Abyssal undular vortices in the Eastern Mediterranean basin

Abstract

Abyssal temperature and velocity observations performed within the framework of the neutrino mediterranean observatory, a project devoted to constructing a km 3 -scale underwater telescope for the detection of high-energy cosmic neutrinos, demonstrate cross-fertilization between subnuclear physics and experimental oceanography. Here we use data collected south of sicily in the Ionian abyssal plain of the Eastern mediterranean (Em) basin to show for the first time that abyssal vortices exist in the Em, at depths exceeding 2,500 m. The eddies consist of chains of near-inertially pulsating mesoscale cyclones/anticyclones. They are embedded in an abyssal current flowing towards north-northwest. The paucity of existing data does not allow for an unambiguous determination of the vortex origin. A local generation mechanism seems probable, but a remote genesis cannot be excluded a priori. The presence of such eddies adds further complexity to the discussion of structure and evolution of water masses in the Em.

Submarine vortices derived from natural gas hydrate conversion: a mechanism for ocean mixing

“…Expressed another way, rotation is more likely where vent orifices are larger and flow velocity smaller. A plume similar to that observed by Rubino et al (2012) with an average velocity value U ~10 cm/s, diameter of emissions L ~1.5 km, and f ~2π/24/hr. has an R o value of ~0.9.…”

“…During the LGM, the GHSZ was over ~500 m thick in the vicinity of the vortices reported by Rubino et al (2012) whereas the present GHSZ is only ~200 to 300 m thick (Praeg et al, 2011). As it can be expected that most of the NGH will be in the lower third of the GHSZ, large volumes of NGH have been, and probably continue to be, converted to constituent gas and water.…”

“…These meso-scale vortices are coherent features spanning over several hundreds of meters vertically and multiple km horizontally. Rubino et al (2012) conclude that there was not enough data for unambiguous identification of the mechanism that produced the vortices. In particular, remote sources for the fresher cooler water could not be identified but they suggested that local, unspecified, causes could have been responsible.…”

“…Mean ambient deep water temperatures and salinity are ~13 ˚C and 38.5 0 / 00 respectively, in the vicinity of the vortices (Rubino et al, 2012) which places the NGH stability field at depths below ~1000 m in the water column (Fig. 2).…”

“…Current profilers recorded an abyssal current flowing NNW at ~1.9 cm/s at depths exceeding 2,500 m with dipole mesoscale vortices embedded into the flow. Within the current, the profilers measured in-situ background temperature values of ~13.87°C at the upper and ~13.84 °C at the lower depths (Rubino et al, 2012). The sensors also measured the anomalous intermittent passage of ~0.05 °C colder water within the interior of the mesoscale vortices.…”