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| Titel |
Influence of (sub)mesoscale anticyclones on the coastal biogeochemical processes in the western part of the Gulf of Lion (NW Mediterranean) |
| VerfasserIn |
Francesco Nencioli, Andrea M. Doglioli, Anne A. Petrenko, Francesco d'Ovidio |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250051152
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| Zusammenfassung |
| The Gulf of Lion (GoL) extends from Toulon to the French-Spanish border in the
North-Western Mediterranean. The basin is occupied by a large continental shelf, and
includes the delta of the Rhône river, which represents the largest fresh water and nutrient
source of the region. The coastline is one of the most densely populated areas of the whole
Mediterranean basin. Due to the several human activities which are dependent on the
ecological conditions and the water quality of the basin, environmental management is
crucial. Biogeochemical characteristics of coastal regions are heavily influenced by
cross-shelf exchanges, therefore understanding these processes is a key aspect. In the GoL
exchanges between the coastal zone and the northwestern Mediterranean open waters are
limited by the presence of the Northern Current (NC) which flows along the continental slope
delimiting the basin.
The LAgrangian Transport EXperiment (LATEX, 2008-2011) was designed to
study the mechanism of formation of anticyclones in the western part of the GoL,
and their influence on the cross-shelf exchanges. Field observations along with
numerical simulation results, showed that large (~ 20 km radius), persistent (up
to 60 days) anticyclones can be generated by strong wind events under stratified
water column conditions. The horizontal transport and mixing associated with these
features have a profound impact on the ecological communities, as evidenced by the
signature in surface chlorophyll concentration associated with the eddies often
visible in satellite imagery. These structures can potentially be influenced by the
Rhône river plume, and they can interact with the NC. In the later stages of their life
time a portion of the eddy can get entrained within the NC and transported out of
the GoL. Therefore, these anticyclonic eddies play an important role in regulating
cross-shelf transport, and, thus, the biogeochemical characterisics of the coastal
region.
Lagrangian methods are emerging as powerful tools for the analysis of transport
properties in the oceans. In particular Lagrangian Coherent Structures (LCSs) derived from
satellite altimetry have shown a good correlation with many advected tracers in open ocean.
During the Latex10 campaign (September 1-24, 2010) we attempted a mapping of coastal
LCSs with an adaptive strategy that combined satellite data, ship-based Acoustic Doppler
Current Profiler (ADCP) measurements, and iterative Lagrangian drifter releases. This
strategy allowed to successfully localize and track the LCSs present in the region for
about 12 days from September 12 to 24. The in-situ observed LCSs confirmed that
satellite derived LCSs are not as accurate in coastal regions, due to the limitations
of altimetry data closer to the coast. Improvements on altimetry measurements
in the coastal zone, will be crucial to allow reliable analysis on the influence of
anticyclones on the coastal biogeochemical processes in the GoL from satellite derived
LCSs. |
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