New Insights on the Formation and Breaking Mechanism of Convective Cyclonic Cones in the South Adriatic Pit during Winter 2018

The deepwater formation in the northern part of the South Adriatic Pit (Mediterranean Sea) during winter 2018 is investigated using in-situ glider data. After a period of about 2 weeks from the beginning of the mixing phase, a homogeneous convective area ∼110-km-wide and ∼300-m deep, breaks up due to the baroclinic instability process in cyclonic cones made of geostrophically adjusted fluid. The base of these cones is located at the bottom of the mixed layer, and they extend up to the theoretical critical depth Z_c. These cones, with a diameter on the order of internal Rossby radius of deformation (∼6 km), populate the convective site, develop beneath it, and have a short lifetime of weeks. Later on, they extend deeper and intrusion from deep layers makes their inner core denser and colder. The breaking mechanism of these cyclonic spinning features occurring during the spreading phase and some bio-geochemical aspects associated to their evolution are also addressed. The observed cones differ from the long-lived cyclonic eddies sampled in other ocean sites and formed at the periphery of the convective area in a postconvection period. In-situ data are also corroborated by theoretical studies, laboratory experiments and model simulations.