Western boundary current variability off french-guiana as observed from moored current measurements

• Main Authors: Colin, C, Bourles, B, Chuchla, R, Dangu, F
• Format: Article in Journal/Newspaper
• Language: English
• Published: Gauthier-Villars 1994
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: https://archimer.ifremer.fr/doc/00098/20897/18510.pdf; https://archimer.ifremer.fr/doc/00098/20897/

Moored current measurements carried out from 31 March 1990 to 15 September 1991 in two stages at a point (near 6 degrees N) located over the mid-continental slope off French Guiana are presented. Six current meters were positioned between 200 and 2700 m depth. Upper level mean current data showed a northwestward flowing North Brazil Current (NBC) with mean velocity values decreasing from 10 cm/s in the range 200-250 m to almost zero at 800 m depth, the level of the Antarctic Intermediate Waters. In the range 500-800 m, the current reversed in spring in the presence of the southeastward Western Boundary Under Current (WBUC); the mean velocity from February to June 1991 is around 2 cm/s. Deep currents over the continental rise show a strong southeastward Deep Western Boundary Current extending from around 1000 m depth to the bottom (3000 m depth in this case) with mean core speeds of 20 cm/s at 2000-2070 m depth. Transport estimates based on these data and a few Pegasus sections for the mean vertical and lateral extensions of the DWBC yield a value of 21 x 10(6) m(3)/s at that location. Low-frequency current fluctuations were dominated by a well-defined 50- to 70-day period oscillation with peak-to-peak northwestward velocity amplitude of around 90 cm/s at the upper level. The mean vertical eddy kinetic energy distribution showed an abrupt decrease of the energy down to 800 m depth and a slight decrease below and down to the bottom.