Articles | Volume 21, issue 5
https://doi.org/10.5194/os-21-2681-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-21-2681-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
29 Oct 2025
Research article |
| 29 Oct 2025
| 29 Oct 2025
Flow structure and mixing near a small river plume front: Winyah Bay, SC, USA
Christopher Papageorgiou
School of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC, USA
School of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC, USA
Alexander E. Yankovsky
School of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC, USA
Diane Bennett Fribance
Department of Marine Science, Coastal Carolina University, Conway, SC, USA
Cited articles
Arneborg, L., Fiekas, V., Umlauf, L., and Burchard, H.: Gravity Current Dynamics and Entrainment – A Process Study Based on Observations in the Arkona Basin, J. Phys. Oceanogr., 37, 2094–2113, https://doi.org/10.1175/JPO3110.1, 2007.
Bouguet, J.-Y.: Camera calibration toolbox for Matlab (1.0), CaltechDATA [data set], https://doi.org/10.22002/D1.20164, 2022.
Britter, R. E. and Simpson, J. E.: Experiments on the dynamics of a gravity current head, Journal of Fluid Mechanics, 88, 223–240, 1978.
Burchard, H. and Hofmeister, R.: A dynamic equation for the potential energy anomaly for analysing mixing and stratification in estuaries and coastal seas, Estuarine, Coastal and Shelf Science, 77, 679–687, https://doi.org/10.1016/j.ecss.2007.10.025, 2008.
Caulfield, C. P.: Layering, instabilities, and mixing in turbulent stratified flows, Annu. Rev. Fluid Mech., 53, 113–145, https://doi.org/10.1146/annurev-fluid-042320-100458, 2021.
de Boer, G. J., Pietrzak, J. D., and Winterwerp, J. C.: On the vertical structure of the Rhine region of freshwater influence, Ocean Dyn., 56, 198–216, https://doi.org/10.1007/s10236-005-0042-1, 2006.
de Boer, G. J., Pietrzak, J. D., and Winterwerp, J. C.: Using the potential energy anomaly equation to investigate tidal straining and advection of stratification in a region of freshwater influence, Ocean Modell., 22, 1–11, https://doi.org/10.1016/j.ocemod.2007.12.003, 2008.
Delatolas, N., MacDonald, D. G., Goodman, L., Whitney, M., Huguenard K., and Cole. K.: Comparison of structure and turbulent mixing between lateral and leading-edge river plume fronts: microstructure observations from a T-REMUS AUV, Estuarine, Coastal and Shelf Science, 283, 108234, https://doi.org/10.1016/j.ecss.2023.108234, 2023.
Dillon, T. M.: Vertical overturns: A comparison of Thorpe and Ozmidov length scales, J. Geophys. Res., 87, 9601–9613, https://doi.org/10.1029/JC087iC12p09601, 1982.
Edson, J. B., Raju, J. V. S., Weller, R. A., Bigorre, S., Plueddemann, A., Fairall, C. W., Miller, S., Mahrt, L., Vickers, D., and Hersbach, H.: On the Exchange of momentum over the open ocean, J. Phys. Oceanogr., 43, 1589–1610, https://doi.org/10.1175/JPO-D-12-0173.1, 2013.
Fairall, C. W., Bradley, E. F., Hare, J. E., Grachev, A. A., and Edson, J. B.: Bulk Parameterization of Air–Sea Fluxes: Updates and Verification for the COARE Algorithm, J. Climate, 16, 571–591, https://doi.org/10.1175/1520-0442(2003)016<0571:BPOASF>2.0.CO;2, 2003.
Fong, D. A. and Geyer, W. R.: The Alongshore Transport of Freshwater in a Surface-Trapped River Plume, J. Phys. Oceanogr., 32, 957–972, https://doi.org/10.1175/1520-0485(2002)032<0957:TATOFI>2.0.CO;2, 2002.
