UNIVERSITI PUTRA MALAYSIA

COASTAL CIRCULATION OFF KUALA TERENGGANU

MAGED MAHMOUD MARGHANY

FPV 1994 1

COASTAL CIRCULATION OFF KUALA TERENGGANU

MAGED MAHMOUD MARGHANY

MASTER OF SCIENCE UNIVERSITI PERTANIAN MALAYSIA

1994

COASTAL CIRCULATION OFF KUALA TERENGGANU

By

MAGED MAHMOUD MARGHANY

Thesis Submitted in Fulfilment of the Requirements for the Degree of Master Science in the Faculty of

Fisheries and Marine Science, Universiti Pertanian Malaysia

September 1994

ACKNOWLEDGEMENTS

The author would like to thank the Almighty Allah for

making him be the first Arab, to do research on physical

oceanography in this part of the South China Sea, which

has been ignored by scientists. Everything has been done

by the action of Allah, who has given patience to the

author for continuing his study to a desire goal.

The author wants to express his gratitude and thanks

to his committee members Dr. Mohd. Nasir Saadon, Dr. Mohd.

Lokman Husain and Professor Dr. Mohd. Ibrahim B.Hj.

Mohamed for their all-round support, valuable suggestions

and encouragement without which would not have been made

possible.

The author also extends his thanks to the staff of

UNIPERTAMA I and UNIPERTAMA III boats especially Encik

Mohammed Embong and captain Rahman Muda who helped him to

collect the data under bad weather conditions of the sea.

ii

The support from the staff of the Faculty of Fisheries

and Marine science, Universiti Pertanian Malaysia in Kuala

Terengganu are also acknowledged especially Encik Sukiman

Sengat who supported him with basic programmes to calculate

temperature and salinity. Thanks are also to Encik Suliman

Kassim and Johari Mohamed.

The author thanks his friends Muhamad Saini, Mustapha

othman and Kamel Bahrin who prepare the figures in this

thesis. He also thanks his friend Rosland Salim who

translated the abstract to the Bahasa Malaysia.

Finally the author wants to express his deep gratitude

to Mr Cornelius Anwar Abdullah of Kolej Agama Sultan Zainal

Abidin in Kuala Terengganu who edited this thesis.

iii

TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS ii

L I ST OF TABLES viii

L I ST OF F IGURES ix

LIST OF PLATES xiii

ABSTRACT xiv

ABSTRAK xvi

CHAPTE R

I INTRODUCTION 1

Factors Inducing Water Circulation 1

II

III

Water Circulation in the South China Sea . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Problem and Importance of Water Circulation in Kuala Terengganu

Objectives

L I TERATURE REVI EW

Previous Work in the Study Area

Features of Water Circulation

Upwelling

Tidal Current

Residual Current

MATERIALS AND METHODS

Study Area

Sampling Design

iv

8

12

1 4

1 4

2 1

23

23

24

2 6

2 6

2 9

IV

V

Data Collection 3 2

Fi eld Wo rk and Observational Pro c edure . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2

Temperature Measurements 3 2

Sal inity Measurement s 3 6

Sampling Met hods 4 0

Temperature and Sal inity Distributions . . . . . . . . . . . . . . . . . . . 4 2

Current Measurements 4 2

Meteo rological Data 5 0

Tidal Data 5 1

RESULTS AND ANALYSI S 5 2

Temperature and Sal inity . . . . . . . . . . . . . . 5 2

Temperature Dist ribution 5 8

Sal inity Distribution 6 1

S urfac e Current 6 4

Sout h-west Monsoon 6 4

Transition Period 6 8

S ubsurface Current 7 0

Scatter Plots 7 2

Progressive Vector Plots 8 1

Component o f Current Velocity . . . . . 8 4

Tidal Current E l l ipses 9 0

Residual Current 9 0

DI SCUSSION 1 0 1

Temperature D i f f erences 1 0 1

Temperature Strati fication 1 0 4

v

VI

Sal inity Di f ferences 1 0 6

Water Sal inity Di stribution 1 1 3

Upwel l ing and Downwel ling 1 1 3

Surface Current 1 21

S urfac e Wat er Flow 1 2 1

Meander 1 2 3

S ubsurface Current 1 2 4

Subsurfac e Water Flow 1 2 4

Tidal Current 1 2 6

SUMMARY AND CONCLUSION 1 2 9

Temperature and Sal inity Distribution . . . . . . . . . . . . . . . . . . . . . . 1 2 9

