Strong horizontal density gradients, or fronts, in the ocean drive the
physical dynamics necessary to sustain circulation. Vertical motions associated with
fronts force water to subduct out of, or upwell into, the mixed layer. Subduction
helps sequester organic carbon fixed from the atmosphere (Johnston et al. 2009).
Upwelling conversely introduces limiting nutrients from deeper water, promoting
primary productivity (Li et al. 2012). Frontal regions where horizontal density
changes span O(10-100 km), referred to as the mesoscale, occur abundantly in the
California Current Ecosystem (CCE) (Marchesiello et al. 2003, Capet et al. 2008).
A mesoscale feature (E-Front ) was studied in the CCE using a SeaSoar/ADCP survey
conducted during Summer 2012. Horizontal currents are obtained by objective
analysis (Bretherton et al. 1976, Le Traon et al. 1990) of the data. Resulting maps
help visualize the potential density and current fields, and provide a means to
calculate ageostrophic secondary circulation – vertical velocities (Rudnick 1996).
Biologically relevant fluxes, whether upwelling of nutrients or subduction of
biomass, will be found from these inputs.