LaCasce, J. H., Escartin, J., Chassignet, E. P., & Xu, X. (2018). Jet instability over smooth, corrugated and realistic bathymetry.
J. Phys. Oceanogr., .
Abstract: The stability of a horizontally- and vertically-sheared surface jet is examined, with a focus on the vertical structure of the resultant eddies. Over a flat bottom, the instability is mixed baroclinic/barotropic, producing strong eddies at depth which are characteristically shifted downstream relative to the surface eddies. Baroclinic instability is suppressed over a large slope for retrograde jets (with a flow anti-parallel to topographic wave propagation), and to a lesser extent for prograde jets (with flow parallel to topographic wave propagation), as seen previously. In such cases, barotropic (lateral) instability dominates if the jet is sufficiently narrow. This yields surface eddies whose size is independent of the slope but proportional to the jet width. Deep eddies still form, forced by interfacial motion associated with the surface eddies, but they are weaker than under baroclinic instability and are vertically aligned with the surface eddies. A sinusoidal ridge acts similarly, suppressing baroclinic instability and favoring lateral instability in the upper layer.
A ridge with a 1 km wavelength and an amplitude of roughly 10 m is sufficient to suppress baroclinic instability. Surveys of bottom roughness from bathymetry acquired with shipboard multibeam echosounding reveal that such heights are common, beneath the Kuroshio, the Antarctic Circumpolar Current and, to a lesser extent, the Gulf Stream. Consistent with this, vorticity and velocity cross sections from a 1/50° HYCOM simulation suggest that Gulf Stream eddies are vertically aligned, as in the linear stability calculations with strong topography. Thus lateral instability may be more common than previously thought, due to topography hindering vertical energy transfer.
Penduff, T., Barnier, B., Dewar, W. K., & O'Brien, J. J. (2004). Dynamical Response of the Oceanic Eddy Field to the North Atlantic Oscillation: A Model-Data Comparison.
J. Phys. Oceanogr., 34(12), 2615–2629.
Arruda, W., Zharkov, V., Deremble, B., Nof, D., & Chassignet, E. (2014). A New Model of Current Retroflection Applied to the Westward Protrusion of the Agulhas Current.
J. Phys. Oceanogr., 44(12), 3118–3138.
Sturges, W., & Bozec, A. (2013). A Puzzling Disagreement between Observations and Numerical Models in the Central Gulf of Mexico.
J. Phys. Oceanogr., 43(12), 2673–2681.
Bunge, L., & Clarke, A. J. (2014). On the Warm Water Volume and Its Changing Relationship with ENSO.
J. Phys. Oceanogr., 44(5), 1372–1385.
Yan, Y., Chassignet, E. P., Qi, Y., & Dewar, W. K. (2013). Freshening of Subsurface Waters in the Northwest Pacific Subtropical Gyre: Observations and Dynamics.
J. Phys. Oceanogr., 43(12), 2733–2751.
Skiba, A. W., Zeng, L., Arbic, B. K., Müller, M., & Godwin, W. J. (2013). On the Resonance and Shelf/Open-Ocean Coupling of the Global Diurnal Tides.
J. Phys. Oceanogr., 43(7), 1301–1324.
Nof, D., Zharkov, V., Arruda, W., Pichevin, T., Van Gorder, S., & Paldor, N. (2012). Comments on “On the Steadiness of Separating Meandering Currents”.
J. Phys. Oceanogr., 42(8), 1366–1370.
Nof, D., Jia, Y., Chassignet, E., & Bozec, A. (2011). Fast Wind-Induced Migration of Leddies in the South China Sea.
J. Phys. Oceanogr., 41(9), 1683–1693.
Kara, A. B., Hurlburt, H. E., Rochford, P. A., & O'Brien, J. J. (2004). The Impact of Water Turbidity on Interannual Sea Surface Temperature Simulations in a Layered Global Ocean Model*.
J. Phys. Oceanogr., 34(2), 345–359.