Variability of the horizontal velocity structure in the upper 1600 m of the water column on the equator at 10°W

被引:19
作者
Bunge, Lucia
Provost, Christine
Lilly, Jonathan M.
D'Orgeville, Marc
Kartavtseff, Annie
Melice, Jean-Luc
机构
[1] Univ Paris 06, CNRS,UMR 7617, IRD,MNHN, LODYC, Paris, France
[2] CNRS, UMR 6523, IFREMER,UBO, LPO, Plouzane, France
[3] Univ Cape Town, Dept Oceanog, Inst Rech Dev, ZA-7700 Rondebosch, South Africa
关键词
D O I
10.1175/JPO2908.1
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
This paper presents initial results from new velocity observations in the eastern part of the equatorial Atlantic Ocean from a moored current-meter array. During the "EQUALANT" program (1999-2000), a mooring array was deployed around the equator near 10 W that recorded one year of measurements at various depths. Horizontal velocities were obtained in the upper 60 m from an upward-looking acoustic Doppler current profiler (ADCP) and at 13 deeper levels from current meters between 745 and 1525 m. To analyze the quasiperiodic variability observed in these records, a wavelet-based technique was used. Quasiperiodic oscillations having periods between 5 and 100 days were separated into four bands: 5-10, 10-20, 20-40, and 40-100 days. The variability shows (i) a strong seasonality (the first half of the series is dominated by larger periods than the second one) and (ii) a strong dependence with depth (some oscillations are present in the entire water column while others are only present at certain depths). For the oscillations that are present in the entire water column the origin of the forcing can be traced to the surface, while for the others the question of their origin remains open. Phase shifts at different depths generate vertical shears in the horizontal velocity component with relatively short vertical scales. This is especially visible in long-duration events (>100 days) of the zonal velocity component. Comparison with a simultaneous lowered acoustic Doppler current profiler (LADCP) section suggests that some of these flows may be identified with equatorial deep jets. A striking feature is a strong vertical shear lasting about 7 months between 745 and 1000 m. These deep current-meter observations would then imply a few months of duration for the jets in this region.
引用
收藏
页码:1287 / 1304
页数:18
相关论文
共 51 条
  • [1] [Anonymous], 1999, WAVELET TOUR SIGNAL
  • [2] [Anonymous], 1993, SPECTRAL ANAL PHYS A, DOI [10.1017/cbo9780511622762, DOI 10.1017/CBO9780511622762, 10.1017/CBO9780511622762]
  • [3] Kinematic elements of Antarctic Intermediate Water in the western South Atlantic
    Boebel, O
    Schmid, C
    Zenk, W
    [J]. DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 1999, 46 (1-2) : 355 - 392
  • [4] Seasonal variability of deep currents in the equatorial Atlantic:: a model study
    Böning, CW
    Kröger, E
    [J]. DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, 2005, 52 (01) : 99 - 121
  • [5] The deep currents in the Eastern Equatorial Atlantic Ocean -: art. no. 8002
    Bourlès, B
    Andrié, C
    Gouriou, Y
    Eldin, G
    du Penhoat, Y
    Freudenthal, S
    Dewitte, B
    Gallois, F
    Chuchla, R
    Baurand, F
    Aman, A
    Kouadio, G
    [J]. GEOPHYSICAL RESEARCH LETTERS, 2003, 30 (05) : CLI2 - 1
  • [6] Annual cycle and interannual variability of the mid-depth tropical Atlantic Ocean
    Brandt, P
    Eden, C
    [J]. DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, 2005, 52 (02) : 199 - 219
  • [7] COLIN C, 1988, OCEANOL ACTA, V11, P139
  • [8] ASYMPTOTIC WAVELET AND GABOR ANALYSIS - EXTRACTION OF INSTANTANEOUS FREQUENCIES
    DELPRAT, N
    ESCUDIE, B
    GUILLEMAIN, P
    KRONLANDMARTINET, R
    TCHAMITCHIAN, P
    TORRESANI, B
    [J]. IEEE TRANSACTIONS ON INFORMATION THEORY, 1992, 38 (02) : 644 - 664
  • [9] Break-up of the Atlantic deep western boundary current into eddies at 8° S
    Dengler, M
    Schott, FA
    Eden, C
    Brandt, P
    Fischer, J
    Zantopp, RJ
    [J]. NATURE, 2004, 432 (7020) : 1018 - 1020
  • [10] ERIKSEN CC, 1985, J PHYS OCEANOGR, V15, P1085, DOI 10.1175/1520-0485(1985)015<1085:MOODLF>2.0.CO