Investigating the Influence of Tides in the Sulu Archipelago

Satellite observations and modeling the Sulu Archipelago suggest that tides cause the persistent increased chlorophyll concentration and cooler waters in the region throughout the year. The velocity shear created by these tides facilitates the mixing of waters, bringing the nutrient-rich, cold bottom layers to the upper layers. However, there remains no in-depth study for this phenomenon using observational data particularly from tidal gauges. This study aims to investigate the influence of tides in the Sulu Archipelago utilizing satellite observations of sea surface temperature (SST) and chlorophyll-a (chl-a), tidal models, and the tidal datasets of Bongao and Jolo stations. It seeks to explain the ocean dynamics in the region through tide-topography interactions linked to patterns in the geochemical and physical parameters that directly correlate to productivity zones. Further, it aims to quantify the estimated energy generated by tides to cause the vertical mixing, and how much energy is transferred from barotropic to baroclinic tides. Preliminary results of the power spectral density analysis confirmed the strong presence of tides. Bongao station was predominated by M2 and S2 indicating the presence of a semidiurnal tidal cycle and a less unobstructed flow. Meanwhile, O1 and K1 tides peaked in Jolo station with the presence of shallow water overtides (M3-M6) and an ENSO (3-year) signal indicating a diurnal tidal cycle affected by shore topography and bathymetry as well as large-scale climate oscillations, respectively.