productivity and omz over the last 40ka in the arabian sea during late quaternary t~655

147 Pages·2017·7.5 MB·English

V ,
a r ia b il it y o f s s t m onsoon
PRODUCTIVITY AND OMZ OVER THE LAST
40KA IN THE ARABIAN SEA DURING
LATE QUATERNARY
A THESIS SUBMITTED TO 60A UNIVERSITY FOR THE AtfARD OF THE
DEQREEOF
DOCTOR OF PHILOSOPHY'
IN
MARINE SCIENCES
5 7 7 7
BV / V a X
SHTTAL PAULU GOD AD
7^
DR P. DIYAKAR HAIDU
RESEARCH 6U II«
NATIONAL INSTITUTE OF OCEANOGRAPHY
DONA PAULA GOA INDIA
GOA UNIVERSITY,
TALEI6A0 GOA,
INDIA
2014
~ T - 6 5 5
T ~ 6 5 5
DecRcatecC to
My Tarents, SiBCmgs ancCLcrvecCOne
Declaration
I here By state that the present thesis entitled "Varia6iCity qfSS%
Monsoon (Productivity and OMZ over last 40hg in the jlrafnan Sea
during late Quaternary" is original contrihution and the same has not
een suhmitted on any previous occasions. Ho the 6est of my knowledge,
6
the present study is first comprehensive worf^of its hind for the area
mentioned Hhe literature related to the proBlem investigated has 6een
cited. <Due acknowledgements have 6een made wherever facilities and
suggestions have 6een availed of
Shitdl<Paulu (jodad
- TT^T *PpT fetUR ^8JR
(JisiiPta, qcf ihejiRi* qfcrc')
CSIR-national institute of oceanography
(Council of Scientific & Industrial Research)
Dr. P. Divakar Naidu
Chief Scientist
CERTIFICATE
JAs required under the (joa 'University ordinance O'B-9.9> I
certify that the thesis entitCed '‘Variability of SST, Monsoon
Productivity andOMZ over last 40ha in the Arabian Sea during
(ate Quaternary", submitted by MsShital Taulu (jo dad for the
award of the degree of Doctor of Philosophy in Marine Sciences
is based on original studies carried out by her under my
supervision. The thesis or any part thereof has not been
previously submitted for any other degree or diploma in any
university or institution.
cTRT WF\J TTTcfT 403 004 WH
DONA PAULA, GOA - 403 004, India
* : 91-(0)832-2450 450 e-mail: [email protected] Regional Centres
fax :91-{0)832-2450 602/03 URL : http://www.nio.org Mumbai, Kochi,Visakhapatnam
C O N TEN TS
Certificates
List of Figures vi
List of Tables xii
Preface xiii
Acknowledgement xvi
CHAPTER I
Introduction
1 . Climatic Variations 1
2. Indian Monsoon
2
3- Oceanography of the Arabian Sea 3
3.1. Southwest Monsoon
4
3.1 J. Surface Circulation
4
3.1.2. Sea Surface Temperature
4
3.1.3. Sea Surface Salinity
6
3.1.4. Productivity
6
3.2. North East monsoon
8
3.2.1. Surface circulation
8
3.2.2 Sea Surface Temperature
9
3.2.3. Sea Surface Salinity
9
j 2 4 Productivity 10
4. Oxygen Minimum Zone
11
5 . Previous research related to the objectives of the present study
13
5.1. Sea surface temperature reconstructions in the Arabian Sea
13
5.2. Reconstruction of Carbonate ion
14
5.2.2. Paleocarbonate ion Proxies
15
5.3. Monsoon productivity and OMZ variability 16
5.4. NE Monsoon and Winter cooling 17
6. Proxies used in the study 17
6.1. Planktonic foraminifer 17
6.2. Oxygen isotopes 19
6.2.1. Oxygen Isotope as a Stratigraphic Tool in 20
Paleoceanograpghy
6.3. Carbon Isotopes (S13C) 21
6.4. Geochemical Elements 22
6.5. Nitrogen isotopes (S15N ) 23
6.6. Calcium carbonate 23
6.7. Organic carbon 23
7. Objectives 24
CHAPTER II
Study Area, Material and Methods
Geographic Setting of the Arabian Sea
1. 25
2. Sediment Cores 26
Chronologies of Cores
3. 27
4. Methods 29
4.1. Processing of Sediment 29
4.2. Census counts of Planktonic Foraminifera 29
4.3. Oxygen and carbon isotopes 30
4.4. Nitrogen and carbon isotopes 30
4.5. Elemental Analysis 30
4.6. Calcium Carbonate 31
4.7. Planktonic foraminifera Shell weights 31
4.8. Artificial Neural Network 32
11
CHAPTER III
Sea Surface Temperature Changes During May and August in the
Western Arabian Sea over the last 22kyr: Implications as to Shifting
of the Upwelling Season
1. Introduction 34
2. Materials and Methods 35
3. Results 33
4^ Discussion 38
4.1. Difference in SST between May and August 4\
S. Conclusions 42
CHAPTER IV
What Controls The Planktonic Foraminifer Shell Weights In The
Arabian Sea?
