I've heard so many times the argument of a melting iceberg floating in fresh water that will not change the volume of water when melting. But this is of course not valid for an iceberg floating in salted water!
It is a so simple experiment to do, why are people still not convinced?
Perhaps people think that temperature also rises and thus there is more water evaporation
There's a quick blog post about this topic from a couple of years ago: http://moregrumbinescience.blogspot.com/2009/04/ice-and-sea-level.html That post links to a paper by Peter D. Noerdlinger and Kay R. Brower (The Geophysical Journal International, 170, pp. 145-150, 2007: The melting of floating ice raises the ocean level DOI: 10.1111/j.1365-246X.2007.03472.x). I think than answer to your question is just that "most people" don't know that salt water and fresh water have such different densities, so just rely on Archimedes' principle to argue that there is not sea-level change from melting ice.
Well, it is clear that the density of salt water and fresh water is different, and that can affect the volume of ice floating on the water surface, but once the ice is defrozen, the sea level should anyway be increased.
It does indeed seem that the appropriate section of the 2007 IPCC report on the The Physical Science Basis doesn't mention this (http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-5-6.html).
However, the difference is a small percentage of the rise from other, dominant, sources (thermal expansion, land-ice melt). It does look like it should be taken into account though and perhaps it will be in the next report.
The Noerdinger and Brower, 2007 paper estimates that 4 cm of rise would result from the melting of all floating ice. Projected thermal expansion in the 21st century is something like 20 cm and the rise from other sources is similar. So, it looks like it should be noted in the accounting somewhere but it also is one of the weaker contributions to global sea-level.
The previously mentioned paper also notes that the rates of rise that correspond to this contribution from melting, floating ice will be very small.
Presumably this 4 cm of rise will only occur if all floating sea-ice melts completely forever. I don't think that this is likely in any projection of the near future since new ice will still form in winter. This annual growth will actually reduce global sea-levels. Again, the amount will be very small, perhaps undetectable among the other factors.
On the point about additional evaporation I think this will have no net contribution (unless storage of water on land is changed as well). The mean lifetime for a particular water vapour molecule in the atmosphere is quite short (days to weeks) and the additionally evaporated molecules will end up back in the ocean before very long resulting in a net sea-level change of zero.
OK, no answer, just thanks indeed. I will read the references mentioned by Ed
Ok, floating ice may be negligeable compared to continental ice and thermal expansion. But I think we should take everything in account, especially when it's an argument used to discredit scientists claiming increased sea levels.
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