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Influence of the sun on the temperature of the ocean

  1. Jun 15, 2010 #1
    We did an experiment to find out how water is heated as a result of sunlight. We had a bowl of water which we heated with a copper plate on the water surface, through which we sent a sinusoidal current. We didn't use a lamp, because water doesn't absorb visible light very well and since our bowl is not very deep, the effect wouldn't be as pronounced with a lamp.

    In the bowl we had a number of temperature sensors at varying depths. We found that, with increasing depth, the output of the sensors had decreasing amplitudes and increasing phase shifts:

    http://img15.imageshack.us/img15/1381/wstr3.png [Broken]

    We are now looking for a real world example where this effect occurs as well. Our teacher said the deeper layers of the ocean might be applicable, because convection won't be a factor there (we only want to see how the sunlight heats the water) and the water doesn't move much. If you put a number of temperature sensors in a deeper layer of the ocean, would you get a similar result as the one in the above graph?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jun 15, 2010 #2
    The temperature of the ground exhibits the same behaviour as well.

    Water is a bad example, because it is at its most dense at about 4C.
  4. Jun 15, 2010 #3


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    Staff: Mentor

    I'm afraid that your teacher forgot that light rarely penetrates ocean water deeper than 200 meters (656 feet).

  5. Jun 15, 2010 #4
    I thought, based on the experiment outlined in the OP, that he was more interested in heat conduction than direct absorption.
  6. Jun 15, 2010 #5


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    Staff: Mentor

    Yeah, but he said "we only want to see how the sunlight heats the water". The teacher said "the deeper layers of the ocean".

    His thread title says 'Influence of the sun on the temperature of the ocean".

    But I could be wrong. :biggrin: It won't be the first time.
    Last edited: Jun 15, 2010
  7. Jun 16, 2010 #6
    This is only true of fresh water.
    Seawater does not exhibit this anomalous behaviour.
  8. Jun 16, 2010 #7


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    Obviously the sun heats the ocean, but it's so large that solar cycle variations in the suns output are not noticeable in the bulk temperature of the ocean.

    Keep in mind that the temperature of an object is a function of both input vs output.
    So, if the heat loss of the ocean were reduced, it's temperature would rise.
    Convection will eventually mix surface warming towards the depths, but the time scale for that is immense.

    As an aside, sea water reaches it's maximum density near it's freezing point, which would be about -2C. However, salinity differances within the ocean are significant
    Last edited by a moderator: Jun 16, 2010
  9. Jun 16, 2010 #8
    I'm with NeoDevin. The nonpenetration of sunlight is the reason why the OP's experiment is relevent to the manner in which the sun would be expected to influence the temperature of deeper layers of the ocean.
    Last edited: Jun 16, 2010
  10. Jul 11, 2010 #9
    That is a surprise! :smile:
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