Diapycnal Mixing in the Southern Ocean Diagnosed Using the DIMES Tracer and Realistic Velocity Fields
2018
In this work, we use realistic
isopycnalvelocities with a 3‐D
eddy diffusivityto
advectand diffuse a tracer in the Antarctic Circumpolar Current, beginning in the Southeast Pacific and progressing through Drake Passage. We prescribe a diapycnal diffusivity which takes one value in the SE Pacific west of 67°W and another value in Drake Passage east of that longitude, and optimize the diffusivities using a cost function to give a best fit to experimental data from the DIMES (Diapycnal and
IsopycnalMixing Experiment in the Southern Ocean) tracer, released near the boundary between the Upper and Lower
Circumpolar Deep Water. We find that diapycnal diffusivity is enhanced 20‐fold in Drake Passage compared with the SE Pacific, consistent with previous estimates obtained using a simpler
advection‐diffusion model with constant, but different, zonal velocities east and west of 67°W. Our result shows that diapycnal mixing in the ACC plays a significant role in transferring buoyancy within the Meridional Overturning Circulation.
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