Effects of winter convection on the deep layer of the Southern Adriatic Sea in 2012

Abstract

We analyze aspects concerning the thermohaline changes observed in the near‐bottom layer of the Southern Adriatic Pit (SAP), in the Eastern Mediterranean, after the arrival of abundant and exceptionally dense water (σθ > 30 kg m−3) produced in the shallow Northern Adriatic Sea during winter 2012. For this purpose, we use temperature (T), salinity (S), and current time series collected at the E2M3A deep‐ocean observatory of the Southern Adriatic, and Conductivity‐Temperature‐Depth data obtained both in the Southern and Middle Adriatic from freely drifting profiling floats. The dense water produced in the Northern Adriatic arrived in the central and deepest part of the SAP as a series of individual pulses starting on 10 March 2012; while, a stronger and prolonged signal that significantly modified the local deep water stratification arrived after 10 April 2012. As a consequence, T and S suddenly decreased (≈0.15°C and ≈0.015), thus interrupting positive T and S bottom trends observed during the previous 5 years and producing a density increase of ≈0.02 kg m−3. Such variability has been rarely observed in the area. We ascribe its occurrence to the concomitance of exceptionally harsh and long‐lasting Bora wind, scarce precipitation, and low river discharge over the Northern Adriatic during winter 2011/2012. Eventually, this newly formed AdDW reached the Strait of Otranto during July 2012. Its characteristics profoundly differed from those observed in the previous decade. Hence, a noticeable variability in structure and circulation of the abyssal layers of the Ionian basin is likely to occur in the near future.

Extreme winter 2012 in the Adriatic: an example of climatic effect on the BiOS rhythm

“…According to recent papers (Bensi et al, 2013;Mihanović et al, 2013;Vilibić et al, 2013) the winter of 2012 was very harsh in the northern Adriatic resulting in the formation of extremely dense bottom water in the shelf area. Density anomaly recorded in the northernmost end of the Adriatic attained 30.59 kg m −3 , the value reached only twice in the last 100 years.…”

Interannual variability of the Mediterranean trophic regimes from ocean color satellites

“…3). Intense deep convection events were reported in 2005, 2006winters (Civitarese et al, 2010Bensi et al, 2013) when the area is classed as "Bloom #5". Less intense convection, reported for the winters 2000, 2008, 2009(Gacic et al, 2002Bensi et al, 2013), seems to be associated with "Intermediate #4" or "No Bloom #5" regimes.…”

River runoff influences on the Central Mediterranean overturning circulation

“…Moreover the SAd deep layers are partially filled by the NAd dense water which partially the MAd Pit and partially flows southward over the Italian western shelf and reaches the Bari Canyon, usually 2 months after its generation. Here the boundary current of NAd dense water mixes turbulently with adjacent warmer and less saline waters and sinks to the Southern Adriatic Pit (Vilibić and Orlić 2001;Bensi et al 2013b). Figure 12 shows the dense water volume formed in the NAd, MAd and SAd sub-regions computed as the water volume with larger potential density anomaly than the threshold value, 29.2 kg m −3 .…”

“…1). The lower branch of the CMOC is connected with the outflowing of the Southern Adriatic dense waters (Artegiani et al 1997a;Orlić 2001-2002;Manca et al 2002;Lascaratos 2004, 2008;Wang et al 2007;Bensi et al 2013b) in the Ionian abyssal basin. Several authors discussed that, during the EMT, the Adriatic source of Ionian abyssal waters could have been replaced by the Cretan Sea deep waters (Roether et al 1996;Roussenov et al 2001;Curchitser et al 2001;Manca et al 2003;Rubino and Hainbucher 2007;Ursella et al 2011;Rubino et al 2012;Bensi et al 2013a).…”