• Bachman, S. D., B. Fox-Kemper, J. R. Taylor, and L. N. Thomas, 2017: Parameterization of frontal symmetric instabilities. I: Theory for resolved fronts. Ocean Modell., 109, 7295, https://doi.org/10.1016/j.ocemod.2016.12.003.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Balwada, D., J. H. LaCasce, and K. G. Speer, 2016: Scale-dependent distribution of kinetic energy from surface drifters in the Gulf of Mexico. Geophys. Res. Lett., 43, 10 856–10 863, https://doi.org/10.1002/2016GL069405.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Boccaletti, G., R. Ferrari, and B. Fox-Kemper, 2007: Mixed layer instabilities and restratification. J. Phys. Oceanogr., 37, 22282250, https://doi.org/10.1175/JPO3101.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Capet, X., J. C. McWilliams, M. J. Molemaker, and A. Shchepetkin, 2008: Mesoscale to submesoscale transition in the California Current System. Part II: Frontal processes. J. Phys. Oceanogr., 38, 4464, https://doi.org/10.1175/2007JPO3672.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Carpenter, J. R., A. Rodrigues, L. K. P. Schultze, L. M. Merckelbach, N. Suzuki, B. Baschek, and L. Umlauf, 2020: Shear instability and turbulence within a submesoscale front following a storm. Geophys. Res. Lett., 47, e2020GL090365, https://doi.org/10.1029/2020GL090365.

    • Crossref
    • Export Citation
  • Chrysagi, E., L. Umlauf, P. Holtermann, K. Klingbeil, and H. Burchard, 2021: High-resolution simulations of submesoscale processes in the Baltic Sea: The role of storm events. J. Geophys. Res. Oceans, 126, e2020JC016411, https://doi.org/10.1029/2020JC016411.

    • Crossref
    • Export Citation
  • D’Asaro, E., C. Lee, L. Rainville, R. Harcourt, and L. Thomas, 2011: Enhanced turbulence and energy dissipation at ocean fronts. Science, 332, 318322, https://doi.org/10.1126/science.1201515.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dauhajre, D. P., and J. C. McWilliams, 2018: Diurnal evolution of submesoscale front and filament circulations. J. Phys. Oceanogr., 48, 23432361, https://doi.org/10.1175/JPO-D-18-0143.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dauhajre, D. P., J. C. McWilliams, and Y. Uchiyama, 2017: Submesoscale coherent structures on the continental shelf. J. Phys. Oceanogr., 47, 29492976, https://doi.org/10.1175/JPO-D-16-0270.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Edson, J. B., and et al. , 2013: On the exchange of momentum over the open ocean. J. Phys. Oceanogr., 43, 15891610, https://doi.org/10.1175/JPO-D-12-0173.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fairall, C., E. F. Bradley, J. Hare, A. Grachev, and J. Edson, 2003: Bulk parameterization of air-sea fluxes: Updates and verification for the COARE algorithm. J. Climate, 16, 571591, https://doi.org/10.1175/1520-0442(2003)016<0571:BPOASF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Feistel, R., and et al. , 2010: Density and absolute salinity of the Baltic Sea 2006–2009. Ocean Sci., 6, 324, https://doi.org/10.5194/os-6-3-2010.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Golub, G. H., and C. F. V. Loan, 2013: Matrix Computations. 4th ed. The Johns Hopkins University Press, 784 pp.

  • Grisouard, N., 2018: Extraction of potential energy from geostrophic fronts by inertial–symmetric instabilities. J. Phys. Oceanogr., 48, 10331051, https://doi.org/10.1175/JPO-D-17-0160.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gula, J., M. J. Molemaker, and J. C. McWilliams, 2014: Submesoscale cold filaments in the Gulf Stream. J. Phys. Oceanogr., 44, 26172643, https://doi.org/10.1175/JPO-D-14-0029.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Haine, T. W., and J. Marshall, 1998: Gravitational, symmetric, and baroclinic instability of the ocean mixed layer. J. Phys. Oceanogr., 28, 634658, https://doi.org/10.1175/1520-0485(1998)028<0634:GSABIO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., 1982: The mathematical theory of frontogenesis. Annu. Rev. Fluid Mech., 14, 131151, https://doi.org/10.1146/annurev.fl.14.010182.001023.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Johnson, L., C. M. Lee, E. A. D’Asaro, L. Thomas, and A. Shcherbina, 2020: Restratification at a California Current upwelling front. Part I: Observations. J. Phys. Oceanogr., 50, 14551472, https://doi.org/10.1175/JPO-D-19-0203.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., 2016: Submesoscale currents in the ocean. Proc. Roy. Soc. London, 472, 20160117, https://doi.org/10.1098/rspa.2016.0117.

