Is the top of an iceberg floating above the waterlevel equal to the expanding of the whole iceberg? When water freezes it expands and is getting less dense. But is this expansion of the total iceberg equal to the top of an iceberg floating just above sealevel?

 A: Yes. An equivalent way of saying this is that if an ice cube (or iceberg...) melts, the water level remains unchanged. (I.e.: the melted iceberg exactly fits in the 'hole' it creates underwater.)
To see this, think of what is holding the ice up: it's buoyancy, which is the upward force due to the pressure of the surrounding water. This force is directly proportional to the volume that the object occupies below water level. (This is conceptually simple: imagine replacing the object by water [till the surface level], then of course the water is stable, meaning the weight of the water equals the buoyancy force, and of course the weight of the water is directly proportional to the volume.) Now the weight of the ice = weight of the water that it would melt into, which means that the melting process will keep the volume under the surface level unchanged. This means we're done: the volume of the iceberg under water corresponds to the volume of the melted iceberg.
A: Imagine a portion of the(liquid) water. It will be in equilibrium with the whole fluid. The buoyancy force $E_1$ over this portion matches its weight. Now freezes this same portion. The buoyancy force $E_2$ on the ice equals its weight. Since the weights are the same, the buoyancy forces are equal. This implies the volume of fluid dislocated in both situations is the same. Therefore, the volume of the ice above the liquid level is exactly the increased volume the portion gained when it froze.
