Tide of the Time: Global tidal characteristics observed from in-situ measurements

Abstract. Tide gauges have been critical sources for sea level research, enabling the development of tidal theory and an understanding of local variations that occur across the global oceans. Tides play important roles in a variety of oceanographic and geodetic applications, and characterising their spatial variability is valuable for applications ranging from fishing to flood risk management. This manuscript presents the coastal characteristics of ocean tides based on 3,591 high-frequency tide gauge observations from the recently updated GESLA-4 database. These characteristics range from tidal datums such as Mean High Water (MHW) and the Great Diurnal Range to metrics like the Age of the Tide, Form Factors, Dodginess, updated amplitude trend estimates, and new insights into the regional duration of high tides. Our analysis finds that 125 out of 237 long-time series show statistically significant trends in one or more constituents, from -1.47 mm/yr to +1.80 mm/yr, while the duration of the high-water stand during spring tides is shown to vary from 1 to 14 hours, for an inundation depth of 20 cm. It is anticipated that the results presented will be useful not only to tidal experts but also to a wide range of cross-disciplinary researchers and local communities, aiding their understanding of a vital component of the global Earth system.