@article{fdi:010077124,
  title = {{S}ubsurface mesoscale eddy generation in the ocean off {C}entral {C}hile},
  author = {{C}ontreras, {M}. and {P}izarro, {O}. and {D}ewitte, {B}oris and {S}epulveda, {H}. {H}. and {R}enault, {L}ionel},
  editor = {},
  language = {{ENG}},
  abstract = {{O}ff the coast of central {C}hile, subsurface anticyclonic eddies are a salient feature of the oceanic circulation, transporting a significant fraction of coastal water that is rich in nutrients and poor in dissolved oxygen offshore. {I}n this study, the formation mechanism of these eddies is analyzed through a high-resolution (similar to 0.3 km) and low-resolution (similar to 3 km) oceanic model that realistically simulate the regional mean circulation, including the {P}eru-{C}hile {U}ndercurrent ({PCUC}). {A}n analysis of the vorticity and eddy kinetic energy in both simulations indicated that the subsurface eddies can be triggered through a combination of processes that are associated with instabilities of the {PCUC}. {I}n the high-resolution simulation, we observed that the interaction between the {PCUC} and topographic slope generates anticyclonic vorticity and potential vorticity close to zero in the bottom boundary layer. {T}he separation of the undercurrent from the slope favors the intensification of anticyclonic vorticity. {I}t reaches magnitudes that are larger than the planetary vorticity while kinetic energy is converted from the {PCUC} to the eddy flow. {T}hese processes set the necessary conditions for the development of centrifugal instabilities, which can form submesoscale structures. {T}he coalescence of submesoscale structures generates a subsurface anticyclonic mesoscale eddy. {I}n the low-resolution simulations (>3 km) centrifugal instabilities are not simulated, and the barotropic conversion of the mean kinetic energy into eddy kinetic energy appears as the main process of eddy formation. {W}e showed that the vertical structure of these eddies is sensitive to the spatial resolution of the model. {P}lain {L}anguage {S}ummary {S}ubsurface mesoscale eddies are swirling masses of water observed below the surface layer of the ocean (around 100- to 400-m depth). {O}ff central {C}hile, these eddies have typical diameters of few tens of kilometers. {T}hey are formed near the coast, where an intense subsurface poleward flow, namely, the {P}eru-{C}hile {U}ndercurrent ({PCUC}), interacts with the continental slope and the seaward border of the continental shelf. {T}hese eddies can travel long distances, toward the open ocean, transporting coastal waters with low dissolved oxygen and high nutrient concentrations and impacting the regional marine ecosystems. {W}e use a high-resolution numerical oceanic model (similar to 0.3 km) to analyze the formation of an eddy near 33.5 degrees {S} off {C}hile. {W}e showed that the eddy formation process requires the undercurrent to destabilize and detach from the coast, promoting the generation of submesoscale eddies (diameters -10 km). {T}his means that in regions of eddy formation, initially, the {PCUC} drifts offshore transferring momentum to submesoscale eddies. {L}ater on, these eddies begin to coalesce to form an eddy with larger dimensions. {W}e also showed that the spatial resolution of the numerical model can impact the mechanism of transfer of momentum and the vertical structure of eddies.},
  keywords = {{CHILI} ; {PACIFIQUE} {SUD}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {O}ceans},
  volume = {124},
  numero = {8},
  pages = {5700--5722},
  ISSN = {2169-9275},
  year = {2019},
  DOI = {10.1029/2018jc014723},
  URL = {https://www.documentation.ird.fr/hor/fdi:010077124},
}