Summer breakout of trapped bottom dense water from the northern Adriatic

Abstract

[1] The paper deals with an intriguing dense-water breakout episode in mid-August 2004 which has been observed in the bottom layers of the oil rig located in the middle of the northern Adriatic. Various data (temperature series and vertical T-S profiles, currents, meteorological measurements, and satellite images) have been analyzed in order to understand conditions which preceded, were active, and followed the breakout episode. A stationary bottom pool of dense water, generated during the previous winter, has been suspected to be a source of the dense water observed during the breakout, with a permanent position established by a stationary northern Adriatic cyclonic-anticyclonic gyre system. The breakout lasted for 3 days, advecting the bottom waters more than 2°C colder than residing waters at the oil rig site. The main result of modeling experiments concerns the generative force for the observed breakout which was found to be a mesoscale storm that occurred over the open north Adriatic on 8 August 2004. The storm has been reproduced by the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS 1 ) atmospheric model which was then used to force the Princeton Ocean Model (POM) at the surface. Results of simulations reveal the capability of the storm to break the thermohaline fronts through the wind-induced baroclinic transport and downwelling at the exposed shorelines. This is the first study in the Adriatic which evaluates the impact of mesoscale summer storm to the sea, driving bottom layer circulation through the convergence/divergence dynamics in addition to the direct impact on the sea surface through the wind stress forcing.

Long-term variability and trends of sea level storminess and extremes in European Seas

“…Several processes should be incorporated in these series, being characteristic for the Adriatic Sea: (i) the fundamental Adriatic seiche (Cerovečki et al, 1997;Raicich et al, 1999), with a period of 21-22 h and encompassing about 40% of the super-diurnal energy (Fig. 2); (ii) the higher seiche modes, being noticeable in the northern Adriatic (e.g., Manca et al, 1974); (iii) large ocean waves resonantly generated by a travelling pressure disturbances (so-called meteorological tsunamis, Monserrat et al, 2006;Vilibić and Šepić, 2009); (iv) mesoscale storms, which are strongest during the summertime period (Vilibić et al, 2008); and others. We should add that the imposed 22-28 h filter cuts some of the Adriatic seiche energy from the analyses, but only a smaller part, as the peak energy is at 21.6 h and about 35% of seiche energy is found at periods larger than 22 h (as estimated for the 1957-2002 period) (Vilibić, 2006a).…”

Kilometre-Scale Assessment of the Adriatic Dense Water Multi-Decadal Dynamics

“…Dense waters with PDA equal to or larger than 29.2 kg m -3 are generated throughout most of the years, except for 2014 in NA and 1990NA and , 1994NA and -1997NA and , 2007 and 2014 in KB. The years with the strongest dense water generation (indicated by a PDA maximum larger than 29.5 kg m -3 ) are 1989, 1991, 1999, 2000-2006, 2008, 2012, 2013and 2017in NA, and 1987, 1989, 1993, 1999, 2000-2006, 2008, 2012, 2013 and 2017 in KB. Bottom temperature varies between 6.5 and 21.0 °C in NA and between 8.0 and 17.0 °C in KB (Fig.…”

North Adriatic Dense Water: lessons learned since the pioneering work of Mira Zore-Armanda 60 years ago

“…The second pulse occurs a few weeks to a few months later, emptying relatively slowly the north- ern Adriatic shelf as the PDA difference between the vein and the adjacent waters is much lower than during the first pulse (Janeković et al, 2014;Benetazzo et al, 2014). Then, in late spring, bottom dense waters on the shelf are largely replaced by the advected warmer and saline water though the thermohaline circulation (Orlić et al, 2007), while keeping in isolation some pockets of dense water at depressions or flat regions of the northern Adriatic shelf (Vilibić et al, 2008).…”