Net primary production in the Gulf Stream sustained by quasi-geostrophic vertical exchanges
Event: 2015 Ocean Surface Topography Science Team Meeting
Session: Science II: Mesoscale and sub-mesoscale ocean processes: current understanding and preparation for SWOT
Presentation type: Type Poster
Contribution: PDF file
We analyze 12 years of mesoscale vertical motion derived from an observation-based product in the top 1000 m of the North West Atlantic Ocean. Vertical velocities [O(10 m day-1)] associated with Gulf Stream instabilities consist of alternating cells of upwelling and downwelling. Here we show that the magnitude of the vertical motions decays exponentially southwards with an e-folding length scale is informative on the dynamics of the system. We further investigate the impact of the vertical supply of nutrients on phytoplankton growth with a conceptual model incorporating the mean effect of nutrient distribution, quasi-geostrophic dynamics and Ekman suction/pumping. Results confirm that the mean effect of mesoscale vertical velocity variability alone can sustain observed levels of net primary production in the immediate vicinity of the Gulf Stream, while other mechanisms, including horizontal advection and submesoscale dynamics, need to be considered when moving towards the subtropical gyre.