Observational Evidence of the Basin‐Wide Gyre Reversal in the Gulf of Taranto

Abstract

The paper shows for the first time the observational evidence of basin-wide gyre reversal in the Gulf of Taranto (north-western Ionian Sea in the eastern Mediterranean Sea) by means of two specifically designed in situ oceanographic campaigns (based on CTD and ADCP measurements). The analysis of the in situ data shows a change in circulation from anticyclonic in October 2014 to cyclonic in June-July 2016. Furthermore, long-term (1993-2018) analysis using gridded satellite altimetry data in the Gulf of Taranto shows that the cyclonic gyres are more frequent than anticyclonic gyres. The latter occur only for 2 to 3 years at a time in some decades. Plain Language Summary The work shows the observational evidence of a phenomenon named gyre reversal (the circulation changes from cyclonic to anticyclonic), occurring in ocean regions with specific geometry characteristics, among others the Gulfs. In particular, our results unequivocally show for the first time the reversal of the basin-scale gyre circulation in the Gulf of Taranto (north-western Ionian Sea in the eastern Mediterranean Sea), by means of in situ oceanographic measurements and satellite data.

Environmental variables and machine learning models to predict cetacean abundance in the Central-eastern Mediterranean Sea

“…Therefore, when the group size counting is inaccurate, the regression model will be trained on wrong data, affecting the value of the RMSE computed. To test this hypothesis, the dataset S has been split into four subsets, according to the size of the observed groups during the sightings: S 1 contains 585 sightings whose group size ranges from 1 to 30; S 2 counts 362 sightings with group size varying in the interval [31,60]; S 3 contains 135 sightings whose group size ranges from 61 to 90; S 4 counts 145 sightings with group size in the interval [91,150] (see Table 2 and Fig. 1).…”

“…The continental shelves-area shallower than 200 m-cover 10% of the total Gulf area. Wider shelves are present on the eastern side (Apulia), and five main rivers (Bradano, Basento, Agri, Sinni, and Crati) discharge from the western coastline with a relatively low annual mean runoff 91 . The morphology involves a complex distribution of water masses with a mixing of surface and dense bottom waters with the occurrence of high seasonal variability in upwelling currents [92][93][94][95] .…”

“…The morphology involves a complex distribution of water masses with a mixing of surface and dense bottom waters with the occurrence of high seasonal variability in upwelling currents [92][93][94][95] . From the oceanographic point of view, the basin-scale circulation of the Gulf is dominated by cyclonic gyres, with reversals in anti-cyclonic patterns occurring only 10-15 times for the period 1993-2018 91 . The ecosystem variabilities and changes (e.g., anomalous chlorophyll a bloom 96 ) could be affected by the formation of downwelling/upwelling in the case of cyclonic/anti-cyclonic patterns.…”

Variation in the stable isotope trophic position of the bluefish Pomatomus saltatrix (Linnaeus, 1766) from two Mediterranean sites: insights from a global meta-analysis

“…The north-western coasts of the gulf generally consist of low sandy beaches characterized by the mouths of five main rivers (i.e., Bradano, Basento, Agri, Sinni, and Crati) and a wide continental shelf gradually slanting toward the continental slope (Aiello et al, 2013;Verri et al, 2018;Pellicani et al, 2020). The basin-scale circulation is characterized by cyclonic and anticyclonic gyres with a rim current which undergoes instabilities and forms sub-mesoscale structures (Federico et al, 2020). In contrast, the Italian coasts of the Strait of Otranto are characterized by narrow beaches, a negligible hydrographic network and a steep shelf slope, reaching depths of 200 m at less than 8 nautical miles from the coast (Cataudella & Spagnolo, 2011;Pantusa et al, 2018).…”

A Relocatable Ocean Modeling Platform for Downscaling to Shelf-Coastal Areas to Support Disaster Risk Reduction

“…The Taranto Seas are a set of interlinked embayments, the larger of which covering a 7.5 km-wide elliptical embayment with dominant estuarine dynamics (De Pascalis et al, 2015), The larger embayment, called simply the Taranto Sea, is linked to the Taranto Gulf open sea and is an area of relatively intense tidal currents. Complex dynamics characterize the offshore areas of the Taranto Gulf, with basin-wide gyre reversals (Federico et al, 2020) that drive opposite current directions in the near-shore. Thus, a high resolution is required for the Taranto Sea while simultaneously keeping the connection with the open sea area currents.…”