TY  - JOUR
A1  - Calil, Paulo H. R.
T1  - High‐Resolution, Basin‐Scale Simulations Reveal the Impact of Intermediate Zonal Jets on the Atlantic Oxygen Minimum Zones
Y1  - 2023-02-20
VL  - 15
IS  - 2
JF  - Journal of Advances in Modeling Earth Systems
DO  - 10.1029/2022MS003158
PB  - 
N2  - Eastward zonal jets at intermediate depths of 300–800 m connect the oxygen‐rich western boundary of the Atlantic basin with the oxygen minimum zones (OMZs) on the eastern boundary. They 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 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 at low‐resolution as surface, westward jets advect low‐oxygen waters from the eastern boundary much further west than in the climatology. The emergence of robust eastward jets in the high‐resolution run alleviate this problem and reproduce the Atlantic OMZs more accurately. The asymmetry between westward and eastward jets occurs because the former are associated with homogenous potential vorticity regions originating 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 OMZs, higher resolution allows a better representation of the boundary current system and eddying processes at depth which redistribute of low oxygen values from the productive eastern boundary. 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 ocean biogeochemistry. Accurate model predictions provide a pathway to disentangle natural and anthropogenic causes of ocean deoxygenation.
N2  - Plain Language Summary: Long‐term averages of ocean velocities reveal the existence of east‐west, alternating currents along multiple latitudes. These currents are difficult to observe and model because of their small speeds at great depths. Despite their low intensity, in the long‐term they can transport tracers across the ocean basins with oxygen being a very important one as it provides conditions for aerobic respiration in so‐called oxygen minimum zones (OMZs) on the eastern side of the basin. Long‐term measurements show that oxygen concentrations are decreasing in various regions of the ocean and that OMZs are expanding, which can be a problem as these regions may become inhospitable for aerobic life. That is why we need to understand the processes that supply oxygen to OMZs and are important for their evolution with time. Models can be used as tools for testing hypotheses regarding the expansion or contraction of OMZs in the future. However, models must be shown to correctly simulate the dynamics and biogeochemistry of the region as a whole. Our results show that these intermediate east‐west current systems are important in structuring the OMZs and that higher‐resolution, basin‐scale simulations are necessary to correctly simulate their impact on oxygen concentrations in the ocean.
N2  - Key Points: Intermediate, eastward zonal jets are an important oxygen supply route to the oxygen minimum zones and modulate their westward extent. Robust, intermediate zonal jets emerge in a high‐resolution (3 km), basin‐scale simulation with robust eddying motions at depth. A correct representation of the zonal jets in climate models is key for reliable, long‐term forecasts of ocean deoxygenation.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11388
ER  -