Presenter: Alexandra Jones (Massachusetts Institute of Technology)

Description:
Mesoscale eddies modify the vertical resource environment for phytoplankton and affect the horizontal dispersal and mixing of populations. Lateral trapping by eddies can intensify the signature of eddy scale phytoplankton blooms and modify diversity by limiting mixing with surrounding populations. Eddies are routinely identified using a Eulerian framework, by which the boundaries are closed contours surrounding local maxima and minima in altimeter satellite sea level anomaly (SLA) fields. However, these boundaries are not material and features vary in their isolating properties. Lagrangian approaches are better suited to provide metrics of the material coherence, or trapping nature, of water masses. Here we identify rotationally coherent Lagrangian vortices (RCLVs) in the North Pacific subtropical gyre using the Lagrangian-averaged vorticity deviation method developed by Haller et al. 2016. By combining satellite altimeter data with contemporary ocean color products, we examine the hypothesis that subtropical gyre eddies with a coherent core are characterized by more intense surface chlorophyll signatures. Preliminary results indicate that there are differences in the chlorophyll response to coherent and leaky eddies, and that only RCLVs located inside of the boundaries of SLA eddies are unique compared with background chlorophyll concentrations. Capitalizing on decades of available satellite data, we seek to determine if eddy trapping is biologically relevant in the subtropical gyres and understand the impacts on biogeochemical cycling.