Oct 15, 1998 - on hydrography and Lagrangian drifters and floats [Le Traon ... Hydrographic Surveys, Deployment Time for the Surface Drifters and Deep.
JOURNAL OF GEOPHYSICAL
RESEARCH, VOL. 103, NO. Cll, PAGES 25,009-25,027, OCTOBER 15, 1998
Large structures and temporal change in the Azores Front during the SEMAPHORE experiment A. Tychensky ServiceHydrographiqueet Oc6anographique de la Marine, Centre Militaire d'Oc6anographie, Toulouse,France
P.-Y.
Le Traon
and F. Hernandez
CollecteLocalisationSatellites,RamonvilleSt.-Agne,France
D. Jourdan ServiceHydrographiqueet Ocfianographique de la Marine, Centre Militaire d'Ocfianographie, Toulouse,France
Abstract. The Structuredes EchangesMer-Atmosphere, Proprietesdes Heterogeneites Oceaniques:RechercheExperimentale(SEMAPHORE) mesoscaleexperimenttook place from July to November 1993 in the northern Canary Basin,where the circulationis dominatedby the eastwardflowingAzoresCurrent (AC). A large data setwas acquired from three hydrographicarrays(phases1, 2, 3), currentmeter moorings,surfacedrifters droguedat 150 m, and 2000 m deep RAFOS floats.The analysisconfirmedthe large-scale observations previouslymade in this regionbut alsoprovidednew insightsinto fine-scale dynamicsof the AC. The front was observedover the 6-monthperiod. It was narrow
(100km)andmostly surface intensified (velocities reaching 40-50cms-•). Whereas at the beginningof the experiment(phase1) the AC wasmainlyzonalwith weak oscillations, large meridionalmeanderswere observedfrom phase2 until the end of the experiment. They seemto be related to the arrivalof two Mediterraneaneddies(Meddies),which interactedwith the AC [Kiiseand Zenk, 1996;Tychensky and Carton,this issue].The front had a deep dynamicalsignature(downto 2000 m), with a 16-18 sverdrup(Sv) volume transport(0-2000 m depthintegrated).The southwardrecirculationbranchof the AC near 22ø-23øW[Kleinand Siedler,1989]corresponds to meridionaltransportof 5-6 Sv. Then, 4.5 Sv of thesewatersare recirculatingwestward(along31ø-32øN).Someinteresting new oceanographicresultswere obtainedby examiningthe RAFOS float trajectoriesover the abyssalplain. The circulationis similar to that observedat the surface,with mean
velocities of about1-3 cms-• andeddykineticenergy
