The century old sustained rising of oceans, at a rate of 2-4 mm/y, remains a unexplained phenomenon; there is no correlation with temperature variations, so it is not due to the thermal variation of the volume of the oceans or to a decrease of Antarctic ice (which in fact is increasing).
A possibility, given that this raise of the oceans is not absolute but relative to coast, is that it is not the oceans’ absolute level that is raising but the continents that are sinking. A possible cause is global oscillations of the mantle surface level, and tectonic plates move up and down besides drifting. Another cause is the solidification of the mantle under continental plates due to the decrease of Earth internal temperature. What do you think? Are the oceans rising or the continents going down (in average)? Only satellite measurements can solve the riddle?