04 Jun 2024
 | 04 Jun 2024
Status: this preprint is open for discussion.

Semi-analytical approach to study the role of abyssal stratification in the propagation of potential vorticity in a four-layer ocean basin

Beatrice Giambenedetti, Nadia Lo Bue, and Vincenzo Artale

Abstract. Observations of abyssal variability performed in the Ionian Sea (Mediterranean Sea) revealed the presence of a dense stable abyssal layer, whose thermohaline and dynamical properties changed drastically over a decade. Building upon these available observations, we aim to investigate the role that stratification can have on the propagation of vorticity throughout the water column to the abyss, and in turn on the redistribution of the energy stored in the deep sea, with a set of stationary states. A quasi-geostrophic equation with four coupled layers, a free surface, and a mathematical artifice for parametrizing decadal time evolution has been considered, proving that the relative layer thicknesses and the density difference among the layers are the two critical factors that determine the dynamical characteristics of this propagation. The variability of the ocean stratification is a relevant aspect that can activate the deep and intermediate dynamics engaging in the propagation and stabilization of signals throughout the water column. This demonstrates the non-negligible active connection of the dynamics of the bottom layers with the surface. The theoretical framework and the parametrization used were based on specific observations made in the Ionian Sea in the last decades, but without losing general applicability in all ocean basins that are characterized by the presence of a stratified dense water mass in the deep and intermediate layers.

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Beatrice Giambenedetti, Nadia Lo Bue, and Vincenzo Artale

Status: open (until 30 Jul 2024)

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Beatrice Giambenedetti, Nadia Lo Bue, and Vincenzo Artale

Data sets

Post-processed CTD Near-full-depth Data at ER-0121 Site Beatrice Giambenedetti

NEMO-SN1 observatory data Nadia Lo Bue and Giuditta Marinaro

Model code and software

QG4L Beatrice Giambenedetti

Beatrice Giambenedetti, Nadia Lo Bue, and Vincenzo Artale


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Short summary
We applied a simplified model to investigate how the stratification changes in the abyss can impact the propagation of vortices in the ocean. The abyss stratification is typically considered stable, but observations revealed that this is not always a good approximation. We found that changing the deep stratification can introduce variability in the vortices' pattern. Despite the assumption made in our model, our results are confirmed by seafloor observations in the Ionian Sea.