Oceanography Chapter 9- Tides

What causes the tides?

gravitational pull of the Moon, Earth, and Sun

barycenter

the center of mass of two or more bodies that orbit around one gravity point

centripetal forces

amount of force needed to keep objects in orbit, supplied by the gravity between the Earth and Moon

gravitational forces

attractive force that exists between any two objects, as mass increases gravity increases, as distance increases gravity decreases

Zentih

the point directly above an observer, has the greatest gravitational force, point closest to the Moon

Nadir

the point directly below an observer, has the lowest gravitational force, point furthest from the Moon

resultant forces

the difference between the gravitational force of celestial bodies and the centripetal force required to keep Earth in orbit that generates tides

Tide generating forces vs gravity distance difference

tide generating forces drop off with distance faster than gravity does

lunar tidal bulges

two bulges of water created by resultant forces due to the opposing effects of the centripetal and gravitational forces on the Earth’s oceans, one going towards the Moon and the other away

tidal period

the time it takes for a pair of high or low tides to occur, around 12 hours and 25 minutes

Why does the Sun have less effect on tides than the Moon?

the Sun is further away than the Moon, so less gravitational pull

lunar day

the time it takes for the Moon to complete one rotation on its axis, about 24 hr and 50 min

spring tides

occur when the Earth, Moon, and Sun are aligned, have the highest and lowest tides

neap tides

occur when the Sun and Moon are not aligned with the Earth in a straight line, don’t have as extreme of tides

conjunction

new Moon

opposition

full Moon

perihelion

the point in Earth’s orbit closest to the Sun

aphelion

the point in Earth’s orbit furthest from the Sun

perigee

the point in the Moon’s orbit closest to the Earth

apogee

the point in the Moon’s orbit furthest from the Earth

Where is the biggest tidal range?

perigee

proxigean tides (king tides)

tides that occur during spring tide at perigee

flood tide

an incoming tide; approaching shore

ebb tide

an outgoing tide; receding from shore

slack tide

tidal point that occurs at the highest of high tides and lowest of low tides

tidal cells

large-scale rotating systems of tidal movement created by the movement of the tidal bulges, rotate around amphidromic points

amphidromic points

points in the ocean where the tidal range is zero

diurnal tides

one high and one low tide per day, very similar, occur in shallow inland seas

semidiurnal tides

two high and low tides per day, not the same but similar

mixed tides

two high and low tides per day, very different, most common type