I Introduction 43
2. Factors controlling shell calcification on millennial timescales in 45
the Arabian Sea
2.1 Factors controlling shell calcification in the eastern 45
Arabian Sea
2 1 j Quantification of surface water carbonate ion 4g
concentrations using shell weights
2.2 Factors controlling shell calcification in the western 52
Arabian Sea
3. Factors affecting shell calcification on a seasonal timescale: a 57
comparison between (sediment trap studies)
4. Conclusion 61
iii
CHAPTER V
OMZ Variability in the Eastern Arabian Sea: Implications of
Productivity
1. Introduction 63
2. Chronology 65
3. Results and Discussion 66
3.1 Early to Late Holocene contrast in productivity, 66
denitrification,
OMZ intensity and calcite dissolution.
3.2 Changes in surface productivity, denitrification and bottom- 67
water oxygenation intensity
3.3 Calcite dissolution due to variations in bottom-water 71
oxygenation
3.4 Variations in denitrification, bottom water oxygenation and 74
calcite dissolution during the last 70 kyr.
4. Conclusions 77
CHAPTER VI
Variability of Winter Cooling in the NE Arabian Sea: Implications
for the NE Monsoon
1. Introduction 7g
2. Material and Methods 79
2.1. Chronology 80
3. SST variation at the core location 80
4. Results 81
4.1. Oxygen and carbon isotopes 81
4.2. Fertile Planktonic foraminifer species 82
4.3. Calcium carbonate 83
4.4. SST 83
IV
Discussions
5. 83
5. ]. Variability of Winter Cooling
84
5.2. Relationship between SW and NE Monsoon Variability
86
5.3. Periodicity of NE Monsoon
88
6. Conclusions 90
CHAPTER VII
Summary and Conclusions 91
References 96
Publications:
1. Godad, S. P., Naidu, P. D. and Malmgren, B. A. (2010). Sea Surface
Temperature Changes During May and August in the Western Arabian Sea
over the last 22 kyr: Implications as to Shifting of Upwelling Season. Marine
Micropaleontology, doi: 10.1016/j.marmicro.2010.09.006.
2. Naik, S. S., Naidu, P. D., Govil, P., and Godad, S. P. (2010). Relationship
between weights of planktonic foraminifer shell and surface water CO 3=
concentration during the holocene and last glacial period. Marine Geology,
275, 278-282.
3. Naik, S. S., Godad, S. P. and Naidu, P. D. (2011). Does carbonate ion control
planktonic foraminifera shell calcification in upwelling regions? Current
Science, 101, No. 10.
4. Naik, S.S., Godad, S. P., Naidu, P. D. and Ramaswamy, V. (2013). A
comparison of Globigerinoides ruber calcification between upwelling and
non- upwelling regions in the Arabian Sea. J.Earth Syst. Set, 122, No. 4,
1153-1159.
5. Naik, S.S., Godad, S. P., Naidu, P. D. and Tiwari, M. (2013). Early to Late
Holocene contrast in Productivity. OMZ intensity and Calcite Dissolution in
the Eastern Arabian Sea.The Holocene, Doi:10.1177/09596833614526936.
v
LIST OF FIGURES
Fig. No. Title
Fig. 1.1 Low pressure on continent during Summer Monsoon.
Fig. 1.2 High Pressure on the Continent during Winter Monsoon.
Fig. 1.3 A schematic representation of identified current
branches during the Southwest Monsoon,. Current
branches indicated are the South Equatorial Current
(SEC), South Equatorial Countercurrent (SECC),
Northeast and Southeast Madagascar Current (NEMC
and SEMC), East African Coast Current (EACC),
Somali Current (SC), Southern Gyre (SG) and Great
Whirl (GW) and associated upwelling wedges, Socotra
Eddy (SE), Ras al Hadd Jet (RHJ) and upwelling
wedges off Oman, West Indian Coast Current (WICC),
Laccadive High and Low (LH and LL), East Indian
Coast Current (EICC), Southwest and Northeast
Monsoon Current (SMC and NMC), South Java
Current (JC) and Leeuwin Current (LC).(Schott and
McCreary,2001).
Fig. 1.4 Sea Surface Temperature during South West Monsoon
in the Arabian Sea.
Fig. 1.5 Sea Surface Salinity during Southwest Monsoon in the
Arabian Sea.
Fig. 1.6 Productivity during Southwest Monsoon
Fig. 1.7 A schematic representation of identified current
branches during the Northeast Monsoon, Current
branches indicated are the South Equatorial Current
(SEC), South Equatorial Countercurrent (SECC),
Northeast and Southeast Madagascar Current (NEMC