All Climate Events

Wednesday, March 20, 2019. 10:30AM. Jet drift over topography and jet-topography interactions. Hemant Khatri, Imperial College London. Sponsored by NOAA GFDL. More information here.

Alternating jet patterns have been observed in altimetry and float observations. The jets play an important role in the heat and tracer transport in the oceans. Oceanic jets are seen to possess spatio-temporal variability in the presence of topography. For example, over a zonally sloped topography, the jets tend to tilt from the zonal direction and drift in the meridional direction. In this talk, I will discuss why the jets tilt and drift over topography, and what implications these jets can have on the large-scale circulation. In a baroclinic quasi-geostrophic model, the jets drift to compensate for the potential vorticity (PV) advection across PV isolines by the mean flow. In addition, the drifting jets are directly forced by the imposed vertical shear via coupling through topography. On the other hand, eddies oppose the jets, which is opposite to the case of eddy-driven zonal jets. Also, eddy fluxes are significantly enhanced over topography. Furthermore, in addition to the tilted jets, other large-scale spatial patterns are observed, which efficiently interact and exchange energy. This indicates that oceanic zonal flow patterns can appear due to interactions among various large-scale modes and eddies can transfer energy to meridional scales larger than the jet-width scale set by Rossby waves and eddy energy.