Lagrangian Drifter Dispersion in the Southwestern Atlantic Ocean

• DOI: 10.1175/2011jpo4541.1
• Publication Date: 2011-03-29T17:02:32Z
• Authors: Stefano Berti; Francisco Alves D...; Guglielmo Lacorata; Angelo Vulpiani
• Keywords: 550; FOS: Physical sciences; 2-DIMENSIONAL TURBULENCE; [SDU.STU.OC] Sciences of the Universe [physics]/Earth Sciences/Oceanography; 530; 01 natural sciences; CALIFORNIA CURRENT SYSTEM; 14. Life underwater; SUBMESOSCALE TRANSITION; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; 0105 earth and related environmental sciences; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere; Fluid Dynamics (physics.flu-dyn); Physics - Fluid Dynamics; Nonlinear Sciences - Chaotic Dynamics; SOUTH-ATLANTIC; Physics - Atmospheric and Oceanic Physics; 13. Climate action; Atmospheric and Oceanic Physics (physics.ao-ph); RELATIVE DISPERSION; Chaotic Dynamics (nlin.CD); atlantic ocean; dispersion; lagrangian circulation/transport

Abstract In the framework of Monitoring by Ocean Drifters (MONDO) project, a set of Lagrangian drifters were released in proximity of the Brazil Current, the western branch of the subtropical gyre in the South Atlantic Ocean. The experimental strategy of deploying part of the buoys in clusters offers the opportunity to examine relative dispersion on a wide range of scales. Adopting a dynamical systems approach, the authors focus their attention on scale-dependent indicators, like the finite-scale Lyapunov exponent (FSLE) and the finite-scale (mean square) relative velocity (FSRV) between two drifters as a function of their separation and compare them with classic time-dependent statistical quantities like the mean-square relative displacement between two drifters and the effective diffusivity as functions of the time lag from the release. The authors find that, dependently on the given observable, the quasigeostrophic turbulence scenario is overall compatible with their data analysis, with discrepancies from the expected behavior of 2D turbulent trajectories likely to be ascribed to the nonstationary and nonhomogeneous characteristics of the flow, as well as to possible ageostrophic effects. Submesoscale features of ~O(1) km are considered to play a role, to some extent, in determining the properties of relative dispersion as well as the shape of the energy spectrum. The authors also present numerical simulations of an ocean general circulation model (OGCM) of the South Atlantic and discuss the comparison between experimental and model data about mesoscale dispersion.