Area L: Large-Scale and Balanced Processes

Both the large-scale currents and mesoscale eddies in the ocean are essentially quasi-geostrophically balanced in the horizontal and hydrostatically in the vertical. Area L focuses on those processes in the ocean.

Eddies in the ocean

Mesoscale eddies in the ocean, sometimes referred to as the oceanic equivalent of atmospheric storms, derive their energy from the large-scale flow mainly through baroclinic instability processes. These processes are parameterized in climate models with down-gradient parameterizations using eddy diffusivities. In geostrophic turbulence, eddies then tend to transfer their energy upscale in an inverse cascade. But ultimately, this energy has to be dissipated and it is largely unknown how and where.

Our scientists specifically assess one important pathway to dissipation, the spontaneous emission of gravity waves by the quasi-balanced flows, and analyze drifter and float data to estimate eddy production and Lagrangian mixing from observations, models and theory.

Specific research questions in Area L are:

  • How is the balanced flow dissipated in the ocean, and how important is the route to dissipation via spontaneous wave generation?
  • What are the limits and validities of the eddy diffusion model and how can we quantify and parameterize the effects of mesoscale eddies in an energy-consistent way?
  • Neduhal, N., Žagar, N., Lunkeit, F., Polichtchouk, I. & Zaplotnik, Ž. (2024). Decomposition of the Horizontal Wind Divergence Associated With the Rossby, Mixed Rossby-Gravity, Inertia-Gravity, and Kelvin Waves on the Sphere. Journal of Geophysical Research: Atmospheres, 129, e2023JD040427, doi: https://doi.org/10.1029/2023JD040427

  • Oliver, M. & Tiofack Kenfack, M.A. (2024). Deterministic and stochastic surrogate models for a slowly driven fast oscillator. SIAM J. Appl. Dyn. Syst. 23(2), 1090-1107, doi: https://doi.org/10.1137/23M1602176

  • Schmitt, M., Pham, H.T., Sarkar, S., Klingbeil, K. & Umlauf, L. (2024). Diurnal warm layers in the ocean: energetics, non-dimensional scaling, and parameterization. J. Phys. Oceanogr. 54(4), 1037-1055, doi: https://doi.org/10.1175/JPO-D-23-0129.1.

  • North, R., Dräger-Dietel, J. & Griesel, A. (2024). Characterization of physical properties of a coastal upwelling filament with evidence of enhanced submesoscale activity and transition from balanced to unbalanced motions in the Benguela Upwelling Region. Ocean Science 20, 103–121, doi: https://doi.org/10.5194/os-20-103-2024

  • Žagar, N., Neduhal, V., Vasylkevych, S. et al. (2023). Decomposition of vertical velocity and its zonal wavenumber kinetic energy spectra in the hydrostatic atmosphere. J. Atmos. Sci. 80(11), 2747–2767, doi: https://doi.org/10.1175/JAS-D-23-0090.1.

  • Chouksey, M., Eden, C., Masur, G. & Oliver, M. (2023). A comparison of methods to balance geophysical flows. J. Fluid Mech. 971, A2, doi: https://doi.org/10.1017/jfm.2023.602

  • Shevchenko, R., Hohenegger, C., & Schmitt, M. (2023). Impact of diurnal warm layers on atmospheric convection. J. Geophys. Res. - Atmospheres 128(14), e2022JD038473, doi: https://doi.org/10.1029/2022JD038473

  • Umlauf, L., Klingbeil K., Radke, H., Schwefel, R., Bruggeman, J. & Holtermann, P.L. (2023). Hydrodynamic control of sediment-water fluxes: Consistent parameterization and impact in coupled benthic-pelagic models. J. Geophys. Res. - Oceans 128, e2023JC019651, doi: https://doi.org/10.1029/2023JC019651

  • Shi, J., Stepanek, C., Sein, D., Streffing, J., & Lohmann, G. (2023). East Asian summer precipitation in AWI-CM3: Comparison with observations and CMIP6 models. International Journal of Climatology, 1– 16, doi: https://doi.org/10.1002/joc.8075

  • Pithan, F., Athanase, M., Dahlke, S., Sánchez-Benítez, A., Shupe, M. D., Sledd, A., Streffing, J., Svensson, G., & Jung, T. (2023). Nudging allows direct evaluation of coupled climate models with in situ observations: a case study from the MOSAiC expedition. Geosci. Model Dev. 16(7), 1857–1873, doi: https://doi.org/10.5194/gmd-16-1857-2023