The Interaction of Large-Scale Yanai Waves with the Seychelles Plateau

Satellite observations over multiple years (1994-2010) suggest wind-driven quasi-biweekly Yanai waves are generated in the Western Equatorial Indian Ocean, and their eastward propagating energy has the potential to interact with the nearby Seychelles Plateau. We use daily output (2005-2009) from the global 0.1º Parallel Ocean Program (POP) model to examine the relationship between equatorial Yanai waves and baroclinic activity around the Seychelles Plateau. POP output reproduces, on average, the Yanai wave sea level anomalies (SLA) signal observed in satellite data and shows a velocity structure matching that of the literature. The model also reveals a strong coherence between SLA associated with equatorial Yanai waves and periodic sub-thermocline temperature anomalies around the Seychelles Plateau. The period and wavelength of these propagating temperature anomalies are characteristic of a resonant seamount-trapped wave, according to an idealized model. Energy fluxes estimated using POP output suggest that seamount-trapped waves could be a pathway by which a fraction of Yanai wave energy eventually dissipates.