ENERGETICS OF GLOBAL OCEAN TIDES FROM GEOSAT ALTIMETRY

The authors' global ocean tide maps derived from Geosat altimetry are here improved in quality and coverage; they compare favorably with ground truth data at about the same rms level as Schwiderski's models, slightly better in lunar than in solar tides. Diurnal admittances clearly show Kelvin wave structure in the southern ocean and confirm Platzman's resonant mode at 28.5 +/- 0.1 hours with an apparent Q of about 4. Driving energy enters dominantly in the North Pacific for the daily tides and is strongly peaked in the tropical oceans for the half-daily tides. Global rates of working on all major tide constituents except S2 agree well with independent results from analyses of gravity through satellite tracking. Comparison at S2 is improved by allowing for the air tide in gravitational results but suggests deficiencies in all solar tide models. Estimates of Q factors based on potential energy (approximately 8 for daily tides and 13 for half-daily tides) agree reasonably well with hydrodynamic models.