Oceanic mesoscale eddy depletion catalyzed by internal waves

Abstract

The general circulation of the ocean is strongly constrained by the pathways that kinetic and available potential energy take from the basin-scale forces that inject them to centimeter scales, where they are depleted. To determine the ocean's response to future climate scenarios, these energy pathways, from forcing to dissipation, must be understood and quantified.Mesoscale eddies, with horizontal scales on the order of 100 km and timescales longer than many days, are well known as the dominant reservoir of kinetic energy (KE) in the oceans (Wunsch & Ferrari, 2004). But because their dynamics are constrained by an approximate geostrophic and hydrostatic force balance, they are characterized by an inverse KE cascade, and by themselves do not provide the necessary forward scale-transfer to dissipation (Müller et al., 2005). Possible mechanisms to interrupt the mesoscale inverse cascade include interaction with the bottom topography and boundary layer (

Spatio‐Temporal Coarse‐Graining Decomposition of the Global Ocean Geostrophic Kinetic Energy

“…In order to understand the multiscale nature of oceanic flows, while simultaneously resolving them in space and in time, we use a "coarse-graining" framework that is relatively new in physical oceanography (Aluie et al, 2018;Barkan et al, 2021;Busecke & Abernathey, 2019;Contreras et al, 2023;Haigh et al, 2021;Khani & Dawson, 2023;Khatri et al, 2023;Loose et al, 2023;Rai et al, 2021;Schubert et al, 2020;Srinivasan et al, 2019).…”

The influence of merger and convection on an anticyclonic eddy trapped in a bowl

“…In the LV case, Fer et al (2018) showed through high-resolution turbulence measurements that the background shear as well as near-inertial waves trapped by the negative vorticity of the LV are the dominant sources of kinetic energy loss. More generally, internal waves are suspected to drain a significant part of the energy of such mesoscale eddies (Barkan et al, 2021). These mechanisms are hardly resolved in the simulations discussed in the present paper, and are mainly controlled by the numerical parameterization (i.e., the vertical mixing induced by the KPP scheme).…”

The effect of model tidal forcing on virtual particle dispersion and accumulation at the ocean surface

“…These months coincide with the maximum probability of internal waves observation in the Açores Islands (C. R. Jackson & Apel, 2004). Considering that internal waves promote the transfer of energy from the mesoscale to the submesoscale (Barkan et al, 2021), that their presence is more pronounced with tidal forcing, and that bFTLEs capture better the fine-scale and the GKDE the mesoscale transport dynamics; the tidal forcing is affecting differently the FTLE and GKDE diagnostics. We expect then an increase in the bFTLE fields (fine-scales) and a decrease in the GKDE fields (mesoscale) with the tidal forcing simulation.…”

“…Several explanations could be behind these results. Barkan et al (2021) found that when internal wave forcing was used in their simulations (which could be analogous to the tidal forcing used here, as it creates a higher presence of internal waves), less mesoscale kinetic energy is present both in summer and winter. The energy is transferred towards submesoscale fronts and filaments, particularly in winter (Barkan et al, 2021), and this could impact on the coherence of the mesoscale eddies, reducing their capacity to trap particles in a higher presence of submesoscale structures (Haza et al, 2016).…”

“…Barkan et al (2021) found that when internal wave forcing was used in their simulations (which could be analogous to the tidal forcing used here, as it creates a higher presence of internal waves), less mesoscale kinetic energy is present both in summer and winter. The energy is transferred towards submesoscale fronts and filaments, particularly in winter (Barkan et al, 2021), and this could impact on the coherence of the mesoscale eddies, reducing their capacity to trap particles in a higher presence of submesoscale structures (Haza et al, 2016). This effect could explain the results obtained in winter, especially the opposite effect observed in winter for the GKDE (representative of eddy accumulation) and backward FTLE (more representative of accumulation at fronts and filaments) results.…”