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| Titel |
Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems |
| VerfasserIn |
V. Rossi, C. López, E. Hernández-García, J. Sudre, V. Garçon, Y. Morel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 16, no. 4 ; Nr. 16, no. 4 (2009-08-27), S.557-568 |
| Datensatznummer |
250013235
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| Publikation (Nr.) |
 copernicus.org/npg-16-557-2009.pdf |
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| Zusammenfassung |
| Eastern Boundary Upwelling Systems (EBUS) are characterized by a
high productivity of plankton associated with large commercial
fisheries, thus playing key biological and socio-economical roles.
Since they are populated by several physical oceanic structures
such as filaments and eddies, which interact with the biological
processes, it is a major challenge to study this sub- and
mesoscale activity in connection with the chlorophyll
distribution. The aim of this work is to make a comparative study
of these four upwelling systems focussing on their surface
stirring, using the Finite Size Lyapunov Exponents (FSLEs), and
their biological activity, based on satellite data. First, the
spatial distribution of horizontal mixing is analysed from time
averages and from probability density functions of FSLEs, which
allow us to divide each areas in two different subsystems. Then we
studied the temporal variability of surface stirring focussing on
the annual and seasonal cycle. We also proposed a ranking of the four
EBUS based on the averaged mixing intensity. When investigating
the links with chlorophyll concentration, the previous subsystems reveal
distinct biological signatures. There is a global negative
correlation between surface horizontal mixing and chlorophyll
standing stocks over the four areas. To try to better understand
this inverse relationship, we consider the vertical dimension by
looking at the Ekman-transport and vertical velocities. We suggest
the possibility of a changing response of the phytoplankton to
sub/mesoscale turbulence, from a negative effect in the very
productive coastal areas to a positive one in the open ocean.
This study provides new insights for the understanding of the variable
biological productivity in the ocean, which results from both dynamics
of the marine ecosystem and of the 3-D turbulent medium. |
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