    • Crossref
    • Export Citation
  • Millero, F. J., R. Feistel, D. G. Wright, and T. J. McDougall, 2008: The composition of standard seawater and the definition of the reference-composition salinity scale. Deep-Sea Res. I, 55, 5072, https://doi.org/10.1016/j.dsr.2007.10.001.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Molinari, R., and A. D. Kirwan, 1975: Calculations of differential kinematic properties from Lagrangian observations in the western Caribbean Sea. J. Phys. Oceanogr., 5, 483491, https://doi.org/10.1175/1520-0485(1975)005<0483:CODKPF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ohlmann, J. C., M. J. Molemaker, B. Baschek, B. Holt, G. Marmorino, and G. Smith, 2017: Drifter observations of submesoscale flow kinematics in the coastal ocean. Geophys. Res. Lett., 44, 330337, https://doi.org/10.1002/2016GL071537.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pearson, J., B. Fox-Kemper, R. Barkan, J. Choi, A. Bracco, and J. C. McWilliams, 2019: Impacts of convergence on structure functions from surface drifters in the Gulf of Mexico. J. Phys. Oceanogr., 49, 675690, https://doi.org/10.1175/JPO-D-18-0029.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Peng, J.-P., 2020: Frontal instability and energy dissipation in submesoscale fronts. Ph.D. thesis, Leibniz-Institut für Ostseeforschung Warnemünde (IOW), Universität Rostock, 65 pp.

  • Peng, J.-P., P. Holtermann, and L. Umlauf, 2020: Frontal instability and energy dissipation in a submesoscale upwelling filament. J. Phys. Oceanogr., 50, 20172035, https://doi.org/10.1175/JPO-D-19-0270.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Poje, A., T. M. Ozgokmen, D. J. Bogucki, and A. D. Kirwan, 2017: Evidence of a forward energy cascade and Kolmogorov self-similarity in submesoscale ocean surface drifter observations. Phys. Fluids, 29, 020700, https://doi.org/10.1063/1.4974331.

    • Crossref
    • Export Citation
  • Pollard, R. T., 1970: On the generation by winds of inertial waves in the ocean. Deep-Sea Res. Oceanogr. Abstr., 17, 795812, https://doi.org/10.1016/0011-7471(70)90042-2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Simpson, J. H., J. Brown, J. Matthews, and G. Allen, 1990: Tidal straining, density currents, and stirring in the control of estuarine stratification. Estuaries, 13, 125132, https://doi.org/10.2307/1351581.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Skyllingstad, E. D., and R. Samelson, 2012: Baroclinic frontal instabilities and turbulent mixing in the surface boundary layer. Part I: Unforced simulations. J. Phys. Oceanogr., 42, 17011716, https://doi.org/10.1175/JPO-D-10-05016.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stone, P. H., 1966: On non-geostrophic baroclinic stability. J. Atmos. Sci., 23, 390400, https://doi.org/10.1175/1520-0469(1966)023<0390:ONGBS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sun, D., and et al. , 2020: Diurnal cycling of submesoscale dynamics: Lagrangian implications in drifter observations and model simulations of the northern Gulf of Mexico. J. Phys. Oceanogr., 50, 16051623, https://doi.org/10.1175/JPO-D-19-0241.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Taylor, J. R., and R. Ferrari, 2010: Buoyancy and wind-driven convection at mixed layer density fronts. J. Phys. Oceanogr., 40, 12221242, https://doi.org/10.1175/2010JPO4365.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thomas, L. N., 2005: Destruction of potential vorticity by winds. J. Phys. Oceanogr., 35, 24572466, https://doi.org/10.1175/JPO2830.1.

