Mapping low‐mode internal tides near Hawaii using TOPEX/POSEIDON altimeter data

Objective maps of M2 internal‐tide variability are derived from TOPEX/POSEIDON altimeter data obtained near the Hawaiian Ridge. An estimate of the wavenumber spectrum shows that the radiation is dominated by a few spectral peaks at wavenumbers consistent with the theoretically expected value for mode‐1 internal tides. The data are not always consistent with the traveling wave model. Because the spacing of the altimeter tracks is larger than the internal‐tide wavelength, the objective map underestimates the energy between the altimeter tracks. With this caveat, the maps are used to determine that 2.6 GW of power is radiated from a 1700 km section of the Hawaiian Ridge. Time series of hydrographic data obtained at the HOT site north of Oahu, Hawaii show that changes in mode‐1 phase speed, caused by variations in stratification, have only a small effect on the propagation of the mode‐1 internal tides.