Garvine, R. W.: Radial spreading of buoyant, surface plumes in coastal waters, J. Geophys. Res., 89, 1989–1996, https://doi.org/10.1029/JC089iC02p01989, 1984.
Gregg, M. C., D'Asaro, E. A., Riley, J. J., and Kunze, E.: Mixing efficiency in the ocean, Annual Review of Marine Science, 10, 443–473, https://doi.org/10.1146/annurev-marine-121916-063643, 2018.
Hetland, R. D.: The effects of mixing and spreading on density in near-field river plumes, Dynamics of Atmospheres and Oceans, 49, 37–53, https://doi.org/10.1016/j.dynatmoce.2008.11.003, 2010.
Horner-Devine, A. R., Chickadel, C. C., and MacDonald, D. G.: Coherent Structures and Mixing at a River Plume Front, in: Coherent Flow Structures at Earth's Surface, edited by: Venditti, J. G., Best, J. L., Church, M., and Hardy, R. J., https://doi.org/10.1002/9781118527221.ch23, 2013.
Horner-Devine, A. R., Jay, D. A., Orton, P. M., and Spahn, E. Y.: A conceptual model of the strongly tidal Columbia River plume, Journal of Marine Systems, 78, 460–475, https://doi.org/10.1016/j.jmarsys.2008.11.025, 2009.
Horner-Devine, A. R., Hetland, R. D., and MacDonald, D. G.: Mixing and transport in coastal river plumes, Annual Review of Fluid Mechanics, 47, 569–594, https://doi.org/10.1146/annurev-fluid-010313-141408, 2015.
Huguenard, K., Bears, K., and Lieberthal, B.: Intermittency in Estuarine Turbulence: A framework toward limiting bias in microstructure measurements. J. Atmos. Oceanic Technol., 36, 1917–1932, https://doi.org/10.1175/JTECH-D-18-0220.1, 2019.
Huppert H. E. and Simpson, J. E.: The slumping of gravity currents, J. Fluid Mech., 99, 785–799, https://doi.org/10.1017/S0022112080000894, 1980.
Howland, C. J., Taylor J. R., and Caulfield, C. P.: Mixing in forced stratified turbulence and its dependence on large-scale forcing, J. Fluid Mech., 898, A7, https://doi.org/10.1017/jfm.2020.383, 2020.
Imberger, J.: Tidal Jet Frontogenesis, Transactions of the Institution of Engineers, Australia, Mechanical Engineering, ME8, 171–180, 1983.
IOC, SCOR, and IAPSO: The international thermodynamic equation of seawater – 2010: Calculation and use of thermodynamic properties, Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp., https://www.teos-10.org/pubs/TEOS-10_Manual.pdf (last access: 10 September 2025), 2010.
Ivey, G. N., Bluteau, C. E., Gayen, B., Jones, N. L., and Sohail, T.: Roles of shear and convection in driving mixing in the ocean, Geophys. Res. Lett., 48, e2020GL089455, https://doi.org/10.1029/2020GL089455, 2020.
Kastner, S. E., Horner-Devine, A. R., and Thomson, J.: The influence of wind and waves on spreading and mixing in the Fraser River plume, J. Geophys. Res., 123, 6818–6840, https://doi.org/10.1029/2018JC013765, 2018.
Kay, D. J. and Jay D. A.: Interfacial mixing in a highly stratified estuary 1. Characteristics of mixing, J. Geophys. Res., 108, 3072, https://doi.org/10.1029/2000JC000252, 2003.
Kilcher, L. F., Nash, J. D., and Moum, J. N.: The role of turbulence stress divergence in decelerating a river plume, J. Geophys. Res., 117, C05032, https://doi.org/10.1029/2011JC007398, 2012.
Kim, Y. H. and Voulgaris, G.: Effect of channel bifurcation on residual estuarine circulation: Winyah Bay, South Carolina. Estuarine, Coastal and Shelf Science, 65, 671–686, https://doi.org/10.1016/j.ecss.2005.07.004, 2005.
