 ZG205981

37-2. Nimbus-7. Orbit 2646. 3 May 1979. CZCS Pigment Image.

37
7 May

The CZCS pigment image (38-1) shows the entire zonal extent of the

North American slope water and the frontal zones which border it,

between Cape Hatteras and Scotian Shelf. The slope water is the site of the

largest horizontal pigment variability in the image, in keeping with the

nature of transition zones. The contrast between the slope water and the

Sargasso Sea is clearly visible. Meanders and rings viewed in the other

images are also evident in this scene. The shelf front separating the slope

water and the water on the continental shelf can be traced here as a sharp

decrease in pigment as one proceeds into shallow water (depths _200 m).

Low pigment concentrations on the outer shelf in comparison to the

slope waters are somewhat unexpected. The spring bloom on the mid to

outer shelf in the Mid Atlantic Bight typically occurs in late March to early

April (Walsh, 1983), while the inner shelf bloom is later, with the mean

euphotic-zone chlorophyll peaking in mid-May. In the time period in

question, the shelf should have a uniform pigment distribution from

Walsh's (1983) curves. This is, in fact, the case for April and May 1982

(Evans, 1985). By June 1979, the shelf has nearly uniform pigments (not

shown) as viewed from space (Gordon et aL, 1982). The slope water also

has lower pigment concentrations in these later images in 1979.

The appearance of low, near-surface pigment concentrations on the

outer shelf (38-1) in comparison to the normal conditions (Walsh, 1983)

suggests that there are strong interannual variations in the phytoplankton

community on the North American shelf. This anomaly may just reflect a

deeper or better mixed distribution of pigments in the vertical in 1979. It

might also be a result of different offshore Ekman transports (Walsh,

1983) or perhaps an earlier reduction in phytoplankton by grazing.

The Scotian Shelf also shows very low pigment concentrations in this

image. This may be a more common situation set up by the seasonal

decrease in surface salinities in this region tied to the spring melt and

increased fresh water output from the Gulf of St. Lawrence. Both Georges

Bank and Nantucket Shoals appear as high-pigment areas. This is a

consequence of tidal mixing in the shallow waters which leads these areas

to have more than double the annual primary production of the upwelling

zone off Oregon or at the Mid Atlantic Bight (Walsh, 1981).

The temporal variations in the area covered are largest in the slope

water, which typically contains streamers of extremely low pigment fluid

drawn in from the Sargasso Sea and high-chlorophyll waters from the

shelf. In the image (38-1), the shelf is an apparent source of the lowpigment waters in the slope region, with the highest chlorophyll

concentrations appearing in the slope water south of the Scotian Shelf. In

contrast, a month and a half later in the June imagery (not shown),

Gordon et al. (1982), show that this region has very low pigments,

suggestive of a large flux of Sargasso Sea waters across the Gulf Stream

downstream of the New England Seamounts between May and June.

Much of this sort of entrainment of fluid into the slope water is tied to the

presence of warm-core rings in the slope and large-amplitude meanders in

the stream. These are discussed in relationship to the CZCS pigment image

of 8 May.

8 May

The last CZCS pigment image in this group (38-2) covers the eastern

portion of the slope water and gives the best coverage of the meandering of

the Gulf Stream. A comparison of all the images shows that the large

meanders in the stream evolve on a longer time scale than the two weeks

covered here. In addition, a careful inspection of the images reveals small

changes in the northern edge of the stream in connection with smallamplitude features over the period, but no major changes in the large

38
82N

ORBIT 02701 OTHA'fT9 155332 TO 155532 GHT GAIN i-4=1 THRESHOLD OFF TILT ANGLE 20,0

GRID CENTER DATA: 155432 GHT 38.96N 068.35N SUN EL 66 AZ 158 ROLL 0.2 PITCH -0.1 YAM 0.2

+ 2 + 56N

T8N + 2

PIGMENT

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

970 SCAN LINES PROCESSED 0 SCAN LINES HISSING

38-1. Nimbus-7. Orbit 2701. 7 May 1979. CZCS Pigment Image.

56N

CIP VER CRT NO DPS VER SPEC, # FRAME #

V810811 ZE55101- V820288 FT32040 ZG055101

OF PQQ£ _.......

86N

N

83N

PIGMENT IN MILLIGRAMS/METERS_3

ORBIT 02715 08MAYT9 16113T TO 161337 GHT GAIN I-4=i THRESHOLD OFF TILT ANGLE 20.0

GRID CENTER DATA: 16123T GHT 36.95N OT2.33N SUN EL 69 AZ 158 ROLL 0.2 PITCH -0.0 YAN 0.2

+ 1 + 61N

1 I I 1 t t | t ! ! I I

+ 1 +

PIGMENT

......................................................................................................... ......

59N

0 .06 @8 .12 • 19 i2T i39 .ST i83 1,28 2 111 3 i_-6 5.69 9 .:_5 11-98 25.25 32.0

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00 CZP VER CRT NO DPS VER SPEC. # FRAME #

970 SCAN LINES PROCESSED 0 SCAN LINES HISSING V800710 ZE05301- V820401 FT32040 ZG005301

38-2. Nimbus-7. Orbit 2715. 8 May 1979. CZCS Pigment Image.
meanderpatterncenteredaround69° W.In combination,thewarm-core

ring and the largecyclonic,meander/ringform a perturbationin the

streampathof over300km.Thispattern,withahighpressurecell(warmcorering)to thepolewardsideof ameanjet andacycloniccell(cyclonic

eddy)to theequatorwardsideof thejet, issimilarto blockingpatterns

whicharecommonintheatmosphericjet stream.Theselarge,long-lived

perturbationsto thepathof theGulfStreamarejustupstreamoftheNew

EnglandSeamounts(opentriangles).Againthis is reminiscentof the

atmosphericasein whichblockingsituationsareoftentiedcloselyto

topographicfeatures.Thepresenceof largemeandersandflowdownthe

axisoftheseamounts, depictedintheschematic(35-1),isfairlycommonin

theGulfStream(Richardson,1981).

The meanderpatternobservedon this day (38-2)eventuallybroke

down.Thewarm-corering proceededonto thewestandwasfoundat

69° W in June (Gordon et al., 1982). It is not known whether or not the

cyclonic portion of the pattern separated from the stream to form a ring. A

full description of the events which took place in the slope water during

1979, based on thermal infrared data, can be found in Fitzgerald and

Chamberlin (1981).

Acknowledgments

The author wouM like to thank Howard Gordon, Otis Brown, and

Robert Evans for comments concerning these images; and particularly,

Jim Brown for actually bringing up the 8 May image on a display system

and checking the returns on the low-pigment waters on the shelf.

References

Arthur, R. S., 1965: On the calculation of vertical motion in eastern boundary currents

from determinations of horizontal motion. J. Geophys. Res., 70, 2799 2803.

Brink, K. H., D. W. Stuart, and J. C. Van Leer, 1983: Observations of the coastal upwelling

region near 34°30 ' N off California: Spring 1981. Submitted to J. Phys. Oceanogr.

Evans, R. E., 1985: Personal Communication.

Fisher, A., Jr., 1972: Entrainment of shelf water by the Gulf Stream northeast of Cape

Hatteras. J. Geophys. Res., 77, 3248-3255.

Fitzgerald, J., and J. L. Chamberlin, 1981: Anticyclonic warm-core Gulf Stream eddies

off the northeastern United States during 1979. Annales Biologiques, 36, 44-51.

Ford, W. L., and A. R. Miller, 1952: The surface layer of the Gulf Stream and adjacent

waters, J. Marine Res., 11, 267-280.

Gordon, H. R., D. K. Clark, J. W. Brown, and R. E. Evans, 1982: Satellite measurement of

the phytoplankton pigment concentration in the surface waters of a warm-core Gulf

Stream ring. J. Marine Res., 40, 491-502.

Richardson, P. L., 1981: Gulf Stream trajectories measured with free-drifting buoys.

J. Phys. Oceanogr., 11, 999-1010.

Walsh, J. J., 1981: Shelf-sea ecosystems. In Analysis of Marine Ecosystems, edited by A. R.

Longhurst, Academic Press, New York, 159-196.

, 1983: Death in the sea: Enigmatic phytoplankton losses. Prog. Oceanogr., 12,

1-86.

Wiebe, P. H., E. M. Hulburt, E. J. Carpenter, A. E. Jahn, G. P. Knapp Ill, S. H. Boyd,

P. B. Ortner, and J. L. Cox, 1976: Gulf Stream cold-core rings: Large-scale interaction

sites for open-ocean plankton communities. Deep-Sea Res., 23, 695-710.

39
3B Cape Hatteras/Cape Cod

Charles S. Yentsch

Bigelow Laboratory of Ocean Sciences

West Boothbay Harbor, Maine

Mesoscale eddies are common features of the Gulf Stream System,

especially in the region north of Cape Hatteras. These eddies or Gulf

Stream rings, as they are often called, form from extensive meanders of the

Gulf Stream System as a whole. Such meanders at times close, pinching off

portions of the water masses on either side of the stream. The eddies

approach being in geostrophic balance and continue to rotate in a manner

not unlike the parent flow of the Gulf Stream. Eddies that become

entrained in the slope waters contain a warm core of Sargasso Sea water

and are referred to as warm-core rings, while eddies that reside in the

Sargasso Sea contain a cold core of slope water and are designated coldcore rings.

i_'_iENTIONALLY BLANI_

41
Gulf Stream Eddies--Circulation Features

April 1979 and April 1982

CZCS pigment images for 21 April 1979 (42-1), and 24 April 1982

(42-2), show that both warm- and cold-core rings are defined in terms of

ocean color which is traceable to the gradients in measured phytoplankton

pigment (Gordon et aL, 1983). The gradients of pigment observed in these

eddies is due to the fact that they are rotating, which influences the density

field within the eddy. Nutrient-rich water is vertically mixed along the

sloping isopycnals of the eddies. In the anticyclonic mode, the sea surface

level, due to geostrophy, domes-up around the axis of a warm-core ring;

while in a cyclonic mode, it is depressed around a cold-core ring.

Therefore, in an anticyclonic eddy (warm-core ring) lighter, nutrient-poor

water will accumulate at its center and heavier, nutrient-rich water will be

swept to its rim. This distribution of nutrient-rich and-poor water dictates

the pattern of phytoplankton distribution observed in the eddies. In the

case of the warm-core ring (42-2) the higher concentrations of

phytoplankton will be found at the outer rim of the eddy, whereas in the

cold-core ring (42-1), the reverse will be true, with the central region

containing most of the phytoplankton-rich water. The false-color CZCS

pigment image (43-1) of the warm-core ring example (42-2), illustrates

how dramatically these differences can be displayed by the color

presentation.

In summary, the explanation for the observed distribution of

phytoplankton pigments in rings argues that geostrophic principles apply

to these rings. Associated with this is the idea that these are the forces of

enrichment, thus the rotary motion induces nutrient transport along

isopycnals and phytoplankton production occurs when these isopycnals

intersect the euphotic layers of the ring water masses.

Reference

Gordon, H. R., D. K. Clark, J. W. Brown, O. B. Brown, R. H. Evans, and W. W.

Broenkow, 1983: Phytoplankton pigment concentrations in the Middle Atlantic Bight:

Comparison of ship determinations and CZCS estimates. Applied Optics, 22, 20 36.

42
81N

ORBIT 02488 21APRT9 16_-_T16 TO 160916 GNT GAIN 1-4=2 THRESHOLD OFF TILT ANGLE 8.@

GRID CENTER DATA: 16081T GMT 33.96N i-!TP.51H q:UN EL _::_ H_ 160 ROLL -0.1 PITCH -O.f! YAH -0.0

+ 1 + 62H

2

9 -

N

T8N

ORIGIN.&I, >_&GE IS

I I I I .t_l | I I I 1 | I I I I+ | I I I 6@HI

PIGMENT

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

809 SCAN LINES PROCESSED 161 SCAN LINES MISSING

CIP VER CRT NO DPS VER 8PEC. # FRAME #

V801005 ZE40401- V820501 FT32040 ZGO4040IA

S

2

-N

42-1. Nimbus-7. Orbit 2480. 21 April 1979. CZCS Pigment Image.

81N

ORBIT IT668 24APR82 155806 TO 160006 GMT GAIN i-4=i THRESHOLD OFF TILT ANGLE 10.0

GRID CENTER DATA: 155906 GNT 38.26N 069.48H 8:UN EL 63 AZ 160 ROLL 0.3 PITCH -0.i-! YAH 0.3

+ i + 60N

T8_i i + t i I _ i I I + 59N

PIGMENT

.....

PIGMENT IN MILLIGRANS/ME]%RS_3

@ .06 .08 .i'2 .i'9 .2T ._q..... .ST .83 1.28 2.11 3._6 5.69 9.35 11.98 ...... :>_.:::= 32.0

ALGORITHMS: 02 01 0! 00 00 03 02 00 00 00

9T0 SCAN LINES PROCESSED @ SCAN LINES MISSING

CIP VER CRT NO DPS VER SPEC. # FRAME #

V ZE2T@661 V821015 FT_2040 ZG£T@661

42-2. Nimbus-7. Orbit 17668. 24 April 1982. CZCS Pigment Image.
43-1.Nimbus-7. Orbit17668. 24April1982.CZCSFalse-Color PigmentImage.

43
3C Cape Hatteras/Gulf of Maine

Charles S. Yentsch

Bigelow Laboratory of Ocean Sciences

West Boothbay Harbor, Maine

In early spring, highly diverse patterns of phytoplankton distribution

are present in the oceanic regions off Cape Hatteras, Cape Cod, and the

Gulf of Maine. In terms of seasonal change, this period is the onset of

vernal warming--a transition between winter and summer. This climatic

transition gives rise to the spring bloom of phytoplankton in the slope

waters of the region. This bloom constitutes one of the most important

periods of photosynthetic carbon fixation for the ecosystem of this region.

45
__. ,_':'._1:_. PAGE

Phytoplankton Distribution

May 1979

in Early Spring

The CZCS pigment image (46-2) shows the high diversity of

phytoplankton distribution in the coastal and offshore region from Cape

Hatteras to the Gulf of Maine. The region can be subdivided into four

areas, based on pigment content, as identified in the locator map (46-1).

Area 1 consists of shallow coastal waters (less than 25 m) which extend

from Cape Hatteras to Cape Cod and over Nantucket Shoals and Georges

Bank. In this area, the pigment concentrations are generally greater than

2 mg m -3. Area 2 consists of deep coastal waters which extend from the

edge of the Continental Shelf, circumnavigating Georges Bank, and into

the eastern regions of the Gulf of Maine. Pigment concentrations in this

area range from 0.2 to 0.5 mg m -3. These are generally lower than the

values found on either side of this area. Area 3 encompasses all slope and

basin waters greater than 100 m deep, with the seaward limit being the cold

wall of the Gulf Stream. It is in this area where the largest diversity in

pigment concentration occurs: ignoring the intrusive features, the pigment

content ranges from 0.5 mg m -3 to values in excess of 2 mg m -3. Area 4 is

characterized by the most prominent feature observed in the image: the

frontal cold north wall of the Gulf Stream. This strong frontal feature

extends from Cape Hatteras meandering eastward to the waters of the

open North Atlantic.

Some of the Gulf Stream meanders form eddies which are large rotating

ceils of water composed of Gulf Stream, Sargasso Sea, and slope water. A

warm-core ring, seen in Area 3, is a good example. This is an anticyclonic

eddy consisting of a central core of Gulf Stream or Sargasso Sea water

surrounded by slope water. A cold-core ring (cyclonic eddy) is also seen in

the lower part of the image. This ring was spawned from an encirclement

of coastal water by Sargasso Sea or Gulf Stream water. The difference in

the pigment content of the water masses, which compose the eddies, allows

them to be identified by ocean color. The four pigment-content areas are

clearly observed in the enlargement (47-1).

The high diversity of phytoplankton distribution can be explained in

terms of variation in the growth of phytoplankton, which is regulated by

light and the vertical mixing in the water columns. The amount of vertical

mixing regulates the mean light intensity reaching phytoplankton which,

in turn, controls their growth. A simple rule of thumb is that water

columns which are deep and well-stirred, which is the case of those in

Area 2, will promote less phytoplankton growth than those where the

mixing depth is retarded by the shoalness of the bottom, which is the case

in Area 1. The energy for stirring of these water columns can come from

water movements by tides or from other sources across the bottom and/or

wind blowing across the surface of these waters. In shallow waters, the

tidal components may be the most important during this period. Area 3

differs from Areas 1 and 2 in that the bottom depths are greater and hence

the frictional forces which stir the column are much less. In Area 3, the

surface layers become more buoyant than the underlying waters because

of an increase in solar radiation coinciding with a decrease in surface wind

mixing. The combination of these events promotes an intense growth of

phytoplankton activity. Area 3 is scarred by water mass intrusions from

the coast and Gulf Stream. The fluid motions associated with these

intrusions tend to inhibit or destroy buoyancy which essentially retards the

onset of the phytoplankton blooms.

