Roles of the Ocean Mesoscale in the Horizontal Supply of Mass, Heat, Carbon, and Nutrients to the Northern Hemisphere Subtropical Gyres. Issue 10 (2nd October 2018)

• Record Type: Journal Article
• Authors: Yamamoto, Ayako; Palter, Jaime B.; Dufour, Carolina O.; Griffies, Stephen M.; Bianchi, Daniele; Claret, Mariona; Dunne, John P.; Frenger, Ivy; Galbraith, Eric D.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 10(2018)
• Page Start: 7016
• Page End: 7036
• Publication Date: 2018-10-02
• Subjects: mesoscale eddies -- subtropical gyre -- ocean tracers -- oceanic jet -- circulation/dynamics -- lateral transport; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2018JC013969
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: 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 air‐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 eddy‐rich ocean component of a climate model (Geophysical Fluid Dynamics Laboratory Climate Model version 2.6) coupled to a simple biogeochemical model (mini‐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 time‐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 coarse‐resolution model and thus further highlighting the importance of horizontal nutrient transport. Key Points: Kuroshio and Gulf Stream act as main gateways for horizontal mass and tracer exchanges Mass, heat, and DIC are principally supplied by the time‐mean circulation to the subtropical gyres, while eddies act to remove them Horizontal transport explains more than three quarters of the total nutrient supply, with downgradient eddy mixing playing a key role