The altimeters use satelite data. In the last year I have very extensively calculated the flyby anomaly data. I found that my 60-page calculations essentially solved the ridlle which was not consistent with Relativity Theory of Einstein. But I solved it and results are updated to my website and also described in a few articles that there actually is no riddle. Such an anomaly doesn’t exist if one properly applies the Relativity Laws. I later realized it as a simple understanding as a ratio of Schwarzchild Radii of earth and the satelite’s separation from earth plus the exact trajectory of the satelite and the Doppler effects [since radar is on earth and satelite in Earth’s field] Then it turns out that Earth’s S-radii being 9 mm, the order ranges for a given satelite Flyby-II its observed variations of 3.92 or 2.62 mm/s at whatever positions. Perigee/remote-gravity.
If you use that idea here you can see that 3 mm/year is really not a concern if they haven’t used the Relativistic corrections to their satelite data. But if they have taken all Relativistic effects which per a year can be really a large value compared to 3 mm/year then 3 mm/year can be studied to be some other effect. This question of any possible Relativistic error must be addressed first before any thing can be claimed about growing Oceanic water levels.