Cross-frontal processes and the transport of physical and biogeochemical tracers into the North Pacific and North Atlantic subtropical gyres
Ayako Yamamoto1, Carolina O. Dufour2, Jaime B Palter1,3, Stephen Matthew Griffies4, Ivy Frenger2, Daniele Bianchi5, Mariona Claret6, John P Dunne4 and Eric D Galbraith6,7, (1)McGill University, Atmospheric and Oceanic Sciences, Montreal, QC, Canada, (2)Princeton Univ, Princeton, NJ, United States, (3)University of Rhode Island, Graduate School of Oceanography, Narragansett, RI, United States, (4)Geophysical Fluid Dynamics Laboratory, Princeton, NJ, United States, (5)University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, (6)McGill University, Earth and Planetary Sciences, Montreal, QC, Canada, (7)ICREA Catalan Institution for Research and Advanced Studies, Barcelona, Spain
Abstract:
Cross-frontal exchange at the boundaries of the subtropical gyres is an important source of nutrients fueling subtropical primary productivity. Exchange across the fronts bounding the subtropical gyres has been shown to occur principally near the surface by Ekman transport and at the critical levels beneath the jet core via mesoscale structures, such as rings shed from frontal systems. Here, we quantitatively assess the role of each of these cross-frontal processes for the transport of physical and biogeochemical tracers across the boundaries of the North Pacific and North Atlantic subtropical gyres using a preindustrial control simulation of an eddying climate model (GFDL's CM2.6) coupled to a biogeochemical model (mini-BLING). The role of mesoscale coherent vortices in the cross-frontal exchanges of the tracers is diagnosed using a recently published algorithm that detects and tracks such mesoscale structures. We address the similarities and differences between the gyres, with a particular focus on the mechanisms supplying nutrients across the Gulf Stream and Kuroshio, motivated by conflicting reports of the importance of ring formation across each of these western boundary currents.
