For sea ice, I assume you mean icebergs. I mean glaciers, which are not just floating icecubes. So yes, when glacier ice melts, it adds water to the ocean.
Well, I was thinking of floating sea ice around the North Pole. It's not icebergs, but it's completely supported by the sea, so it has maximum displacement.

Of course glaciers add to the oceans. Glaciers often melt to a degree during summer... the question then becomes a matter of averages, over time. And those averages are only as accurate as the independant numbers. Our ability to measure accurately what's actually going on is limited to the last few decades at best, which means it's unreasonable to make determinations based on century-long averages.

Our concept of "average" is not an ideal average based on small sample size.