Temperature Di f f erences

Sal inity Di ff erences

Water Stratification

Upwel ling and Downwel ling

S urfac e Current

Surfac e Current Flow

Meander

Subsurface Current

Subsurface Current Flow

Tidal Current

1 3 0

1 3 0

1 3 1

1 3 2

1 3 2

1 3 3

1 3 3

1 3 3

133

134

BIBLIOGRAPHY 1 3 6

APPENDI X

A Basic Computer Pro grams Used to Calculate True Temperature and Sal inity . ....... . 1 4 3

vi

B Fortran Computer Program Used to D raw I sothermal and I sohaline Contours .. . . . . . 1 4 8

C Fortran Computer Program Used to Draw progressive Vector Plots . . ... . ... . .... . 1 5 5

BIOGRAPHICAL SKETCH 1 5 9

vii

LI ST OF TABLES Table Page

1 . Maximum Current Speed during the Rising and Fal l ing Tide for E ach Observation Period . . . . . . . 7 6

2 . Summary of Average Ma j or Axis Speed and Minor Axi s Speed for Each Observation Period . . . . . . . . . 9 7

3 . Average Range of Residual Flow in the South-west and North-east Monsoon Periods . . . . . . . . . . . . . . . . 1 0 0

4 . Temperature Differences ( OC ) and their Average Value ( OC ) for E ac h Transect . . . . . . . . . . . . . . . . . . 1 0 2

5 . Sal inity D i f ferences ( ppt ) and their Average Value ( ppt ) for Each Transect . . . . . . . . . . . . . . . . . 1 0 8

viii

LI ST OF F I GURES

F igure Page

1 . Geographical Location of South China Sea ( From Pohlmann , 1 9 87 ) . . . . . . . . . . . . . . . . . . . . . 4

2 . Wind Stress Distribution in January ( From Hel l erman , 1 9 6 8) . . . . . . . . . . . . . . . . . . . . . . . . 6

3 . Wind Stress Distribution in July (From Hel lerman , 19 6 8) . . . . . . . . . . . . . . . . . . . . . . . 7

4 . Surface Current i n the South China Sea in the Month of February ( From Morgan and Val encia, 1 9 83 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5 . Surface Current in the South China Sea in the Month of August ( From Morgan and Valencia , 1 9 83 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0

6 . Study Areas Showing the Bottom Topography i n Kuala Terengganu Water . . . . . . . . . . . . . . . . . . . . . . 2 7

7. The Loc ation o f Stations i n Phase 1 for Col lection of Temperature , Sali nity , Current Meter and D rogue Deployment from May 1 9 9 2 to February 1 9 9 3 . . . . . . . . . . . . . . . . . . . . . 3 0

8 . The Location o f Stations Phase 2 for Temperature , Salinity and Current Measurements in the Month of March 1 9 9 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1

9 . Current Meter Deployment System . . . . . . . . . . . . . . . 4 5

1 0 . D rogue Deployment System

1 1 . Temperature and Salinity Pro f i l e s in Transect

4 9

1 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 3

1 2 . Temperature and Salinity Profiles in Transect 2 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 4

1 3 . Temperature and Sal inity Pro f i l es in Transect 3 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 5

1 4 . Temperature and Sal inity Pro f i l e s in Transect 4 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 6

ix

15 . Temperature and Salinity Profiles in Transect 5 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 7

16 . The Track of a Dri fting Drogue Re l eased on 2 0th June 19 9 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5

17 . The Track o f a Dri fting Drogue Rel eased on 2 1th June 19 9 2

18 . The Track of a Dri fting Drogue Re leased on 19th S eptember 19 9 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19 . The Track of a Dri fting Drogue Re leased at Station 3 from 4th to 6th Apri l 19 9 3 . . . . . . . . .

2 0 . The track of a dri fting drogue released at Station 5 f rom 7th to 9th April 19 9 3 . . . . . . . . .

