Kumar, N., S. H. Suanda, J. A. Colosi, K. Haas, E. Di Lorenzo, A. J. Miller and C. A. Edwards, 2019:

Semidiurnal internal tide generation and propagation in the Santa Maria Basin, California: Observations and model simulations.


Journal of Geophysical Research-Oceans, sub judice

Abstract. A series of five realistic, nested, hydrostatic numerical ocean model simulations are used to study semidiurnal internal tide generation and propagation from the continental slope, through the shelf break and to the mid- and inner-shelf adjacent to Point Sal, CA. The statistics of modeled temperature and horizontal velocity fluctuations compare favorably to mid-shelf mooring observations (30-50 m water depth). Time- and frequency-domain methods are used to decompose semidiurnal internal tides into components that are coherent and incoherent with the barotropic tide, and roughly 50/50 partition is found at the mid-shelf locations in both the realistic model and observations. In contrast, the coastal internal tide remains 70-80% coherent in a simulation with neither atmospheric forcing or mesoscale currents and idealized stratification. Both the realistic and idealized simulation identify negligible conversion from barotropic to baroclinic energy at the local shelf break. Instead, the dominant internal tide energy sources are regions of small-scale near-critical to supercritical bathymetry located on the Santa Lucia escarpment (1000-3000 m water depth), 70-80 km from continental shelf observation locations. Near the generation region, semidiurnal baroclinic energy is strongly coherent, and rapidly decays adjacent to the shelf-break. In the realistically-forced model incoherent energy is relatively constant throughout the domain, with no clear bathymetric connection or generation region. Backward ray tracing from the mid-shelf to the Santa Lucia escarpment identifies multiple energy pathways potentially leading to spatial interference. As internal tides shoal on the predominantly subcritical slope/shelf system, temporally-variable stratification and Doppler shifting from mesoscale and submesoscale features appear equally important in leading to the loss of coherence.

Preprint (pdf)