Circulation and Sediment Dispersal on the Louisiana-Mississippi-Alabama Continental Shelf.

190 Pages·2017·5.77 MB·English

by  Scott Page Dinnel

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LSU Historical Dissertations and Theses Graduate School
1988
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Scott Page Dinnel
Louisiana State University and Agricultural & Mechanical College
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Dinnel, Scott Page, "Circulation and Sediment Dispersal on the Louisiana-Mississippi-Alabama
Continental Shelf." (1988). LSU Historical Dissertations and Theses. 4632.
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Circulation and sediment dispersal on the Louisiana-Mississippi-Alabama
continental shelf
Dinnel, Scott Page, Ph.D.
The Louisiana State University and Agricultural and Mechanical Col., 1988
U M I
300 N. Zeeb Rd.
Ann Aibor, MI 48106
CIRCULATION AND SEDIMENT DISPERSAL
ON THE
LOUISIANA-MISSISSIPPI-ALABAMA
CONTINENTAL SHELF
A Dissertation
Submitted to the Graduate Faculty of the
Louisiana State University
Agriculture and Mechanical College
in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy
in
The Department of Marine Sciences
by
Scott Page Dinnel
B. S., University of South Carolina
M.S., Louisiana State University
December 1988
ACKNOWLEDGMENTS
This research was sponsored by the Louisiana Universities
Sea Grant Program and Louisiana State University and the
Mississippi-Alabama Sea Grant Consortium and the University
of Alabama. The Rockefellar Scholarship Program, Louisiana
Governor's Education Commission, and the Coastal Studies
Institute, Louisiana State University provided additional
support throughout my graduate student career. Dauphin
Island wind data was provided by the Dauphin Island Sea Lab,
Alabama.
No simple words can thank my advisor Bill Wiseman, his
supervision, support and confidence enabled me to overcome
many problems and complete my research. Will Schroeder
contributed more that just research materials, ideas or
collaboration, his unflagging enthusiasm got me over many
rough spots. The rest of my committee, Harry Roberts, R.
Eugene Turner, Shih-Ang Hsu, and Rick Shaw, all have aided
me with interest, ideas and discussion.
Gerry Newman, the watchdog of the Marine Sciences
Department, has saved me numerous times from missing
deadlines, improper forms, and incorrect thoughts. Celia
Harrod and Kerry Lyle have produced most of the figures in
the dissertation and the eventual publications.
Most of all I would like to thank my wife, Beverly, for
her companionship on a long, arduous, frustrating, sometimes
tedious and trying, but eventually successful journey.
ii
TABLE OF CONTENTS
page
ACKNOWLEDGMENTS n» «
LIST OF TABLES V
LIST OF FIGURES vii
ABSTRACT xii
1. INTRODUCTION 1
2. SEASONAL FLOW ON THE OUTER SHELF AND UPPER SLOPE 13
HYDROGRAPHIC DATA 13
ANALYSIS 17
Geopotential Calculations 17
Fresh Water Content Calculations 23
RESULTS 24
Dynamic Height Topography 24
Fresh Water Content 32
DISCUSSION 35
3. SEASONAL FLOW ON THE INNER SHELF 38
DATA 38
Data Description 38
Data Analysis 41
Complex Spectrum Analysis 43
Complex EOF Analysis 44
Momentum Balance Analysis 47
RESULTS 48
Deployment MSI 48
General Data Description 48
Complex Spectrum Analysis 57
Complex EOF Analysis 63
Momentum Balance Analysis 68
Discussion 71
MS2 Deployment 72
General Data Description 72
Complex Spectrum Analysis 79
Complex EOF Analysis 82
Momentum Balance Analysis 91
Discussion 91
MS3 Deployment 94
General Data Description 94
Complex Spectrum Analysis 102
Complex EOF Analysis 102
Momentum Balance Analysis 108
Discussion 113
DISCUSSION 114
iii
page
4. PROCESSES OF SEDIMENT DISPERSION 120
SURFACE SEDIMENT DISTRIBUTION 120
SEDIMENT TRANSPORT MECHANISMS 123
DISCUSSION 137
5. SUMMARY 141
REFERENCES 146
APPENDIX I: EOF Rotation 155
APPENDIX II: Momentum Balance Equations 160
APPENDIX III: EOF Results 165
VITA 173
iv
LIST OF TABLES
Table page
1. Seasonal specific volume anomaly values for each 22
transect at the reference pressure 500 db. Units are
xlO m /kg.
2. Fresh water volumes, calculated from a reference 25
salinity of 36.6 ppt, and the shelf volume percentage
sampled for each season, for the upper 100 m of the
LMAS region from 87° to 89.5° W.
3. Locations of current meter moorings, coastal water 39