O_ pO()K QUALI'I"_

46
ORIGINAL PAGE IS

OE POOR QUALIT_

82N + +

I

Gulf of Maine

Cape Cod _ 2 "--'--

antucket ,____ _ _

( Geu'-1/_ Legend:

\ _ 1 - Shallow coastal water

2- Deep coastal water

3- Slope and basin water

warm-core 4- Gulf Stream north wall

ring

3

56N

Cape Hatteras cold-core

ri ng

u u ! u u

TBN + 2 + 5614

46-1. Locator Map for 46-2 and 47-1.

ORBIT @2701 OTMA"/T9 155332 TCI 1 =___,_.,_:,..-:.,. .... -_ GMT GAIN 1-4=1 THRE::._-.HOLDOFF TILT ANGLE 2@..0

GRID CENTER DATA: lo_4_, =% 7,> GMT 38 .9@,4 @68.35N :?:UN _ EL 66 AZ 15:_=: ROLL @.Z PITCH -0 • 1 '(AN @• £

82N + £ + 56N

TSN + 2 + 56N

PIGMENT

ALGORITHMS: 81 0(4 @0 80 0@ @2 01 00 00 O@

9T0 SCAN LINES PROCESSED 0 SCAN LINES MISSING

CIP VER CRT NO DPS VER SPEC. # FRAME #

V810811 ZE55101- V82@208 FT3£@_rO ZG0551@I

46-2. Nimbus-7. Orbit 2701. 7 May 1979. CZCS Pigment Image.
47-1.EnlargedView.Nimbus-7. Orbit2701.7May1979.CZCSPigment Image.
47
3D Cape Hatteras/Sargasso Sea

Charles S. Yentsch

Bigelow Laboratory of Ocean Sciences

West Boothbay Harbor, Maine

The density fields of large ocean currents such as the Gulf Stream are

baroclinic analogues of upweUing and represent the largest and perhaps

most important mechanism in the world's ocean for the vertical transport

of nutrients. The conceptual model (49-1) illustrates this mechanism.

When the earth's rotation (CO is considered as balancing the pressure

gradient (Pg), there is a secondary cross-stream flow--that is an

aegeostrophic flow--associated with the horizontal advection of the

current. This cross-stream flow is transported along lines of equal density

from the Sargasso Sea into the slope waters off New England. This flow

transports nutrients such as nitrogen and is the reason the slope waters are

more heavily populated with phytoplankton than the Gulf Stream proper.

Of • '_ Pg

49-1. Conceptual Model of Vertical Transport of Nutrients.

49
The Gulf Stream--A Distinct Ocean Color Front

May 1979

The CZCS pigment image on 3 May (51-1) shows the Gulf Stream

System off the U.S. East Coast. Attention is directed to the very sharp

distinction in ocean color of the slope waters (light tones) from that of the

main body of the Gulf Stream (dark tones). This distinction in ocean color

is due to augmentation of phytoplankton growth associated with the

geostrophic flow of the Gulf Stream proper (49-1).

As discussed before, the density fields of large ocean currents such as the

Gulf Stream are baroclinic analogues of upwelling and represent the

largest and perhaps the most important mechanism for vertical transport

of nutrients in the oceans. The CZCS pigment image shows how easily

Gulf Stream meanders and eddies (warm-core rings) can be located

through the use of remote sensing of ocean color by earth-orbiting

satellites.

50
ii ̧i i

i?iili

N

ORBIT 02646 03MAYT9 162242 TO 162442 GMT GAIN 1-4=1 THRESHOLD OFF TILT ANGLE 20.0

GRID CENTER DATA: 162342 GMT 3T.65N OT5.2TN SUN EL 6T AZ 159 ROLL 0.i PITCH -0.I YAM 0.3

88N + 2 + 64N

I I I ! ! ! . I

I

86N + 2 + 62N

PIGMENT

PIGMENT IN MILLIGRAMS/METERS_3

0 .86 .68 .12 .19 .2T .39 .5T .83 1.28 2.11 3.46 5.69 9.35 11.98 25.25 32.0

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

9T0 SCAN LINES PROCESSED 0 SCAN LINES MISSING

CIP VER CRT NO DPS VER SPEC. # FRAME #

V ZE205981 V820401 FT32040 ZG__05981 r_

51-1. Nimbus-7. Orbit 2646. 3 May 1979. CZCS Pigment Image.

51
3E New England Seamount Chain

James F. R. Gower

Institute of Ocean Sciences

Sidney, B.C., Canada

Besides mapping the distribution of phytoplankton pigments in the

surface layer of the ocean, CZCS imagery shows spatial patterns that

contain valuable information on water movement and mixing. In the

following example, a particularly striking turbulent eddy field is visible in

the water north of the Gulf Stream, which appears to be affected by the

New England Seamount chain.

53
Effects of the New England Seamount Chain

on Gulf Stream Surface Flow

May 1979

The relative levels of the pigment concentrations of the Gulf Stream

System have been described by Yentsch (Section 3, page 45) in terms of the

different water masses present, and the influence of tidal mixing in shallow

areas. In addition, the spatial patterns visible in the CZCS pigment images

are also of interest as tracers of the surface flow.

The complex mesoscale eddy field in the water north of the Gulf Stream

is well-illustrated in the CZCS pigment image on 7 May (55-2). (Refer to

55-1 for geographical reference purposes.) Such spatial patterns can be

quantized in terms of their two-dimensional spatial spectrum (Gower

et al., 1981). Any variations in this spectrum, such as those suggested by

the increase in high frequency structure on the right side of the pigment

image, would be expected to correlate with the changing dynamics of

different ocean areas. Such a change is apparent between Area A to the

west and Area B to the east. The mean flow is from west to east at

0.5-1.0 m s-1. The chain of New England Seamounts (plotted as triangles)

crosses the image where this change in structure is observed. The

seamounts extend up from the bottom (5,000 m) to depths of between

1,000 and 2,000 m, and therefore intercept the Gulf Stream which flows in

the top 2,500 m of the ocean. Richardson (1981) has reported the effect of

these seamounts on the surface flow as traced by buoy tracks. He observed

meanders and small-scale (20 km) eddies, near and extending eastward

from individual seamounts. The CZCS pigment image illustrates this

effect more fully, with several instances of smaller eddies near the

seamounts, and a generally more disorganized flow to the east.

The Gulf Stream is the major source of warm water for the North

Atlantic and has a strong influence on North American and European

climates, as well as on the Atlantic fisheries. New data on large-scale

distortion of the flow and the resulting mixing of the water, such as are

provided by CZCS pigment images, can make an important contribution

to our understanding of the global climate and food resources.

References

Gower, J. F. R., K. L. Denman, and R. J. Holyer, 1981: Phytoplankton patchiness

indicates the fluctuation spectrum of mesoscale turbulence. Nature, 288, 157-159.

Richardson, P. L., 1981: Gulf Stream trajectories measured with free-drifting buoys. J.

Phys. Oceanogr., 11, 999-1010.

54
"'_...._iC_!gY_!ii!i!i!iiiii!iiii

• i_il

A A

T',_qN + 2 + %6N

55-1. Locator Map for 55-2.

ORE',ITi-!:::.Ti2!l @THA'Y'T9 iSSggZ TO 15553:.. GHT GAIN l-_r=l THRE:£HOLD OFF TILT ANGLE 2@.i,:!

GRIn CENTER DATA: 155_32 GHT P,-:',.96N i-!6F-',.3_=.,N :S:I_INEL 66 AZ 1_:=,8 ROLL @.2 F'ITCH -@,i ",:"RN @.2

',L:',ZH + 2 + 56H

N

1

I....... t ................ t .......... : t ..... ..... i .................. t

T8N + 2 + 56N

F'TGHENT ........

