da iawn

ok, so I may be missing something, but unfortunately I don't know what. I posted a while back asking for help on the very old question of why melting arctic ice doesn't raise sea levels. I understand that a given mass of ice displaces its equivelant mass of water, and so when it melts it just 'occuppies the space it made' so no overall change in water volume (and consequently level). This is demonstrated with ice melting in a glass and observing the water level. BUT When I sit down and produce calculations , I have the added complication that in the Arctic mature sea ice is fresh water, and the liquid it is displacing is higher density salt water. A 1000kg block of fresh water ice melts to produce a cubic metre of fresh water, but when floating in salt water this block will not displace a cubic metre. The 1000kg of higher density salt water displaced will have a slightly smaller volume. When the ice melts, there should be a cubic metre of melt water trying to fit into the slightly smaller space it displaced due to the differences in density. I could be wrong (very likely - if so its probably due to one of my assumptions), if I'm right is it not mentioned because the effect is so small as to be of no consequence? This is not my field, but I am a teacher and feel I have a duty to understand thiis fully. Sorry for the length of the post, but I simply cannot find an answer to this, hope someone can help.

I'm new to this forum so please excuse an oft repeated question i understand that when a given mass of ice floats in water it diplaces a similar mass of that water. on melting it will effectively 'occupy' this volume, resulting in no overall change in volume of the water and so no increase in water level Basic physics I know, and easily demonstrated Here's the rub When I consider that mature sea ice is mainly fresh water, and the salinity of sea water means it has a higher density, a smaller volume of sea water will be displaced than in the the freshwater eaxmple. when the fresh water sea ice melts, it will produce a larger volume of lower density fresh water than the equivelent displaced mass of higher density sea water. I've done the maths over and over, and checked my facts as much as possible, but every answer i get tells me i'm wrong. I would be really greatfull for an explanation of where I've gone wrong, as its driving me a bit nuts i noticed a couple of references the idea but no definitive answers