August 10th, 2010, 08:41 AM
Total idiot question, not much of a science person.
When it comes to ice, what dictates how high it floats in the water? Is there a standard % of it that sticks out of the top of the water? Would ice cube A float higher than ice cube B if it had a few extra air bubbles in it?
Dont know why this interests me, but anyway.
Cheers in advance
by the way sry if this is in the wrong section
August 10th, 2010, 10:52 AM
The exact height will depend upon the density of the water and the density of the ice. As you rightly point out ice may contain pockets of air, which will reduce it bulk density - it wioll tend to sit higher in the water.Originally Posted by Sopsop
the density of the water it is in will be determined by its salinity and its temperature, both of which vary.
The resaon ice floats is because of buoyancy. Buoyancy is a force which is governed by Archimedes principle, which simply states that:
The force of buoyancy is equal and opposite to the weight of the displaced fluid.
Consider a block of ice that has a density equal to 90% the density of water, sitting in a pool of water in equilibrium. This situation can be restated: the weight of the ice is balanced exactly by the buoyancy force given back by the water.
By Archimedes' principle, that means that the block of ice displaces its own weight of water.
Now because the ice is 90% the density of the water (meaning that it is 100/90 = 1.111 times bigger per unit of weight), that means that only 90% of the ice need be submerged into the water so that the required weight of water is displaced. The other 10% of the ice does not displace any water: it is seen to float above the water.
Question: what happens to the level of the water once the ice has melted?
Since nobody else answered...
The level remains the same.
Close.Since nobody else answered...
The level remains the same.
There's be a slight rise due to the fresh water sea ice melting into the ocean because it is less dense therefore holding higher volume than the more dense water it's displacing. Probably not more than a few cm.
I didn't see the term "sea" or "Arctic ice" in his question anywhere, nor do I agree with your assumed assessment without visiting the math.Close.Since nobody else answered...
The level remains the same.
There's be a slight rise due to the fresh water sea ice melting into the ocean because it is less dense therefore holding higher volume than the more dense water it's displacing. Probably not more than a few cm.
Or I could say I didn't know Archimedes experimented with ice in the Arctic Ocean. I thought it was in a laboratory.
Nor did his question explicitly assume the composition of the ice and the water were the same. They often aren't, even when the ice originally formed from the water it floats in (sea ice is one example). Obviously this effects density which changes the answer to the question.
Still, by your assumption, wouldn't such a senario lower the sea level rather than raise it?
Buoyancy has specific known properties. If there is a level change from absorbed salts and other molecules, it seems to me it would decrease rather than increase. I still think it would remain the same though.
What topic would that be under for research?
several including oceanography, hydrology, geology, cryology with like many things application to other fields including climatology.Still, by your assumption, wouldn't such a senario lower the sea level rather than raise it?
Buoyancy has specific known properties. If there is a level change from absorbed salts and other molecules, it seems to me it would decrease rather than increase. I still think it would remain the same though.
What topic would that be under for research?
But the concept is simple. Imagine if a block of ice were floating on a sea of liquid mercury. Since mercury is much more dense the most of the ice would be above the level "sea level," and not displace very much. If you melted that ice the combine volume of mercury and water would lead to a higher "sea level."
Floating ice whether by brime extraction from frozen sea water or from calving of glaciers is mostly fresh water. Fresh water has density of about 1000kg/m^3, sea water about 1030 kg/m^3. Floating ice displaced less volume than it contributed once it melts. --
(Anyone can confirm in the comfort of their own kitchen with fresh water ice cubes and their own hand made brimy sea water and a tall graduated measuring cup.)
I disagree.several including oceanography, hydrology, geology, cryology with like many things application to other fields including climatology.Still, by your assumption, wouldn't such a senario lower the sea level rather than raise it?
Buoyancy has specific known properties. If there is a level change from absorbed salts and other molecules, it seems to me it would decrease rather than increase. I still think it would remain the same though.
What topic would that be under for research?
But the concept is simple. Imagine if a block of ice were floating on a sea of liquid mercury. Since mercury is much more dense the most of the ice would be above the level "sea level," and not displace very much. If you melted that ice the combine volume of mercury and water would lead to a higher "sea level."
Floating ice whether by brime extraction from frozen sea water or from calving of glaciers is mostly fresh water. Fresh water has density of about 1000kg/m^3, sea water about 1030 kg/m^3. Floating ice displaced less volume than it contributed once it melts. --
(Anyone can confirm in the comfort of their own kitchen with fresh water ice cubes and their own hand made brimy sea water and a tall graduated measuring cup.)
The difference is that your example used dissimilar materials. The volume of water, with absorbed brine, has no significant difference with the water without brine. The absorbed brine has a marginal change in volume, if any. I forget how that works, but an example between ice to water in mercury is no comparison to the question at hand.
? Dude I even gave you the difference in densities. It's an easy to verify fact. (look it up or do the kitchen thing). The 3% difference is pretty significant and for many things including driving a lot of the oceanographic ocean currents.The volume of water, with absorbed brine, has no significant difference with the water without brine.
Anyhow back to sea level; A few folks have already done the work summed up the floating sea ice and concluded the difference would amount something like a to 4-6 cm average rise across the globe. Here's one extract.
http://onlinelibrary.wiley.com/doi/1...472.x/abstract
There are probably other sources if you dig around.
Ans the water floats higher. Maybe what I'm missing is how you are allowing for displacement to change a level. I don't know the term for what I am thinking about, but when a fluid absorbs a salt, there is far more density change than volume change.
What happens if I put 100 grams of NaCl in a liter of water? Does the level change once it's dissolved? maybe it does. I simply forget. I don't think it changes my any significant amount if it does. Now when the salts are distributed to the new fresh water, then even is salinity affects volume, doesn't this balance it out?
Now as I think about it, I think you are correct. If the ice melted, it would mix with warmer water and become less dense that way. I don't have access to the material, but does it go one with the average ocean temperature increasing as a result of no ice?
I just found that article online that at a site that doesn't require a subscription or payment to read it. I am reading it now. Still, a 4 cm rise is minuscule.
Ok, I see what I missed. Thank-you for the article. I actually learned something today. I even saved if for future use.
For those wanting to know where the "free" file is:
The Melting of Floating Ice Raises the Ocean Level
Peter D. Noerdlinger & Kay R. Brower
1St. Mary’s University, Department of Astronomy and Physics
It lowers sea-level. An ionic radius is larger than a hydrogen bond.
Then how do you explain the experimental results in the last couple links posted? It appears you are thinking pure water, as my original answer was. That however is accounted for in the buoyancy.
Now on a technicality, I would say that if you could control which of the three forms of water the H2O is using by MO theory makes a difference also, and the angle between hydrogen atoms changes too. but it seems to be another discussion.
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