Impact of sub-mesoscale physics on production and subduction of phytoplankton in an oligotrophic regime
Using a protocol of numerical experiments where horizontal resolution is progressively increased, we show that small-scale (or sub-mesoscale) physics has a strong impact on both mesoscale physics and phytoplankton production/subduction. Mesoscale and sub-mesoscale physics result from the nonlinear equilibration of an unstable baroclinic jet. The biogeochemical context is oligotrophy. The explicitly resolved sub-mesoscales, at least smaller than one fifth of the internal Rossby radius of deformation, reinforce the mesoscale eddy field and contribute to double the primary production and phytoplankton subduction budgets. This enhancement is due to the reinforced mesoscale physics and is also achieved by the small-scale frontal dynamics. This sub-mesoscale physics is associated with density and vorticity gradients around and between the eddies. It triggers a significant small-scale nutrient injection in the surface layers, leading to a phytoplankton field mostly dominated by fine spatial structures. It is believed that, depending on wind forcings, this scenario should work alternately with that of Abraham (1998) which invokes horizontal stirring of nutrient injected at large scales. Results also reveal a strong relationship between new production and negative vorticity, in the absence of wind forcing and during the period of formation of the eddies.
Lévy, Marina, Patrice Klein, and Anne-Marie Treguier. 2001. "Impact of sub-mesoscale physics on production and subduction of phytoplankton in an oligotrophic regime." Journal of Marine Research 59, (4). https://elischolar.library.yale.edu/journal_of_marine_research/2401