A. Tychensky et al., LARGE STRUCTURES AND TEMPORAL CHANGE IN THE AZORES FRONT DURING THE SEMAPHORE EXPERIMENT, J GEO RES-O, 103(C11), 1998, pp. 25009-25027
The Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneit
es Oceaniques: Recherche Experimentale (SEMAPHORE) mesoscale experimen
t took place from July to November 1993 in the northern Canary Basin,
where the circulation is dominated by the eastward flowing Azores Curr
ent (AC). A large data set was acquired from three hydrographic arrays
(phases 1, 2, 3), current meter moorings, surface drifters drogued at
150 m, and 2000 m deep RAFOS floats. The analysis confirmed the large
-scale observations previously made in this region but also provided n
ew insights into fine-scale dynamics of the AC. The front was observed
over the 6-month period. It was narrow (100 km) and mostly surface in
tensified (velocities reaching 40-50 cm s(-1)). Whereas at the beginni
ng of the experiment (phase 1) the AC was mainly zonal with weak oscil
lations, large meridional meanders were observed from phase 2 until th
e end of the experiment. They seem to be related to the arrival of two
Mediterranean eddies (Meddies), which interacted with the AC [Kase an
d Zenk, 1996; Tychensky and Carton, this issue]. The front had a deep
dynamical signature (down to 2000 m), with a 16-18 sverdrup (Sv) volum
e transport (0-2000 m depth integrated). The southward recirculation b
ranch of the AC near 22 degrees-23 degrees W [Klein and Siedler, 1989]
corresponds to meridional transport of 5-6 Sv. Then, 4.5 Sv of these
waters are recirculating westward (along 31 degrees-32 degrees N). Som
e interesting new oceanographic results were obtained by examining the
RAFOS float trajectories over the abyssal plain. The circulation is s
imilar to that observed at the surface, with mean velocities of about
1-3 cm s(-1) and eddy kinetic energy <4 cm(2) s(-2). In agreement with
the analysis of current meter data this reveals a significant barotro
pic component in the Azores-Madeira flow field of roughly 3-3.5 cm s(-
1).