Barotropic Tide

The barotropic tide is the depth-uniform tidal flow in which the whole water column moves together in phase, treating the ocean as a single homogeneous layer with the surface tide as its signature. It is the large-scale astronomical tide that propagates as a long shallow-water wave and is what tide gauges and altimeters mainly record. The barotropic tide drives the baroclinic, or internal, tide when it flows over ridges, slopes, and shelf breaks, converting surface-tide energy into internal waves on the density stratification. Global models compute the barotropic M2 and S2 fields to predict tidal currents and elevations across deep ocean basins.