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Variations of water properties in surface and intermediate layers along 32°S in the southern Indian Ocean were examined using
a 50-year (1960–2010) time series reproduced from historical hydrographic and Argo data by using optimum interpolation. Salinity
in the 26.7–27.3σθ density layer decreased significantly over the whole section, at a maximum rate of 0.02 decade−1 at 26.8–26.9σθ, for the 50-year average. Three deoxygenating cores were identified east of 75°E, and the increasing rate of apparent oxygen
utilization in the most prominent core (26.9–27.0σθ) exceeded 0.05 ml l−1 decade−1. The pycnostad core of Subantarctic Mode Water (SAMW) and the salinity minimum of Antarctic Intermediate Water shifted slightly
toward the lighter layers. Comparisons with trans-Indian Ocean survey data from 1936 suggest that the tendencies found in
the time series began before 1960. Interestingly, cores of many prominent trends were located just offshore of Australia at
26.7–27.0σθ, which is in the SAMW density range. Spectrum analysis revealed that two oscillation components with time scales of about
40 and 10 years were dominant in the subsurface layers. Our results are fairly consistent with, and thus support, the oceanic
responses in the southern Indian Ocean to anthropogenic climate change predicted by model studies. 相似文献