If salt melts ice on my sidewalk, why does the salt in the ocean not melt iceburgs?

Answer 1

When rock salt dissolves on the sidewalk, it produces an exothermic reaction that melts the snow.

Salt is already in the dissolved form in the ocean, so there is no exothermic reaction. Also, the salt in the ocean lowers the freezing point, which causes water temperatures to become supercooled in polar regions during winter, so salt in polar waters sometimes keep the ice from melting.

Answer 2

Because icebergs are actually chunks of frozen freshwater that float on the saltwater. Freshwater actually has a higher freezing point than salt water....

So while the temperature isn't enough to freeze the ocean, it is cool enough to keep the freshwater icebergs frozen.