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High-resolution, basin-scale simulations reveal the impact of intermediate zonal jets on the Atlantic oxygen minimum zones
  • Paulo H. R. Calil
Paulo H. R. Calil
Helmholtz-Zentrum Hereon, Helmholtz-Zentrum Hereon

Corresponding Author:paulo.calil@hereon.de

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Intermediate, eastward zonal jets are important conduits of oxygen across the Atlantic Ocean as they connect the oxygen-rich western boundary of the basin with the oxygen minimum zones (OMZs) on the eastern boundary. These jets are not well represented in climate models because the relatively low horizontal resolution of these models usually yields excessive viscosity. We use two physical-biogeochemical model configurations of the Tropical Atlantic Ocean at different resolutions to show that the increase in resolution results, on average, in more robust intermediate, eastward zonal jets. Larger viscosity in the low resolution runs inhibits strong eastward jets at depth. The upper ocean circulation is not significantly affected by the difference in resolution. This causes westward jets in the upper 300 m to advect low oxygen waters further west than in the climatology, thus distorting the vertical structure of the OMZ by making them thinner and wider. Potential vorticity analysis confirms that surface westward jets are associated homogenized PV contours while eastward jets are associated with regions of potential vorticity gradients. Eastward jets constrain the westward expansion of the OMZs by supplying oxygen to the western edge of the OMZs. Model diagnostics show that advection dominates oxygen transport in the OMZ core, with increased transport in the high-resolution run. Basin-scale, high-resolution runs are necessary to simulate the transfer of energy across scales that results in robust zonal jets as well as their impact on the ocean biogeochemistry. This provides a pathway to disentangle natural and antrhopogenic causes of ocean deoxygenation.