Ocean self‐attraction and loading in numerical tidal models

The formalism for handling ocean tidal self‐attraction and loading in numerical tide models is reviewed. These forcing terms require global integrations of the tidal elevations, turning the dynamical differential equations into integro‐differential equations. Following Accad and Pekeris, many authors approximate the self‐attraction/loading terms by a simple scalar multiplier of the local tidal elevation, but the choice of multiplier is not obvious and is often confused. The one recommended by Accad and Pekeris generates large errors in the open ocean. Other scaling factors are examined here; none is recommended in general, and most serious applications should use the full integral formulation. New estimates of the self‐attraction/loading fields, based on global tidal measurements from recent satellite altimeters, are now readily available.