F'I,::-;HENT I N I"11LLI GRAH::.-b.TIETER:S:mm3

@ .@6 .@8 • 12 •1'9 .2T .g9 .ST .8g 1 .28 2.11 3 ._6 5.69 9 .$5 11.98 25.25 g2 .@

AL,:]OF.'.ITHH::.-::-" @i @@@@@@ @,7!@2 @i @@@@ 80

'_-3.Ti-.1:".-%A1",4LII'4E:,-:: F'F.'.OCE::-;:S:En @ SE:AN LINE:S I'tI:S::S:INC_

CIP 'v'ER C:RT NO DPS ',/ER SPEC. # FF..'.flHE #

',,,,,',2',1@.R1 .............. 1 ZES51@1- vm.:.?@::@P, FTT...s:O'_O L-'(-",a==_, .._:,_:,1@1_.

55-2. Nimbus-7. Orbit 2701. 7 May 1979. CZCS Pigment Image.

55
3F New England Coast

Charles S. Yentsch

Bigelow Laboratory of Ocean Sciences

West Boothbay Harbor, Maine

During summer months the stirring of shallow water columns along

coastal regions by tides promotes phytoplankton growth which is reflected

in the pattern of pigment distribution. The following CZCS images are

excellent examples of this phenomenon in the waters off New England,

due to the strength of tidal currents and the many large shoals throughout

the region.

_,ECED_iNG pA_g_ BL&_r K NOT FILM .ED

_l_mF.,__ INTENTIONALLY BLANP(

57
Enhancement of Phytoplankton Growth by Tidal Mixing

June 1979

Regions of high pigment concentration are strongly correlated with

water temperature; that is, pigment concentrations are highest in regions

where water temperatures are coolest. On 14 June, such regions of intense

tidal mixing on the CZCS pigment image (58-2) and the corresponding

false-color CZCS pigment image (59-1) are outlined by sharp ocean color

fronts. Inside these frontal boundaries the pigment concentration is

greater than 2.0 mg m -3. Outside these fronts, on the warm side, pigment

values are less than 0.5 mg m -3. Note that the areas of intense mixing

outline the major shoal regions such as Nantucket Shoals and Georges

Bank.

The augmentation of phytoplankton growth by tidal stirring is

explained as follows: Surface waters, heated by sunlight, become more

buoyant than the waters they overlie. This layer of warm water over cold

tends to stabilize the water column, thereby isolating the deeper cold water

from the warm surface layers. The cold layers contain large concentrations

of nutrient fertilizers while the warm surface layers do not. Therefore,

isolation of the two layers tends to retard phytoplankton growth. Intense

phytoplankton growth occurs when these two layers are actively stirred,

such as occurs over the Georges Bank. _

The Georges Bank is a shoal region off the New England coast. The

energy for stirring the shallow water column over the Georges Bank comes

from tidal flow. As these currents move across the bottom, the friction

creates turbulent stirring (58-1). Generally speaking, the intensity of the

stirring is proportional to the speed of the current and the water depth.

58
58-1. Schematic

of Mixing Process

in Shoal Regions.

TSN

ORBIT 07226 14JUN79 153752 TO 157952 GHT GAIN 1-4=i THRESHOLD OFF TILT ANGLE 2k_._3

GRID CENTER DATA: 157852 GHT 79.74N 064.62N SUN EL 71 AZ 150 ROLL 0.2 PITCH -0.0 YAN 0.7

+ 2 +

! .......... ! ........................... ! ! ..... !

T4N + 2 +

PIGHENT

PIGHENT IN HILLIGRAH$,/HETERS_7

0 .06 ,08 .12 .19 .27 .39 .57

ALGORITHMS: 01 00 00 00 00 02 01 00 00 00

970 SCAN LINES PROCE$SED 0 8CAN LINE8 MISSING

5ZN

52N

•83 1.28 2 •11 3.46 5.69 9.35 11.98 25.25 32,0

CIP VER CRT NO DPS VER $PEC. # FRAHE #

V ZE211581 V820208 F732040 ZG211581

58-2. Nimbus-7. Orbit 3226. 14 June 1979. CZCS Pigment Image.
..... "_iSiiii

_'_ T y-_

59-I. Nimbus-7. Orbit 3226. 14 June 1979. CZCS False-Color Pigment image.

59
Section 4

Gulf of Mexico/Caribbean Sea

4A Florida West Coast/Central Gulf of Mexico

The Loop Current--Augmentation of Primary Production

Yentsch ....................................................... 63

4B Gulf of Mexico/Cuba

The Loop Current/Mesoscale Eddies

E1-Sayed, Ichiye, and Trees ..................................... 67

PRITCED_O PACE PL_,__K NOT FIL_

PAGE_I_TENTIONALLy BLAf_K

61
4A Florida West Coast/Central Gulf of Mexico

Charles S. Yentsch

Bigelow Laboratory of Ocean Sciences

West Boothbay Harbor, Maine

An example of phytoplankton growth being augmented by a major

ocean current is observed in the CZCS images of Florida and the eastern

Gulf of Mexico in this case study. In this region, the thermal Loop Current

forms a front which is due to the entry of equatorial water into the eastern

Gulf of Mexico through the Straits of Yucatan. The equatorial water

penetrates as far north as 27 ° N, which encompasses most of the eastern

Gulf of Mexico.

63
The Loop Current-- Augmentation of

Primary Production

March 1979

The CZCS pigment pattern on 15 March (65-2) correlates with the

general thermal pattern shown by the CZCS infrared channel (65-1).

Warm equatorial waters are associated with low concentrations of

phytoplankton pigment (dark tones) and cooler waters are associated with

higher levels (light tones) of pigment. This temperature/pigment

relationship is reflecting the difference in levels of nutrient enrichment.

The increased phytoplankton abundance is due to increased vertical

mixing which arises from the flow of the Loop Current and from

constraints placed on that current by the shape of the Florida peninsula

and its continental shelf (64-1). The dynamic topography on the eastern

side of the gulf demonstrates that the mean flow is augmented in the region

of the Florida escarpment. Associated with this increase in flow is the

imbalance between the Coriolis and pressure forces which create the

isopycnal flow, causing enrichment of the waters adjacent to the Florida

peninsula by deep nutrient-rich water.

64-1. Gulf of Mexico

Continental Shelf

and Loop Current

Velocity Profile.

-30 °

1.0 2.0

64
F......

 ̧!9 ̧ ̧

I:I:,F.'.E',IT i._;!19i3'9ISI.IAF'.T'_q.li3S::_.i-!_=. .,TII]IIii354i-.-!4GMT I:]AII..I1-4=2 THRE:!_:;HI:I:ILB OFF TILT ANGLE li::..i.-:!

GF.'.IEIF:ENTEP. EIATA: 16_E7i-!_<,GMT 2',-',.TYNi-._',-',i-!.5i_!H :!-I:I_IN EL _:<SAZ 26:-. ROLL -i-!.i-!F'ITF:H -i-!.2 YAH i-!.4

'921 _ + i + T iii

I I I ! I I I I I I I I ! ! ! ! ! I I ! ! I

-.

__

i t i

65-1. Nimbus-7. Orbit 1969. 15 March 1979. CZCS Infrared Image.

.7:,F.'.E',IT i-!i'_.69 15MAF.'.T9 16_<,:.2i-!_<, TO 16_+i-!+ .GHT .::4AII.Ii-+=2 THF.'.E::E;:HOLFI .:-:.FFTILT AI..F_LE 16.i-!

GF.'.IFICENTER FIATA: 16_E_i..:!5,::4I.IT2',-',.7TIIi]!',-', i]!._=., i]!H ::f;:l_IIl EL _<",-', AZ IC.,:2 F.'..:Z:,LL -i-!.if!F'ITCH -i-!.2 YAH i-!._

'93._ + i + Y iI_

I i i i i l i i i I I _ ! I _ l ............. ! ....... i i i i .... i

:,ii ............................................. ."'. ................................................. _!!i:_ :iiiii',:,i;i. ............................................................................................................................................

i i l i i i i i i i i i i i i i i l i i

:-:'9_ 1 + i + TOLl

P I,-_t IEt _T

.................................. ........... 1,,.k:kj,_ l_i

QUAMTY :

F'IGtIEIITIIa}ilLLI,]F'Hi{:!

0 • Oi_--, • 0',-I • 12 • 1 '9 • : T • 79 • ST • I5',T i • 2',-', 2 • 11 C • +6 S. 69 9. T3 11 • '9',-', 25.2_< :72. i-!

