Preprints
https://doi.org/10.5194/os-2020-91
https://doi.org/10.5194/os-2020-91

  12 Oct 2020

12 Oct 2020

Review status: a revised version of this preprint was accepted for the journal OS and is expected to appear here in due course.

Zonal Current Characteristics in the Southeastern Tropical Indian Ocean (SETIO)

Nining Sari Ningsih1, Sholihati Lathifa Sakina2, Raden Dwi Susanto3,2, and Farrah Hanifah1 Nining Sari Ningsih et al.
  • 1Research Group of Oceanography, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Indonesia
  • 2Department of Oceanography, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Indonesia
  • 3Department of Atmospheric & Oceanic Science, University of Maryland, USA

Abstract. Zonal current characteristics in the Southeastern Tropical Indian Ocean (SETIO) adjacent to the southern Sumatra-Java coasts have been studied using 64 years (1950–2013) data derived from simulated results of a 1/8° global version of the HYbrid Coordinate Ocean Model (HYCOM). This study has revealed distinctive features of zonal currents in the South Java Current (SJC) region, the Indonesian Throughflow (ITF)/South Equatorial Current (SEC) region, and the transition zone between the SJC and ITF/SEC regions. Empirical orthogonal function (EOF) analysis is applied to investigate explained variance of the current data and give results for almost 95–98 % of total variance. The first temporal mode of EOF is then investigated by using ensemble empirical mode decomposition (EEMD) for distinguishing the signals. The EEMD analysis shows that zonal currents in the SETIO vary considerably from intraseasonal to interannual timescales. In the SJC region, the zonal currents are consecutively dominated by semiannual (0.140 power/year), intraseasonal (0.070 power/year), and annual (0.038 power/year) signals, while semiannual (0.135 power/year) and intraseasonal (0.033 power/year) signals with pronounced interannual variations (0.012 power/year) of current appear consecutively to be dominant modes of variability in the transition zone between the SJC and ITF/SEC regions. In contrast, there exist dominant interannual signal (0.017 power/year) with prominent intraseasonal variability (0.012 power/year) of the current in the ITF/SEC region. In response to El Niño–Southern Oscillation (ENSO) event, El Niño (La Niña) events are favourable for an eastward (westward) zonal current. Meanwhile, an eastward (westward) anomaly of the current exists during negative (positive) Indian Ocean Dipole (IOD), which is associated with the presence of anomalous surface winds over the study area during those events. This work may contribute to further understanding of the variability of zonal current characteristics in the SETIO both in space and time as well as identification of its dominant time scales.

Nining Sari Ningsih et al.

 
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Nining Sari Ningsih et al.

Nining Sari Ningsih et al.

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Short summary
Zonal current anomaly variations in the SETIO using 64-year HYCOM output are identified, varying from intraseasonal to interannual timescales. Distinctive features of zonal currents in the regions of SJC, ITF/SEC, and transition zone between them are found, with difference of dominant signals in each region. This work may contribute to further understanding of zonal current characteristics variabilities in the SETIO both in space and time as well as identification of its dominant time scales.