Presenter: Jasen Jacobsen (University California Santa Cruz)

Description:
Conversion of the barotropic (surface) tides to internal tides at mid-ocean ridges represents a possible mechanism that may enhance deep chlorophyll maxima. We examined this process using an idealized framework by coupling the Regional Ocean Modeling System (ROMS) to a simple nutrient, phytoplankton, zooplankton, detritus (NPZD) model. The model is forced by an oscillating body force at an M2 frequency and in domains that vary the energy conversion rate through adjustment of the ridge height. Simulation results reveal that a larger vertical nutrient flux drives increased primary production. Primary production is greater at higher conversion rates. Phytoplankton concentrations increased adjacent to the idealized ridge where internal tidal beams are directed. Periodic heaving of density surfaces into shallower, more well-lit, waters allow these blooms to persist at a distance from the ridge. Our results demonstrate that high-mode internal tides can increase nutrient availability near mid-ocean ridges, and lower-mode internal tides may contribute to a deep chlorophyll maximum farther from the ridge by ameliorating light limitation.