ALG,:I:,F.tlTHM:I-;:-" i..-!:-/ O l 01 i_!i..-.! O0 i-!g i._.-.!:7:. ' i.-.-!i-!i..:!i-! i..-.!i-!

%t5 :L:;:F:AN LINE::.-; PF.:OF:E::.-;::.-;EFI iT :L:;FAN LINE::.-I: MI::.-;:::.-;:IN,:-4

F:IF' 'v'ER I-:F..:T HIT) ITF'::.-;:",,,"ER :!-;:F'EL-:. # FRAME #

'v' ZE_£T_TI ',,,,,",-',21i-Ii __._:, FY_F!+i..-__ _ _. Z,.I_22Y_Tl

65-2. Nimbus-7. Orbit 1969. 15 March 1979. CZCS Pigment Image.

65
4B Gulf of Mexico/Cuba

Sayed Z. EI-Sayed

Takashi Ichiye

and

Charles C. Trees

Department of Oceanography

Texas A&M University

College Station, Texas

The Gulf of Mexico is a semi-enclosed basin with inflow through the

Yucatan Channel and outflow through the Florida Straits. The most

prominent single physical feature of the gulf is the Loop Current. The

Loop Current's path and extent of intrusion into the gulf are highly timedependent, with apparent annual cycles (Leipper, 1970) and significant

variability in the year-to-year pattern (Maul, 1977). Mesoscale eddies

(rings), which are the second major phYSical feature in the Gulf of Mexico,

are pinched off the Loop Current and drift westward.

The total pigment concentrations (chlorophyll a + phaeopigment) in the

Gulf of Mexico exhibit marked contrast between inshore and offshore

waters; the offshore waters were characterized by Bogdanov et al. (1968),

and E1-Sayed (1972), as being highly oligotrophic as compared to the more

productive neritic regions.

PA_'_ ,_ INTENTIONAtLY B[:_,'_"

67
The Loop Current/Mesoscale Eddies

October 1979

The CZCS pigment image on 3 October (68-2) shows a portion of the

Loop Current between two cloud banks in the eastern gulf, with total

pigment concentrations in the Loop Current of less than 0.06 mg m -3. The

circulation patterns in the western gulf are characterized by the presence of

mesoscale eddies (68-1, Inset A). The belt of relatively clear water in this

region seems to be the boundary of a cyclonic eddy which was also

observed during the cruise of the R/g Gyre (80 G-l) in April 1980 (Brooks

and Eble, 1982). An enlarged view of this area (69-1) shows more distinctly

the relatively higher pigmented (chlorophyll) water mass occupying the

central area of the cyclonic eddy which is caused by the convergence of the

surface waters in the eddy. In the western Gulf of Mexico (68-2) the width

of the coastal front, judging from the high pigment concentrations, is

narrower than that found off the Yucatan Peninsula. A major

contribution to the increase in predicted pigment off the Yucatan

Peninsula is caused by suspended sediment and not phytoplankton.

In the Caribbean Sea, some interesting circulation patterns are observed

just south of the western tip of Cuba (68-2; and 68-1, Inset B). In the

enlarged view of this area (69-2) a cyclonic eddy is observed between the tip

of Cuba and Islas de Pinos. This eddy is formed by a countercurrent along

the northern coast of Cuba. Such a countercurrent is not often observed,

but was inferred from the geostrophic current pattern (Ichiye et aL, 1973).

This countercurrent entrains coastal waters southward and forms a 40-km

eddy. Associated with this eddy are turbulent structures which are also

observed south of the eddy.

The CZCS pigment image on 8 October (70-2) in the northern Gulf of

Mexico shows the northward intrusion of the Loop Current to within

approximately 60 km of the Mississippi Delta (70-1). The intrusion of

clear water extends westward to about 92 ° W (71-1) and represents the

farthest westward penetration of the Loop Current recorded in the

literature. There is a narrowing of the Loop Current around 85 ° W which

suggests that an eddy could be spinning off at some future time. Leipper

(1970) and Whitaker (1971) found that the maximum intrusion of the

Loop Current occurred in October, whereas Robinson (1973) and Maul

(1977) observed this maximum several months earlier. These results

emphasize the temporal and spatial variabilities of the Loop Current.

As the Loop Current passes south of the Mississippi Delta, it entrains

coastal waters some 100--150 km out into the Gulf of Mexico. The western

edge of the Loop Current generates a cyclonic eddy of coastal waters and

entrains this water some 50 km southward.

In the western gulf, coastal waters with high pigment concentrations are

transported offshore just east of Browns,ville, Texas. This entrainment is

caused by two eddies: a northern cyclonic eddy located around 27 ° N,

94 ° W, and a southern anticyclonic eddy located at 26 ° N, 94 ° W. Brooks

and Legeckis (1982) observed the same features in 1980 using satellitederived surface temperatures.

Around 26 ° N, 92 ° W there is entrainment of coastal waters into the gulf

(70-1, stippled area). This transport was observed by El-SaTed and Trees

(1980), with total pigment concentrations around 0.39 mg m -3, which

agrees well with that predicted from the CZCS images.

68
N

99N + 1 + 80N

l

1

pigmented

water

clear water

cyclonic eddies

suspended

sediment

YUCATAN

PENINSULA:

:yclonic

eddy

Islas de

Pinos

9TN + i + TBN

////

////

////

////

////

////

//

68-1. Locator Map for 68-2, 69-1, and 69-2.

,C!_..:__,:-.-,:._:f_v PAGS

t;e r_.tJr_ C}YU:_kg.f '

ORBIT O_rV61 0302TT9 iZZOiV TO IT321-TGRT--GAIF_'Is'LF--:TWHRESHOLD OFF TILT ANGLE 16,0

GRID CENTER DATA: iT311T GMT 22.41N 088.T9N SUN EL 63 AZ it3 ROLL 0.i PITCH -0.1 YAN 0.2

99N + 1 + 80N

1

9TN + 1 + TBN

PIGMENT

....... ......

PIGMENT IN MII_LIGRAMS/METERS_3 ii!_ii_i

0 .06 .08 .12 .19 .LT .39 .5T .83 1.28 2.11 3.46 5.69 9.35 11.98 25.25 32.0

ALGORITHMS: 02 O1 O1 O0 00 03 02 00-00 O0 ........ : CIP VER CRT NO DPS VER SPEC. # FRAME #

9T0 SCAN LINES PROCESSED 0 SCAN LINES MISSING V810306 ZE51901- V820821 FT32040 ZG051902

68-2. Nimbus-7. Orbit 4761. 3 October 1979. CZCS Pigment Image.

t": "¢ 7 ''--_ ",:'-_:, 7" A -_ _ ._ #'_
69-1. Enlarged View of Inset A. bus-7. Orbit 4761. 3 October 19791 CZCS Pigment Image.

69-2. Enlarged View of Inset B' Nimbus-7. Orbit 4761 3 October 1979. CZCS Pigment Image.

69
98N + 1 + TgN

...................... ........... :................. ........

• " anticyclonic J

eddy

Gulf of Mexico

Mississippi

Delta

iiiii!!!iiii!iiii!i:i..........

:.:.:,:.:.:.:.:.:.:.:..

...................... iiiiiiiiiiiiiiiiii.:i':::::::::::::::'.'.........

Loop Current

narrows

96N + 1 + TBN

70-1. Locator Map for 70-2 and 71-1.

ORBIT 0_r830 1480CTT9 1T22_r2 TO 1T2_r2 GHT GAIN 1Jr=l THRESHOLD OFF TILT ANGLE 1:-".0

GRID CENTER nATA: iT23_r2 GHT 28.081`.1 088.0514 SUN EL 56 AZ iTS ROLL 0.2 PITCH _Z._.k]YAN 6.2

98N + 1 + TgN

'9i_--;,_.4 + 1 + T8N

F'IGHENT

F'IGI'IEI'4T IN MILLIGRAMS/I'ETERS_:*:_;

0 ,06 .08 •12 •19 .2T ,39 ,ST ,83 1.28 2,11 3 ,_r6 5,69 9.35 11,98 25.25 32.0

ALGORITHH,-_-': .):-. i-._l k.-_l 00 00 Og OZ 00 _,10 00

9T(! :!_-':CANLINE:S: F'ROZ:EB::E:E£ _1 SCAN LII'IES HISSII'IG

CIP VER CRT 1'40 DPS VER SPEC. # FRAME #

',.,'818121 ZE38901- V820821 FT326_r8 ZGO38982A

70-2. Nimbus-7. Orbit 4830. 8 October 1979. CZCS Pigment Image.

