Why does the ocean elevate?

Discussion in 'Earth Science' started by Krazie, Sep 19, 2004.

  1. Krazie Registered Senior Member

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    Why does the ocean elevate? Does it elevate? Or do all the oceans stay at see level constantly. If it doesn't elevate then what is the purpose of barges and the such? If it does elevate, then why?
     
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  3. Hypercane Sustained Winds at Mach One Registered Senior Member

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    Are you talking about tides? It elevates and drops everyday because of the tidal forces produced by the gravity from the moon and sun.
     
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  5. curioucity Unbelievable and odd Registered Senior Member

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    Suddenly I have a question: If you fill up a glass with water to a point that it almost overflows at dusk or dawn, and you put it outdoor during a full moon night, would it overflow?
     
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  7. Boris2 Valued Senior Member

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    >>>>..... full moon night, would it overflow?

    why would the phase of the moon make a difference? the whole moon is still up there regardless of phase. and the glass would not overflow.
     
  8. Catastrophe Registered Senior Member

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    "during a full moon night, would it overflow?"

    The Moon has a greater influence than the Sun, so at Full Moon they oppose each other. Higher tides are expected at New Moon.

    The glass would not overflow although the pull would be greater at New Moon. Tides on Earth are a redistribution of the total water in the sea. The water in the glass is fixed (apart from evaporation) and cannot be redistributed in analogous fashion.
     
  9. curioucity Unbelievable and odd Registered Senior Member

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    Wait, so you mean that tides are actually sea-water moving from a one hemisphere to another?
     
  10. river-wind Valued Senior Member

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    edit: yep, though the amount of water involved means that you don't notice much of a current, like you would in a river.
    ----


    Here's a question for you: why is the pacific ocean an average of 24 cm higher than the atlantic(at the panama canal)?

    http://www.nationmaster.com/encyclopedia/Panama-Canal
    I've never figured this one out myself.
     
  11. Krazie Registered Senior Member

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    "The Pacific end of the canal is 24 cm higher than the Atlantic end and has much greater tides."
    THIS IS EXACTLY WHAT I WAS WONDERING! Why is this? Does anybody know?
     
  12. philocrazy Banned Banned

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    melting of ice at the poles
     
  13. Catastrophe Registered Senior Member

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    Only melting of ice on land and draining to ocean has any effect on sea level.

    Ice floating on water has already displaced its own weight of water (Archimedes Principle) so does not increase sea level when it melts.
     
  14. Krazie Registered Senior Member

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    I still don't understand why the pacific end of the panama canal is 24 cm higher than the Atlantac end. Could someone please explain.
     
  15. river-wind Valued Senior Member

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    2,671
    I've been doing some reading on ocean currents, thinking that maybe the pacific side had an unbalanced amount of water coming into the panama area (via the El Nino or Humbolt/Peru currents), but it seems that the Atlantic side has a similar current pattern:
    http://oceancurrents.rsmas.miami.edu/caribbean/caribbean.html
    the caribbean current pushing water against the Panama shores.

    Maybe it's due to the Carribean current only hitting panama via a whirl-pool switchback, while the pacific currents ride up the western coast of S. America and slam right into the panama 'S'??? (total guess).


    The spinning of the earth can't be the reason, the earth spins toward the east, so I'd expect that any pillow of water caused by the earth pushing the water along would occur on the eastern coast.

    edit: full map of world currents:
    http://www.uwsp.edu/geo/faculty/ritter/images/maps/ocean_currents.jpg
     
  16. Avatar smoking revolver Valued Senior Member

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    People tend to forget that there is only one world ocean. Naming different parts of it by various names dont' make them seperate.
     
  17. YadaYada subspace being Registered Senior Member

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  18. Catastrophe Registered Senior Member

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    With waves and tides to consider, how do you actually define/measure sea level?
     
  19. Facial Valued Senior Member

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    Tidal datum.
     
  20. Andre Registered Senior Member

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    Interesting indeed the higher Pacific elevation. Now there are lots of reasons for the variation of sea level. An important one is water mass temperature. Warmer water is obviously less dense and rises relatively higher than surrounding colder water to achieve equilibrium of forces. So obviously yes, El Niño might be the main cause of the water elevation difference as illustrated here

    By the way, it's now official, a new El Niño has started
     
  21. Fraggle Rocker Staff Member

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    I know that you really want to know what happens as your part of the earth rotates out from under the moon and back again, not as the phase of the moon changes -- which only affects its light, not its tides. And I also know that you don't really think that moving the glass outdoors into the fresh night air is going to change the effect on it of the moon's gravity.

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    The answer is no. There will be a tidal effect in the glass, but immeasurably small. The difference between the moon's gravity on the water at the rim on the side of the glass closest to the moon and its gravity on the water a couple of inches away on the other rim will create a difference in water level measured in millionths or billionths of an inch. The meniscus effect (the surface tension that causes the surface of the water to be convex as viewed from above) will have more influence on the shape of the surface of that water than the tidal effect.

    The wording of your question implies that somehow more water is going to find its way into the glass when it's close to the moon, or perhaps that the water already there will expand and its density will decrease. Neither of those things happens as a result of tides. Tides are simply the water at the very surface of the sea "falling" from a place where the sum of the earth's positive gravity and the moon's negative gravity is slightly smaller, to a place where that sum is slightly larger because the moon is further away.

    Sure I suppose water gets denser as more of it is piled upon itself and it expands and contracts like all matter under pressure. But the effect of the differential in the moon's gravity making the water in the glass a tiny bit lighter and therefore allowing it to expand will be the least observable of all the phenomena involved in this scenario. That change in the water level would probably be measured in trillionths or quadrillionths of an inch. Perhaps just a few molecules. Another movement completely masked by the meniscus effect.
     
  22. philocrazy Banned Banned

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    Catastrophe
    Registered User (127 posts) 09-21-04, 01:06 AM
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    Only melting of ice on land and draining to ocean has any effect on sea level.

    Ice floating on water has already displaced its own weight of water (Archimedes Principle) so does not increase sea level when it melts.
    ------------------------------------------------------
    which weighs more solid or liquit???????huh liquit or gass??????huh!!!!
     
  23. Catastrophe Registered Senior Member

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    "which weighs more solid or liquit???????huh liquit or gass??????huh!!!!"

    It is a question of density, not weight.

    Ice is less dense than water, hence it floats.

    I don't see the relevance.
     

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