High‐Resolution Observations and Tracking of a Dual‐Core Anticyclonic Eddy in the Algerian Basin

Abstract

AbstractMesoscale dynamics in the Mediterranean Sea have been investigated for years, and anticyclonic eddies are regularly observed features in the Algerian Basin. Here we used the AMEDA eddy detection algorithm to track and monitor a particular anticyclonic eddy from its birth to its death. The analysis of remote sensing data sets (AVISO and sea surface temperature) revealed that this anticyclone split from an Algerian eddy, in October 2015, interacted with the North Balearic Front and merged 7 months later, in May 2016, with a similar Algerian eddy. In early spring 2016, a field experiment during the ProtevsMed 2016 cruise thoroughly investigated this eddy, when it was located near the North Balearic Front, taking high‐resolution (Seasoar) hydrological transects, several Conductivity‐Temperature‐Depth (CTD) casts, and Lowered Acoustic Doppler Profiler measurements. In addition, four drifting buoys were released in the eddy core. These in situ measurements revealed that the vertical structure of this anticyclone was made of two water lenses of very different origins (Atlantic Water above and Western Intermediate Water below) spinning together. In the vicinity of the North Balearic Front, which may act as a dynamical barrier to such oceanic structures, the eddy interacted with a subsurface anticyclonic eddy made of modal water, which fostered cross‐front exchanges generating filaments by stirring. The high‐resolution sampling revealed fine‐scale structures both adjacent to the eddy and within its core.