Tides Lecture PDF

Tides Lecture - What causes Ocean tides?. Intro to Tides + Tides are the largest of all oceans waves in terms of wavelength + Fundamently, very long and regular shallow water waves Tides are the large scale motion of water + Almost all ocean areas experience rides + Anything that has the ability...

Tides Lecture - What causes Ocean tides?. Intro to Tides + Tides are the largest of all oceans waves in terms of wavelength + Fundamently, very long and regular shallow water waves Tides are the large scale motion of water + Almost all ocean areas experience rides + Anything that has the ability to ow will exhibit some measurable tides Leg. large lakes, atmosphere can have tides) + Gravitation pull on the oceans produce tidal waves and tidal currents + Tides are generated by celestial forces, especially the sun and moon, changes in the relative positions of the sun, moon, and Earth will change the size and velocity of tidal waves and currents + Tides exist on Earth as Forced waves from celestial forces (mostly) moon) + Rate of travel is ~1400 km/hr + Tidal bulge waveform moves, not water itself Tide Generating Forces: Gravity and Centripal Forces + Simplistically, the gravitational forces between the sun and the moon on Earth create tides + The rotation of the moon around Earth + The two bodies rotate around a common center of mass or balance point called the bary center Tide Generating Forces: Gravity + From Newton's Law of Universal Gravitation: Fg = Gm, mz /rz + If mass increases (T), the gravitational force increases (4) + If distance increases (^), then the gravitational force greatly decreases (77) + Zenith (2): point of greatest gravitational force + Nadir (N): point of least gravitational force Tide Generating Forces: Centripetal Forces + Centripetal force tethers the Earth and Moon to each other + Centripetal Force is equal on parts of the Earth Tides are generated by the resultant forces + The resultant force is the difference between the graviation and centripetal force fl Centripetal force is equal on parts of the Earth 、 + Simutaneously create two bulges one toward and one away from the moon Tidal Bulges: The Moon's Effect Idcalized Earth and ocean (not including depth changes, friction at sea cor) + Earth has 2 tidal bulges due to whar cycle · I toward Moon. I away from Moon + Lunar Day: time the moon is directly overhead (meridian of an observer) until the next time it is directly overhead + Duration is: 24 hrs 50 minutes 28 seconds (additional 50 mins required to Catch up) + Tidal cycle is half this point: 12 hrs 25mins + Tidal period: 12hrs 25 minutes based on the Lunar Day (24 hrs, 50m) Lunar VS Solar Day. Lunar Day is longer than solar pay + High tides are normally 50 min later cach sucessive day + Moon rises 50 min later each sucessive night + During Lunar Day, moon traveled 12.2° around in its orbit around Earth + Earth has to rotate another 12.20 to 'catch up on the moon' Solar Day (24 hrs) + Time for Earth to make I full rotation Tidal Bulges: The Sun's Effect + Sun is 390x furthur from Earth than the Moon + Tide generating force of the sun is about 44% that of the Moon + Solar bulges are only -46% the size of the lunar bulges Earth's Rotation and the Tides. + Tioles appear to move water in and out of the shore + According to the laws of nature, Earth's rotation moves a spot into and ou of the tidal Dulges. + Bulges are in xed position Ebb Tide: water moves away from Shore Flow Tide: water moves toward shore - How do tides vary in the monthly cycle?. Monthly Tidal Cycle fi fi + Monthly tidal cyclc is 29.5 days + This is the time it takes the moon to orbit around the Earth Monthly Tidal Cycle and Moon Phases + New Moon: cannot be seen at night because its in between the sun and Earth + Full Moon: Moon is on the opposite side of Earth than the Sun + Quarter Moon: Half of the disu is visible from Earth + we only see half of the side that is facing the Sun Complications: Declination of Moon and Sun + Sun and Moon are usually not overhead at equator t Usually north or south of equator + Declination: angular distance of the sun or moon above or below Earth's cquatorial plane + + Maximum angle of declination is 28.5. N/S of the equator Earth's tilt" (23.5) + Moon's orbit is tilted 5. Depends on time of year Solar angle Complications: Elliptical orbits + Tidal ranges are largest during Perinelion and Perigce + Tidal ranges are smallest during Aphelion and Apogee Predicting idealized Tiaes + Declination of the moon determines the position of the tidal bulges Amphidromic Point and Cotidal Lines T Adding continents to an ideal aqua plane+' adds physical obstacles and friction which impedes tidal ow + Tides ao nor ow in straight lines, they respond to the Coriolis Force, and They tend To slosh around' in ocean basins + Amphidromic Point: point in ocean basin or bays where there is no change in water levels related to tidal actions radiating out from these points are coridal lines, which connet areas where nigh tides occur simultaneously + Cotida! lines are mapped when the moon has crossed o degrees longitude (Greenwich Meridian) + Almost 400 total factors together impact tides at any given point on Earth -What are the different types of tidal patterns.? - The Three Primary Tidal Partems fl fl + In theory, most places on Earth should experience 2 high rides during a lunar day + In practice variability in ocean basins modify tides so they experience 3 patterns primary globally A) Diurnal Tides B) Semidiurnal Tides C) Mixea Tidal Pattems A) Diurnal Tides + I high and I low tide cach day + Tidal period is 24hr 50min - Gulf of Mexico + Shallow Inland Seas 3) Semidiurnal Tides + 2 high tides and 2 low tides each day + Tidal period is 12hr 25min + Atlantic Coast + Eastern side of atlantic C) Mixed Tidal Pattems + High and low tides have large differences + Tidal period is 12 hr and 25min + Most common type of tides + Paci c Coast of North America + Carribean Sea -Tides and the Grunion Spawn- Grunion Spawn + Two species: Leures thus tenius (Californian Grunion) and the L. Sardinas (Gulf Grunion) + Grunions are the only marine sh that come completely out of the water to spawn, time precisely with the tides + After spring tide they come ashore to bury their eggs. + Sand is eroded during high tides, deposited during low tides + Fish come into spawn after Spring tide so the eggs won't be disturbed during low tide while preparing to hatch + Once high tide returns in 10 days eggs are exposed by erosion eggs hatch within 3 minutes of being freed into water fi fi