tides and currents notes
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Tides and Currents Notes. How often do tides occur?. There is about 12 hours and 25 minutes between two high tides or between 2 low tides. If it is high tide in the afternoon today, then a week from today it will be low tide in the afternoon. What causes tides?. Sun’s gravitational pull - PowerPoint PPT PresentationTRANSCRIPT
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Tides and CurrentsNotes
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How often do tides occur?
• There is about 12 hours and 25 minutes between two high tides or between 2 low tides.
• If it is high tide in the afternoon today, then a week from today it will be low tide in the afternoon.
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What causes tides?
• Sun’s gravitational pull • Moon’s gravitational pull
– Because of the nature of gravity and proximity the moon’s pull is over twice that of the much larger sun
• These result in tidal bulges (high tides) on opposite sides of the Earth
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Why is there a bulge on the opposite side from the gravitational pull?
• Inertia– Tendency of an object to
stay moving in a straight line
• On the far side, the gravitational pull of the moon is weaker because it is farther away
• On the far side, the force of inertia is greater than the gravitational pull so it bulges
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What is a spring tide?
• Extreme differences between high and low tide
• Sun, earth and moon are in a straight line
• Effects of moon and sun are cumulative
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What is a neap tide?
• Moderate differences between high and low tide
• Sun, earth and moon are at right angles (90o) and the effect of the sun and moon slightly cancel each other out.
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What else can affect tides?
• Shape of the shoreline– Isolated islands tend to have smaller tide differences
• Shape of a estuary– Funnel shape=large tidal differences– Narrow inlet and shallow water=smaller tidal differences
• Local wind patterns– Can move water in or out exacerbating tides
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What are the tidal ranges of the Bay?
• Not very large difference between high and low tide– CBBT: 2-4 feet– Huntington Beach: 2-3
feet– Mobjack Bay: 2-2.5 feet
– Bay of Fundy: spring tide is 47.5 feet
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What are surface currents?
• Continuous, directed movement of water
• Mostly caused by wind– Move at 45o angle to
wind due to Coriolis effect
– Responsible for about 40% of the global heat transport
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What else causes currents?• Thermohaline circulation
– Thermotemperature– Halinesalt
• Differences in the density of water due to heat fluxes and freshwater input results in water circulation
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What are the major ocean currents?
Describe the location and direction of the following: Gulf Stream, Labrador, Equatorial Counter, California, Antarctic Circumpolar
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Why do currents matter to marine life?
• Move nutrients from deep water to the surface
• Disperse waste• Act as boundaries to animals because of
changes in temperature