Mesoscale eddies modify the vertical structure of the resource environment for phytoplankton and also affect the horizontal dispersal and mixing of populations. Lateral trapping can intensify the signature of eddy-scale phytoplankton blooms and modify community structure by limiting mixing with surrounding populations. We address the hypothesis that coherent eddies, which trap material, will exhibit more intense chlorophyll blooms than leaky eddies due to reduced lateral dilution. We employ a Lagrangian approach, which provides metrics of the material coherence, to identify and track coherent vortices over two decades of remote sensing observations in the North Pacific Subtropical Gyre. We co-locate satellite ocean color data in eddies and find enhanced chlorophyll in both cyclonic and anticyclonic coherent eddies relative to the background and dispersive eddies. Enhancement via eddy trapping is greatest to the south of 23N in fall and winter. Our results highlight that Lagrangian coherency enhances the chlorophyll signature of North Pacific Subtropical Gyre eddies and that there are bio-physical differences seasonally and latitudinally.

Primary Presenter: Alexandra Jones, MIT-WHOI Joint Program in Oceangraphy (jonesae@mit.edu)

Authors:

Alexandra Jones, MIT  (jonesae@mit.edu)

Mick Follows, MIT  (mick@ocean.mit.edu)