I tested it too with a saturated mix. I had a considerable increase in level, which I did expect. Only problem, being saturated at 1.1972 gm/mL, I wondered what thermal expansion is for saltwater that concentrated. I couldn't find the data in a short time, not sure where to look. Consider that as soon as you put that much ice in a small volume of water, the water cools considerable. When you melt it and its at room temperature, how much is due to thermal expansion? I doubt it was significant, but I cannot say that with any certainty.
Maybe you had some water evaporate? I covered my glass.
Sea water is so much less saturated. From the data I could find, that are changing the brine mix from 1.1972 gm/mL to about 19.5 gm/mL. (I'm assuming 3 part brine 1 parts ice.) This alone changes the brine mix to a density of 1.1378, which is an increase of 5.22% in volume.
The same chemistry handbook I referenced has a different percentage when using lower salinity with the same ration. If I use 4 to 3 gm/mL, instead of 26 to 19.5 gm/mL, I get a change from 1.0268 to 1.0196 gm/mL, which is only a 0.7% increase in volume.
I mentioned somewhere about the this, I told one person to do the math. I also gave the ocean dilution example.
Thing is, the percentage of displacement change is so much less at the salinity of the ocean than it is in a saturated mix.
As I said, this experiment is flawed for the conclusion claimed. It only shows that there is an effect. But when you take it to the scale of the ocean, you have an insignificant change in salinity, with an insignificant change in density.
