In this section
@article{Lefauve:2026:10.1029/2025JC023905,
author = {Lefauve, A and Bassett, C and Plotnick, DS and Lavery, AC and Geyer, WR},
doi = {10.1029/2025JC023905},
journal = {Journal of Geophysical Research Oceans},
title = {The Structure and Lifecycle of Stratified Mixing by Shear Instabilities in Continuously Forced Flows},
url = {http://dx.doi.org/10.1029/2025JC023905},
volume = {131},
year = {2026}
}
TY - JOUR
AB - The turbulent energy cascade of ocean mixing remains poorly understood at geophysically large Reynolds numbers ((Formula presented.)). Here we propose a new conceptual model for the structure of small-scale mixing grounded in high-resolution multibeam echosounding observations from the mouth of the Connecticut River, a shallow salt-wedge estuary. Tidal forcing and bottom topography slope the pycnocline, sustaining interfacial shear and Kelvin–Helmholtz instabilities well below the marginal instability threshold on a vertical scale of order 1 m. Acoustic backscatter, used here as a proxy for salinity microstructure dissipation, provides time-resolved two-dimensional imagery of the structure and evolution of turbulent mixing. At (Formula presented.), we find that mixing is dominated not by the collapse of slowly evolving billow cores as at (Formula presented.), but instead by fast turbulence within the (Formula presented.) m thin, shallow-sloping braids that connect them, energized by baroclinic shear. We interpret these observations using two-dimensional direct numerical simulation at field-matched parameters, which predicts the emergence of secondary Kelvin–Helmholtz instabilities and turbulence within the braids, pre-empting further steepening and primary overturn. We then estimate turbulent dissipation and scalar variance dissipation at the pycnocline and braid scales using physics-based scalings involving only the local slope, shear and layer thickness. Laboratory experiments in an inclined duct, an analog of the turbulent braid regime, visualize mixing down to dissipative scales, where it remains organized in myriad thin, sheared, intense filaments rather than overturns. We conclude that high- (Formula presented.) mixing hotspots with sustained shear forcing follow fundamentally different dynamics than previously thought.
AU - Lefauve,A
AU - Bassett,C
AU - Plotnick,DS
AU - Lavery,AC
AU - Geyer,WR
DO - 10.1029/2025JC023905
PY - 2026///
SN - 2169-9275
TI - The Structure and Lifecycle of Stratified Mixing by Shear Instabilities in Continuously Forced Flows
T2 - Journal of Geophysical Research Oceans
UR - http://dx.doi.org/10.1029/2025JC023905
VL - 131
ER -
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