Chapter 11
Satellite Observations of Oceanic Eddies
Around Africa
Werner Alpers, Dominique Dagorne and Peter Brandt
Abstract Oceanic eddies having scales from several hundred meters to several hundred kilometers are ubiquitous phenomena in the World’s ocean. This became evident
only after they could be observed from satellites and space shuttles. Here we present
several images taken in different spectral bands which show signatures of eddies of
different spatial scales in sea areas around Africa. In particular, we present a series
of satellite images showing the propagation of a small-scale cyclonic (cold) eddy
generated at Cap-Vert at the coast of Senegal into the open ocean. We show that this
small-scale eddy transported nutrients from the Senegal upwelling region westward
into the oligotrophic North Atlantic thus giving rise to enhanced chlorophyll-a concentration there. Since eddies are also areas of high fish population, knowledge of
their position and properties is of great importance for fishery.
11.1 Introduction
Oceanic eddies of horizontal scales ranging from several hundred meters to several
hundred kilometers are ubiquitous phenomena in the World’s ocean (McWilliams
1985). This came as a great surprise to many oceanographers when the first images
taken over the ocean from spacecraft became available. (see e.g., Cresswell and
Legeckis 1986; Stevenson 1998; Munk et al. 2000; Siegel et al. 2001). Boundaries
of strong currents, like the Gulf Stream and the Agulhas Current, and upwelling
regions, like the Canary upwelling area, are preferred regions of eddy generation.
W. Alpers ()
Institut för Meereskunde, Universität Hamburg,
Hamburg, Germany
e-mail: werner.alpers@zmaw.de
D. Dagorne
US Imago, Institut de Recherche pour le Développement,
Plouzané, France
P. Brandt
GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel,
Kiel, Germany
V. Barale, M. Gade (eds.), Remote Sensing of the African Seas,
205
DOI 10.1007/978-94-017-8008-7_11,
© Springer Science+Business Media Dordrecht 2014
Satellite Observations of Oceanic Eddies
Around Africa
Werner Alpers, Dominique Dagorne and Peter Brandt
Abstract Oceanic eddies having scales from several hundred meters to several hundred kilometers are ubiquitous phenomena in the World’s ocean. This became evident
only after they could be observed from satellites and space shuttles. Here we present
several images taken in different spectral bands which show signatures of eddies of
different spatial scales in sea areas around Africa. In particular, we present a series
of satellite images showing the propagation of a small-scale cyclonic (cold) eddy
generated at Cap-Vert at the coast of Senegal into the open ocean. We show that this
small-scale eddy transported nutrients from the Senegal upwelling region westward
into the oligotrophic North Atlantic thus giving rise to enhanced chlorophyll-a concentration there. Since eddies are also areas of high fish population, knowledge of
their position and properties is of great importance for fishery.
11.1 Introduction
Oceanic eddies of horizontal scales ranging from several hundred meters to several
hundred kilometers are ubiquitous phenomena in the World’s ocean (McWilliams
1985). This came as a great surprise to many oceanographers when the first images
taken over the ocean from spacecraft became available. (see e.g., Cresswell and
Legeckis 1986; Stevenson 1998; Munk et al. 2000; Siegel et al. 2001). Boundaries
of strong currents, like the Gulf Stream and the Agulhas Current, and upwelling
regions, like the Canary upwelling area, are preferred regions of eddy generation.
W. Alpers ()
Institut för Meereskunde, Universität Hamburg,
Hamburg, Germany
e-mail: werner.alpers@zmaw.de
D. Dagorne
US Imago, Institut de Recherche pour le Développement,
Plouzané, France
P. Brandt
GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel,
Kiel, Germany
V. Barale, M. Gade (eds.), Remote Sensing of the African Seas,
205
DOI 10.1007/978-94-017-8008-7_11,
© Springer Science+Business Media Dordrecht 2014