Statistics of submesoscale fronts in the upper ocean

Abstract

Recent studies with regional numerical models suggest that the upper ocean hosts vigorous submesoscale fronts. With a typical width of 1-10 km, these fronts are associated with intense air-sea interactions and, consequently, could affect global climate. This project will perform a statistical analysis of these fronts using novel observations recently collected with four saildrones (robotic sailboats) in the California Current region offshore the Bay of San Francisco. Sailing in quad formation with 1-km spacing, the saildrones collected velocity data in the upper 100 m with a RD Instruments 300-kHz ADCP (Acoustic Doppler Current Profiler) and surface temperature/salinity data with a Seabird37 CTD (Conductive, Temperature and Depth profiler). These data will be used to estimate two-dimensional velocity and density gradients as well as derived properties such as vertical vorticity, horizontal divergence and frontogenetic tendency. These properties will in turn be analyzed statistically through the estimation of joint-probability functions (joint-PDFs) and horizontal wavenumber spectra. We expect to produce a detailed observational description of submesoscale fronts that advance the knowledge of the physics of these features. This description could then be used to assess the skill of regional numerical models in correctly representing these phenomena and their consequences.