2 1 . S catter Plots o f Current Speed against

6 6

6 7

6 9

7 1

Direction during South-west Monsoon Period 7 3

2 2 . Scatter Plots o f Current Speed against Direction during North-east Monsoon Period 7 4

2 3 . A Plot o f Maximum Current Speed against Tidal Height during the Rising Tide . . . . . . . . . . . . . . . . 7 7

2 4 . A Plot o f Maximum Current Speed against Tidal Height during the Fal l ing Tide . . . . . . . . . . . . . . . 7 7

2 5 . Scatter Plots of Wind Stress during the South-west Monsoon Season . . . . . . . . . . . . . . . . . . . . 7 9

2 6 . S c atter Plots o f Wind Stress during the North-east Monsoon Season . . . . . . . . . . . . . . . . . . . 8 0

2 7 . Progres sive Vector Plots during the South-west Monsoon Season . . . .. . . . . . . . . . . . . . . . . . . . . . . 8 2

28 . Progre ssive Vector Plots during the North-east Monsoon Season . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3

2 9 . U and V Current Speeds Components during the South-west Monsoon Season . . . . . . . . . . . . . . . . . . . . 8 6

3 0 . U and V Current Speeds Components during the North-east Monsoon Season . . . . . . . . . . . . . . . . . . . . 8 7

3 1 . A Plot o f Variance U Component against the Variance o f Tidal E l evation . . . . . . . . . . . . . . . . . . 8 8

x

32. A Plot o f Variance V Component against the Variance of Tidal E levat ion ................... 88

33. Tidal Current E l l ipses i n the Month o f May 1992 ......... "................................ 90

34. Tidal Current E l l ipses in the Month o f June 1992 .......................................... 91

35. Tidal Current E l l ipses in the Month o f July 1992 .......................................... 92

36. Tidal Current E l l ipses in the Month o f August 1992 ............................................. 93

37 . Tidal Current E l l ipses in t he Month o f October 1992 .................................. 94

38. Tidal Current E l l ipses in the Month o f March 1993 .......................................... 95

39. Tidal Current E l l ipses in the Month o f April 1993 .......................................... 96

40. Residual Currents for Each Observational Period ........................................ 98

41. The Net residual Current Flow f or Each Observation ................................ . .. 100

42. Temperature Distribution during the South-west Monsoon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

43. Rainfal l Distribution for Each Observational Period ( Malaysian Meteoro logical S e rv ice , 1 9 9 3 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 9

44. ( a ) Temperature and ( b ) Sal inity Distribut ion of Transect 1 in February 1993 ............. 110

45. Temperature D i stribution in Transect 5 Through August and october . . ...... . . . .... . ... . . . . .. . 112

46. Upwe l l ing Observation f rom ( a) I sotherm and ( b ) I sohaline Contours During South-west Monsoon ................. . .................. 115

47. Temperature and Sal inity Distribution in the Month o f May 1992 .. . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 7

xi

4 8 . Downwel l ing observation from ( a ) I sotherm and ( b ) I sohaline Contours During North-east Monsoon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 9

4 9 . Temperature Distribution in the Month of February 1 9 9 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 2

xii

LIST OF PLATES

Plate

1. The River Mouth o f Kual a Terengganu

page

Viewe d f rom the North . . . . . . . . . . . . . . . . . . . . . . . . . 2 8

2 . Reversing Thermometer 3 3

3 . Nansen Bott le . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4

4 . I n ductivel y Coupled Sal inometer Mo de l 6 0 1 Mkv . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 8

5 • UNIPERTAMA I I I 4 1

6 . ONO S e l f Recording Current Meter . . . . . . . . . . . . . . . 4 3

7 . Drogue Used i n this Study . . . . . . . . . . . . . . . . . . . . . . 47

xi i i

Abstract o f thesis submitted to the S enate o f Universiti Pertanian Malaysia i n ful fi lment of the requirements for the degree o f Master o f S cience

COASTAL C IRCULATION OFF KUALA TERENGGANU

By

MAGED MAHMOUD MI�RGHANY

SEPTEMBER 1994

Chairman Mohd. Nas ir Saadon,Ph.D

Faculty Faculty of Fisheries and Marine Science

The aim of this study was to determine the t ype o f

the current patterns i n the coastal waters o f Kua l a

Terengganu. This study was divided in two parts . The

first part was to determine the pattern of thermohaline

c irculation . This was done by s ampling 2 5 stations along

the coastal water of Kua l a Terengganu . The second part

was to measure the subsurface current by aNa-self

recording current meter and drogue .

The thermohaline c ircu l ation was dominated by

mixing during the north-east monsoon period ( October

1992, February and March 1993) due to the turbulence

xiv

resulting from the action of wind and tide . A dominant

feature of this study was the oc currence of upwe l l ing

during the south-west monsoon period ( May to August

19 9 2 ) . The do wnwe l l ing occurrences are in the north-east

monsoon .

