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Post by buckleymanor1 on May 29, 2013 21:50:48 GMT 1
What confusion, the only confusion I see is yours or your atempts to obscure.It does not matter if it ascends or decends. 4 999.9720 -30 983.854 0 999.8395 -20 993.547 −10 998.117 -10 998.117 −20 993.547 0 999.8395 −30 983.854 4 999.9720 The figures speak for themselfs.What are you trying to say that water at 4C is not denser than water at 0C or -30C or that water at 4c is still ice. Water at 4C is liquid and denser than water at any other temperature or state.
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Post by buckleymanor1 on May 29, 2013 22:30:13 GMT 1
Because water from the ice melt would eventualy reach 4C and sink and take up less room than warmer water.
Ice is less dense than liquid water but it's displacement is never less than it's bulk content - not slightly not even a teeny weeny bit even if it's snowed upon by very light snow. A floating body displaces it's own weight of water. Full stop no more no less.Go try in your bath.
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Post by mrsonde on May 30, 2013 5:59:04 GMT 1
What confusion, the only confusion I see is yours Like what? I'm attempting to get to the bottom of whatever the hell it is you're trying to say! You believe water freezes at 4 degrees, do you? They're ascending from the frozen state. The supercooled state, indeed. That's right. Unless the water at 0C has phase shifted into ice, of course. Not if it's not already been frozen. It's still got four degrees to go before it turns into ice. Has it never occurred to you why the centigrade scale starts where it starts? No - water at 3C is still liquid and denser. Water at 2C is even denser still. Water at 1C is still denser and then, suddenly, it turns into ice. And, as I mentioned to p, there are several forms of ice that are considerably denser still - half a dozen denser forms known so far. It sometimes seems a new one is seemingly "discovered" with every year, but it's possible they've found the last, Ice Fifteen - almost the last anyway. There are of course also many varieties of structured liquid water - dodecahedral, isocahedral, and vastly more complicated supercrystalline macromolecular structures. Some of these will be much denser than ordinary water at 4 degrees. All the water in your brain cells, for example, or in every tubulin fibre in every one of your cells, and between them too. But what I want to know is why on earth you consider this in any way relevant to your claim that sea level will fall as the sea ice melts? Ice is lighter than water, seems to be the fact that's led you to this mistake. But how? What's the chain of reasoning? Oh - wait a minute, I remember. You're not going to explain yourself because "I wouldn't understand." Your thinking's too deep for us ordinary mortals.
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Post by mrsonde on May 30, 2013 6:20:44 GMT 1
Because water from the ice melt would eventualy reach 4C and sink and take up less room than warmer water. What "warmer water" is it supposedly displacing? Where does this "warmer water" go? I see. And where exactly do you think this weight of water is being displaced to? Into the holes made by our coal mines and oil wells, is that the idea? ;D The only difference when this ice melts is caused by its relative buoyancy compared to the salt water its melting into, because its fresh. The sea level will therefore rise slightly.
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Post by buckleymanor1 on May 30, 2013 9:12:54 GMT 1
They are ascending so how do account for this.
You are not helping try looking at the chart water cannot be denser at 3C 2C or 1C if it's ascending. That applies to density as well as temp. To explain further here is an extract from wiki.
Make a special note of where it says at approximately 4C it reaches its maximum density and as it is cooled further it expands and becomes LESS DENSE. So for the umpteenth time it's less dense above 4C and its also less dense below 4C. Water at 3C 2C and 1C is not denser than water at 4C. Do you understand?
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Post by fascinating on May 30, 2013 20:15:23 GMT 1
Suppose the temperature increases by 1C in the Arctic and therefore 10 cubic km of ice is melted from 0C to 1C. That 10 cubic km becomes 9 cubic km of water, because water is more dense than the ice. Thus the volume of water has increased, but the volume of ice has decreased, and the total volume of the system is 1 cubic km less. Over the 14 million sq km of the arctic ocean, I reckon that means the level will reduce by 0.07mm. That is such a miniscule amount, and it would surely soon be swamped by water from outside the Arctic. That would theoretically lead to a theoretical reduction in worldwide sea level, but over the 500 million sq km of the world's oceans that would be an amount so tiny (less than one-hundredth of a millimeter) that it is really negligible.
So I think mrsonde is right and that the melting of Arctic ice would not cause a reduction in world sea level.
