Near‐inertial motion on the shelf‐slope front off northeast Spain

Abstract

Near‐inertial motion on the shelf‐slope front off northeast Spain was monitored using surface drifters and moored current meters. On the shelf, strong inertial currents were generated by a wind burst. The inertial current amplitude was about 70 cm/s at the surface, 30 cm/s at the base of the mixed layer, and 10 cm/s in the interior. The observed near‐inertial frequency on the shelf was about 10% lower than the local inertial frequency, suggesting that the near‐inertial motion was embedded in region of strong anticyclonic shear. Also, the phase of near‐inertial motion increased through the water column, indicating that the energy propagation was downward. By contrast, the surface inertial currents were only about 10 cm/s in the center of the shelf‐slope front. Indirect evidence suggests that the observed small surface inertial currents were the result of rapid downward transfer of near‐inertial energy in the front.