Self Tide

The self-tide, or self-attraction and loading (SAL) effect, is the correction to ocean tides from the redistributed tidal water mass attracting itself, loading and deforming the elastic seafloor, and changing Earth’s gravitational potential through that deformation. A coarse rule puts SAL near 5 percent of the local tide amplitude and roughly 180 degrees out of phase with it, but accurate models show it can shift amplitude by up to 20 percent and alter phase. Modern barotropic tide models compute SAL by expanding the tidal mass into spherical harmonics scaled by load Love numbers. Omitting it degrades the modeled M2 and S2 fields used for prediction and satellite-altimeter de-aliasing.