Island-induced eddies in the Canary islands

Abstract

Cyclonic and anticyclonic eddies were observed downstream of Gran Canaria (Canary Islands), an almost circular island of about 50 km diameter, located in the path of the Canary Current. Temperature data were obtained from five AXBT and one CTD surveys carried out during two years (April, May and December, 1989; February, May and June, 1990), and from NOAA AVHRR (Advanced Very High Resolution Radiometer) sea surface temperature (SST) satellite images. The presence of eddies in most of the surveys and in many SST images suggests that they are common mesoscale features in the flow past the island througout the year. In general, eddy diameter is similar to the width of the island, while the vertical extent is from the near-surface layers down to at least 400 m depth. However, vertical sections across the eddies show distinct patterns in their structures which could correspond to different stages of development. Wakes of relatively warm surface water develop in the lee of the island, interacting with the eddies and affecting their upper mixed layer structure. It is hypothesized that eddies are sequentially spun off from the island with a period ranging from several days to two weeks. If this is the case, they could contribute to the high levels of eddy kinetic energy observed recently downstream of the Canarian archipelago from moored current meters.