Abstract's details
Near-inertial wave trapping inside a fine-scale anticyclonic eddy during the BioSWOT-Med 2023 cruise: Turbulence and energy flux
Event: 2025 SWOT Science Team Meeting
Session: Oceanography: Tides and Inertia-Gravity Waves
Presentation type: Oral
The breaking of near-inertial waves (NIWs) trapped in anticyclones after strong wind events is a well-known pathway for kinetic energy dissipation below the mixed layer in the ocean and one of the mechanisms by which the ocean responds to modified wind patterns under climate change. In the Mediterranean Sea, where turbulence is generally low far from topographic boundaries, NIW trapping has been documented only in a few large (>100 km) and energetic mesoscale features. Whether NIW trapping is restricted to these few isolated and semi-permanent features or is a more widespread phenomenon remains a key open question, whose answer is hindered by the difficulty of tracking, in space and time, typical Mediterranean eddies characterized by both low energy and small radii.
Here we present an in-situ experiment conducted during the BioSWOT-Med 2023 cruise (doi.org/10.17600/18002392) that addressed this problem by surveying a moderately energetic small meander (<50 km, Ro ≈ 0.5) of the North Balearic front assisted by the first high-resolution SSH images of the SWOT mission. We explore how the fine scales control the spatio-temporal variability of turbulence (the dissipation of turbulent kinetic energy) around a fine-scale front in a moderately energetic area (compared to western boundary current and upwelling systems) after experiencing two consecutive strong wind events. We show that the turbulence remains low in the front and its cyclonic side while turbulence is greatly enhanced in the anticyclonic side. The latter side is dominated by a small anticyclone (~25 km in diameter) that trapped NIWs down to 300 m, generating intense shear and turbulence reaching up to several 10-8 W/kg. The vertical kinetic energy flux induced by NIWs is estimated from Acoustic Doppler Current Profiler (ADCP) and drifter's data. The flux reaches 10 mW/m2 at 60 m and 5 mW/m2 at 200 m. This is about one order of magnitude stronger than previous estimations outside anticyclones (0.5 to 2.5 mW/m2) and about 1 to 3 times previous estimations inside large and energetic mesoscale anticyclones (3 to 10 mW/m2). The wind power input to inertial motions, estimated from a high-resolution data-assimilative simulation (WMOP), reached 25 mW/m2. In the context of the Mediterranean Sea, where this kind of eddies are widespread, this work raises the question of the contribution of this process to the turbulence budget of the Mediterranean Sea. More generally, these results suggest that moderately energetic fine-scale fronts and eddies are as important to structure turbulence as strong fronts and eddies found in western boundary current and upwelling systems, addressing new challenges for their parameterization in Earth system models.
Back to the list of abstractHere we present an in-situ experiment conducted during the BioSWOT-Med 2023 cruise (doi.org/10.17600/18002392) that addressed this problem by surveying a moderately energetic small meander (<50 km, Ro ≈ 0.5) of the North Balearic front assisted by the first high-resolution SSH images of the SWOT mission. We explore how the fine scales control the spatio-temporal variability of turbulence (the dissipation of turbulent kinetic energy) around a fine-scale front in a moderately energetic area (compared to western boundary current and upwelling systems) after experiencing two consecutive strong wind events. We show that the turbulence remains low in the front and its cyclonic side while turbulence is greatly enhanced in the anticyclonic side. The latter side is dominated by a small anticyclone (~25 km in diameter) that trapped NIWs down to 300 m, generating intense shear and turbulence reaching up to several 10-8 W/kg. The vertical kinetic energy flux induced by NIWs is estimated from Acoustic Doppler Current Profiler (ADCP) and drifter's data. The flux reaches 10 mW/m2 at 60 m and 5 mW/m2 at 200 m. This is about one order of magnitude stronger than previous estimations outside anticyclones (0.5 to 2.5 mW/m2) and about 1 to 3 times previous estimations inside large and energetic mesoscale anticyclones (3 to 10 mW/m2). The wind power input to inertial motions, estimated from a high-resolution data-assimilative simulation (WMOP), reached 25 mW/m2. In the context of the Mediterranean Sea, where this kind of eddies are widespread, this work raises the question of the contribution of this process to the turbulence budget of the Mediterranean Sea. More generally, these results suggest that moderately energetic fine-scale fronts and eddies are as important to structure turbulence as strong fronts and eddies found in western boundary current and upwelling systems, addressing new challenges for their parameterization in Earth system models.