New Insights of the Sicily Channel and Southern Tyrrhenian Sea Variability

Abstract

The dynamics of the Sicily Channel and the southern Tyrrhenian Sea are highly influenced by the seasonal variability of the Mediterranean basin-wide circulation, by the interannual variability of the numerous mesoscale structures present in the Channel, and by the decadal variability of the adjacent Ionian Sea. In the present study, all these aspects are investigated using in-situ (Lagrangian drifter trajectories and Argo float profiles) and satellite data (Absolute Dynamic Topography, Sea Level Anomaly, Sea Surface Temperature, wind products) over the period from 1993 to 2018. The availability of long time series of data and high-resolution multi-sensor surface currents allow us to add new details on the circulation features and on their driving mechanisms and to detect new permanent eddies not yet described in literature. The structures prevailing in winter are mainly driven by wind, whereas those prevailing in summer are regulated by topographical forcing on surface currents. The strength of the surface structures located at the western entrance of the Ionian Sea and of the mesoscale activity along the northern Sicily coast is modulated by the large-scale internal variability. The vertical hydrological characteristics of these mesoscale eddies are delineated using the Argo float profiles inside these structures.

Sea Surface Circulation Structures in the Malta-Sicily Channel from Remote Sensing Data

“…In spring we identify some of the winter structures indicated in Jouini et al [3] and Menna et al [4,5] like the ATC, BAC, MCC, MG, MSG, MRV and the PV as shown in Figure 4b. The ATC flows towards Sicily where two gyres are detached, the cyclonic MG and the anticyclonic MCC circling around Linosa island, most likely due to the influence of the LT at 36°N.…”

“…Due to baroclinic instabilities, the Atlantic current (AC) regularly forms meanders that eventually detach from the current and become either cyclonic or anticyclonic eddies [36] like the ones observed by Jouini et al [3] and Jebri et al [37,38]. Figure 3 shows the SC inter-annual geostrophic circulation derived from the ADT data depicting some of the AC-born structures described in Jouini et al [3] and Menna et al [5] such as the cyclonic Medina Gyre (MG), the cyclonic Messina Rise Vortex (MRV), the anticyclonic Pantelleria Vortex (PV, which in the literature is mentioned as cyclonic), the anticyclonic MSG, the AIS, the Bifurcation Atlantic Current (BAC) and the Atlantic Tunisian Current (ATC). From ADT and SGV, the MSG shows a seasonal semi-permanent behavior and contributes to the channel's circulation along with the AIS.…”

“…• Monthly • Ssalto/Duacs multi-mission L4 altimeter products in the period January 1993 to December 2015 containing daily multi-mission ADT on a 1/8 • × 1/8 • mercator projection grid, and distributed by the Copernicus Marine and Environment Monitoring Service (CMEMS) [4,5,31] were used to calculate SGV where,…”

Ocean Exchange and Circulation

“…A combined use of satellite measurement data and Hybrid Coordinate Ocean Model (HYCOM) reanalysis data, together with the self-organizing map (SOM) method, was used to investigate the east branch of the Kuroshio bifurcation where four coherent patterns associated with mesoscale eddies in the Pacific Ocean were found [4]. On the other hand, generation mechanisms like wind curl and dense water flow of the mesoscale eddies in the Ionian Sea (central Mediterranean) were addressed and some comparisons between the two forcing mechanisms were discussed in the paper by Menna et al [5]. The Sicily Channel, in between the eastern and western Mediterranean basins, is another area characterized by large mesoscale variability and water mass exchanges that was analyzed in the paper by Reyez-Suarez et al [6].…”

“…Geostrophic flow obtained from the altimetry data fits very well with the HF radar data averaged over a few weeks. The paper presented by Menna et al [5] deals with such variability more or less in the same area using a combination of long-term, time-series altimetry data, Sea Surface Temperature (SST), and remotely sensed wind data in order to study the seasonal and multiannual variability of mesoscale structures. Wind data allowed the authors to discuss in detail the generation mechanism of mesoscale eddies and the importance of wind stress and wind stress vorticity fields on their seasonal variability.…”