Abstract
The mesoscale variability in the Mediterranean Sea is investigated through eddy detection techniques. The analysis is performed over 24 years (1993–2016) considering the three-dimensional (3D) fields from an ocean re-analysis of the Mediterranean Sea (MED-REA). The objective is to achieve a fit-for-purpose assessment of the 3D mesoscale eddy field. In particular, we focus on the contribution of eddy-driven anomalies to ocean dynamics and thermodynamics. The accuracy of the method used to disclose the 3D eddy contributions is assessed against pointwise in-situ measurements and observation-based data sets. Eddy lifetimes ≥ 2 weeks are representative of the 3D mesoscale field in the basin, showing a high probability (> 60%) of occurrence in the areas of the main quasi-stationary mesoscale features. The results show a dependence of the eddy size and thickness on polarity and lifetime: anticyclonic eddies (ACE) are significantly deeper than cyclonic eddies (CE), and their size tends to increase in long-lived structures which also show a seasonal variability. Mesoscale eddies result to be a significant contribution to the ocean dynamics in the Mediterranean Sea, as they account for a large portion of the sea-surface height variability at temporal scales longer than 1 month and for the kinetic energy (50–60%) both at the surface and at depth. Looking at the contributions to ocean thermodynamics, the results exhibit the existence of typical warm (cold) cores associated with ACEs (CEs) with exceptions in the Levantine basin (e.g., Shikmona gyre) where a structure close to a mode-water ACE eddy persists with a positive salinity anomaly. In this area, eddy-induced temperature anomalies can be affected by a strong summer stratification in the surface water, displaying an opposite sign of the anomaly whether looking at the surface or at depth. The results show also that temperature anomalies driven by long-lived eddies (≥ 4 weeks) can affect up to 15–25% of the monthly variability of the upper ocean heat content in the Mediterranean basin.
Highlights
Mesoscale eddies can originate nearly everywhere in the ocean, and typically exhibit different properties with respect to their surroundings, which can be transported as they move around the ocean (Chelton et al, 2007; Chelton et al, 2011b; Zhao et al, 2018)
The eddy population in the Mediterranean Sea was investigated by means of eddy detection and tracking algorithms applied to the 3D dimensional ocean fields from MED-REA over a 24-year period (1993–2016)
We focused on the contributions to ocean dynamics and thermodynamics of eddy-induced anomalies
Summary
Mesoscale eddies can originate nearly everywhere in the ocean, and typically exhibit different properties (e.g., heat, salt, carbon) with respect to their surroundings, which can be transported as they move around the ocean (Chelton et al, 2007; Chelton et al, 2011b; Zhao et al, 2018). Pegliasco et al (2015) observed ACEs with a lens-like structure of isopycnals in the eastern boundary upwelling regions In this context, eddy-detection systems (e.g., Dong et al, 2012; Petersen et al, 2013; Xu et al, 2014; Faghmous et al, 2015; Frenger et al, 2015; Lin et al, 2015) are an ad-hoc diagnostic tool designed to isolate mesoscale features, track them in time, and exclusively analyze the parcel of water trapped inside. Combining multiple observing system networks, from in-situ and remote-sensing, it is possible to investigate eddy-induced anomalies in water mass structures, estimate ocean heat, and salt transport by advective trapping The temporal and spatial co-location with the available Argo profiling floats in certain areas of the ocean is affected by uneven data coverage and sampling frequency (e.g., Liu et al, 2020), which can represent a shortcoming to investigate the properties of water masses induced by the occurrence of 3D eddies
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
