Sea Level as a Point of Measurement

Discussion in 'Earth Science' started by Acitnoids, Sep 18, 2018.

  1. Acitnoids Registered Senior Member

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    Sea Level. This hypothetical point in space plays an important role in some measurements that have real world applications. Atmospheric Pressure, important for aviation and forecasting the weather. Geological altitude such as the height of Mt. Everest is another example.

    As we all know sea levels are rising. Does this fact have an impact on the altitude measurement systems? I have never heard of Mountains getting "shorter" because of sea level rise.

    Is "Sea Level" considered a fixed point in space or is it in flux? If so then when was it considered fixed and what was the year it was determined the "hight of sea level"? How much higher is the actual "sea level" now compared to its "agreed on point in space"?

    If it is not fixed then why do mountains stay at the same height? Should that difference have an impact on predicting the weather?
     
    Last edited: Sep 18, 2018
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  3. Seattle Valued Senior Member

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    It's just an average for one point. You don't hear of mountains getting "shorter" because the change i msl isn't significant given the size of mountains.
     
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  5. Acitnoids Registered Senior Member

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    I understand that but, if Greenland melts, that average is no longer. When was that "average" considered the agreed on point?
     
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  7. Seattle Valued Senior Member

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    It changes all the time. It has varied a lot over the years.
     
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  8. Acitnoids Registered Senior Member

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    https://www.topchinatravel.com/mount-everest/the-height-of-mount-everest.htm

    Once again, understand that but I am not sure if that is a "standard". This link suggests Mt. Everest is rising at 4mm per year. I assume that is based on some sort of "standardization" of sea level. Yet it does not give an average (i.e. 4mm per/yr +/- 2mm). A mention of an average sea level is completely absent from the literature would you disagree?

    On average yes, I can understand but what I am suggesting is this is not a standard. Yet this measurement is used for real world applications!

    Sea level as a "standard of measurement" is useless as an average if we wish to know weather patterns for example.

    I guess the point is going over your head. Could you please share when, as you say, this measurement has "changed all the time" in the scientific use of this particular measurement ?

    Aviation, Cartography, Meteorology are just a few that require this measurement, averaged or not. Accuracy/prediction depends on this point in space.
     
    Last edited: Sep 18, 2018
  9. Seattle Valued Senior Member

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    Aviation is based on barametric pressure and not msl.
     
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  10. Acitnoids Registered Senior Member

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    Last edited: Sep 18, 2018
  11. Acitnoids Registered Senior Member

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    You have failed to answer any of my questions. Obviously this conversation is way above your head. Thanks for trying but I'm looking for intelligent people
     
  12. Seattle Valued Senior Member

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    No, you're not.
     
  13. Acitnoids Registered Senior Member

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    Where is Atmospheric pressure measured as a baseline? I'll start simple for you.
     
  14. Acitnoids Registered Senior Member

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    There is no need to be rude. I know the Internet sucks now but i remember this sight as being thoughtful and intellectual.
     
  15. Acitnoids Registered Senior Member

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    I haven't posted here in a few years
     
  16. Seattle Valued Senior Member

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    Are you still living in your parents basement? How did the community college certificate work out for you?
     
  17. iceaura Valued Senior Member

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    ? It isn't. It's measured at sea level, often - but it's also measured at other altitudes. Some common measurement units were calibrated at a defined altitude, is all, for convenience in weather reporting relative to sea travel - "sea level" was handy. Others were not.
    It varies by time and location.
     
  18. Acitnoids Registered Senior Member

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    Lol ... sorry you are upset but I was asking a legitimate question.
     
  19. Acitnoids Registered Senior Member

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    Thank you iceaura,
    As I said, I understand "average sea level" but where in the literature dose it give an "average" (I.E. Mount Everest rises +4mm per year +/- 2mm per year)? Everest rises 4mm per/yr according to what?
     
    Last edited: Sep 18, 2018
  20. Acitnoids Registered Senior Member

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    What is mount everest rising above to quantify a measurement of 4mm per year?
     
  21. iceaura Valued Senior Member

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    Some of the analysis of satellite measurements of topography derive the reported number from a defined planetary center of gravity, others from an abstraction whose name I've forgotten but amounts to an idealized, perfectly smoothed surface of a homogenous planet the oblate shape of Earth (which one might label "sea level"), still others from an idealized great circle satellite orbit centered on the earth's center of gravity, still others define local sea levels relative to local shore features (such as survey markers) after averaging out tides and waves and vertical motions of the land, and so forth.
    There's nothing simple about it. The papers analyzing post-glacial rebound and sea rise are both complicated and controversial, for example - everything is moving, everything moved in the past.
     
    Last edited: Sep 18, 2018
  22. Acitnoids Registered Senior Member

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    lol .... are you saying there is no standard Mount Everest has for it's altitude? Including its growth?
     
  23. Acitnoids Registered Senior Member

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    Your answer suggests GPS is a benchmark. ... Is that your stance?
     

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