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Ice caps melting = water rising?

  1. May 25, 2007 #1
    I've heard that if the ice caps melt the oceans will rise.

    but i thought that water expands when freezing.

    is this a myth?
     
  2. jcsd
  3. May 25, 2007 #2
    It does but the ice they are talking about is sitting on land rather than the sea.
     
  4. May 25, 2007 #3

    Pythagorean

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    It just won't be proportional to the size of the ice that melts, but it will still contribute to the sea level.
     
  5. May 27, 2007 #4

    It's true that most of the melting ice is on top of land, like the ice cap of Greenland.

    But then for the floating ice:

    Take a glass of water and put an ice cube into it. Wait until it melts. Which way did the surphase of the water in the glass move, up or down?

    Where will the expanded part of the wather when freasing to ice normally be located, for a floating ice cube ?
     
  6. May 27, 2007 #5

    cristo

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    Neither.. the water level remains the same.
     
  7. May 27, 2007 #6

    DaveC426913

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    The density of floating ice vs. water has no effect on water level. See diagram.
     

    Attached Files:

  8. May 27, 2007 #7
    Yes, you are right. I should not speak about experiments without performing them. The volume above the surphase should be exaclty the same as the expansion volume so there should be no change at all - right ?!

    :blushing: Shame, stupid me ..
     
  9. May 27, 2007 #8
    In the short term we shouldn't be too worried about ice bergs and ice shelves melting, because they are floating so when they melt they do not contribute to sea level rise. It is grounded ice that melts that will contribute to sea level rise, the largest ice caps on earth are grounded (e.g. Greenland, Anterctica).

    Q/What is the single largest contributor to sea level rise?

    A/Thermal expansion. Because when you heat water up it becomes less dense (i.e. its volume increases), and because water is a fluid, it will spread its volume evenly over the entire ocean (ignoring self-gravitational effects).
     
  10. May 27, 2007 #9

    Pythagorean

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    I think he's referring to ice on land, as from the North and South (an) arctic.
     
  11. Jun 21, 2007 #10
    True, but would you say this is an appropriate analogy, to compare the earth's oceans to a cup of water?
     
  12. Jun 21, 2007 #11

    Evo

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    Ice melt from ice over water will not increase sea level, only ice melt from ice over land will have an impact and it will not be uniform, there will be variations with rises in some areas, while other areas could see a fall.
     
  13. Jun 21, 2007 #12

    Ivan Seeking

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    The main concerns are the melting ice in Greenland and the Antarctic. Expansion of the water from heating is also a factor.

    Evo, I was not aware of any predictions that water levels could fall in some areas. Where does this come from?
     
    Last edited: Jun 21, 2007
  14. Jun 21, 2007 #13

    Evo

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    From the IPCC, from the EPA...

    http://www.epa.gov/climatechange/effects/coastal/index.html
     
  15. Jun 21, 2007 #14
    The most likely cause I can think of for the variability would be uplift and subsidence of the crust. E.g. SE England's coast will become submerged even if global sea levels do not change, the land is subsiding as mantle material diverges towards the north of Britain which is currently undergoing isostatic rebound in response to the melting of the ice cover at the end of the last glacial maximum.
     
  16. Jun 21, 2007 #15
    Meanwhile Hudson Bay and the Baltic sea are on it's way to become land.
     
  17. Jun 21, 2007 #16
    A rapid melt in arctic ice with an inhibited flow into the Atlantic could submerge islands in the arctic. The situation depends on whether the melting of ice is uniform or a sudden gush. I have to believe that either way, the melting of the artic ice cannot be felt uniformly throughout the world's oceans. If say for some reason, a large iceberg cuts off the Berring, and the arctic ice melts, there may be a chance the coastal regions of the Atlantic in England, North America and Europe could suddenly sea a sharp rise in ocean levels.
     
  18. Jun 21, 2007 #17
    It would have to be a very rapid melting for the effects to be felt locally at the scale that you are discussing, and besides even if there were a great flood, it would soon disperse.
     
  19. Jun 21, 2007 #18

    DaveC426913

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    How would a floating iceberg cut off water flow? The water flows under it.
     
  20. Jun 22, 2007 #19
    Think of an iceberg not as a surficial chunk of ice but as massive structure which remains largely submerged. If icebergs floa, in terms of mass, on the surface, the Titanic would not have sunk.

    Has anyone considered the change in salinity of the ocean water as a major factor in ocean rise with ice cap melt in the arctic?
     
  21. Jun 23, 2007 #20
    I have been looking at this type stuff all over the world. And if you look very closely at land terrain on google earth, you will notice tons of villages and cities are built in a valley or an old river bed. So when the caps do melt, obviously the water will increase. Some people say between 20 to 200 feet the levels will increase.

    Whatever it may be, I only hear them (the media) speaking about the sea level.
    We all know how the media omits what they want to and what the government wants them to. So won't a lot of the river systems be affected as well? I would think so.

    And I'm wondering if anyone has drew up some pictures using these predictions of earths future. The signs are already there that the water has been been there, so why not fill in the dots and see what earth looks like with a complete meltdown so we can begin preparing to move to higher ground.
     
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