Open-ocean validation of TOPEX/POSEIDON sea level in the western equatorial Pacific

During the verification phase of the TOPEX/POSEIDON radar altimeter mission an open-ocean validation experiment was conducted. Two Tropical Ocean and Global Atmosphere (TOGA) Tropical Atmosphere Ocean moorings were outfitted with additional temperature, salinity, and pressure sensors to measure the dynamic height from the surface to the bottom at 5-min intervals directly beneath two TOPEX/POSEIDON crossovers. Bottom pressure gauges and inverted echo sounders were deployed as well. Energetic steric sea level availability was found to exist on short timescales of order hours to a few days, most notably, the quasi-permanence of strong semidiurnal internal tides. A possible nonlinear rectification of the internal tide was observed occasionally to change the dynamic height by as much as 30 cm. On the timescale longer than the 10-day repeat of the TOPEX/POSEIDON satellite, the low-frequency fluctuations of dynamic height were related to interannual variations corresponding to the 1991-1993 El Nino-Southern Oscillation, to the seasonal cycle, and to intraseasonal variations. -from Authors