Inertial Oscillations on the Continental Shelf of the Gulf of Lions—Observations and Theory

Observations in the Gulf of Lions (northwestern Mediterranean Sea) in summer have shown that gusts of wind lasting a few days generate transient upwellings and inertial motions. Oscillations at the inertial frequency were observed in current meter data near the shore and at a frequency 10% greater in the temperature data. Vertical coherences in current meter data show a strong baroclinic mode at frequencies greater than inertial frequency. A simple one-dimensional two-layer transient model suggests that these motions are associated with two different physical processes. The first process describes the local response of the ocean to meteorological forcing, the second is associated with the propagation of long internal waves generated in the transient phase of the geostrophic adjustment process. As suggested by the model, the direction of propagation of the internal waves is computed from current and temperature data measured at one point and it is found that the shore is the source zone.