Abstract
Abstract. In the frame of the REP14-MED sea trial in June 2014, the hydrography and circulation west of Sardinia, observed by means of gliders, shipborne CTD (conductivity, temperature, depth) instruments, towed devices, and vessel-mounted ADCPs (acoustic doppler current profilers), are presented and compared with previous knowledge. So far, the circulation is not well-known in this area, and the hydrography is subject to long-term changes. Potential temperature, salinity, and potential density ranges as well as core values of the observed water masses were determined. Modified Atlantic Water (MAW), with potential density anomalies below 28.72 kg m−3, showed a salinity minimum of 37.93 at 50 dbar. Levantine Intermediate Water (LIW), with a salinity maximum of about 38.70 at 400 dbar, was observed within a range of 28.72<σΘ/(kg m−3) < 29.10. MAW and LIW showed slightly higher salinities than previous investigations. During the trial, LIW covered the whole area from the Sardinian shelf to 7°15′ E. Only north of 40° N was it tied to the continental slope. Within the MAW, a cold and saline anticyclonic eddy was observed in the southern trial area. The strongest variability in temperature and salinity appeared around this eddy, and in the southwestern part of the domain, where unusually low saline surface water entered the area towards the end of the experiment. An anticyclonic eddy of Winter Intermediate Water was recorded moving northward at 0.014 m s−1. Geostrophic currents and water mass transports calculated across zonal and meridional transects showed a good agreement with vessel-mounted ADCP measurements. Within the MAW, northward currents were observed over the shelf and offshore, while a southward transport of about 1.5 Sv occurred over the slope. A net northward transport of 0.38 Sv across the southern transect decreased to zero in the north. Within the LIW, northward transports of 0.6 Sv across the southern transects were mainly observed offshore, and decreased to 0.3 Sv in the north where they were primarily located over the slope. This presentation of the REP14-MED observations helps to further understand the long-term evolution of hydrography and circulation in the Western Mediterranean, where considerable changes occurred after the Eastern Mediterranean Transient and the Western Mediterranean Transition.
Highlights
From 6 to 25 June 2014, an extensive experiment called REP14-MED was carried out west of Sardinia in the area between 39◦12 N and 40◦12 N and between 7◦15 E and 8◦18 E (Onken et al, 2017)
The circulation is not well-known in this area, and the hydrography is subject to long-term changes
Within the Modified Atlantic Water (MAW), a cold and saline anticyclonic eddy was observed in the southern trial area
Summary
From 6 to 25 June 2014, an extensive experiment called REP14-MED was carried out west of Sardinia in the area between 39◦12 N and 40◦12 N and between 7◦15 E and 8◦18 E (Onken et al, 2017). These AEs embed less saline water of Atlantic origin and circulate cyclonically within a gyre around the Algerian Basin with a mean speed of a few centimetres per second They have lifetimes of up to 3 years (Puillat et al, 2002), often extending from the surface to about 350 m or deeper, and bring relatively fresh MAW from the Algerian coast to the Sardinian Sea (Millot, 1999; Testor and Gascard, 2005; Olita et al, 2013).
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