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| Titel |
Glider and satellite high resolution monitoring of a mesoscale eddy in the Algerian basin: effects on the mixed layer depth and biochemistry |
| VerfasserIn |
Yuri Cotroneo, Giuseppe Aulicino, Simón Ruiz, Ananda Pascual, Giorgio Budillon, Giannetta Fusco, Joaquin Tintoré |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123954
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| Publikation (Nr.) |
 EGU/EGU2016-3299.pdf |
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| Zusammenfassung |
| Despite of the extensive bibliography about the circulation of the Mediterranean Sea and its
sub-basins, the debate on mesoscale dynamics and its impacts on biochemical processes is
still open because of their intrinsic time scales and of the difficulties in sampling. In order to
clarify some of these processes, the “Algerian BAsin Circulation Unmanned Survey -
ABACUS” project was proposed and realized through access to JERICO Trans National
Access (TNA) infrastructures between September and December 2014. In this framework, a
deep glider cruise was carried out in the area between Balearic Islands and Algerian coasts to
establish an endurance line for monitoring the basin circulation. During the mission, a
mesoscale eddy, identified on satellite altimetry maps, was sampled at high-spatial horizontal
resolution (4 km) along its main axes and from surface to 1000 m depth. Data were
collected by a Slocum glider equipped with a pumped CTD and biochemical sensors
that collected about 100 complete casts inside the eddy. In order to describe the
structure of the eddy, in situ data were merged with new generation remotely sensed
data as daily synoptic sea surface temperature (SST) and chlorophyll concentration
(Chl-a) images from MODIS satellites as well as sea surface height and geostrophic
velocities from AVISO. From its origin along the Algerian coast in the eastern part of
the basin, the eddy propagated to north-west at a mean speed of about 4 km/day
with a mean diameter of 112/130 km, a mean elevation of 15.7 cm and clearly
distinguished by the surrounding waters thanks to its higher SST and Chl-a values.
Temperature and salinity values along the water column confirm the origin of the
eddy from the AC showing the presence of recent Atlantic water in the surface
layer and Levantine Intermediate Water (LIW) in the deeper layer. Eddy footprint is
clearly evident in the multiparametric vertical sections conducted along its main
axes.
Deepening of temperature, salinity and density isolines at the center of the eddy is
associated with variations in the Chl-a, oxygen concentration and turbidity pattern. In
particular at 50 m depth, along the eddy borders, Chl-a values are higher (1.1-5.2 μg/l) than in
correspondence of the eddy center (0.5-0.7 μg/l) with maxima values registered in the
southeastern sector of the eddy.
Calculation of geostrophic velocities along transects and vertical quasi geostrophic
velocities (QG-w) over a regular 5 km grid from glider data, helped in describing the
mechanism and functioning of the eddy.
QG-w presents an asymmetric pattern, with associated relatively strong downwelling in
the western part of the eddy and upwelling in the southeastern part of it. This asymmetry in
the vertical velocity pattern, bringing LIW in the euphotic layer, as well as eventual advection
from the northeastern sector of the eddy may justify the observed increase in Chl-a values. |
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