Abstract

Intermediate, eastward zonal jets connect the oxygen-rich western boundary of the Atlantic Ocean with the oxygen minimum zones on the eastern boundary. These jets are not well represented in climate models because the low horizontal resolution of these models yields excessive viscosity. We use two physical-biogeochemical model configurations of the Tropical Atlantic Ocean to show that the increase in resolution results in more robust intermediate zonal jets and a better representation of the OMZs. The OMZ structure is distorted in the low-resolution run as westward jets advect low-oxygen waters from the eastern boundary further west than in the climatology. The emergence of more robust eastward jets in the high-resolution run alleviate this problem and provide a more realistic structure of the OMZs. The asymmetry between the effect of westward and eastward jets occurs because the former are associated with homogenous potential vorticity regions in the eastern boundary while the latter are associated with potential vorticity gradients. Intermediate, eastward jets constrain the westward expansion of the OMZs by supplying oxygen to their western edge. Within the isotropic OMZs, high resolution better represents the boundary current system and eddying processes at depth which are important in the redistribution of low oxygen values from the eastern boundary. Our results show that basin-scale, high-resolution simulations reproduce more accurately the transfer of energy across scales that results in robust zonal jets as well as their impact on the biogeochemistry . Accurate model predictions provide a pathway to disentangle natural and anthropogenic causes of ocean deoxygenation.