Turbulence and mixing along a microtidal and stratified estuary-shelf transition
- 1Universidade Federal do Rio Grande (Rio Grande, Brazil)
Abstract
This study investigates the hydrodynamic and mixing processes at the estuary–shelf transition of a microtidal system, and the buoyant plume generated at the Patos Lagoon mouth (Brazil). Using measurements of current velocities, salinity, temperature, and turbulent kinetic energy (TKE) dissipation ( ϵ ) during a high-discharge period (∼ 9400 m ³ s ⁻¹ ), we characterize the spatial evolution of turbulence and mixing along the channel, from the source to the buoyancy-driven plume region. Diagnosed using the internal Froude number, the observations showed a transition from sub-critical flow in the channel to super-critical flow in the buoyant plume liftoff zone, and back to sub-critical flow offshore. Despite strong stratification, intense shear-driven turbulence was observed, with TKE dissipation rates reaching 10 ⁻³ W kg ⁻¹ near the mouth, comparable to values reported in high-energy mesotidal and macrotidal systems. Analysis of the buoyancy Reynolds number ( Re b ) and the gradient Richardson number ( Ri ) indicates that inertial forcing overcomes buoyancy suppression, maintaining a predominantly turbulent regime ( Re b > 200) at the plume front. These results demonstrate that, in narrow, high-discharge estuarine outlets, the spatial evolution of turbulence and mixing reflects the combined influence of channel morphology, secondary circulation, and plume adjustment processes operating within a sustained supercritical flow regime, maintaining vigorous mixing even under pronounced density stratification.
Versions
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BibTeX
@article{barros2026turbulence,
title = {{Turbulence and mixing along a microtidal and stratified estuary-shelf transition}},
author = {Débora Barros and Lauren Ross and Carlos A. F. Schettini},
journal = {Ocean Science},
year = {2026},
month = oct,
doi = {10.5194/os-22-3121-2026},
url = {https://os.copernicus.org/articles/22/3121/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Turbulence and mixing along a microtidal and stratified estuary-shelf transition
AU - Débora Barros
AU - Lauren Ross
AU - Carlos A. F. Schettini
PY - 2026
DA - 2026/10/08
JO - Ocean Science
DO - 10.5194/os-22-3121-2026
UR - https://os.copernicus.org/articles/22/3121/2026/
AB - This study investigates the hydrodynamic and mixing processes at the estuary–shelf transition of a microtidal system, and the buoyant plume generated at the Patos Lagoon mouth (Brazil). Using measurements of current velocities, salinity, temperature, and turbulent kinetic energy (TKE) dissipation ( ϵ ) during a high-discharge period (∼ 9400 m ³ s ⁻¹ ), we characterize the spatial evolution of turbulence and mixing along the channel, from the source to the buoyancy-driven plume region. Diagnosed using the internal Froude number, the observations showed a transition from sub-critical flow in the channel to super-critical flow in the buoyant plume liftoff zone, and back to sub-critical flow offshore. Despite strong stratification, intense shear-driven turbulence was observed, with TKE dissipation rates reaching 10 ⁻³ W kg ⁻¹ near the mouth, comparable to values reported in high-energy mesotidal and macrotidal systems. Analysis of the buoyancy Reynolds number ( Re b ) and the gradient Richardson number ( Ri ) indicates that inertial forcing overcomes buoyancy suppression, maintaining a predominantly turbulent regime ( Re b > 200) at the plume front. These results demonstrate that, in narrow, high-discharge estuarine outlets, the spatial evolution of turbulence and mixing reflects the combined influence of channel morphology, secondary circulation, and plume adjustment processes operating within a sustained supercritical flow regime, maintaining vigorous mixing even under pronounced density stratification.
SN - 1812-0792
ER -