70 oF. Poo& _&Ll_il
....._i_iii_i_ili_i_i!

i

References

Bogdanov, D. V., V. Sokolov, and W. S. Khromov, 1968: Regions of high biological

productivity in the Gulf of Mexico and Caribbean Sea. Oceanology, 8, 371-381.

Brooks, D. A., and M. C. Eble, 1982: Hydrographic observations in the western Gulf of

Mexico. Texas A&M University, Dept. of Oceanography, Ref. 82-2-T, 174 pp.

Brooks, D. A., and R. V. Legeckis, 1982: A ship and satellite view of hydrographic features

in the western Gulf of Mexico. J. Geophys. Res., 87(C5), 4195-4206.

E1-Sayed, S. Z., 1972: Primary productivity and standing crop of phytoplankton. In

Chemistry, Primary Productivity, and Benthic Marine Algae of the Gulf of Mexico,

Serial Atlas of the Marine Environment, Folio 22, edited by V. C. Bushnell, American

Geographical Society, 8-13.

EI-Sayed, S. Z., and C. C. Trees, 1980: Ecological studies of phytoplankton in the Gulf of

Mexico during NOAA/NMFS Oregon H Cruise. Texas A&M University, Dept. of

Oceanography, Ref. 80-8-T, 53 pp.

Ichiye, T., H.-H. Kuo, and M. Carnes, 1973: Assessment of currents of hydrography of the

eastern Gulf of Mexico. Texas A&M University, Dept. of Oceanography, Ref. 601,

2.10-2.29, 5.10-5.15, and 6.1-6.7.

Leipper, D. F., 1970: A sequence of current patterns in the Gulf of Mexico. J. Geophys.

Res., 75, 637-657.

Maul, G. A., 1977: The annual cycle of the Gulf Loop Current Part 1: Observations during

a one-year time series. J. Marine Res., 35(1), 29-47.

Robinson, M. K., 1973: Atlas of monthly mean sea surface and subsurface temperature

and depth of the top of the thermocline, Gulf of Mexico and Caribbean Sea. Scripps

Institution of Oceanography, La Jolla, Calif., Ref. 73-8, 105 pp.

Whitaker, R. E., 1971: Seasonal variations of steric and recorded sea level of the Gulf of

Mexico. M.S. Thesis, Texas A&M University, Dept. of Oceanography, College

Station, Texas, 109 pp.

OE POOl{ Q_UA_ITY

71-1. Enlarged View. Nimbus-7. Orbit 4830. 8 October 1979' CZCS Pigment Image'

71
Section 5

Western European Basin

5A Celtic Sea/Bay of Biscay

Phytoplankton (Coccolithophores)

Holligan and Viollier ........................................... 75

pR_EDR_G PAGE BLANK N_,_k__

PAB'E .'7__--._tNTEN$1ONALL¥BLANI_

73
5A Celtic Sea/Bay of Biscay

Patrick M. Holligan

Marine Biological Association

Plymouth, United Kingdom

and

Michel Viollier

Station d'Oc6anologie et de Biologie Marine

Roscoff, France

Each year during the early summer, extensive patches of water giving

high reflectance of visible light are observed along the outer shelf margin

between 45 ° and 60 ° N. Observations taken at sea in 1982 established that

these are caused by coccolithophores; phytoplankton with external plates

or coccoliths of calcite, which become dominant after the main spring

diatom bloom has declined. These organisms, particularly the widespread

temperate species Emiliania huxleyi, are of particular importance in the

biogenic sedimentation of carbon (as calcite) in the oceans. The reflectance

of light by the coccoliths must be taken into account in the development of

accurate atmospheric correction and chlorophyll algorithms for the

processing of remotely sensed ocean color data.

PRECEDING PAGE

PArlE_'-_ INTENTIONALLY B[/ll_

BLANK NOT FLI,_

,S: 75
Phytoplankton (Coccolithophores)

June 1979

Frontal boundaries between water masses with distinct hydrographic

properties and plankton communities (Pingree et al., 1982) are seen on

CZCS images on 19 June (76-1) as regions with relatively high diffuse

attenuation coefficients (upper image) and pigment values (lower image).

The shelf break frontal system (SBF, 77-1), which follows the 200-m

isobath, represents the eastern extent of surface mesoscale eddies

characteristic of the deep waters of the Bay of Biscay. On the shelf between

southwestern England and northwestern France, the tidal front (TF)

marks the transition from seasonally stratified and relatively warm water

in the Celtic Sea to tidally mixed water in the English Channel. The

coccolithophore populations appear on the Channel 3 image (77-2,

Subsurface Radiance) as areas of high reflectance in outer shelf waters.

The coccolithophores give maximum reflectance in Channel 1 (blue)

and, relative to clear offshore and turbid coastal waters, significant

reflectance in Channel 4 (red; Holligan et al., 1983). The latter property

affects the atmospheric corrections so that appropriate adjustments

should be made for water-leaving radiance by correlation with Channels

1-3, or the Channel 4 radiance values for pixels adjacent to the bloom

used. These channels are in reference to Level I images, which are not

shown in this publication.

The influence of coccolith reflectance on the chlorophyll algorithm is

more difficult to define, as no correlation between coccolith density and

pigment concentration is expected for the scene as a whole. This problem

is illustrated by the comparison between the Channel 3 image (77-2) and

either the diffuse attenuation coefficient or pigment image (76-1). In the

coastal, tidally mixed water, for which the levels of suspended material

and chlorophyll can be considered proportional, the spatial patterns of

high reflectance are positively correlated. By contrast, no such

relationship holds for the coccolithophore water.

The maximum chlorophyll a levels observed in the coccolithophore

blooms are generally 2-3 mg m -3 compared to values of up to 5 mg m -3

associated with persistent diatom populations at the shelf break. A more

important parameter to derive from the CZCS imagery, however, is

coccolith abundance as a measure of calcite-carbon that will be lost to the

bottom sediments. The reflectance signal is generated both by living cells

and detached coccoliths, and preliminary calibration values suggest that

typical maximum reflectance values correspond to about 1gm m -3 CaCO3

in the surface water.

fi:

I"

Referene_

Holligan, 1_. M., M. Viollier, D. S. Harbour, P. Camus, and M. Champagne-Philippe,

1983: Satellite and ship studies of coccolithophore production along a continental shelf

edge. Nature, 304, 339-342.

Pingree, R. D., G. T. Mardell, P. M. Holligan, D. K. Griffiths, andJ. Smithers, 1982: Celtic

Sea and Armorican current structure and the vertical distribution of temperature and

chlorophyll. Continental Shelf Research, 1, 99-116.

,," 76
__ i_ _'

NIMBUS T CZCS

ORBIT 03293 19JUNT9 120132 TO 120332 GMT GAIN 1-4=1 THRESHOLD OFF TILT ANGLE 16,0

GRID CENTER DATA: 120232 GMT 46,30N _)12,56N SUN EL 65 AZ 153 ROLL 0,1 PITCH 0,0 YAM -0,1

2TN + 1 + 2N

23N + i + 1E

DIFFUSE ATTENUATION COEFFICIENT

2TN + i + 2N

i

23N + i + IE

PIGMENT

DIFFUSE ATTENUATION COEFFICIENT IN METERS_-I

0 .028 ,034 .041 ,050 ,OGi .075 .09_ ,li2 ,i3T .16T ,204 .249 .304 ,3Tl .453 ,500

....

PIGMENT IN MILLIGRAMS/METERS_

0 .06 .08 ,12 .19 .2T ,39 .ST ,83 1.28 £ .11 3.46 5.69 9.35 ii .98 25,25 32.8

ALGORITHMS: 01 08 00 08 00 02 Of 00 00 08 C IP VER CRT NO DPS VER SPEC. # FRAME #

970 SCAN LINES PROCESSED 0 SCAN LINES MISSING V801005 ZE09301- V820401 FT32040 ZG009302

76-1. Nimbus-7. Orbit 3293. 19 June 1979. CZCS Diffuse Attenuation Coefficient (upper) and Pigment (lower) Images.
2TN

tJH_:_iNAL PAGE _S

D__ pg"_d"_]ClP tf"3iTT A T _w"_'_7

200 m

/shelf

lend

I

\

\

\

%

\

\

\

\

\

\

iENGLAND!

