Actually, that is not the real question. Indeed that question is meaningless.
Satellite based sea level measurements are made with RADAR altimeters or LASER altimeters. The satellite instruments measure distance between the satellite and the sea surface (which is far from level). The satellite is in a known orbit, at a known distance from Earth's center of mass ... difference gives "sea level". The real data processing is somewhat more complex than that, but that's the basic theory of it.
" Actually, not so meaningless. The tectonic plates are in constant motion. Most of the northern (and southern) land masses, which were covered by miles-thick ice sheets, in the last ice age, are still rising. As the continental land masses rise, the plates underneath the oceans could fall, because of the displaced magma. This post ice-age rebound is well documented. It is not the only reason that plates are “rising” or “falling”. (Convection currents in the mantle are probably more important.)
If the ocean were to get deeper (ie the plates underlying the water were to “fall”) then the surface of the ocean would also drop, relative to the centre of the earth.
I'm not saying this is what's happening here — just saying that the original question isn't meaningless.
Here's a link to an interesting graphic on the subject:
