Vertical Structure of Semi-diurnal Tidal Currents in the Bay of Biscay

Abstract

IN the winter of 1970–71 the National Institute of Oceanography deployed four current meter moorings on the continental slope in the north of the Bay of Biscay near 47° 30′ N 08° 30′ W (Fig. 1). Here we report data from two of these moorings, with serial numbers 072 (47° 39.6′ N 07° 14.2′ W) and 074 (47° 31.4′ N 08° 27.9′ W). One (072) was on the continental shelf in 190 m of water with a single record (07201) at 54 m. The other had a total of six records (07401–6) at depths of 91, 292, 492, 990, 1,487 and 1,986 m, the lowest record being 15m above the sea bed. The data were obtained with Aanderaa¹ current meters and both the moorings had subsurface buoyancy to decouple the mooring lines from surface wave activity. The records were all of duration approximately 20 d, that on 072 being from February 1 to February 22, 1971, and those on mooring 074 lasting from February 5 to February 26. Current speed and direction were measured every 5 min in each record.