Roles of the Ocean Mesoscale in the Horizontal Supply of Mass, Heat, Carbon, and Nutrients to the Northern Hemisphere Subtropical Gyres

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Yamamoto, Ayako, Palter, Jaime B., Dufour, Carolina O., Griffies, Stephen M., Bianchi, Daniele, Claret, Mariona, Dunne, John P., Frenger, Ivy, Galbraith, Eric D.
• Format: Text
• Language: unknown
• Published: DigitalCommons@URI 2018
• Subjects: North Atlantic
• Online Access: https://digitalcommons.uri.edu/gsofacpubs/520; https://doi.org/10.1029/2018JC013969; https://digitalcommons.uri.edu/context/gsofacpubs/article/1506/viewcontent/Palter_RolesOfTheOcean_2018.pdf

Horizontal transport at the boundaries of the subtropical gyres plays a crucial role in providing the nutrients that fuel gyre primary productivity, the heat that helps restratify the surface mixed layer, and the dissolved inorganic carbon that influences airâ€sea carbon exchange. Mesoscale eddies may be an important component of these horizontal transports; however, previous studies have not quantified the horizontal tracer transport due to eddies across the subtropical gyre boundaries. Here we assess the physical mechanisms that control the horizontal transport of mass, heat, nutrients, and carbon across the North Pacific and North Atlantic subtropical gyre boundaries using the eddyâ€rich ocean component of a climate model (Geophysical Fluid Dynamics Laboratory Climate Model version 2.6) coupled to a simple biogeochemical model (miniâ€BLING). Our results suggest that horizontal transport across the gyre boundaries supplies a substantial amount of mass and tracers to the ventilated layer of both Northern Hemisphere subtropical gyres, with the Kuroshio and Gulf Stream acting as main exchange gateways. Mass, heat, and dissolved inorganic carbon supply is principally driven by the timeâ€mean circulation, whereas nutrient transport differs markedly from the other tracers, as nutrients are mainly supplied to both subtropical gyres by downgradient eddy mixing across gyre boundaries. A budget analysis further reveals that the horizontal nutrient transport, combining the roles of both mean and eddy components, is responsible for more than three quarters of the total nutrient supply into the subtropical gyres, surpassing a recent estimate based on a coarseâ€resolution model and thus further highlighting the importance of horizontal nutrient transport.