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Ann. Geophys., 21, 33-47, 2003
www.ann-geophys.net/21/33/2003/
© European Geosciences Union 2003
Seasonal variability and geostrophic circulation in the eastern Mediterranean as revealed through a repeated XBT transect
V. Zervakis1, G. Papadoniou2, C. Tziavos1, and A. Lascaratos2
1National Center for Marine Research, Aghios Kosmas, GR-16 604 Hellenikon, Greece
2University of Athens, Department of Applied Physics, University Campus, Bldg. Phys-V, GR-15 784 Athens, Greece
Abstract. The evolution of the
upper thermocline on a section across the eastern Mediterranean was recorded
bi-weekly through a series of XBT transects from Piraeus, Greece to Alexandria,
Egypt, extending from October 1999 to October 2000 on board Voluntary Observing
Ships in the framework of the Mediterranean Forecasting System Pilot Project.
The data acquired provided valuable information on the seasonal variability of
the upper ocean thermal structure at three different regions of the eastern
Mediterranean: the Myrtoan, Cretan and Levantine Seas. Furthermore, the
horizontal distance (~12 miles) between successive profiles provides enough
spatial resolution to analyze mesoscale features, while the temporal distance
between successive expeditions (2–4 weeks) allows us to study their
evolution. Sub-basin scale features are identified using contemporaneous sea
surface temperature satellite images. The cross-transect geostrophic velocity
field and corresponding volume fluxes for several sub-basin scale features of
the Levantine Sea are estimated by exploiting monthly q /
S diagrams from operational runs of the Princeton Ocean Model in use at
NCMR. A southwestward transport in the proximity of the southeast tip of Crete
was estimated between 1–3 Sv. The transport increases after the winter
formation of dense intermediate water in the Cretan Sea strengthens the
pressure gradient across the Cretan Straits. The Mersah-Matruh anticyclone was
identified as a closed gyre carrying about 2–6 Sv. This feature was stable
throughout the stratified period and disappeared from our records in March
2000. Finally, our data reveal the existence of an eastward-flowing coastal
current along the North African coast, transporting a minimum of 1–2 Sv.
Key words. Oceanography: physical
(eddies and mesoscale processes; currents; marginal and semi-closed seas)
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