Editorial Type:
Article
Article Type:
Research Article

25-Day Period Large-Scale Oscillations in the Argentine Basin Revealed by the TOPEX/Poseidon Altimeter

Lee-Lueng Fu Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California

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Benny Cheng Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California

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Bo Qiu Department of Oceanography, University of Hawaii, Honolulu, Hawaii

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Print Publication:
01 Feb 2001
DOI:
https://doi.org/10.1175/1520-0485(2001)031<0506:DPLSOI>2.0.CO;2
Page(s):
506–517
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Abstract

The measurement of the global sea surface height made by the TOPEX/Poseidon satellite has provided the first synoptic view of large-scale oceanic variability at intraseasonal scales from weeks to months. Areas of significant intraseasonal variability were found primarily in the Tropics and the high-latitude oceans, the Southern Ocean in particular. The focus of the paper is the finding of large-scale oscillations at a period of 25 days in the Argentine Basin of the South Atlantic Ocean. These oscillations exhibit a dipole pattern of counterclockwise rotational propagation centered at 45°S, 317°E over the Zapiola Rise. The scale of the dipole is about 1000 km. The peak-to-trough amplitude is on the order of 10 cm. The amplitude of these oscillations has large seasonal-to-interannual variations. These oscillations are shown to be associated with a free barotropic mode of the basin as a solution to a linearized barotropic vorticity equation. Closed f/H contours provide a mechanism for the confinement of the waves to the topographic feature of the Zapiola Rise. Results from a numerical model simulation reproduced the patterns of the observed oscillations. The resultant mass transport variability is on the order of 50 Sv (Sv ≡ 106 m3 s−1). Deep current meters in the Argentine Basin reveal signals consistent with the altimetry observations.

Corresponding author address: Dr. Lee-Lueng Fu, MS 300-323, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109-8099.

Abstract

The measurement of the global sea surface height made by the TOPEX/Poseidon satellite has provided the first synoptic view of large-scale oceanic variability at intraseasonal scales from weeks to months. Areas of significant intraseasonal variability were found primarily in the Tropics and the high-latitude oceans, the Southern Ocean in particular. The focus of the paper is the finding of large-scale oscillations at a period of 25 days in the Argentine Basin of the South Atlantic Ocean. These oscillations exhibit a dipole pattern of counterclockwise rotational propagation centered at 45°S, 317°E over the Zapiola Rise. The scale of the dipole is about 1000 km. The peak-to-trough amplitude is on the order of 10 cm. The amplitude of these oscillations has large seasonal-to-interannual variations. These oscillations are shown to be associated with a free barotropic mode of the basin as a solution to a linearized barotropic vorticity equation. Closed f/H contours provide a mechanism for the confinement of the waves to the topographic feature of the Zapiola Rise. Results from a numerical model simulation reproduced the patterns of the observed oscillations. The resultant mass transport variability is on the order of 50 Sv (Sv ≡ 106 m3 s−1). Deep current meters in the Argentine Basin reveal signals consistent with the altimetry observations.

Corresponding author address: Dr. Lee-Lueng Fu, MS 300-323, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109-8099.

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