Lavey, A. C., Geyer, W. R., and Scully, M. E.: Broadband acoustic quantification of stratified turbulence, J. Acoust. Soc. Am., 134, 40–54, https:/doi.org/10.1121/1.4807780, 2013.
Lewin S. F. and Caulfield, C. P.: Evidence for layered anisotropic stratified turbulence in a freely evolving horizontal shear flow, Journal of Fluid Mechanics, 983, A20, https://doi.org/10.1017/jfm.2024.121, 2024.
Lozovatsky, I. D. and Fernando, H. J. S.: Mixing efficiency in natural flows, Philos. T. R. Soc A., 371, 20120213, https://doi.org/10.1098/rsta.2012.0213, 2013.
Lueck, R.: Calculating the rate of dissipation of turbulent kinetic energy, Rockland Scientific International, RSI Technical Note 028, 18 pp., https://datadocs.bcodmo.org/docs/302/Filter_Feeders_Physics_and_Phosphorus/data_docs/768011/1/TN_028_Dissipation.pdf (last access: 10 September 2025), 2016.
Li, C., Nelson, J. R., and Koziana, J. V.: Cross-shelf passage of coastal water transport at the South Atlantic Bight observed with MODIS Ocean Color/SST. Geophys. Res. Lett., 30, 1257, https:/doi.org/10.1029/2002GL016496, 2003.
Luketina, D. A. and Imberger, J.: Characteristics of a Surface Buoyant Jet, J. Geophys. Res., 92, 5435–5447, https:/doi.org/10.1029/JC092iC05p05435, 1987.
MacDonald, D. G. and Geyer, W. R.: Turbulent energy production and entrainment at a highly stratified estuarine front, J. Geophys. Res., 109, C05004, https://doi.org/10.1029/2003JC002094, 2004.
MacDonald, D. G., Goodman, L., and Hetland, R. D.: Turbulent dissipation in a near-field river plume: A comparison of control volume and microstructure observations with a numerical model, J. Geophys. Res., 112, C07026, https://doi.org/10.1029/2006JC004075, 2007.
Mater, B. D. and Venayagamoorthy, S. K.: The quest for an unambiguous parameterization of mixing efficiency in stably stratified geophysical flows, Geophys. Res. Lett., 41, 4646–4653, https://doi.org/10.1002/2014GL060571, 2014.
Mater, B. D., Venayagamoorthy, S. K., St Laurent, L., and Moum, J. N.: Biases in Thorpe-scale estimates of turbulence dissipation. Part I: Assessments from large-scale overturns in oceanographic data, J. Phys. Oceanogr., 45, 2497–2521, https://doi.org/10.1175/JPO-D-14-0128.1, 2015.
Marmorino, G. O. and Trump, C. L.: Gravity current structure of the Chesapeake Bay outflow plume, J. Geophys. Res., 105, 28847–28861, https://doi.org/10.1029/2000JC000225, 2000.
Münchow, A. and Garvine, R. W.: Buoyancy and wind forcing of a coastal current, J. Mar. Res., 51, 293–322, https://doi.org/10.1357/0022240933223747, 1993.
O'Donnell, J., Ackleson, S. G., and Levine, E. R.: On the spatial scales of a river plume, J. Geophys. Res., 113, C04017, https://doi.org/10.1029/2007JC004440, 2008.
Orton, P. M. and Jay, D. A.: Observations at the tidal plume front of a high-volume river outflow, Geophys. Res. Lett., 32, L11605, https://doi.org/10.1029/2005GL022372, 2005.
Osborn, T. R.: Estimates of the Local Rate of Vertical Diffusion from Dissipation Measurements, J. Phys. Oceanogr., 10, 83–89, https://doi.org/10.1175/1520-0485(1980)010<0083:EOTLRO>2.0.CO;2, 1980.
