Variability of wind wave field by realistic mesoscale and submesoscale eddy field

Abstract

Abstract. Recent altimeters and numerical studies have shown that wind waves interact strongly with small scale open ocean currents, and subsequently modify their amplitude, frequency, and direction. In the present paper we investigate the interactions of wind waves with a large realistic cyclonic eddy. This eddy is subject to instabilities leading to the generation of specific features both at mesoscale and submesoscale. We use the WAVEWATCH III framework to force wind waves in the eddy before and after instabilities occurred. Our findings show that the spatial variability of wave direction frequency and amplitude is very sensitive to the presence of underlying submesoscale structures resulting from the eddy destabilisation. As the surface current vorticity, the intrinsic frequency of incident waves is key in the wave response of the current modulation. Our findings also suggest that surface current gradients can be retrieved thanks to wave height gradients at scale where traditional altimeter measurements fail.

Turbulent Dissipation in the Surface Mixed Layer of an Anticyclonic Mesoscale Eddy in the South China Sea

“…On the other hand, mesoscale eddies and currents do affect local surface winds and waves (e.g., Frenger et al, 2013;Ma et al, 2015;Marechal & de Marez, 2021;Wang et al, 2020), but these effects are not likely to be represented in the ERA5 wind and wave data used here. Despite the mesoscale-permitting resolution of the ERA data, our analysis indicates that no imprints from the mesoscale eddy are found in the wind and wave fields (Text S2 in Supporting Information S1).…”

“…Anticyclonic eddies deepen the SML, while cyclonic ones thin it, with anomalies up to tens of meters (Gaube et al., 2019). Surface wave characteristics are also potentially modulated at mesoscale eddies (Marechal & de Marez, 2021; Wang et al., 2020). Moreover, the strong buoyancy gradient and velocity shear within the SML associated with mesoscale eddies favor submesoscale instabilities.…”

Modulation Effects of Mesoscale Eddies on Sea Surface Wave Fields in the South China Sea Derived From a Wave Spectrometer Onboard the China‐France Ocean Satellite

“…The WW3 model results of Villas Bôas et al (2020) indicate that the spatial variability of SWH is highly sensitive to the underlying current, especially at scales from 15 to 200 km. Using the same model, Marechal and de Marez (2021) described the variations in wave bulk parameters such as wave height, mean wave period, and wave direction between the inside and outside of an isolated eddy. They found that the unstable submesoscale processes around mesoscale eddies contribute most to the wave variation, and variations are larger as incident waves are shorter.…”