EGU25-15550, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-15550
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Internal Tides on the Al-Batinah Shelf: Predictability and Generation
Gerd Bruss1, Estel Font2, Bastien Queste2, and Rob Hall3
Gerd Bruss et al.
  • 1Sultan Qaboos University , Muscat, Oman, gerd@squ.edu.om
  • 2University of Gothenburg, Gothenburg, Sweden
  • 3University of East Anglia, Norwich, United Kingdom

Internal tides, generated by the interaction of barotropic tides with topography, are key drivers of shelf dynamics, influencing cross-shelf transport, stratification, and mixing processes critical to coastal ecosystems and regional circulation. Using data from moorings and underwater gliders, we observed frequent large-amplitude internal tides over the Al-Batinah shelf and slope. These tides predominantly occur within the diurnal band, although semidiurnal patterns can become prominent, particularly when spring tides coincide with a low-energy phase of the diurnal amplitude modulation. In contrast, local barotropic tides are dominated by M2, with a less energetic diurnal component evident in both currents and sea level. This raises questions about the origin and predictability of the observed internal tides.
To assess predictability, we applied a skill score that compares harmonic predictions to observed signals over varying window lengths. For on-shelf baroclinic currents in summer, the skill score begins at 96% for short windows of a few days, declining to about 75% for a three-week period, after which further decreases are more gradual. This places internal tides on the Al-Batinah shelf at the high end of predictability compared to other regions.
Potential energy conversion was estimated using barotropic body forcing based on TPXO and WOA datasets, while reflection and transmission coefficients (α) were derived as the ratio of topographic to internal wave slopes. The body force map reveals enhanced energy conversion in the K1 band approximately 170 km across the Sea of Oman, where α > 1 indicates internal tide reflection toward the southeast. This aligns with the incoming direction of the internal tide energy flux observed on the Al-Batinah shelf, potentially explaining their dominance in the diurnal band. A comparison of a two-year temperature record from the local shelf edge with barotropic transport at the remote generation site shows high wavelet coherence in the K1 band. Fortnightly patterns are delayed by approximately two days, consistent with phase speeds associated with second- and third-order vertical modes.
In summary, internal tides on the Al-Batinah shelf are remarkably predictable. The dominance of the diurnal band could be explained by remote generation, while semidiurnal components likely reflect contributions from local generation processes. Understanding and predicting internal tides on the Al-Batinah shelf has implications for understanding how tidal energetic processes act to enhance diapycnal fluxes, which ventilate the regional oxygen minimum zone and drive coastal productivity.

How to cite: Bruss, G., Font, E., Queste, B., and Hall, R.: Internal Tides on the Al-Batinah Shelf: Predictability and Generation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15550, https://doi.org/10.5194/egusphere-egu25-15550, 2025.