Variability of ITF front at 115°E in the Eastern Indian Ocean: from 15-years Gridded CTD Argo Float Data

Abstract

This study aims to investigate a depth-latitude spatial and temporal variability of ITF front at 115°E, using 15-years (2004–2018) of monthly gridded CTD Argo float dataset in the Indo–Australia Basin. The Empirical Orthogonal Function method was performed to analysis these time-series data. It is shown that mean meridional extent of ITF front is established between 14°S and 10°S. The ITF front can be described by the first five modes of potential temperature and salinity EOF’s, which accounted for 88.6% and 80.7% of the total variance, respectively. The first EOF mode (67.9%) of depth-latitude temperature reveals spatial pattern which is out-of-phase between near-surface layer (<100 m) and thermocline layer, for example, during the northwest monsoon period, warmer and saltier water in the upper-layer and colder and fresher thermocline water are frequently observed, which differ to those observed during the southeast monsoon period. EOF principal components of temperature and salinity exhibit strong annual variation, followed by intraseasonal and interannual scales. On inter-annual scales, fluctuation of temperature and salinity is well correlated with ENSO and IODM, as previously expected.