|Mass, volume, and density|
And, let's refine it down to the nitty gritty: "The crucial point to be noted is that the steric component does not account for volume changes but does for volume changes per mass unit (i.e., density changes). This indicates that the steric component only represents actual volume changes when the mass of the considered water body remains constant. This is for instance the case of thermal expansions/contractions due to surface heat fluxes" (ibid).
Immediately, then, we must consider what changes "the mass of the considered water body," and how significant that change is.
In yesterday's post I wrote "Think of mass as how many molecules of seawater there are in a layer or zone, and think of volume as how far apart from one another those molecules are at a given temperature and salinity" (On Thermal Expansion & Thermal Contraction - 18).
What primarily changes ocean mass is melt water and ice bergs flowing into it from Greenland, Antarctica, and land glaciers around the globe.
Evaporation of seawater changes the ocean's mass, as does rain falling back onto the ocean surface.
By the way, that change of mass also changes the volume, but it is not steric volume change.
So, assume that after the ocean mass has been changed then becomes stable and constant for a time, only the volume can be changed by thermal factors ("the steric component only represents actual volume changes when the mass of the considered water body remains constant").
Thus, this is "... the case of thermal expansions/contractions due to ... heat fluxes."
In other words, sunlight impacting the surface of the ocean or heat radiating from the ocean does not change its mass (the number of ocean water molecules), even though any resulting change in temperature / salinity can change the ocean's volume.
The formula for that volume change (V1 = V0(1 + β ΔT) was also discussed in yesterday's post.
As a final thought, note that Jorda & Gomis, 2013 (link up-thread) did not mention gravity (The Gravity of Sea Level Change, 2, 3, 4) or ghost-water (The Ghost-Water Constant, 2, 3, 4, 5, 6, 7, 8).
Those two dynamics can change the mass and sea level on a regional basis because relocation of ocean water takes place.