English

Celtic Sea / Channel

/

(. -

\\ "_o

\ "_"

\ 0% .

, %

\

\

\

Bay of \

Biscay \

\

20o

27N + i +

FRANCE 1

77-1. Locator Map for 76-1 and 77-2.

2TN

5

1

I I ....- 1 ............ t " | "

234 + 1 +

UPWELLED RADIANCE

. 4

El

77-2. Nimbus-7. Orbit 3293. 19 June 1979. CZCS Upwelled Radiance Image.

77
Section 6

Atlantic South American Coast

6A Amazon River

The Amazon River Outfall

Yentsch ....................................................... 81

_RECFA)RqG PAGE BLANK _

I:)AaE- 7oC" INTENTIONALLYBILANI_

79
6A Amazon River

Charles S. Yentsch

Bigelow Laboratory of Ocean Sciences

West Boothbay Harbor, Maine

During the early studies of primary production, the distinguished

marine biologist Einer Steeman Nielsen demonstrated a correlation

between ocean color (as measured by Forel standards) and photosynthetic

carbon fixation. He observed that green waters were most productive, blue

waters less so. However, a major deviation from this correlation occurs in

the region of the Amazon River outfall.

FRNCED.._qG PAGE BL,_NK NOT FIL_FA)

P_A&E ,_ INTENTIONALLY BLANt_

81
The Amazon River Outfall

August 1979

The false-color CZCS pigment image on 17 August (83-1) of the ocean

region off the Amazon shows changes in water color from yellow near the

coast to dark blue offshore, just prior to the onset of the rainy season. This

distinct color distribution highlights the Amazon outfall area. In this

region, major color change is due to input of river water heavily laden with

yellow organic material, and not due to changes in concentration of

photosynthetic phytoplankton. The outfall of the Amazon is diverted

north by the Guiana Current, but eventually curves out from the coast to

the open ocean.

82
Q V (U. "

83-1. Nimbus-7 Orbit 4110. 17 August 1979. CZCS False-Color Pigment Image.

83
Section 7

South Africa

7A South Africa West Coast

The Benguela Current--Coastal Upwelling

Shannon and Anderson ......................................... 87

7B South Africa South Coast

The Agulhas Current--Surface Temperature,

Eddies, Water Content

Schumann ..................................................... 91

P_E-_--_JNTENTIONALLY BLANI_

85
7A South Africa West Coast

L. Vere Shannon

Sea Fisheries Research Institute

Cape Town, South Africa

and

Frank P. Anderson

National Research Institute for Oceanology

Stellenbosch, South Africa

The Benguela Current region off the west coast of southern Africa,

particularly the southern portion of the region, is characterized by intense

upwelling driven by specific wind events, well-defined frontal systems, and

high concentrations of primary plankton. Because of the pulsed nature of

the upwelling, this region is ideal for the study of the initiation, growth,

and decay of upwelling events, in contrast to regions further north where

upwelling occurs almost continuously. However, because of the high

frequency of events, the use of conventional shipboard techniques is

impractical. The CZCS with its large spatial coverage, high resolution,

and comparatively high repetition frequency is ideal for the study of these

upwelling events.

_F_qG PAG_ _LANK NOT IeIL,_FA)

87
The Benguela Current--Coastal Upwelling

February 1979

The false-color CZCS pigment image on 19 February (89-1) shows the

distribution of chlorophyll off the west coast of South Africa. The

chlorophyll concentrations range from less than 0.1 mg m -3 to over

10.0 mg m -3. Clearly shown is the extent of coastal waters with a cool

surface layer and chlorophyll concentrations exceeding 0.1 mg m -3

separated from the warmer, chlorophyll-poor oceanic water by a welldefined front. The corresponding thermal infrared image (89-2) shows the

surface temperature distribution and confirms that the thermal and color

fronts coincide. The thermal infrared image temperature range is +12 ° C

(dark blue) to +20 ° C (red).

There are three areas of high chlorophyll concentrations within the

coastal waters (89-1). The first area of high chlorophyll, off the Cape

Peninsula, is separated from the land by a strip of very cold, freshly

upwelled water (89-2) containing comparatively low concentrations of

chlorophyll. This cold surface water is forced offshore fairly rapidly by the

continued upwelling; and the plankton, needing time to grow, achieves its

maximum concentration some distance offshore. Growth is also

accelerated by the warming of the surface water as it moves offshore.

The second area of high concentration, off Saldanha Bay, is most likely

the result of the same wind event, but because of the less rugged

topography along the coast, the upwelling is not as intense and hence

chlorophyll has had time to develop alongside the coast without being

inhibited by a strong flow of very cold upwelled water, as is the case offthe

Cape Peninsula.

The third high-chlorophyll area in the north is the southern extremity of

the quasi-stationary "straight-coast" upwelling which extends northward

along the entire west coast of southern Africa.

Other features of note are the meanders in the front, with a large

cyclonic eddy west of Saldanha Bay, probably the result of a breakdown in

the front following intensification of the front by a previous upwelling

event. Such intensification is evident west of the peninsula where there are

signs that the meander in that area could develop into an eddy at some

later stage.

North of Cape Columbine, the complex flow regime in the area is clearly

illustrated by the chlorophyll concentration patterns which confirm the

extreme patchiness of the chlorophyll distribution.

The patch of high chlorophyll in St. Helena Bay could be evidence of a

cyclonic eddy entraining high chlorophyll concentrations from the

northern extension of the Saldanha Bay upwelling cell, or it could be a

result of the input of nutrients from the Berg River which runs into the St.

Helena Bay at about the point where the plankton "plume" touches the

land.

Both the thermal infrared and the pigment images show very clearly the

expected north to northwesterly flow of surface water away from the coast

under the influence of the prevailing southeasterly wind that maintains the

intense offshore oceanic front during the summer months. Winter imagery

available does not show evidence of a continuous, intense oceanic front.

Although the CZCS does not provide data on the vertical distribution of

chlorophyll in the water columns, it does provide a major step forward in

the study of upwelling regions such as that of the southern Benguela

region, and could play a role in fisheries management if imagery was

routinely available which could be processed to provide a quantitative

assessment of primary production.

88
CHLOROPHYLL

CONCENTRATION

m gm -3

<1.0

1.0 - 3.0

3.0 - 1.0

1.0 - 3.0

Algorithm developed and images produced by

Mr. N. Walters, National Physical Research Laboratory, South Africa.

3.0 - 10.0

>10.0

89-1. Nimbus-7. Orbit 1634. 19 February 1979.

CZCS False-Color Pigment Image.

89'2. Nimbus'71 Orbit 1634' 19 February 1979..............

CZCS False-Color Infrared Image.

89
7B South Africa South Coast

Eckart H. Schumann

Department of Oceanography

University of Port Elizabeth

Port Elizabeth, South Africa

The dominating oceanographic feature along the southern tip of Africa

is the Agulhas Current. This current flows poleward along the eastern edge

of the Agulhas Bank, paralleling the southern coast of South Africa, and

turns into the West Wind Drift of the Circumpolar Current. It is a warmwater current, generally very low in nutrients in the surface waters. Large

eddies are a common feature on the northern front of the current, and a

cold-eddy can be enclosed within the bight of such a meander. Upwelling

also takes place along the inshore frontal region, and may be an important

source of nutrients for the whole bank area.

_RECEDENG PAGE BLANK NOT _]5_im

PAtIE. _'/--)

"-_'_---- tNTEN'TIO?IALLY BLA_t_

91
92

The Agulhas Current--Surface Temperature,

Eddies, Water Content

June 1979

The false-color CZCS pigment images (93-1 and 93-2) cover the area

from the Breede River in the west to Cape Seal in the east, and extend

about 200 km offshore. Off Cape Seal the Agulhas Bank shelf width is

about 80 km, widening rapidly westward to about 270 km off Cape Infanta

(not shown, west of Breede River).

The relative difference in surface temperature makes the Agulhas

Current very easy to identify in thermal infrared images (93-1). The image

shows the main flow of the current in the bottom right hand corner. An

eddy with a scale of 100 to 200 km is observed inshore of this flow,

enclosing a cold core. There is an indication of an increase in total

suspended solids (TSS), perhaps due to the upwelling known to be

associated with such a cold core.

