@article{fdi:010090124,
  title = {{W}ind dependencies of deep cycle turbulence in the equatorial cold tongues},
  author = {{M}oum, {J}. {N}. and {S}myth, {W}. {D}. and {H}ughes, {K}. {G}. and {C}herian, {D}. and {W}arner, {S}. {J}. and {B}ourl{\`e}s, {B}ernard and {B}randt, {P}. and {D}engler, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{S}everal years of moored turbulence measurements from xpods at three sites in the equatorial cold tongues of {A}tlantic and {P}acific {O}ceans yield new insights into proxy estimates of turbulence that specifically target the cold tongues. {T}hey also reveal previously unknown wind dependencies of diurnally varying turbulence in the near-critical stratified shear layers beneath the mixed layer and above the core of the {E}quatorial {U}ndercurrent that we have come to understand as deep cycle ({DC}) turbulence. {I}solated by the mixed layer above, the {DC} layer is only indirectly linked to surface forcing. {Y}et, it varies diurnally in concert with daily changes in heating/cooling. {D}iurnal composites computed from 10-min averaged data at fixed xpod depths show that transitions from daytime to nighttime mixing regimes are increasingly delayed with weakening wind stress t. {T}hese transitions are also delayed with respect to depth such that they follow a descent rate of roughly 6 m h-1, independent of t. {W}e hypothesize that this wind-dependent delay is a direct result of wind-dependent diurnal warm layer deepening, which acts as the trigger to {DC} layer instability by bringing shear from the surface downward but at rates much slower than 6 m h-1. {T}his delay in initiation of {DC} layer instability contributes to a reduction in daily averaged values of turbulence dissipation. {B}oth the absence of descending turbulence in the sheared {DC} layer prior to arrival of the diurnal warm layer shear and the magnitude of the subsequent descent rate after arrival are roughly predicted by laboratory experiments on entrainment in stratified shear flows. {SIGNIFICANCE} {STATEMENT}: {O}nly recently have long time series measurements of ocean turbulence been available anywhere. {I}mportant sites for these measurements are the equatorial cold tongues where the nature of upper ocean turbulence differs from that in most of the world's oceans and where heat uptake from the atmosphere is concentrated. {C}ritical to heat transported downward from the mixed layer is the diurnally varying deep cycle of turbulence below the mixed layer and above the core of the {E}quatorial {U}ndercurrent. {E}ven though this layer does not directly contact the surface, here we show the influence of the surface winds on both the magnitude of the deep cycle turbulence and the timing of its descent into the depths below.},
  keywords = {{T}ropics ; {A}tmosphere-ocean interaction ; {D}iapycnal mixing ; {D}iurnal effects ; {M}ixed layer ; {M}ixing ; {ZONE} {TROPICALE}},
  booktitle = {},
  journal = {{J}ournal of {P}hysical {O}ceanography},
  volume = {53},
  numero = {8},
  pages = {1979--1995},
  ISSN = {0022-3670},
  year = {2023},
  DOI = {10.1175/jpo-d-22-0203.1},
  URL = {https://www.documentation.ird.fr/hor/fdi:010090124},
}