Mesoscale Eddy Connectivity in the Atlantic Ocean

Abstract:

The global ocean is filled with mesoscale eddies the presence of which strongly modifies the ocean circulation and the transport or trapping of water masses. In this study, we examine, with the help of satellite observations, the possible connection between remote areas that is achieved by mesoscale eddies in the Atlantic Ocean. To accurately identify and track mesoscale eddies, we use the newly TOEddies detection and tracking algorithm developed at LMD-IPSL (Laxenaire et al., 2018). Applied on daily satellite observations (AVISO/DUACS) of Absolute Dynamic Topography (ADT), TOEddies algorithm provides information on the eddy dynamical characteristics as well as on the interactions between eddies (splitting/merging events). Over the 24 year period (1993-2017) that we analyzed, numerous eddy trajectories with different characteristics, lifetimes and pathways were identified. Several long-lived and coherent mesoscale eddies stand out with lifetimes that could exceed 2 years. However, these large scale mesoscale eddies are not isolated in the turbulent oceanic fields, but both, anticyclonic and cyclonic eddies may undergo complex interactions. The consecutive merging or splitting events that a single eddy may experience, modifies the concept of a unique trajectory associated with one single eddy. In terms of mesoscale connectivity, the TOEddies algorithm reconstructs a complex eddy network that allows for an original assessment of the main eddy routes as well as the eddy origins in the Atlantic ocean. Thus, we demonstrate how long-lived mesoscale eddies could materialize the climatically important link between the eastern and western boundaries of the ocean basins (for example, the southern Africa and American continental slopes). Eventually, we show that when ocean eddies disappear from the altimetry fields, in most cases this does not coincide with a dissipation process but rather to a subduction of the eddy structure.