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Post by buckleymanor1 on May 30, 2013 23:49:30 GMT 1
I am not going to dispute your figures but as for denser water being soon swamped.I presume that is what you are hinting at. How would that happen, water at 4C is denser and sinks. Water is also a good insulator so what mechanism would warm that water quickly.
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Post by alancalverd on May 30, 2013 23:50:11 GMT 1
Fascinating:
Some inconsistency there. First you say it would reduce, then you say it wouldn't.
Also a considerable misunderstanding about the physics of melting. There is no temperature change when ice melts at 0 deg C. You have to add 334 joules of energy to convert a gram of water from 1.1 cc of solid at 0 deg C to 1 cc of liquid at 0 deg C. If you add another 16.8 joules it will warm up to 4 deg C and shrink still further.
"Increasing the temperature of the Arctic by 1 deg C" is a pretty meaningless concept. Nothing much will change if the main ice cap is at -40 degrees or so, and clearly the absolute perimeter, being ice in contact with liquid water, cannot exist at 1 deg C. You have instead to ask what will happen if you add a certain amount of heat energy to the ice cap. Easy enough to calculate the effect thereof, but whatever the numbers turn out to be, it will result in a reduction of sea level until you have added enough energy to melt it all and raise the resulting liquid through another 4 degrees, at which point the sea level will begin to rise again.
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Post by alancalverd on May 30, 2013 23:55:36 GMT 1
Mr S:
Supercooled water is not ice. Ice is not supercooled water. We scientists use words very precisely, and don't like to have them misused by amateurs. Not understanding the significance of supercooling can kill you in real life, or get you laughed at in a science forum.
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Post by fascinating on May 31, 2013 6:57:48 GMT 1
"I am not going to dispute your figures but as for denser water being soon swamped.I presume that is what you are hinting at. How would that happen, water at 4C is denser and sinks." It would be swamped simply by gravity. Simple example: if you have a swimming pool and for some reason decide to fill it in 2 sections, putting in a temporary waterproof barrier in the middle, on filling you might see that one section has a slightly higher level of water than the other. Now take away the barrier, the water at the higher level will flow into the section at the lower level, until all of the water is at the same level. As there is no barrier between the Arctic ocean and the rest of the world's oceans, any theoretical reduction in Arctic ocean level will be swamped by water moving in from elsewhere.
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Post by alancalverd on May 31, 2013 8:30:08 GMT 1
Except that (1) sea water is denser than fresh water at any temperature
(2) in the absence of any external force, the sea water in contact with ice or fresh melt will be at the same temperature
(3) the temperature of sea water generally decreases with depth
(4) by "swamping" you presumably mean mixing. Since water is pretty much incompressible, mixing two blocks of water at the same temperature will not alter the total volume.
(5) if block A is at 0 deg C (e.g. fresh melt) and B is above, the final temperature of the mix will be below the starting temperature of B.
I think we can agree that NOAA is authoritative:
Therefore melting floating ice will reduce the volume of the world's oceans.
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Post by buckleymanor1 on May 31, 2013 10:48:28 GMT 1
So melting floating ice will lower the temperature of the oceans and the density, making them shrink. Pretty neat. Thanks for the clear explanation.
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Post by alancalverd on May 31, 2013 11:36:43 GMT 1
So melting floating ice will lower the temperature of the oceans and the density, making them shrink. Pretty neat. Thanks for the clear explanation. Small pedantic addition: ...and thus increase the density.... otherwise, I think you have grasped it.
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Post by buckleymanor1 on May 31, 2013 12:56:41 GMT 1
It's so easy to get it the wrong way round, increase = smaller size. Lower the density = bigger size. I have similar confusion with entropy.
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Post by mrsonde on Jun 4, 2013 7:18:20 GMT 1
They are ascending so how do account for this. Huh? As opposed to descending? I don't know - that's the way they chose to present their figures, I suppose. In the chart the water at 3C, 2C, and 1C are in a state of ice. If the chart had been descending, on the other hand, they wouldn't be, because water doesn't freeze until 0 degrees - it would be liquid still. Thankyou, buckley. If this is true, it's very surprising to me, and I appreciate the education. I shall check my own tables. I understand the claim, though the physics that would account for it completely elude me. I must check the assertion.
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