Chapter 11 - Tides

Notes Complete

Tide

periodic short-term change in the height of the ocean surface at a particular place, generated by long-wavelength progressive waves that are caused by the interaction of gravitational force and inertia; movement of Earth beneath tide crests results in the rhythmic rising and falling of sea level

½

Tides have wavelengths _____ Earth’s circumference:

Pytheas

_____ was the first to connect tides to the moon

Newton

Understanding of tides was developed by _____ in Principia

Newton’s Law of Gravitation

F = G(M₁M₂/r²)

Tide Generating Force

T = G(M₁M₂/r³)

46

The Sun’s gravitational influence is _____ % of the moon’s influence

Equilibrium Theory of Tides

idealized model of tides that considers Earth to be covered by an ocean of great and uniform depth capable of instantaneous response to the gravitational and inertial forces of the sun and the moon

1650

The center of the Earth-Moon system lies _____ km inside the Earth:

Gravity ; Inertia

The tidal bulges formed by the moon result from _____ and ____ :

Equal and Opposite

Gravitational and inertial forces are _____ at CE:

Tractive Forces

the net force of gravity and inertia, responsible for the two tidal bulges

Inertia

_____ causes the bulge opposite the moon

High Tide

the high-water position corresponding to a tidal crest

Low Tide

the low water position corresponding to a tidal trough

Lunar Tide

tide caused by gravitational and inertial interae-tion of the moon and Earth

24 ; 50

A tidal day is _____ hours and _____ minutes:

28.5

Tidal bulges can offset anywhere from _____ ° N or S due to the moon’s orbit

Solar Tide

tide caused by the gravitational and inertial interaction of the sun and Earth

Spring Tide

Neap Tide

the time of smallest variation between high and low tides occurring when Earth, moon, and sun align at right angles; neap tides alternate with spring tides, occurring at two-week intervals

Perigee

the point in the orbit of a satellite where it is closest o the main body

Apogee

the point in the orbit of a satellite where it is farthest from the main body

Perihelion

the point in the orbit of a satellite where it is closest to the sun

Aphelion

the point in the orbit of a satellite where it is farthest from the sun

30,600

The difference in distance between the perigee and apogee is _____ km:

3.7 million

The difference in distance between the perihelion and aphelion _____ km:

Dynamic Theory of Tides

model of tides that takes into account the effects of finite ocean depth, basin resonances, and the interference of continents on tide waves

1,600 ; 22

An idealized earth-tide model would have tidal waves moving at about _____ km/hr, where the depth of the ocean would have to be _____ km:

Depth

Tidal wave velocity is determined by ocean _____ :

Semidiurnal Tide

a tidal cycle of two high tides and two low tides each lunar day, with the high tides of nearly equal height

Diurnal Tide

a tidal cycle of one high tide and one low tide per day

Mixed Tide

a complex tidal cycle, usually with tvo high tides a tvo low tides of unequal height per day

US Eastern Coast, all Western/Northern European Coasts, Russia Northern Coast, majority of Greenland, all of Africa (except Somalia), Southern Mediterranean + Italy, Brazilian, Peruvian, and Argentinian Coasts, Australia East Coast, and New Zealand

Semidiurnal Tide Locations:

Antarctic Peninsula, Gulf of Mexico, Kamchatka region, Southwest Australia, South China Sea, and the Java Sea

Diurnal Tide Locations:

US West coast, North Mediterranean, Northern Central America, Chilean and Uruguayan coasts, Arabian Sea, Aleutians, Hawaii, Japan, Indonesia, and theGulf of St. Lawrence

Mixed Tide Locations:

Amphidromic Point

a "no-tide" point in an ocean caused by basin resonances, friction, and other factors around which tide crests rotate; about a dozen amphidromic points exist in the world ocean; sometimes called a node

Counterclockwise ; Coriolis Effect

Amphidromic circulation is _____ in the northern hemisphere because the _____ deflects the crest right:

5

The Pacific contains _____ amphidromic points:

Tidal Datum

the reference level (0.0) from which tidal height is measured

Mean Sea Level

the height of the ocean surface averaged over a few years time

Tidal Range

the difference in height between consecutive high and low tides

Small areas

Tidal range is small in _____ like lakes

Large enclosed basins

Tidal range is moderate in _____ like the Baltic or Mediterranean:

Large ocean basin

Tidal range is large in _____ , especially on coasts that concentrate tidal energy because of their shape:

Wide ; Symmetrical

A _____ and _____ basin forms a mini amphidromic point:

Narrow ; Enclosed

A _____ and _____ basin cannot rotate on an amphidromic point:

12 ; 24

Extreme tides occur where arriving tide crests simulation natural oscillations of _____ or _____ hours:

Seiche

The most extreme tides form from a combination with _____ resonance:

Tidal Bore

a high, often breaking wave generated by a tide crest that advances rapidly up an estuary or river

Tidal Wave

the crest of the wave causing tides; another name for a tidal bore; not a tsunami or seisinic sea wave

Higher ; Spilling

A tide crest moving into a river mouth is confined to move at speeds _____ higher than shallow-water wave at that depth, breaking into a _____ wave:

Predictability

The potential danger of tidal bores is combated by their ______ :

Bay of Fundy, southwest China the Amazon river, Ganges delta, and Severn River

Tidal bores are common in:

Maximum velocity

Tidal currents reach _____ midway between high and low tide:

Slower

Tidal currents are _____ in open sea because they are not confined:

1/100s per century

Tidal friction slows the rotation of the Earth a few _____ :

Tidal friction

The moon is tidally locked to the Earth because of:

Tidal Current

mass flow of water induced by the raising or lowering of sea level owing to passage of tidal crests or troughs

Flood Current

water rushing into an enclosed harbor or bay because of the rise in sea level as a tide crest approaches

Ebb Current

water rushing out of an enclosed harbor or bay because of the fall in sea level as a tide trough approaches

Slack Water

a time of no tide-induced currents that occurs when the current changes direction

Historical trends

Tide prediction is based off of:

3

Tide prediction is accurate to about _____ cm:

Meteorological Tide

a tide influenced by the weather; arrival of a storm surge will alter the estimate of a tide’s height or arrival time, as well as a strong, steady onshore or offshore wind

3

Intertidal marine organisms sort themselves into _____ subzones dependent on their toleration of submergence and emergence

Hanztschia

diatoms migrate through the west sand to photosynthesize at low tide

Fiddler Crabs

(Uca) shelter at high tide and feed at low tide

Sand Crabs ; Bean Clams

(Emertia) and (Donax) migrate up and down the beach for shelter and food

Grunion

(Leuresthes) spawn, deposit, and fertilize their eggs at high spring tide, the eggs are protected at low tide, and hatch at the next high spring tide

Tidal power

_____ is the only successfully exploited marine energy at a large scale:

1966 in France

The first tide generator was built in _____ , where both the tides and estuary output for power:

Low operating costs, free power, clean power

Pros of tidal power:

storm damage, easily corroded, alters resonance modes of bays/estuaries, disrupts sensitive marine life, tiny decrease in the rate of Earth’s rotation

Cons of tidal power: