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The T5 expendable bathythermographs reach the greatest depth within the current XBT family. Since the early 1970s, in several areas they have been providing a significant part of available temperature profiles below 1000 m and therefore represent an important resource for ocean climate study. In this paper we present new results from laboratory tests of Sippican T5 and T5/20 probes and analyses of more than 350 XBT–CTD matched pairs from our own field trials and the World Ocean Database (WOD), and we propose an improved fall rate equation (coefficients: A = 6.720 ± 0.025 m s−1, B = 0.001 60 ± 0.000 15 m s−2, Offset = 1.00 ± 0.65 m). Possible influences of probe physical characteristics and initial launch conditions on the probe motion have also been investigated with launching height and probe weight being identified as important factors. Analyses also confirm that fall speed and pure temperature error increase with water temperature, as previously reported for other XBT types. The uncertainties in depth and temperature measurements are then calculated. Finally, a new correction for a global T5 dataset is proposed, with an update of the currently available schemes. [ABSTRACT FROM AUTHOR]

Abstract: We analysed in situ CTD data collected on 36 joint Tunisian–Italian oceanographic cruises in the Tunisia–Sicily Channel (Cap Bon–Mazara del Vallo section) from 1995 to 2009 in order to identify the water masses in the region and to estimate the interannual variability of their hydrological characteristics. Besides the well-known AW (Atlantic Water) and LIW (Levantine Intermediate Water), other water masses have been identified though their presence is neither as steady nor as stable as the aforementioned ones. The WIW (Western Intermediate Water) flows beneath the AW towards the eastern basin while the IW (Ionian Water), with a highly intermittent character, flows within the subsurface layer towards the western basin. The flow of subsurface water (WIW and IW) is affected by intense mixing which modifies the water masses, tending to make them disappear. Moreover, the same hydrological time series produced interesting results concerning the increase in both temperature and salinity in the Tunisia–Sicily Channel. This trend especially concerns the deeper layers (LIW and tEMDW, i.e. transitional Eastern Mediterranean Deep Water) and we hypothesise that this is a direct response to climatic change occurring in the eastern basin. [Copyright &y& Elsevier]

The abyssal Ionian Sea is a deep region of interest for the entire circulation of the Mediterranean since it takes an important role in the ventilation processes of the whole basin (Meccia et al., 2015). To better understand the distribution and transfer of water masses and heat throughout this deep portion of the Mediterranean Sea, we investigate spatial and temporal patterns of diapycnal mixing due to internal waves over the bottom of the Ionian basin. In particular, to identify regional features of the internal wave field in terms of vertical shears and strain, we investigate LADCP and CTD profiles measured across the basin in 2007 (cruise Km3Net), that cover various seafloor morphologies (shelf, shelf break, and abyssal plain). Then, to highlight the crucial role of deep layer mixing processes of the Ionian Sea in changing the baroclinic structure of the whole water column (Artale et al., 2018), we apply the parameterization of dissipation rate of kinetic turbulent energy described by Kunze et al. (2006), by using the largest dataset of deep CTD profiles available from 1977 to nowadays.ReferencesArtale, V., Falcini, F., Marullo, S., Bensi, M., Kokoszka, F., Iudicone, D., & Rubino, A. (2018). Linking mixing processes and climate variability to the heat content distribution of the Eastern Mediterranean abyss. Scientific reports, 8(1), 11317.Meccia, V.L., Borghini, M., Sparnocchia, S. (2015). Abyssal circulation and hydrographic conditions in the Western Ionian Sea during Spring–Summer 2007 and Autumn–Winter 2007–2008. Deep Sea Research Part I, 104, 26-40.Kunze, E., Firing, E., Hummon, J. M., Chereskin, T. K., & Thurnherr, A. M. (2006). Global abyssal mixing inferred from lowered ADCP shear and CTD strain profiles. Journal of Physical Oceanography, 36(8), 1553-1576. [ABSTRACT FROM AUTHOR]

Abstract: An intense observational activity was conducted in the NEMO region, western Ionian Sea, 40nm south-east of Capo Passero (Sicily), in the framework of the KM3NeT project. Several oceanographic cruises were performed from 2006 to 2009 and current measurements carried out. The new data describe the present status of the deep layer and its evolution after the occurrence of a notable change that affected the Eastern Mediterranean water masses and circulation during the 1990’s. In particular, they evidence the presence of a newly formed water mass in the abyssal layer of the Ionian Sea, coming likely from the Adriatic. Deep currents in the region are quite energetic, as already known, and highly variable both spatially and in strength. They are organized in a cyclonic circuit, with a prevalent north-west direction corresponding to the NEMO site. [ABSTRACT FROM AUTHOR]