Work

Estimating oceanic physics-driven vertical velocities in a wind-influenced coastal environment

Year: 2025

Type: article

Abstract: . Despite the challenge to measure them due to their small intensities, oceanic vertical velocities constitute an essential key in understanding ocean dynamics, ocean-atmosphere and biogeochemistry interactions. Coastal events and fine-scale processes (1–100 km / days to weeks) can lead to high-intensity vertical velocities. Such processes can be observed in the Northwestern Mediterranean Sea. In particular, the Gulf of Lion is a region prone to intense north-westerly and easterly wind episodes, that strongly impact the oceanic circulation. The JULIO mooring (JUdicious Location for Intrusion Observation), located on the boundary of the Eastern side of the Gulf of Lion’s shelf at the 100 m isobath, provides Eulerian measurements of tridimensional current velocities since 2012. Vertical velocities measured at JULIO are consistent with the ones measured by two other methods: a Free Fall Acoustic Doppler Current Profiler and an innovative Vertical Velocity Profiler. To measure physics-driven vertical velocities, we developed a method to identify and filter out biology-induced vertical velocities. Combining satellite and in situ observations with wind model outputs, we identify wind-induced downwelling and upwelling events at JULIO associated to physics-driven vertical velocities with maximum amplitudes of -465/138 m day−1. The order of magnitude of w depends on the spatio-temporal scale of its analysis. Hence this multimethod analysis underlines the need for high frequency spatio-temporal measurements in such coastal areas forced by intense wind episodes.

Source: Ocean science

DOI: 10.5194/os-21-2829-2025