INTeRnal waves In angular momeNtum StratifICation (INTRINSIC)

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This project will use a simplified model and a numerical model to examine how a 'rapid' change in water density that has a curved shape, a 'curved front', modifies the propagation and fate of internal gravity waves (IGW) within the ocean surface boundary layer. The investigators will determine if IGW energy increases or decreases within fine-scale fronts that are curved. They will test a new hypothesis that parametric subharmonic instability, initially proposed by Thomas and Taylor (2014) for geostrophic flow, is elevated within curved anticyclonic fronts. The research uses a hierarchy of fine-scale simulations, whereby analytical and idealized numerical models (least complex) are used to inform and facilitate analysis of realistic simulations (most complex).Present understanding of IGW propagation within fronts assumes a geostrophic balance. Although accurate for mesoscale fronts (horizontal scales of 50-200 km), fluid parcels within submesoscale fronts (horizontal scales of 0.1-10 km) often experience pronounced centripetal accelerations owing to frontal curvature. The combined principles of density, vorticity, and absolute angular momentum conservation have a profound influence on fluid parcel motion and modify the IGW dispersion relation. The proposed study advances the scientific community’s understanding of IGWs by examining the combined effects of these conservation laws in the context of semi-analytical, idealized and realistic fine-scale, numerical simulations heavily informed by observations. The expected outcomes of this research include improved understanding of the role of curved fronts on IGW dynamics and delineation of the limits of an analytical model.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.