Internal tides on the Al-Batinah shelf: evolution, structure and predictability

Abstract. Internal tides are a key mechanism of energy transfer on continental shelves. We present observations of internal tides on the northern Oman shelf based on moored temperature and velocity records collected during 2021–2022. The regional shelf exhibits strong shallow summer stratification (Npeak2∼10-2s-2), supporting shoreward-propagating internal tides with pronounced fortnightly modulation in amplitude and energy fluxes. Despite semidiurnal dominance in barotropic forcing, the internal tides appear predominantly in the diurnal band. During summer, the incoming internal tide energy flux at our mooring on the central shelf (23 m depth, 10 km from shore), ranges around FEin∼5–15 W m−1 and we estimate that the onset of main internal-tide dissipation occurs further inshore over the shallow inner shelf. As the thermocline deepens in fall, the onset of the saturation zone migrates seaward from its summer location to reach our central-shelf mooring by early October. There, waveform structures undergo seasonal transition from quasi-linear depression waves in summer to increasingly nonlinear features in fall, including steepening, asymmetry, polarity reversal and a shift toward first-mode dominance . In October FEin increases to ∼ 30 W m−1 primarily driven by the increasing nonlinearity as the internal tides reach their finite-depth shoaling regime over the central shelf. Cross-shelf coherence and phase-speed estimates also confirm that the observed internal tides maintain spatial coherence from the shelf edge inshore beyond the typical internal surf zone. Skill scores indicate that the predictability of the local internal tides decreases by 50 % after around 18 d, which is comparable to high-predictability sites globally. Inshore-directed energy flux, diurnal dominance and multi day phase lags to barotropic forcing still indicate remote generation. For the local barotropic tidal currents, variability in bulk KE and predictability-scores suggest seasonal modulation by the internal tides.