The study showed that the subsurface current i n the

coastal waters of Kual a Terengganu were influenced b y

the tide . The current speed throughout this study varied

from 0 . 0 12 to 2 . 6 m/s . The tide throughout this study

was diurnal in nature . A dominant feature through this

study was tidal current whi l e , the winds have no impact

on the wate r movement . Fina l l y the data of surfac e

current i l l ustrated that the water meanders in the month

o f April 1 9 9 3 . Meande r rotated in c lo ckwise direction

from the no rth to south-west direction with an average

current speed of about 0 . 4 m/s .

xv

Abstrak tesis yang dikemukakan kepada Senat Universiti Pertanian Malaysia sebagai memenuhi keperluan untuk i jazah Master S ains .

PUSINGAN PERSISlRAN DI KUALA TERENGGANU

Oleh

MAGED MAHMOUD M'ARGHANY

SEPTEMBER 1 9 9 4

Pengerus i Mohd. Nas i r Saadon,Ph.D

Fakulti Fakulti Perikanan dan Sains Sarnudera

Tujuan kaji an ini a dalah untuk menentukan jenis corak-

corak arus di perairan pantai Kuala Terengganu . Kajian ini

dibahagikan kepada dua bahagi an . Bahagian pertama adalah

mengenai kitaran termoha li n . Ini di l akukan ke atas 2 5 buah

stesen kaji an sepan j ang perairan pantai Kuala Terengganu .

Bahagian kedua pula adalah untuk mengukur arus sub-permukaan

menggunakan meter arus " ONO s e l f recording" dan " drogue " .

Kitaran termohalin telah di dominasikan percampuran

khasnya semasa tempoh Monsun Timur Laut ( Oktober , 19 9 2 ;

Februari dan Mac , 19 9 3 ) akibat daripada penggeloraan hasi l

xvi

dari t indakan angin dan pasang surut . S atu c iri dominan

dalam kajian ini adalah kejadian julang air yang tinggi

semasa berlakunya Monsun B arat Daya ( Mei hingga Ogos , 1 9 9 2 )

berbanding dalam tempoh Monsun Timur Laut ( Oktober , 1 9 9 2 ;

Februari dan Mac , 1 9 9 3 ) . Tetapi , ke j adian junam air adalah

lebih kerap pada Monsun Timur Laut berbanding Monsun B arat

Daya .

Kajian ini menun j ukkan bahawa arus sub-permukaan di

perairan pantai Kuala Terengganu adalah dipengaruhi o leh

pasang-surut . Kel ajuan arus sepan j ang kaji an adal ah berubah­

ubah dari 0 . 0 1 2 hingga 2 . 6 m/s . Pasang-surut sepanj ang

kajian adalah diurnal . Arus pasang-surut adalah ciri yang

dominan sepanjang kajian , sementara angin tidak mempunyai

kesan t erhadap aliran air . Akhirnya , data bagi arus

permukaan yang dipero lehi menggambarkan bahawa pembelokan

air berlaku pada bulan April 1 9 9 3 . Pembe lokan berlaku

mengikut arah jam dari arah utara ke barat-daya dengan

kelaj uan purata arus lebih kurang 0. 4 m/s .

xvii

CHAPTER I

INTRODUCTION

Factors I nducing Water Circulation

The study of the ocean is always a challen ging and

intri guing process considering its s i z e and the expanse

of the earth it cove rs . Features of sea c i rculation are

complex and a challenge for humans to comprehend . Al l

l i f e and c l imatical c hanges depend on c i rculation . The re

i s no doubt that water c i rculations of the world are

important to l i fe i n this planet . I t is not easy to

unde rstand water c i rculations because there are many

factors cont ro l l ing them . S c ientists cannot study the

factors separately as this wi l l give them an imperfect

answer.

Most scientists identi fy the forces whic h induce

c i rcul ations to be the wind ( Watten , 1 9 7 3 ; Gross , 1 9 7 7 )

and the t ide ( Horrer , 1 9 6 7 ) but there are many othe r

factors that p l ay a role in water c i rculations .

Many of the surface currents are wind driven . So

studies of water movements in the shal low coastal regions

1

as wel l as in the open sea

of atmospheri c forces , including

stress. Momentum exchange is the

require

2

knowl edge

pressure and wind

most di rect and

immediat e l ink between atmospheric and oceanic

c i rculations and occurs whenever wind blows over any part

o f t he sea. Some of the momentum causes turbulence drag,

or shearing stress between the water layers ( Bowden ,

1 9 60 ; Beer, 1 9 8 3 ) . The integrated action of wind system

resul t s i n a large-scale t ranslation of water masses .

