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In this paper a process study aimed at analyzing the low-frequency variability of intrinsically oceanic origin of the Gulf Stream (GS) and GS extension (GSE) is presented. An eddy-permitting reduced-gravity nonlinear shallow water model is implemented in an idealized North Atlantic Ocean, with schematic boundaries including the essential geometric features of the coastline and a realistic zonal basin width at all latitudes. The forcing is provided by a time-independent climatological surface wind stress obtained from 41 years of monthly ECMWF fields. The model response yields strong intrinsic low-frequency fluctuations on the interannual to decadal time scales. The modelled time-averaged GS/GSE flows are found to exhibit several features that can also be deduced from satellite altimeter data, such as the Florida Current seaward deflection, the GS separation at Cape Hatteras, and the overall structure of the GSE. The intrinsic low-frequency variability yields two preferred states of the GSE differing in latitudinal location that also have their counterpart in the altimeter data. A preliminary analysis of the variability in terms of dynamical systems theory is carried out by using the lateral eddy viscosity as the control parameter. A complex transition sequence from a steady state to irregular low-frequency variability emerges, in which Hopf and global bifurcations can be identified.

In this paper, sequential importance sampling is used to assess the impact of observations on an ensemble prediction for the decadal path transitions of the Kuroshio Extension. This particle-filtering approach gives access to the probability density of the state vector, which allows the predictive power—an entropy-based measure—of the ensemble prediction to be determined. The proposed setup makes use of an ensemble that, at each time, samples the climatological probability distribution. Then, in a postprocessing step, the impact of different sets of observations is measured by the increase in predictive power of the ensemble over the climatological signal during one year. The method is applied in an identical-twin experiment for the Kuroshio Extension using a reduced-gravity shallow-water model. This study investigates the impact of assimilating velocity observations from different locations during the elongated and the contracted meandering states of the Kuroshio Extension. Optimal observation locations correspond to regions with strong potential vorticity gradients. For the elongated state the optimal location is in the first meander of the Kuroshio Extension. During the contracted state it is located south of Japan, where the Kuroshio separates from the coast.

In the coastal sector of NW Sicily, the regional correlation of relevant unconformities recognised within the Quaternary sedimentary successions allowed the mapping of seven unconformity-bounded stratigraphic units (UBSUs). The regional unconformities are marine or subaerial erosional surfaces, as well as non-depositional surfaces, locally marked by paleosoils. The erosional surfaces were produced from marine abrasion, surface water overland/concentrated flow, river erosion, karst solution, mass movement, or wind erosion. The main lithofacies of the Quaternary UBSUs consist of: (a) marine and coastal bioclastic calcarenites, (b) aeolian sandstones, (c) river deposits, (d) colluvial deposits, (e) talus slope deposits, (f) landslide deposits, and (g) chemical carbonates (travertines and speleothems). Quaternary environmental changes, due to tectonics, climate, and sea-level oscillations, are the causes that favoured the development of erosion/deposition processes responsible for the genesis of unconformities and deposits. As a result, through the UBSU map of the NW Sicilian coastal belt, it is possible to: (i) recognise stratigraphic units controlled by tectonic, climatic, and environmental processes (and their interplay) and (ii) detect Quaternary sedimentary evolution.

The Campania coastal system (CCS), located in the Tyrrhenian Sea, is characterized by an interesting and complex morphology, being made by a sequence of three gulfs (Gaeta, Naples and Salerno, GG, GN, GS) of different sizes, shapes, and bathymetries. Until now, most of the oceanographic studies in the area have focused on the GN, whereas little is known about the circulation in the GG and GS. Here, for the first time, a high-resolution modelling study of the whole CCS has been carried out, which covers a whole year (2016), allowing for a detailed description of the seasonal variability throughout this year. For each season, the dynamics in the three gulfs have been characterized, assessing the relative roles of the wind forcing, the topographic constraints and the remote large-scale Tyrrhenian Sea circulation. As a first step, the surface circulation patterns in the CCS have been compared with altimeter observations and with the atmospheric forcing. A detailed analysis of the monthly mean surface and intermediate circulation within each gulf has then been performed. Besides, a more quantitative insight into the mechanisms controlling the circulation has been obtained using an integrated vorticity diagnostic, which allows one to separate different contributions to the total barotropic vorticity equation. The results show a strong seasonality of the circulation in the three gulfs, which is mainly controlled by the wind stress input during autumn and winter, whereas in spring and summer the main contribution comes from the combined effect of baroclinicity and topographic gradient (the JBAR term). The exchanges between the gulfs and the Tyrrhenian waters have also been quantified, through the analysis of the transport across specific sections. These transports are found to be highly correlated with the offshore large-scale circulation in the GG, whereas in the GS there is strong correlation with the local wind forcing. Finally, lower correlations are found for the more geometrically complex and semi-enclosed GN.

We present a 1:25.000 scale geological map of the Kumeta-Pizzuta ridge in north-western Sicily (Italy), achieved by integrating stratigraphic, structural and geophysical data. In this area, the tectonic edifice results from the piling-up of deep-water-, carbonate platform- and pelagic platform-derived tectonic units (Imerese and Sicilide, Panormide and Trapanese domains, respectively) resulting from deformations of the former southern Tethyan continental margin. The structural setting shows interference of tectonic events, different types of structural styles and different scales of deformational patterns. Early overthrust of the Imerese on the Trapanese units (since the late Serravallian) was followed by wedging at depth of the Trapanese units (after the Tortonian). The wedging implied re-embrication and shortening into the overlying Imerese tectonic units and so produced the main folding and compressive to transpressive structures along the Kumeta-Pizzuta Ridge. Seismic reflection profiles integrated with field data reveal that the main E-W-trending anticlines have been offset by high-angle reverse faults flattening at depth until they connect with low-angle, regionally widespread, decollement surfaces with a northward tectonic transport. This setting supports backthrusting along transpressional faults in the study area, ruling out that the Kumeta ridge is a positive flower structure related to a near-vertical deep, crustal, shear zone as formerly suggested.