SLO-dynamics-3

Small coastal embayments are ubiquitous features of coastal upwelling systems and play a disproportionately large role in local ecosystem dynamics. In these upwelling bays, persistent nearshore thermal fronts form downstream of coastal topographic features. Due to their small scales, these fronts are dominated by submesoscale dynamics and likely facilitate strong cross-shelf exchange. While these coastal fronts are frequently observed, there have been no targeted observational studies or systematic modeling studies that resolve submesoscale dynamics and turbulence processes that govern exchange across these fronts. Moreover, observational studies of submesoscale features have generally lagged behind numerical modeling efforts due to their small size and transient nature. Small upwelling bays offer a rare opportunity to study the dynamics of submesoscale fronts in the shallow coastal ocean because their formation is often predictably linked to coastal topographic features. This project is targeted in San Luis Obispo Bay in central California, a small embayment whose length scale is on the order of the local Rossby deformation radius, where previous research from our team has revealed the presence of a persistent and narrow front characterized by sharp temperature gradients, convergence downstream of the upwelling jet, and a strong impact on local hypoxia and harmful algal bloom development. This study integrates field observations and numerical modeling experiments to explore the links between submesoscale fronts, turbulent mixing, and bay-ocean exchange. Repeated observations of the persistent front across various dynamical regimes will allow for a broader understanding of the parameters that drive the evolution of the submesoscale front, overcoming traditional observational barriers of these ephemeral features.