Turbulence drag and shearing stress between water l ayers

disturb the seas inherent kinetic energy_ The influence

of the earth's rotation , on t he other hand , is the

p rimary driving force of the world ' s ma j o r current

systems such as the huge anticycl onic gyres ( Csanady ,

1 9 8 0 ) .

Density differences between water masses is another

dri ving force that induces water movement , usually the

ve rtical mo vements . The flow of the ma j or deep water

currents are caused by gravity pul ling the denser water

masses downwards , displacing lighter water masse s upward .

Since the density is cont rol led by the water tempe rature

and salinity , these currents are usually cal l ed

thermohal ine currents ( Horre r , 1 9 67 ; Pickard and Emery ,

1 9 8 2 ) .

The third factor that generates water mo vements i s

the tidal force. Being oscil l ato ry in nature the tides

cause net water movement which is averaged ove r a period

3 o f weeks or months . The re are other l arge scale currents

whic h are superimposed on this type of water movement .

Sma l l -scale o s c i l l atory currents c an sometimes be

observed whe re water is conf ined in harbours or estuaries

( Davis , 1 9 7 7 ) .

Water Circulation in the South China Sea

To understand the water movement pattern of Kual a

Terengganu , one should get more information about water

c i rculation i n the South China Sea. This is because,

Kual a Terengganu wat er is a part of the South China Sea

and there fo re knowing mo re about the water prope rties in

the South China Sea wi l l he lp researchers to unde rstand

the wate r c i rculation o f f Kuala Te rengganu .

The South China S ea i s the l argest water body i n

Southeast Asia ( Fi gure 1 ) . I t is surrounded by the Asian

continent , the I ndonesian Archipe lago , West Malaysia , the

Phi lippines and Formosa . The seafloor of the south china

sea can be divided into 3 dis tinc t areas . They are; (1)

Northern Sunda Shel f , ( 2 ) Gul f of Thailand and ( 3 ) China

sea basin .

The Northern Sunda S he l f extends between Sumatra and

B o rneo north eastwards as a narrow be lt ( 5 0 - 1 0 0 km ) along

the Asian Continent Borneo and Phil ippines. Average depth

of the shelf is 50 m with its deepest part at 10 0 m .

CHINA

SEA

China Sea

�N.ATUNA IS. 'l " - 4 .UU· ...... S ..

BORNEO

BASHI', CHAN�e:L

.0() � ( , D � "'N"""i\) Q " �-z,

� f· �� ('" • � T � ,J. �@jo �'. iP._ SULU qjI.!. .

I\AfABAC :; T"RAI T SEA '''OAHAO . 0 \..�OL'i? t-G c,0 't,.\..

... :.r.,\« �G " CELEBES 'I.

SEA "

Figure 1 . Geographical Location of South China Sea (From Pohlmann, 1987)

4

5

To the north-west is the Gul f of Thail and . The Gul f

i s about 4 0 0 km wide and i t has a maximum depth of 8 5 m .

The China Sea basin is the deepest part o f South China

Sea . This area is c haracteri z ed by a combination of

bathymetric features . Off the Sabah Coast is the Palawan

Trench with a maximum depth of 3 4 7 5 m. Away f rom the

Palawan Trench , the seafloor turn into a broad i rregular

p l ateau . This area posses numerous seamount and f ringing

reef s that protrude to the surface appropriately named

Dangerous Grounds ( Wyrtki 1 9 6 1 ) .

One of the main features of the South China Sea i s

i t s location i n the t ropical low latitudes , whic h have

two important e ffects on the c irculat ion . Firstly , the

reduction of the Corio l i s parameter near the equator

makes nonlinear and frictional force become increasingly

important . S econdly , the South China Sea is dominated by

the monsoon regime and i s strongly inf luenced by semi

annual reversing circulation o f the atmosphere ( Pohlmann ,

1 9 8 7 ) .

Figures 2 and 3 show the wind stress distribution in

January and July . I n January north-easterly winds prevail

over the who l e region with an average magnitude of 9 m/ s .

I n July the wind distribution i s total ly reversed .

Weaker southwesterly winds dominate over most parts o f

the South China Sea with an average magnitude of 6 mls

( He l l erman , 1 9 6 8 ; Pohlmann , 1 9 8 7 ) .

12-LAYEA SHELF-SEA-HOOEL

-- SOUTH CHINA SEA ----

12 15 20 2" 30 '40 50 ao 70 eo 100 120 '.,,0 I ISO 230 --... -.. --- -- .... t::> � VINO-STRESS (mPo)

Figure 2 . wind stress Distribution in January (From Hel lerman, 19 68)

6