Tides (#3)

What is the Tide generating force? What is it proportional to?

-*Proportional to: (mass 1) x (mass 2)/ (distance)^3 -Both SUN and MOON produce tides, but sun is half as important, due to its greater distance

What are slack tides?

-0 velocity -Perfectly still, right before water retreats into water or before moves to shore

Diurnal frequency?

-1 high and 1 low per day

Semi-diurnal frequency? Why?

-2 highs and 2 lows per day -Because of declination

Mixed tide frequency?

-2 highs and two lows per day. But they are not the same height

How long is the lunar cycle? How long does each phase last?

-28 day cycle -7 Days for each step (1 week for each phase) -New moon (unshaded)--> 1st quarter (right side shaded)--> Full moon (all shaded)--> 3rd quarter (left side shaded--> New Moon

How to find a neap tide on a tidal chart?

-Add or subtract 7 days from spring tide. Everything is 7 days apart. -Ex: January 10th (spring)--> January 17th (Neap) -It is the minimum tidal range

What is dynamic tidal analysis?

-Amphidromic systems -Point of 0 amplitude -Tidal range increases with distance from this point

How do you recognize a neap tide?

-Any minimum tidal range -Neap tides occur when the Earth, Moon and Sun are aligned forming a right angle and tidal bulges displaying destructive interference, producing low high tides and high low tides.

What are tidal bulges? Why do they occur? What are the two forces called?

-As the moon circles the earth, the bulge will move with it -Tidal bulge on either side of the earth -Equal and opposite tidal bulges -CENTRIFUGAL force creates bulge of water on left -GRAVITATIONAL force creates bulge of water on right

What three things cause tides?

-Caused by gravitational attraction of moon and sun AND centrifugal forces

Which way does the rotary wave turn in the Southern Hemisphere?

-Clockwise

What do cotidal lines show?

-Come from node -Connect points at which high tide occurs at the same time of the day -

What are corange circles?

-Concentric circles -Anything on the circle experiences the same tidal range -Corange circles are lines connecting points which experience the same tidal range. -The lines form irregular circles which are concentric about the node. -Tidal range increases outward from the node.

Which way does the rotary wave turn in the Northern Hemisphere?

-Counter clockwise

What is an amphidromic system?

-Describes a tide that rotates around a fixed node -Circular motion results in part from the Coriolis deflection and occurs in large seas

What kinds of tides do you get in a polar setting?

-Diurnal tide -Second high tide is so small, it is not really existent

Why is the sun only half as important in its production of tides compared to the moon?

-Due to its greater distance

What third factor is every tide influenced by?

-Every tide is actually influenced by the geometry of the coastline

If the moon's declination was 0, what kind of tides would there be?

-Everywhere on earth would have semidiurnal tides

What moon cycles create neap tides?

-First quarter moon and 3rd quarter moon -Neap tides occur when the Earth, Moon and Sun are aligned forming a right angle and tidal bulges displaying destructive interference, producing low high tides and high low tides.

When do lunar and solar tides add to one another?

-For New moons and Full moons -So during SPRING tides

How are tides formed?

-Formed by the gravitational attraction of the moon and the sun -The moon is so much closer. It has a larger impact on generating tides -Moon is the declaration of the ideal wave

When is the maximum tidal velocity?

-Halfway between high and low tides

What is an EBB current?

-High tide to low tide -Water to ocean -Ebb currents flow away from the coast, and the tide falls

How do you recognize a spring tide?

-Highest highs and lowest lows -Spring tides occur when Earth, Moon and Sun are aligned in a straight line and the tidal bulges display constructive interference, producing very high, high tides and very low, low tides.

When do lunar and solar tides work against one another?

-In NEAP tides -First quarter and 3rd quarter moons

What do orange lines indicate?

-Indicates tidal range anywhere in the basin

What is amphidromic circulation?

-It is one more effect of coriolis -Tide crest enters the basin -Trends toward the right side (in NH) due to coriolis effect

What would happen if you doubled the distance of the moon?

-It would be 1/8th as important -2^3=8

What are cotidal lines?

-Lines across corange lines -Experience tides at the same time -Cotidal lines connect points on the rotary wave that experience high tide at the same time. -Cotidal lines are not evenly spaced because tides are shallow water waves and their celerity depends upon water depth.

When does a spring tide occur in a tidal chart?

-Look for highest highs. Both highest highs

What is a flood current?

-Low tide to high tide -Water to shore -Flood currents transfer water toward the coast, and the tide rises

What is the effect of the lunar day (24 hours and 50 mins)?

-Lunar day length not the same as solar day length -Earth must rotate another 50 mins to "line up" with moon -Earth has to rotate for another 50 minutes every day -So moonrise will be 50 mins later each night -Time between high and low tide will be 12 hours and 25 mins (tidal period) -As earth rotates on axis, moon also revolving around earth -In one solar day (24 hours), moon moves east about 12.2 degrees

What kinds of tides do you get in a mid latitude setting?

-Mixed Tides -Will get one high tide being bigger and one being smaller

Why are there only 3 tides some days?

-Moving over to the next day -Eventually the tide that comes at the end of the day, will get knocked over to the next day. -There are really 4, it is just right after midnight

How long from neap tide to neap tide? From Neap tide to Spring tide?

