Tidal and diurnal wind-driven current variability around Gran Canaria

Abstract

Gran Canaria is an island with a steep and narrow platform in the eastern Atlantic Ocean. Current meter records from 1986 to 1998 were analysed using both harmonic least squares and response methods. Our results confirm that semidiurnal currents are primarily governed by the astronomical tide and exhibit strong spatial variability. The largest tidal currents were observed on the southeastern and western shelf regions, where the velocities oscillate in-phase with the sea level with amplitudes exceeding 40 cm s⁻¹, while the northern and southwestern sectors showed significantly weaker tidal flows oscillating near 90º out-of-phase with respect the sea level. Diurnal wind forcing, particularly from sea breezes, also contributes to current variability, but its influence is spatially heterogeneous. Breeze-induced driven variability appears significant only in sectors where the insular shelf is broad. However, a substantial portion of the variance in the diurnal band is not coherent with either tidal or wind forcing. This suggests the presence of near-inertial oscillations originating in the open ocean. Furthermore, the response method proved to be an effective tool for analysing tidal currents, allowing for the use of short-duration records. It offers a robust alternative to traditional harmonic methods and expands the possibilities for characterizing tides in regions with limited data. The findings also underscore the potential of tidal currents as a source of renewable marine energy, owing to their high predictability and stability, which makes them particularly suitable for small, isolated systems such as oceanic islands.