Tides Along the Mississippi Coast and Mississippi Sound

The tides are a primary force that drives the circulation of water in the Mississippi Sound. Tides are caused by the gravitational attraction of celestial bodies upon the Earth's waters. (The Earth's crust is affected to a lesser extent.) However, the celestial bodies that need to be considered in most tidal work are the moon and sun. Although other celestial bodies whose gravitational influence reaches the Earth create theoretical tide-producing forces, the greater distance or smaller size of such bodies render negligible any effect of this force upon the Earth's tides. The principal factors to be taken into consideration in explaining or predicting the tides are rotation of the Earth, the revolution of the moon around the Earth, the revolution of the Earth around the sun, the inclination of the moon's orbit to the Earth's equator, and the obliquity of the ecliptic. The 21 major tidal potential constituents are listed with their respective periods in Table 1.

The tidal regimes of the Gulf of Mexico are shown in Figure 1. Being located on the northern Gulf, the Mississippi Sound has tides that are primarily diurnal, i.e. usually only one high water and one low water per day. The three principal diurnal components of the tide are K1, O1, and P1 with periods of 23.93 hrs, 25.82 hrs, and 24.07 hrs, respectively. The average diurnal range in tide, i.e. the difference in water level from consecutive high and low water stages, for areas within the Mississippi Sound are Horn Island Pass, 1.7 ft; Pascagoula, 1.5 ft; Biloxi Bay, 1.8 ft; Ship Island Pass, 1.7 ft;  Cat Island (West Point), 1.7 ft; and St. Louis Bay, 1.6 ft. (U.S. Department of Commerce, NOAA, NOS 1978).

The tides of the Mississippi Sound are modified by the bathymetry, geometry of the basin, river outflow, and winds. Sustained south and southeast winds push water into the Sound piling it against the mainland. North winds have the opposite effect, driving the water out.

Symbol Name Period
Semi-diurnal Components
M2 Principal lunar 12.42
S2 Principal solar 12.00
N2 Larger lunar elliptic 12.66
K2 Luni-solar semi-diurnal 11.97
T2 Larger solar elliptic 12.01
L2 Smaller lunar elliptic 12.19
2N2 Lunar elliptic second order 12.91
nu 2 Larger lunar evectional 12.63
lambda 2 Smaller lunar evectional 12.22
µ 2 Variational 12.87
Diurnal Components
K1 Luni-solar diurnal 23.93
O1 Principal lunar diurnal 25.82
P1 Principal solar diurnal 24.07
Q1 Larger lunar elliptic 26.87
M1 Smaller lunar elliptic 24.86
J1 Small lunar elliptic 23.10
Long Period Components
Mf Lunar fortnightly 327.86
Mm Lunar monthly 661.30
Ssa Solar semi-annual 2191.43
--- --- Annual (app.)
--- --- 18.61 years
This text, table, and figure are from Eleuterius, Charles K., and Sheree L. Beaugez. 1979. Mississippi Sound: A Hydrographic and Climatic Atlas. Physical Oceanography Section, Gulf Coast Research Laboratory, Ocean Springs, Mississippi for Mississippi-Alabama Sea Grant Consortium: MASGP-79-009. Page 16 (135pp).
Table 1. Major tidal potential constituents.

Tide Regimes

Figure 1. Tidal regimes of the Gulf of Mexico.