-Neap to Neap= 14 days -Neap to Spring= 7 days

What moon cycles create spring tides?

-New moon and Full moon -Spring tides occur when Earth, Moon and Sun are aligned in a straight line and the tidal bulges display constructive interference, producing very high, high tides and very low, low tides.

What is a micro tide?

-Not much different between high and low tides

*What kind of tides are there in Galveston, Texas?

-Part of the time there are Mixed Tides -Part of the time they are diurnal

What are tides?

-Regular, predictable changes in the elevation of the ocean surface -They are SHALLOW WATER WAVES -Rhythmic. Up and down -Associated with horizontal currents (going in and out) -Ultimate manifestation of shallow water wave phenomenon -Wavelengths= 1000s of kilometers -Wave heights= 0-15+ meters -NOT the same as tidal waves -Creatures limits of organisms that live along the coastline

What happens in a broad basin?

-Rotary wave -This would be a square/round space

What is a rotary wave?

-Rotary wave= rotation of a wave crest around an ocean basin -around the center point (A.P) -A rotary wave is part of an amphidromic system (rotary standing wave) in which the wave progresses about a node (no vertical displacement) with the antinode (maximum vertical displacement) rotating about the basinís edges. -Movement of tides across ocean basins is deflected by Coriolis, blocked by continental landmasses and forms a rotary wave, which each day completes two cycles around the basin if the tide is semidiurnal or one cycle if it is diurnal.

What are the 3 common types of tides? What do they mean?

-Semidiurnal Tide: 2 high tides and 2 low tides. Highs are the same and lows are the same each day. -Diurnal Tide: One high tide and one low tide each day. Second high tide is so small, it is not really existent -Mixed Tide: Highs and Lows, but the 2 highs are not the same height and the 2 low tides are not the same height. Highest highs and the lowest lows

What kinds of tides do you get in an equatorial setting?

-Semidiurnal Tides -Get the same size of high and low tides every day

What kind of waves are tides?

-Shallow rotary waves

What is the tidal range of a semi-diurnal tide? How does this relate to the A.P?

-Small or 0. Close to or at Amphidromic point -Tidal range increases as you go further away

What is the amphidromic point?

-The center point -Rotation of a wave crest around an ocean basin, around the center point= A.P -An amphidromic point is a point of zero amplitude of one harmonic constituent of the tide.[1] The tidal range (the amplitude, or height difference between high tide and low tide) for that harmonic constituent increases with distance from this point.[2] These points are sometimes called tidal nodes. -NO TIDES AT THIS POINT •tidal range of 0

What is the rhythm of tides related to?

-The moon's declination

What are equilibrium tidal predictions?

-They explain how tides would behave if we had a simple earth -Explains how tides move, but not good for predicting -because when the moon circles the earth, it doesn't circle on our equatorial plane

What do high and low tide systems occur as? What is a rotary wave?

-They occur as rotary waves

What is the angle between the moon, orbital plain, and our orbital plain?

-This is called DECLINATION -Declination=28.5º

What is the length of a tidal period? What is the length of a lunar day?

-Tidal Period= 12 hours and 25 mins -Lunar day= 24 hours and 50 mins

If you double the mass of the moon, what would happen to its tidal generating force?

-Tidal generating force would double

How does amphidromic circulation work?

-Tide crest enters basin -High tide on right side. Low tide on the left side -Trends toward the right side in the northern hemisphere to the right of the amphidromic point -High tide in back, falling tide on right side -Trends counter clockwise around A.p -High tide on left side, falling tide in back, low tide on right -Trends counter clockwise around A.P fully

What happens in a narrow basin? What do the cotidal and corange lines look like? (*see diagram)

-Wave just goes in and out -Can create big tidal ranges -In long and narrow basins tides can not rotate. -Currents in these basins simply reverse direction between high and low tide, flowing in with the high tide and out with the low tide. -Cotidal and corange lines are nearly parallel to each other.

How many times per day will a semi-diurnal tide rotate around the A.P?

-Will rotate twice around in 1 day -Movement of tides across ocean basins is deflected by Coriolis, blocked by continental landmasses and forms a rotary wave, which each day completes two cycles around the basin if the tide is semidiurnal or one cycle if it is diurnal.

What 5 biological things are affected by tides?

1) Diatoms: Need to be close to light but don't want to be swept away. Barrow down when tide leaves and comes out when water floods 2) Green flatworms 3) Fiddler crabs: Come up at low tide and down at high tide 4) Coral Reef: Reproduction on coral reef 5) Granion: Come out during spring tide to spawn -Highest high= ride all the way in to bury and fertilize eggs - Lowest low= Eggs develop without water on the sand. Not Eaten -Highest high= Water lifts eggs up out of sand and they hatch

What are the 2 types of tidal currents?

1) Ebb tides 2) Flood tides

Explain the cycle of a rotary tide?

1) High tide at the ocean basinís western edge creates a pressure gradient sloping downward towards the east. 2) As water flows down the gradient, Coriolis deflects water towards the equator, where it accumulates and establishes a pressure gradient sloping downward towards the pole. 3) Water flowing down this gradient is deflected eastward, forming a pressure gradient sloping downward to the west. 4) Westward flow along this gradient is diverted poleward forming a pressure gradient sloping downward toward the equator. 5) Finally, the flow toward the equator is deflected westward, completing the cycle.