Submesoscale Fronts and Their Dynamical Processes Associated with Symmetric Instability in the Northwest Pacific Subtropical Ocean

• DOI: 10.1175/jpo-d-20-0076.1
• Publication Date: 2020-11-12T18:22:37Z
• Authors: Zhiyou Jing; Baylor Fox-Kemper; Haijin Cao; Ruixi Zheng; Yan Du
• Keywords: Frontogenesis; Subtropical front; Geostrophic current; Boundary current; Mixed layer; Anticyclone

Abstract Submesoscale density fronts and the associated processes of frontogenesis symmetric instability (SI) are investigated in northwest Pacific subtropical countercurrent (STCC) system by a high-resolution simulation diagnostic analysis. Both satellite observations realistic show active surface with horizontal scale ~20 km STCC upper ocean. Frontogenesis-induced buoyancy advection is detected to rapidly sharpen these fronts. The direct straining effect larger-scale geostrophic flows primary influence on buoyancy-gradient frontogenetic tendency frontal baroclinic potential vorticity (PV) enhancement. enhanced lateral gradients conjunction atmospheric forced loss can produce negative Ertel PV trigger SI region. Up 30% mixed layer (ML) inside typical eddy has simulation. As result, cross-front ageostrophic secondary circulations tend restratify boundary induce large vertical velocity reaching ~100 m day −1 , substantially facilitating communication system. At same time, identified be responsible for forward cascade kinetic energy region, despite coexistence ML eddies deep winter ML. Therefore, their SI-associated submesoscale play important roles exchanges (e.g., heat, nutrients, carbon) transfer smaller scales eddy-active ocean, as well triggering phytoplankton blooms at periphery eddies.