Eddy tracking south of Canary Islands using satellite observations

Abstract

Eddies generated by the Canary Current south of Canary Islands when the flow passes through the archipelago define a high mesoscale variability of the sea level downstream of the islands. Evidence of zonal propagation of perturbations of sea surface heights was observed by generating longitude-time plots. Hovmoeller diagrams of the altimetric data for 1997 and 1998 at 27°N (south of Cape Jubi), 26°N (Cape Bojador) and 25°N (south of Cape Bojador) are analysed. Both cyclones and anticyclones were observed in the satellite data as anomalies originating south of Gran Canaria or Tenerife islands and moving southward of Gomera and El Hierro islands. The sea level variability associated with these mesoscale features, has the highest intensity during summer and autumn, when Trade winds and incident currents are stronger. An anticyclonic eddy observed in December 1997 is described on the basis of sea level anomalies deduced from ERS-2 altimetry and sea surface temperature data. This mesoscale oceanographic feature was tracked approximately 3 months (november - february), decreasing a the sea surface elevation from 25 cm registered at the end of november at 26.5°N to 15 cm in february. During this period the vortex is moved southwest at 1.7 km/day. Comparisons between sea level anomalies from altimetry and sea surface temperature images from AVHRR agree that the eddy was moved and modified its characteristics during this period.