  • Thomas, L. N., and J. Taylor, 2010: Reduction of the usable wind-work on the general circulation by forced symmetric instability. Geophys. Res. Lett., 37, L18606, https://doi.org/10.1029/2010GL044680.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thomas, L. N., J. R. Taylor, R. Ferrari, and T. M. Joyce, 2013: Symmetric instability in the Gulf Stream. Deep-Sea Res. II, 91, 96110, https://doi.org/10.1016/j.dsr2.2013.02.025.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thomas, L. N., J. R. Taylor, E. A. D’Asaro, C. M. Lee, J. M. Klymak, and A. Shcherbina, 2016: Symmetric instability, inertial oscillations, and turbulence at the Gulf Stream front. J. Phys. Oceanogr., 46, 197217, https://doi.org/10.1175/JPO-D-15-0008.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wang, P., J. C. McWilliams, and C. Ménesguen, 2014: Ageostrophic instability in rotating, stratified interior vertical shear flows. J. Fluid Mech., 755, 397428, https://doi.org/10.1017/jfm.2014.426.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yu, X., A. C. Naveira Garabato, A. P. Martin, D. Gwyn Evans, and Z. Su, 2019: Wind-forced symmetric instability at a transient mid-ocean front. Geophys. Res. Lett., 46, 11 28111 291, https://doi.org/10.1029/2019GL084309.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zemskova, V. E., P.-Y. Passaggia, and B. L. White, 2020: Transient energy growth in the ageostrophic Eady model. J. Fluid Mech., 888, A29, https://doi.org/10.1017/jfm.2019.902.

    • Crossref
    • Search Google Scholar
    • Export Citation
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Diurnal Variability of Frontal Dynamics, Instability, and Turbulence in a Submesoscale Upwelling Filament

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  • 1 a Leibniz-Institute for Baltic Sea Research Warnemünde (IOW), Rostock, Germany
  • | 2 b Institut für Meereskunde, Universität Hamburg, Hamburg, Germany
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Abstract

Recent high-resolution numerical simulations have shown that the diurnal variability in the atmospheric forcing strongly affects the dynamics, stability, and turbulence of submesoscale structures in the surface boundary layer (SBL). Field observations supporting the real-ocean relevance of these studies are, however, largely lacking at the moment. Here, the impact of large diurnal variations in the surface heat flux on a dense submesoscale upwelling filament in the Benguela upwelling system is investigated, based on a combination of densely spaced turbulence microstructure observations and surface drifter data. Our data show that during nighttime and early morning conditions, when solar radiation is still weak, frontal turbulence is generated by a mix of symmetric and shear instability. In this situation, turbulent diapycnal mixing is approximately balanced by frontal restratification associated with the cross-front secondary circulation. During daytime, when solar radiation is close to its peak value, the SBL quickly restratifies, the conditions for frontal instability are no longer fulfilled, and SBL turbulence collapses except for a thin wind-driven layer near the surface. The drifter data suggest that inertial oscillations periodically modulate the stability characteristics and energetics of the submesoscale fronts bounding the filament.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Jen-Ping Peng, jen-ping.peng@io-warnemuende.de

Abstract

Recent high-resolution numerical simulations have shown that the diurnal variability in the atmospheric forcing strongly affects the dynamics, stability, and turbulence of submesoscale structures in the surface boundary layer (SBL). Field observations supporting the real-ocean relevance of these studies are, however, largely lacking at the moment. Here, the impact of large diurnal variations in the surface heat flux on a dense submesoscale upwelling filament in the Benguela upwelling system is investigated, based on a combination of densely spaced turbulence microstructure observations and surface drifter data. Our data show that during nighttime and early morning conditions, when solar radiation is still weak, frontal turbulence is generated by a mix of symmetric and shear instability. In this situation, turbulent diapycnal mixing is approximately balanced by frontal restratification associated with the cross-front secondary circulation. During daytime, when solar radiation is close to its peak value, the SBL quickly restratifies, the conditions for frontal instability are no longer fulfilled, and SBL turbulence collapses except for a thin wind-driven layer near the surface. The drifter data suggest that inertial oscillations periodically modulate the stability characteristics and energetics of the submesoscale fronts bounding the filament.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Jen-Ping Peng, jen-ping.peng@io-warnemuende.de

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