Dynamics of an intensive isolated barotropic eddy in the presence of background vorticity

On Agulhas eddies and Rossby waves travelling by forcing effects

“…An anticyclonic vortex, on the contrary, slides to the bottom of a valley or a trough". This seems to be consistent with Leonov [1995] and Benilov [2005] as well. Leonov [1995] also notes that the average velocities of the eddies crossing the ridge are a little dependent on the initial vertical structure of the eddies, however, there is the following regularity: the greater the advection velocity of a vortex, the greater its meridional displacement per unit of time.…”

“…It is easy to see that the observed anomalies have strong coherence with the passage of topographic features, which indirectly confirms the influence of topography on the speed and direction of the eddy propagation. Leonov [1995] shows that the Agulhas eddies slow down their movement during the crossing of the ridge, and can also be stopped by the ridge or even destroyed [Byrne et al, 1995]. According to Korotayev et al [1997], anticyclones are reluctant to cross the ridges.…”

“…The northern component of the speed decreases when crossing the ridges (see Table 1, tracks 139147, 44929, 61092, 83056, 62705, 116552, 293011, 102254). Korotaev et al [1997] say: "Particularly, a cyclonic vortex tends to drift to the top of a hill or a ridge. An anticyclonic vortex, on the contrary, slides to the bottom of a valley or a trough".…”

“…Another explanation is the large nonlinearity of eddies. Kamenkovich et al [1996] notice that the Agulhas eddies are nonlinear with Rossby number 0 < 0.1. Due to their nonlinearity, eddies have a meridional component to their translation velocity, thereby in the Southern Hemisphere, anticyclonic eddies tend to move to the northwest contrary to cyclones, which move to the southwest.…”

“…Entering the region of the Cape Agulhas, warmer and more salty waters compared to the environment, deflect and deepen isohaline and isotherms in the thermocline [Giulivi and Gordon, 2006] and create in isopycnic medium heterogeneities which can radiate Rossby waves spreading slowly across the South Atlantic [Biastoch et al, 2008;Gnevyshev et al, 2019 sheva et al, 2020a]. Agulhas eddies generated by barotropic and baroclinic instability of the Agulhas Current [Gordon and Haxby, 1990;Guerra et al, 2018;Malysheva et al, 2020aMalysheva et al, , 2020b cross the South Atlantic feeding the surface limb of the Atlantic Meridional Overturning Circulation with warm and salty waters original from the Indian Ocean. Agulhas eddies keep their thermohaline characteristics while moving to the west and transferring heat and salt from the Indian to the Atlantic Ocean.…”