Secular Trends in Global Tides Derived From Satellite Radar Altimetry

Previous studies have demonstrated that tides are subject to considerable changes on secular time scales. However, these rely sea level observations from tide gauges predominantly located in coastal and shelf regions therefore, the large-scale patterns remain uncertain. Now, for first time, satellite radar altimetry (TOPEX/Poseidon & Jason series) has been used study worldwide linear trends tidal harmonic constants of four major (M2, S2, O1, K1). This demonstrates both potential challenges using data quantification such long-term changes. Two alternative methods were implemented. In method, estimated consecutive 4-year periods, which change was then estimated. second estimation integrated analysis. First, assessed by application gauge sub-sampled sampling scheme satellites. Thereafter applied real data. Results show statistically significant decreases increases amplitude up 1 mm/year phase ∼0.1 deg/year. The agreement between altimeter-derived estimates differs per region tide.