THE INFLUENCE OF ISLAND-GENERATED EDDIES ON CHLOROPHYLL DISTRIBUTION - A STUDY OF MESOSCALE VARIATION AROUND GRAN-CANARIA

This study reports hydrographic and biological observations from three cruises where cyclonic and anticyclonic eddies were observed downstre am of Gran Canaria island. Based on field data and remote sensing imag es (AVHRR and CZCS), two mechanisms associated with island-generated e ddies, largely responsible for the formation and distribution of chlor ophyll around the Canary Islands, are proposed. First, nutrient pumpin g and vertical uplifting of the deep chlorophyll maximum by cyclonic e ddies might represent important sources of primary production in the o ligotrophic waters of the Canary region. Second, eddies are responsibl e for the horizontal transport and distribution of chlorophyll origina ting near the islands or off the African coast. Water with high chloro phyll content, resulting from island stirring or local upwelling at th e flanks of the islands, is incorporated into cyclonic eddies in their development and subsequently transported downstream. On the other han d, anticyclonic eddies can also entrain water rich in chlorophyll when interacting with the offshore boundary of the African coastal upwelli ng. This chlorophyll will be advected southward as the eddy drifts. Th e recurrence of cyclonic and anticyclonic eddies, together with the pr esence of upwelling filaments throughout the year, must have important biological consequences in the formation and transport of organic mat ter in the Canary region. (C) 1997 Elsevier Science Ltd.