The temperature gradients across the frontal areas are considerable,

with changes of 3 to 4° C taking place over a few pixels. The structure

within the eddy itself is also apparent, while smaller scale features can be

seen developing on the northern front. This may be part of the "energycascade" to smaller scale processes, and a means whereby the Agulhas

Current surface waters can penetrate onto the shallower bank regions.

The thermal infrared image does not show whether there is a

countercurrent associated with the sheared-off tongue of Agulhas Current

water. However, if it is assumed that the main source of TSS is in the

coastal rivers, then this image tends to indicate total movement toward the

southwest. This would occur by a process of entrainment.

Cooler surface water is shown on the wider reaches of the bank, with the

pronged temperature structure apparently correlating with the pattern of

TSS. With the limited sea surface temperature gradients in this area, it is

not possible to use these for determining circulation patterns.

On the other hand, it is known that the Breede River, and probably also

the Gourits River, were flowing strongly after general rains in their

catchments prior to the image being taken. Other minor contributions

would also have come from smaller rivers along the coast. The resultant

sediment distribution tends to lie in a band less than 20 km wide all along

the coast, giving an indication that alongshore currents dominated the

flow structures.

It is probably the wind that is the primary driving force in these inshore

regions, with westerlies generally dominant in winter when the image was

taken. An eastward coastal jet would result, though the change in coastline

near the Gourits River may affect this flow. Offshore there is a tongue of

TSS apparently progressing further east.

In such an analysis, TSS can be used as a tracer, although to be really

useful a series of such images separated by periods of a day or so could

provide information on the development of current systems. It is also

acknowledged that TSS, whether they be organic or inorganic, play a very

important part in chemical and biological processes operating in the shelf

areas. A knowledge of the distribution of different TSS (confirmed by sea

truth data), their origin and eventual fate would therefore be invaluable in

the determination of trophic pathways. Such information would be

important to the fishing industry.

The actual distribution of sediment deposited in such a shelf region

could also be investigated with the TSS images. In this area it is known

that there is a mud and sediment band parallel to the coast and fairly close

inshore, which tends to tie in with the conclusions reached earlier.
_ _ _i _i ::__:/_:: _ _ ........ _i_

93-1. Nimbus-7. Orbit 3251.

16 June 1979. CZCS False-Color

Infrared Image.

93-2. Nimbus-7. Orbit 3251.

16 June 1979. CZCS False-Color

Suspended-Solids Image.

93
Section 8

Antarctica

8A Drake Passage/Western Scotia Sea

The Polar Front/Cold-Core Rings--Effects on

Abundance and Distribution of Phytoplankton

E1-Sayed and Hofmann ......................................... 97

PREC_.[i:_t PAGE BLANK NOT FILMED

INTENTIONALLYBLANI_

95
8A Drake Passage/Western Scotia Sea

Sayed Z. EI-Sayed

and

Eileen E. Hofmann

Department of Oceanography

Texas A&M University

College Station, Texas

In recent years, several countries have shown increasing interest in

exploiting the Southern Ocean's living resources. If the harvest of these

resources is to be properly managed, we first need an accurate assessment

of the biological productivity in the Southern Ocean. Without adequate

synoptic data, it is difficult to arrive at realistic estimates of phytoplankton

abundance and to develop models of phytoplankton dynamics which will

successfully predict trophic interactions. Although a great deal of useful

information has been obtained on the Southern Ocean's standing crop and

primary production during the past 25 years, these estimates are based

largely on point sources (i.e., stations) and were taken onboard

oceanographic ships at different seasons and often in different years

(E1-Sayed, 1967). As a result, overall estimates reflect broad temporal and

spatial variability in the phytoplankton standing crop and primary

production.

For large and difficult-to-explore areas such as the Southern Ocean, the

CZCS, combined with ground-truth data, makes it possible to arrive at an

accurate estimate of phytoplankton biomass and possibly of primary

productivity. The following case study documents efforts to obtain such

estimates with the CZCS.

97
The Polar FrontCold-Core Rings--

Effects on Abundance and Distribution of Phytoplankton

January 1979

The dramatic CZCS pigment image of the central Drake Passage and

western Scotia Sea taken on 6 January (99-2) and the corresponding

locator map (99-1) show the extensive geographical variability of nearsurface distributions of phytoplankton pigments in these icy waters. This

is in sharp contrast to the relatively smooth pattern of pigment

distribution obtained from shipboard observations made in this region.

The image shows generally low pigment values in the polar front region

(0.05 mg chl m-3). However, there is, within the polar front, a region of

relatively high pigment concentration squeezed between bands of low

pigment concentration. Pigment values north of the polar front are also

generally low, but isolated regions of concentrations in excess of

0.1 mg chl m -3 are observed. The highest pigment values occur to the south

of the polar front. The reasons for these enhanced concentrations are

unknown. The general pattern and values of the pigments shown in the

image are in agreement with shipboard observations made in this region of

the Southern Ocean (E1-Sayed et al., 1964; E1-Sayed, 1967).

The meandering nature of the polar front is apparent in the CZCS

image. Also apparent are cold-core rings which form from meanders in the

polar front (Joyce and Patterson, 1977; Joyce et al., 1981; Peterson et al.,

1982; Hofmann et aL, 1984). Like their counterparts in the Gulf Stream

and Agulhas Current, these rings retain their physical and probably

biological characteristics for long periods. Peterson et al. (1982) suggest

that these rings are an important component of the heat and salt budgets of

the Southern Ocean. It has been shown that within Gulf Stream cold-core

rings, the structure of the planktonic community is conserved (Wiebe

et al., 1976). Furthermore, Wiebe and Boyd (1978) suggest that these coldcore rings are capable of transporting zooplankton communities a long

distance from their usual habitat. Similarly, cold-core rings in the

Southern Ocean may also transport biological and chemical properties

across the Antarctic Circumpolar Current.

It is unfortunate that this region of the Southern Ocean is often covered

by clouds. This makes it difficult to obtain a sequence of CZCS images

from which the time development of phytoplankton blooms and water

movement can be studied. However, the available images do provide

synoptic observations in a region in which logistical constraints make a

comprehensive field study difficult.

References

El-Sayed, S. Z., 1967: On the productivity of the Southwest Atlantic Ocean and the waters

west of the Antarctic Peninsula, Antarctic Research Series. In Biology of the

Antarctic Seas III, ll, edited by Waldo Schmitt and George Llano, American

Geophysical Union, Washington, D.C., 15-47.

, 1972: Primary productivity and standing crop of phytoplankton. In Chemistry,

Primary Productivity, and Benthic Marine Algae of the Gulf of Mexico, Serial Atlas of

the Marine Environment, Folio 22, edited by V. C. Bushnell, American Geographical

Society, 8 13.

EI-Sayed, S. Z., E. F. Mandelli, and Y. Sugimura, 1964: Primary organic production in the

Drake Passage and Bransfield Strait. In Biology of the Antarctic Seas/, 1, edited by

M. O. Lee, American Geophysical Union, Washington, D.C., 1-110.

Hofmann, E., T. Whitworth III, and D. Nowlin, Jr., 1984: Mesoscale flow variability at

Drake Passage. J. Geophys. Res., submitted.

Joyce, T. M., and S. L. Patterson, 1977: Cyclonic ring formation at the polar front in Drake

Passage. Nature, 265, 131 133.

Joyce, T. M., S. L. Patterson, and R. C. Millard, Jr., 1981: Anatomy of a cyclonic ring in

Drake Passage. Deep-Sea Res., 28, 1265-1289.

Peterson, R. G., W. D. Nowlin, Jr., and T. Whitworth III, 1982: Generation and evolution

of a cyclonic ring at Drake Passage in early 1979. J. Phys. Oceanogr., 12, 712-719.

Wiebe, P. H., and S. H. Boyd, 1978: Limits of Nematoscelis megalops in the Northwestern

Atlantic in relation to Gulf Stream and cold-core rings. 1. Horizontal and vertical

distributors. J. Marine Res., 36, 119 142.

Wiebe, P. H., E. M. Halburt, E. J. Carpenter, A. E. Jahn, G. P. Knapp III, S. H. Boyd,

P. B. Ortner, and J. L. Cox, 1976: Gulf Stream cold-core rings: Large-scale interaction

sites for open ocean plankton communities. Deep-Sea Res., 23, 695 710.

98
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99-2. Nimbus-7. Orbit 1029. 6 January 1979. CZCS Pigment Image.

99