Note the "fudge factor" in the experiment:
"Figure 1: A freshwater ice cube floats in a beaker of concentrated saltwater. Note that the ice cube floats much higher in the saltwater than it would in a glass of freshwater because saltwater has a greater density."
The saltwater in that beaker is, apparently, a saturated solution of salt. (Note how absurdly high the ice floats.)
Sea water is far less concentrated with salt than that demo sample, (and, thus, much less dense). The density difference between freshwater ice and sea water is tiny -- almost negligible... (Remember: the vast bulk of an icberg is, notoriously, below the surface -- hence the term, "the tip of the iceberg"...)
That demo is the sort of quacktrickery that is typical of the "Climate Change Religionists".