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Eddy-Mediated Mixing of Oxygen in the Equatorial Pacific
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  • Yassir A. Eddebbar,
  • Daniel Bridger Whitt,
  • Ariane Verdy,
  • Matthew R. Mazloff,
  • Aneesh Subramanian,
  • Matthew C. Long
Yassir A. Eddebbar
Scripps Institution of Oceanography, University of California San Diego

Corresponding Author:[email protected]

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Daniel Bridger Whitt
NASA Ames Research Center
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Ariane Verdy
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Matthew R. Mazloff
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Aneesh Subramanian
University of Colorado
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Matthew C. Long
National Center for Atmospheric Research (UCAR)
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In the tropical Pacific, weak ventilation and intense microbial respiration at depth give rise to a low dissolved oxygen (O2) environment that is thought to be ventilated primarily by the equatorial current system (ECS). The role of mesoscale eddies and diapycnal mixing as potential pathways of O2 supply in this region, however, remains poorly known due to sparse observations and coarse model resolution. Using an eddy resolving simulation of ocean circulation and biogeochemistry, we assess the contribution of these processes to the O2 budget balance and find that turbulent mixing of O2 and its modulation by mesoscale eddies contribute substantially to the replenishment of O2 in the upper equatorial Pacific thermocline, complementing the advective supply of O2 by the ECS and meridional circulation at depth. These transport processes are strongly sensitive to seasonal forcing by the wind, with elevated mixing of O2 into the upper thermocline during summer and fall when the vertical shear of the lateral flow and eddy kinetic energy are intensified. The tight link between eddy activity and the downward mixing of O2 arises from the modulation of equatorial turbulence by Tropical Instability Waves via their eddy impacts on the vertical shear. This interaction of ocean processes across scales sustains a local pathway of O2 delivery into the equatorial Pacific interior and highlights the need for adequate observations and model representation of turbulent mixing and mesoscale processes for understanding and predicting the fate of the tropical Pacific O2 content in a warmer and more stratified ocean.
26 Sep 2023Submitted to ESS Open Archive
30 Sep 2023Published in ESS Open Archive