Manifestation of two meddies in altimetry and sea-surface temperature

Abstract

Abstract. Two meddies were identified in the Iberian Basin using shipboard ADCP (Meddy 1) and ARGO float (Meddy 2) in contrasting background conditions. Meddy 1 was observed while interacting with the Azores current (AzC) while Meddy 2 was observed rather far north from the AzC jet, in much calmer dynamical background. In both cases the meddies produced a clear anticyclonic surface signal, detectable in altimetry as well as in sea-surface temperature (SST). Analysis of the in-situ observations of the dynamic signal over Meddy 1 showed that the signal, generated by the moving meddy, dominated the AzC dynamics at least up to the base of the seasonal thermocline even at the late stages of its interaction with the jet. The center of rotation of the surface signal was shifted south-westward from the axis of the meddy by about 18 km, and its dynamic radius was 2 times bigger than that of the meddy. The SST anomalies in the core of the surface signals were negative in contrast to the positive SST anomalies in surface anticyclones generated by meandering surface currents. The later difference gives ground for identification of meddies (as well as other sub-surface anticyclones) using coupled altimetry – SST remote sensing data. An identification of Meddy 1 previous to the shipboard ADCP measurements was the first successful experience. At the same time, SST anomalies over both meddies were rather weak, often unstable and statistically significant only over periods of months.