level, bottom pressure, coastal and buoy wind stations.
4. Flow statistics for MSI current meter component 50
means, u, y (xl0~2 m/s), low passed variances
S u and S „ (xlO"4 m2/s2), correlation time scales,
t01,f tpV (d), standard errors, SEU, SEV (xlO-2 m/s),
ana rotation angle of principal axes, 0 (deg).
5. Complex empirical orthogonal function statistics: 64
percent total variance, %S4-, 95% significance level,
angle of preferred orientation, individual weights,
0, phase angles, <f>, and percent variation of individual
inputs explained, %S|, for MSI. Inputs were current
meters and DI wind stress.
6. Rms values of momentum balance terms, in both 69
alongshelf and cross-shelf directions, for CM5 and
CM8 of MSI. Units are m/s2 (xlO-7).
7. Flow statistics for MS2 current meter 74
component means, u, v (xlO-2 m/s), low passed
variances S2 and S2V (xl0“4 m2/s2), correlation
time scale, tQ„ , t v (d), standard errors, SEU,
SEy (xl0“2 m/s), ana rotation angle of principal
axis, 0 (deg).
8. Complex empirical orthogonal function statistics: 86
percent total variance, %S*.; 95% significance level,
angle of preferred orientation, individual weights,
0, phase angles, and percent variation of individual
inputs explained, %Sjt, for MS2. Inputs were current
meters and DI wind stress.
9. Rms values of momentum balance terms, in both 93
alongshelf and cross-shelf directions, for CM8 of
MS2. Units are m/s2 (xlO ).
v
Table page
10. Flow statistics for MS3 current meter component 96
means, u, v (xlO-2 m/s), low passed variances
S u and S2V (xlO-4 m2/s2), correlation time scales, .
tQn / tov ' standard errors, SE^, SEV (xlO-2 m/s),
ana rotation angle of principal axis, © (deg).
11. Complex empirical orthogonal function statistics: 107
percent total variance, %S.t-, 95% significance level,
angle of preferred orientation, individual weights,
0, phase angles, <f>, and percent variation of individual
inputs explained, %Sj, for MS3. Inputs were current
meters and DI wind stress.
12 Rms values of momentum balance terms, in both 111
alongshelf and cross-shelf directions, for CM7 and
CM8 of MS3. Units are m/s2 (xlO-7).
13. Sediment grain sizes, determined from the 122
cumulative frequency data in Ludwick (1964).
14. Bottom tidal currents and tidal harmonic current 124
amplitudes for inner continental shelf currents.
Major axes rms values (this study) and harmonic
constants (Seim et al, 1987) in m/s.
15. Unpublished hindcast wave statistics (U.S. Army, 127
Draft Report) and observed data (U.S. Department of
Commerce, 1972) for the LMAS region.
vi
LIST OF FIGURES
Figure page
1. Location map of LMAS region. 2
2. Plan view of hydrographic areal divisions. 15
Dots represent station locations characteristic of
individual divisions. Depth contours in meters.
3. Direct river discharge to the LMAS. Monthly ■ 16
means from Mississippi River and local rivers in
Louisiana, Mississippi, and Alabama, (Schroeder and
Lysinger, 1979; U.S. Department of Commerce, 1974,
1985b).
4. Shelf cross-section at 87.25° W, showing possible 2 0
dynamic height integration path across shelf.
5. Spring dynamic height topographies, 26
0/500 db, 50/500 db. Contours are in dynamic
centimeters, arrows indicate direction of flow.
6. Summer dynamic height topographies, 28
0/500 db, 50/500 db. Contours are in dynamic
centimeters, arrows indicate direction of flow.
7. Fall dynamic height topographies, 29
0/500 db, 50/500 db. Contours are in dynamic
centimeters, arrows indicate direction of flow.
8. Winter dynamic height topographies, 31
0/500 db, 50/500 db. Contours are in dynamic
centimeters, arrows indicate direction of flow,
9. Annual mean surface dynamic height topography, 33
0/500 db, 50/500 db. Contours are in dynamic
centimeters, arrows indicate direction of flow.
10. Seasonal fresh water content for upper 100 m, 34
spring (upper left), summer (upper right),
fall (lower left), winter (lower right).
Units are height of fresh water in meters.
11. Station locations of current meters (CM), 40
bottom pressure gauges (P), Dauphin Island Sea
Lab winds (DISL), buoy winds (BY) and Dauphin
Island water level (DIWL) in the study region.
12. Current meter component mean speeds and 51
standard errors for MSI. Boxes are -2 standard
errors about the means.
vii