Papageorgiou, C. T.: Robocat: An autonomous surface vehicle (ASV) for near-surface hydrodynamic measurements in buoyant plumes, Development and case study, Master's thesis, University of South Carolina, Columbia, SC, USA, https://scholarcommons.sc.edu/etd/7640 (last access: 10 September 2025), 2023.
Papageorgiou, C., Voulgaris, G., Yankovsky, A., and Fribance, D.: Dataset for Manuscript: “Flow Structure and Mixing Near a Small River Plume Front: Winyah Bay, SC, USA”, Zenodo [data set], https://doi.org/10.5281/zenodo.14687081, 2025.
Peters, H.: Spatial and temporal variability of turbulent mixing in an estuary, Journal of Marine Research, 57, 805–845, 1999
Pritchard, M. and Huntley, D. A.: A simplified energy and mixing budget for a small river plume discharge, J. Geophys. Res., 111, C03019, https://doi.org/10.1029/2005JC002984, 2006.
Portwood, G. D., de Bruyn Kops, S. M., Taylor, J. R., Salehipour, H., and Caulfield, C. P.: Robust identification of dynamically distinct regions in stratified turbulence, J. Fluid Mech., 807, R2, https://doi.org/10.1017/jfm.2016.617, 2016.
Rijnsburger, S., Flores, R. P., Pietrzak, J. D., Horner-Devine, A. R., and Souza, A. J.: The influence of tide and wind on the propagation of fronts in a shallow river plume, Journal of Geophysical Research, 123, 5426–5442, https://doi.org/10.1029/2017JC013422, 2018.
Scannell, B. D., Rippeth, T. P., Simpson, J. H., Polton, J. A., and Hopkins, J. E.: Correcting surface wave bias in structure function estimates of turbulent kinetic energy dissipation rate, J. Atmos. Oceanic Technol., 34, 2257–2273, https://doi.org/10.1175/JTECH-D-17-0059.1, 2017.
Scotti, A.: Biases in Thorpe-scale estimates of turbulence dissipation. Part II: Energetics arguments and turbulence simulations, J. Phys. Oceanogr., 45, 2522–2543, https://doi.org/10.1175/JPO-D-14-0092.1, 2015.
Simpson, J. H.: The shelf-sea fronts: implications of their existence and behaviour, Philosophical Transactions of the Royal Society London Series A, 302, 531–546, https://doi.org/10.1098/rsta.1981.0181, 1981.
Simpson, J. E. and Britter, R. E.: The dynamics of the head of a gravity current advancing over a horizontal surface, J. Fluid Mech., 94, 477–495, https://doi.org/10.1017/S0022112079001142, 1979.
Simpson, J. E. and Britter, R. E.: A laboratory model of an atmospheric meso-front, Q. J. Roy. Meteor. Soc., 106, 485–500, https://doi.org/10.1002/qj.49710644907, 1980.
Simpson, J. H., Brown, J., Matthews, J., and Allen, G.: Tidal straining, density currents, and stirring in the control of estuarine stratification, Estuaries, 26, 1579–1590, https://doi.org/10.2307/1351581, 1990.
Simpson, J. H., Williams, E., Brasseur, L. H., and Brubaker, J. M.: The impact of tidal straining on the cycle of turbulence in a partially stratified estuary, Continental Shelf Research, 25, 51–64, https://doi.org/10.1016/j.csr.2004.08.003, 2005.
Smith, J. A.: A comparison of two methods using Thorpe sorting to estimated mixing, J. Atmos. Oceanic Technol., 37, 3–15, https//doi.org/10.1175/JTECH-D-18-0234.1, 2020.
Solodoch, A., Molemaker, J. M., Srinivasan, K., Berta, M., Marie, L., and Jagannathan, A.: Observations of shoaling density current regime changes in internal wave interactions, J. Phys. Oceanogr., 50, 1733–1751, https://doi.org/10.1175/JPO-D-19-0176.1, 2020.
