Meanders and eddy formation by a buoyant coastal current flowing over a sloping topography

Author:

Cimoli Laura,Stegner Alexandre,Roullet Guillaume

Abstract

Abstract. This study investigates the linear and non-linear instability of a buoyant coastal current flowing along a sloping topography. In fact, the bathymetry strongly impacts the formation of meanders or eddies and leads to different dynamical regimes that can both enhance or prevent the cross-shore transport. We use the Regional Ocean Modeling System (ROMS) to run simulations in an idealized channel configuration, using a fixed coastal current structure and testing its unstable evolution for various depths and topographic slopes. The experiments are integrated beyond the linear stage of the instability, since our focus is on the non-linear end state, namely the formation of coastal eddies or meanders, to classify the dynamical regimes. We find three non-linear end states, whose properties cannot be deduced solely from the linear instability analysis. They correspond to a quasi-stable coastal current, the propagation of coastal meanders, and the formation of coherent eddies. We show that the topographic parameter Tp, defined as the ratio of the topographic Rossby wave speed over the current speed, plays a key role in controlling the amplitude of the unstable cross-shore perturbations. This result emphasizes the limitations of linear stability analysis to predict the formation of coastal eddies, because it does not account for the non-linear saturation of the cross-shore perturbations, which is predominant for large negative Tp values. We show that a second dimensionless parameter, the vertical aspect ratio γ, controls the transition from meanders to coherent eddies. We suggest the use of the parameter space (Tp, γ) to describe the emergence of coastal eddies or meanders from an unstable buoyant current. By knowing the values of Tp and γ for an observed flow, which can be calculated from hydrological sections, we can identify which non-linear end state characterizes that flow – namely if it is quasi-stable, meanders, or forms eddies.

Publisher

Copernicus GmbH

Subject

Cell Biology,Developmental Biology,Embryology,Anatomy

Cited by 6 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Parameterizing Eddy Buoyancy Fluxes Across Prograde Shelf/Slope Fronts Using a Slope-Aware GEOMETRIC Closure;Journal of Physical Oceanography;2024-02

2. Scalings for Eddy Buoyancy Fluxes Across Prograde Shelf/Slope Fronts;Journal of Advances in Modeling Earth Systems;2022-12

3. Meanders of the West Greenland Current near Cape Farewell;Deep Sea Research Part I: Oceanographic Research Papers;2022-01

4. Why Does the Deep Western Boundary Current “Leak” around Flemish Cap?;Journal of Physical Oceanography;2020-07-01

5. Submesoscale Turbulence over a Topographic Slope;Fluids;2018-05-07

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