Just like Archimedes discovered millennia ago, it is well known today that the Arctic ice cap displaces it’s own weight in the water so that when it melts it will not cause a rise in global sea level.
Surprisingly, the National Science Foundation has just figured this out (thanks to someone complaining about it) and has issued a correction to their sea ice page.
The error was first pointed out by commenter Steven Skinner on WUWT on March 25th 2010, who wrote:
The NSF, the U.S. Office of Naval Research, and the Japanese government cooperated in funding a research project called SHEBA (Surface Heat Budget of the Arctic) back in 1997. Considering the big names in funding I was surprised they allowed the conclusion in the last sentence past scientific proof reading before publication. The bit from ‘melting sea ice…’
It’s fixed now, see the BEFORE and AFTER.
WUWT reader Dave Burton, who called NSF on the error and asked for a correction writes in an email to them:
Since the error was on your site for over 6.5 years, misleading readers into believing that melting sea ice contributes to coastal sea level rise, I think it is important that you identify the error on your site, with a footnote which explains what was wrong with it.
I always wondered why I’d get the occasional angry email claiming melting Arctic sea ice would raise sea levels dramatically and “why don’t you get it?” …to which I’d reply “look up the principle of buoyancy”. Now I know.
Further suggested reading: 10 Scientific Laws and Theories You Really Should Know
OK,OK it’s sentence and not sentance
Stephen Skinner I agree that the effect of melting sea ice in the arctic would be virtually zero and that statement certainly is wrong.
I have redone the experiment with pure ice in actual seawater from the bay outside my house, and the increase in level is so small that it’s hard to measure, which appears to be what daveburton discovered.
I have again redone the experiment with pure ice in water with much more salt dissolved in it, and there is a definite rise in level when the ice melts.
It is difficult to get ice without bubbles of air in it, and the melting ice blocks keep getting in the way of the meniscus of the water level being measured. I think a physicist should do the experiment with proper laboratory equipment, and explain the physics of the rise,
e.g. stating the volumes of the water and ice at all stages of the melt.
I suggest starting with 1000 ml of pure water and add 1000 g of pure ice. The level should stay at 2000 ml throughout the melting.
Then start with 1000 ml of concentrated brine and add 1000 g of pure ice, and the level should change from say an initial 1950 ml and end up at 2000 ml when the ice has melted. The ice of course floats higher in the brine than in the water.
I will say yet again that I am ONLY discussing whether or not there is a rise in level during this experiment. I maintain that any competent physicist would say there *is* a rise. Therefore the statements at the top of this article are not strictly correct. Is WUWT going to bother getting science right or are we not going to worry about that? If our science is wrong, that will allow the warmists to attack us as being unscientific.
There is no doubt that the level of salt water rises when floating pure ice melts. So the statement “melting sea ice also raises worldwide sea levels” is strictly correct if some sea ice has lower salinity than seawater, although everybody seems to be in agreement that the rise is trivial. A scientist would say that a “trivial rise” is not the same as “no rise”.
The statement ” with POTENTIALLY SIGNIFICANT effects for coastal cities and towns” is of course completely wrong and needed to be changed. I don’t think anybody has disputed that.
Richard, if freshwater ice (floating on the ocean) melts, it will have no effect at all on sea level beyond where its meltwater disperses/mixes and affects salinity. What you get, instead, is a local region of reduced salinity (lower density) surface water, floating on the larger ocean, and a (slightly) locally elevated sea level over that region. But it will have no effect on sea level elsewhere, for a very long time.
Eventually, the salinity reduction will affect the whole ocean, including even the ocean depths (slightly), and therefore have an (immeasurably tiny) effect on coastal sea levels. But that will take hundreds of years.
In the lab, in your 1 liter beaker or graduated cylinder, conditions are different. Your melted ice will not remain in one area of the surface, so the “locally elevated” area will cover the whole container, immediately.
Seawater is about 35 g/L salt. Saturated saltwater is about 10x that.
I wonder if I can make a table in HTML, in wordpress?
Density
freshwater ice0.92
freshwater at 4C1.00
seawater (35g/L salt) at 4C1.028
saturated salt water at 4C1.35
Floating ice displaces the volume of water which weighs what the ice weighs. So if ice floats on freshwater, only 0.92/1.00 = 92% of it is below the waterline, leaving 8% above. Similarly, if ice floats on seawater, 0.92/1.028 = 89.5% of it is below the waterline, leaving 10.5% above. In a saturated salt solution, 0.92 / 1.25 = 68% of it is below the waterline, leaving 32% above.
(Note: The volume of saltwater is only slightly affected by the salt in it; I think that about 60% of the salt’s volume effectively “disappears” into the water when it dissolves.)
After the ice melts and mixes with the rest of the water in the container, the salinity of the whole container is reduced, reducing its density. The floating ice displaced the same mass of original (denser) saltwater, with the excess protruding above the waterline. So the volume of the original saltwater, plus the volume of displaced saltwater due to the floating ice, produces a measured liquid volume X (not counting the ice that rises above that surface) equal to the combined mass of all the saltwater and ice divided by the density of the saltwater. After the ice melts, the salinity of the mixture is reduced, so the density is reduced, but the mass remains the same. Consequently the volume and water level will be higher.
I’m trying to get the NSF to put a footnote on their page on sea ice, to go along with their mea culpa. I don’t know whether I’ll convince them to do so, but I’ve sent them a link to the following page with suggested wording for such a footnote. Does the wording seem right to everyone here? Do you folks have any changes to recommend?
http://www.burtonsys.com/climate/sea_ice/nsf_footnote.html
Dave
Well, the table didn’t work. Let me try a different way:
Density freshwater ice 0.92 freshwater at 4C 1.00 seawater (35g/L salt) at 4C 1.028 saturated salt water at 4C 1.35jaymam says: October 13, 2011 at 7:33 pm “I think a physicist should do the experiment with proper laboratory equipment, and explain the physics of the rise,”
jayman a physicist / scientist / mathematician / engineer, Archimedes, explained the physics over 23 centuries ago. http://en.wikipedia.org/wiki/Archimedes'_principle
I have already stated that the % age volume increase is directly proportional to the density of the salt solution. This follows directly from Archimedes principle and can be calculated fairly simply.
The volume of the melted ice = The volume of the solution displaced before melting x the density of the solution / the density of water (1)
Therefore The percentage volume increase = the density of the solution / the density of water x 100 (2)
The values are approximate because the density of water and the solution will vary slightly with the temperature.
“I suggest starting with 1000 ml of pure water and add 1000 g of pure ice. The level should stay at 2000 ml throughout the melting.” Why? Pure water ice floating on pure water will not make ANY difference in the water levels when it melts as can be seen from equation (2) above . The only difference will be if the solution has a different density to pure water.
Thus to see a big rise
1. have a denser salt solution that is add more salt – saturated salt solution has a relative density of ~ 1.2 which will mean around a 20% increase
2. Have more ice – in absolute terms 20% of a larger quantity will be larger than 20% of a smaller quantity.
I agree that a “trivial rise” is not the same as “no rise” and thus the statement “melting sea ice also raises worldwide sea levels” is strictly correct.
And the statement ” with POTENTIALLY SIGNIFICANT effects for coastal cities and towns” is completely wrong.
And Daveburton for the above reasons your statement “if freshwater ice (floating on the ocean) melts, it will have NO EFFECT AT ALL on sea level beyond where its meltwater disperses/mixes and affects salinity.” is wrong.
It will have an effect, though trivial effect.
And the The percentage volume increase = (the density of the solution – the density of water) / the density of water x 100 (2)