Souza, A. J. and Simpson J. H.: The modification of tidal ellipses by stratification in the Rhine ROFI, Continental Shelf Research, 16, 997–1007, https://doi.org/10.1016/0278-4343(95)00042-9, 1996.
Spicer, P., Huguenard, K., Cole, K. L., MacDonald, D. G., and Whitney, M. M.: Evolving interior mixing regimes in a tidal river plume, Geophys. Res. Lett., 49, e2022GL099633, https://doi.org/10.1029/2022GL099633, 2022.
Spicer, P., Cole, K. L., Huguenard, K., MacDonald, D. G., and Whitney, M. M.: The effect of bottom-generated tidal mixing on tidally pulsed river plumes, J. Phys. Oceanogr., 51, 2223–2241, https://doi.org/10.1175/JPO-D-20-0228.1, 2021.
Tjernstrom, M.: Turbulence length scales in stably stratified free shear flow analyzed from slant aircraft profiles, J. Appl. Meteor., 32, 948–963, https://doi.org/10.1175/1520-0450(1993)032<0948:tlsiss>2.0.co;2, 1993.
Thomson, J., Nylund, S., Moulton, M., de Klerk, A., Talbert, J., Guerra, M., Kastner, S. E., Smith, M. M., Schwendeman, M., and Zippel, S. F.: A new version of the SWIFT platform for waves, currents, and turbulence in the ocean surface layer, 2019 IEEE/OES Twelfth Current, Waves and Turbulence Measurement (CWTM), 1–7, https://doi.org/10.1109/CWTM43797.2019.8955299, 2019.
Thorpe, S. A.: Transitional phenomena and the development of turbulence in stratified fluids: A review, J. Geophys. Res., 92, 5231, https://doi.org/10.1029/JC092iC05p05231, 1987.
von Karman, T.: The engineer grapples with nonlinear problems, B. Am. Math. Soc., 46, 615–683, https://doi.org/10.1090/S0002-9904-1940-07266-0, 1940.
Whitney, M. M., Spicer, P., MacDonald, D. G., Huguenard, K. D., Cole, K. L., Jia, Y., and Delatolas, N.: Mixing of the Connecticut River plume during ambient flood tides: Spatial heterogeneity and contributions of bottom-generated and interfacial mixing, J. Geophys. Res., 129, e2023JC020423, https://doi.org/10.1029/2023JC020423, 2024.
Wiles, P. J., Rippeth, T. P., Simpson, J. H., and Hendricks, P. J.: A novel technique for measuring the rate of turbulent dissipation in the marine environment, Geophys. Res. Lett., 33, L21608, https://doi.org/10.1029/2006GL027050, 2006.
Yankovsky, A. E., Fribance, D. B., Cahl, D., and Voulgaris, G.: Offshore Spreading of a Supercritical Plume Under Upwelling Wind Forcing: A Case Study of the Winyah Bay Outflow, Front. Mar. Sci., 8, 785967, https://doi.org/10.3389/fmars.2021.785967, 2022.
Zeiden, K., Thomson, J., and Girton, J.: Estimating profiles of dissipation rate in the upper ocean using acoustic Doppler measurements made from surface-following platforms, J. Atmos. Oceanic Technol., 40, 1571–1589, https://doi.org/10.1175/JTECH-D-23-0027.1, 2023.
Zippel, S. F., Thomson J., and Farquharson, G.: Turbulence from breaking surface waves at a river mouth, J. Phys. Oceanogr., 48, 435–453, https://doi.org/10.1175/JPO-D-17-0122.1, 2018.
Short summary
This study examines the interaction of river and ocean waters in the coastal ocean and how these mix. High resolution field observations of water properties, flow, and turbulence were collected over a period of ~ 4 h. Flow turbulence is responsible for mixing water near the bed and close to the sea surface, but within the freshly discharged waters mixing efficiency appears to be minimal. This is attributed to turbulence not being uniform but concentrated in layers.
This study examines the interaction of river and ocean waters in the coastal ocean and how these...
