Seasonal and Interannual Sea Levels in the Western Equatorial Pacific from TOPEX/Poseidon

John L. Luick National Tidal Facility, Flinders University, Adelaide, Australia

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Abstract

Seasonal and interannual variability in the western equatorial Pacific is described on the basis of an analysis of data from the Ocean Topography Experimental Satellite Mission (TOPEX/Poseidon) satellite altimeter and from tide gauges. Highest rms variability is found in the countercurrent trough (5°–7°N) and just east of the Solomon Islands at 8°S. Annual phase is symmetric about the equator within the Tropics. An empirical orthogonal function analysis found two dominant modes of variability. The primary mode is characterized by a spatial pattern similar in appearance to the combined intertropical and South Pacific convergence zones, while the second mode is centered over the equator west of the date line. Both modes vary in unison with the Southern Oscillation index over much of the interval, but a difference developed during the 1997 El Niño. This coincided with the slackening, locally, of the trade winds.

Corresponding author address: Dr. J. L. Luick, National Tidal Facility, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia.

Email: john.luick@flinders.edu.au

Abstract

Seasonal and interannual variability in the western equatorial Pacific is described on the basis of an analysis of data from the Ocean Topography Experimental Satellite Mission (TOPEX/Poseidon) satellite altimeter and from tide gauges. Highest rms variability is found in the countercurrent trough (5°–7°N) and just east of the Solomon Islands at 8°S. Annual phase is symmetric about the equator within the Tropics. An empirical orthogonal function analysis found two dominant modes of variability. The primary mode is characterized by a spatial pattern similar in appearance to the combined intertropical and South Pacific convergence zones, while the second mode is centered over the equator west of the date line. Both modes vary in unison with the Southern Oscillation index over much of the interval, but a difference developed during the 1997 El Niño. This coincided with the slackening, locally, of the trade winds.

Corresponding author address: Dr. J. L. Luick, National Tidal Facility, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia.

Email: john.luick@flinders.edu.au

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