Abstract
Numerous studies have indicated that mesoscale eddies play an important
role in diapycnal mixing and drive global water circulation. Although
the relationships between eddy surface features and turbulent mixing
have been discussed for individual cases of typical eddies, global
studies cannot rely on ship-based microstructural measurements.
Fine-scale methods have been developed, wherein either the vertical
shear of velocity or density strain is used to estimate turbulent
mixing. In this study, the turbulent dissipation rate was estimated
using strain information from Argo floats trapped in eddies. Spatially
averaged estimates revealed the global distribution patterns of the
dissipation rates inside the eddies. In addition, the relationships
between eddy features (polarity, radius, vertical extent, and aspect
ratio) and turbulent dissipation rates were analyzed. Three main
conclusions were made from this study. First, turbulent dissipation
rates inside anticyclones were generally larger than those inside
cyclones. Second, turbulent dissipation rates inside eddies are related
to their vertical extent but not to their horizontal scale. For shallow
eddies (with a vertical extent less than 250 m for cyclones and 300 m
for anticyclones), the deeper the vertical extent, the larger the
turbulent dissipation rate. Finally, the relationship between the eddy
aspect ratio and turbulent dissipation rate was characterized by
skewness. The average turbulent dissipation rate reached a maximum value
when the cyclone aspect ratio was approximately 0.007; conversely, no
maximum value was reached for anticyclones. This work establishes a
correlation between eddy features and turbulent dissipation rates, which
will help guide numerical simulations of mesoscale eddies.