The flaw in your argument is accounting for the ice above the sea level - in the south, that's most of the ice. If it melted (it's not), it would raise the sea levels. And, the percentage of the ice above sea level in the north is above water, too - so melting it would raise the sea levels. (it's not).

On paper, if all of the sea ice melted, we would see the sea levels rise. But they're not, other than the cyclic thaw and refreeze that happens every year. And, going by the sun, the earth is entering a cooling phase.