Multiple Lagrangian jet-core structures in the Malvinas Current.

NICOLAS BODNARIUK; MARTIN SARACENO; LAURA A. RUIZ ETCHEVERRY; CLAUDIA G. SIMIONATO; FERNANDO ANDRADE-CANTO; FRANCISCO JAVIER BERON-VERA; JOSEFINA OLASCOAGA

Congreso; 2023 Ocean Surface Topography Science Team Meeting; 2023

CNES

The Malvinas Current in the Southwestern Atlantic is characterized as a system of multiple Lagrangian jets. This is done by applying geodesic theory of Lagrangian Coherent Structures (LCSs) on altimetry-derived velocity, which portrays the jets as shearless-parabolic LCSs. The number, geometry, and spatial disposition of flow-invariant jet-cores organizing the Malvinas Current system are found to vary in time constrained by the regional mesoscale circulation. Independent support for this characterization is provided by trajectories of surface drifters from a deployment of unparalleled dimensions for the region and ocean color images (Fig. 1). The drifters develop the characteristic boomerang-shaped patterns into which passive tracers straddling shearless-parabolic LCSs deform (Fig. 1 left panel). Satellite-derived surface chlorophyll reveals similar ``chevrons,'' which organize about attracting hyperbolic LCSs extracted from altimetry (Fig. 1 right panel). The LCS analysis of altimetry reveals that the jets tend to approach one another upstream, yet not to merge into a single jet as the Eulerian analysis of the data suggests. Consistent with a new solution of arrested topographic wave dynamics, the ocean color imagery also suggests upwelling along the multiple, upstream-approaching Lagrangian jets forming the Malvinas Current system, which may contribute to the modulation of primary productivity in the region. The mesoscale circulation, well-resolved by altimetry, is seen to drive many aspects of the Lagrangian motion in the Southwestern Atlantic, including the effects of mesoscale elliptic LCSs on shaping the evolution of the drifters.