Roles of the ocean mesoscale in the horizontal supply of mass, heat, carbon and nutrients to the Northern Hemisphere subtropical gyres.

Yamamoto, Ayako, Palter, Jaime B., Dufour, Carolina O., Griffies, Stephen M., Bianchi, Daniele, Claret, Mariona, Dunne, John P., Frenger, Ivy and Galbraith, Eric D. (2018) Roles of the ocean mesoscale in the horizontal supply of mass, heat, carbon and nutrients to the Northern Hemisphere subtropical gyres. Open Access Journal of Geophysical Research: Oceans, 123 (10). pp. 7016-7036. DOI 10.1029/2018JC013969.

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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 (DIC) 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 (GFDL's CM2.6) 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 DIC 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 down‐gradient 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.

Document Type: Article
Keywords: Mesoscale eddies; Subtropical gyre; Ocean tracers; Oceanic jet; Circulation/Dynamics; Lateral transport
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2018JC013969
ISSN: 2169-9275
Date Deposited: 05 Sep 2018 07:16
Last Modified: 03 Apr 2019 23:38
URI: http://oceanrep.geomar.de/id/eprint/44139

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