They do take that into account. They calculate that the ocean floor is sinking but then ADD that displacement to their reported measurement of "sea level", which is backwards. When the ocean floor sinks sea level goes down, but they report it as going up instead, using this justification:
currently some land surfaces are rising and some ocean bottoms are falling relative to the center of the Earth (the center of the reference frame of the satellite altimeter).
since the ocean basins are getting larger due to GIA, this will reduce by a very small amount the relative sea level rise that is seen along the coasts.
We apply a correction for GIA because we want our sea level time series to reflect purely oceanographic phenomena. In essence, we would like our GMSL time series to be a proxy for ocean water volume changes. This is what is needed for comparisons to global climate models, for example
This is nonsense, of course. Volume isn't measured in millimeters, that's a measurement of distance. GMSL when talking about satellites is defined as the average distance of the surface of the ocean from the center of the Earth, and the reason people care about it is because if it gets too high then things we care about end up flooded. Changing the definition of GMSL half way through from sea level to sea depth is the kind of slippyness that pervades this space.
https://sealevel.colorado.edu/index.php/presentation/what-gl...
currently some land surfaces are rising and some ocean bottoms are falling relative to the center of the Earth (the center of the reference frame of the satellite altimeter).
since the ocean basins are getting larger due to GIA, this will reduce by a very small amount the relative sea level rise that is seen along the coasts.
We apply a correction for GIA because we want our sea level time series to reflect purely oceanographic phenomena. In essence, we would like our GMSL time series to be a proxy for ocean water volume changes. This is what is needed for comparisons to global climate models, for example
This is nonsense, of course. Volume isn't measured in millimeters, that's a measurement of distance. GMSL when talking about satellites is defined as the average distance of the surface of the ocean from the center of the Earth, and the reason people care about it is because if it gets too high then things we care about end up flooded. Changing the definition of GMSL half way through from sea level to sea depth is the kind of slippyness that pervades this space.