Geophysical Research Letters

Interannual variability in the Indian Ocean using altimeter and IX1-expendable bathy-thermograph (XBT) data: Does the 18-month signal exist?

Authors

  • Irina V. Sakova,

    1. CSIRO Marine and Atmospheric Research, Hobart, Tasmania, Australia
    2. Also at School of Geography and Environmental Studies, University of Tasmania, Hobart, Tasmania, Australia.
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  • Gary Meyers,

    1. CSIRO Marine and Atmospheric Research, Hobart, Tasmania, Australia
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  • Richard Coleman

    1. CSIRO Marine and Atmospheric Research, Hobart, Tasmania, Australia
    2. Also at School of Geography and Environmental Studies, University of Tasmania, Hobart, Tasmania, Australia.
    3. Also at Antarctic Climate and Ecosystems CRC, Hobart, Tasmania, Australia.
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Abstract

[1] The dominant frequency bands in altimeter sea surface height (SSH) variability over the whole Indian Ocean and in temperature profiles near the Sumatra-Java coast are identified and analysed using spectral analysis techniques. We find that in most regions of the Indian Ocean, the low-frequency part of the SSH spectra (corresponding to signals with periods from six months to six years) is concentrated in five frequency bands separated by substantial spectral gaps: semi-annual, annual, 18–20 months, 3 years, and 4–6 years. The existence of semi-annual, annual, 2–3-year, and 4–6-year periodical signals is well known; however, the 18–20-month signal has not previously been described. Further investigation of temporal and spatial characteristics of this later signal point to its relationship with the Indian Ocean dipole events: the signal is particularly strong between 1994 and 2000; it develops near the Sumatra coast and propagates to the Bay of Bengal and into the Indonesian Throughflow.

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