Interannual variations in salt flux at 80°E section of the equatorial Indian Ocean.

The interannual variations in salt flux on the 80°E section in the equatorial Indian Ocean were explored based on the ORAS5 data, which was quite consistent with the observational data among the four available reanalysis datasets. The results indicated that the area with significant interannual variations in salt flux coincided with that of significant climatological mean salt flux in general and was mainly located in the upper 150 m layer. Specifically, three important areas were identified in the north-south direction, i.e., (1) the Equatorial Indian Ocean Area (EIOA, 3°S–3°N), where the mean salt flux was eastward with the largest value on the section and associated with the most significant interannual variations mainly modulated by the Wyrtki Jets and the Equatorial Undercurrent; (2) the South Equatorial Indian Ocean Area (SEIOA, 3°S–6°S), where the mean salt flux changed in the vertical direction from strong eastward flux in the upper layer to weak westward flux in the subsurface layer and associated with significant interannual variations in the upper 100 m layer, which was affected by the South Equatorial Countercurrent; and (3) the North Equatorial Indian Ocean Area (NEIOA, 3°N–6°N), where the mean salt flux changed in the north-south direction from strong westward flux to the north of 5°N to weak eastward flux in the south and associated with relatively significant interannual variations, which was mainly influenced by the South Sri Lanka Coastal Current. Two leading interannual variation modes were revealed by the empirical orthogonal function decomposition. The first mode accounted for 39% of the total variance and had four significant spatial antinodes; two of those in-phase antinodes were located at SEIOA and upper 75 m of EIOA, and the other two opposite in-phase antinodes were located at NEIOA and below 75 m of EIOA. The second mode accounted for 17% of the total variance having four antinodes with two dominant out-of-phase antinodes located at the subsurface of EIOA and SEIOA. The temporal components of the two leading modes showed a 1–4 year variation with a main period of 2 years, in which the first mode showed a greater correlation with the Indian Ocean Dipole, while the second mode showed a weak correlation with the Indian Ocean Dipole and the El Niño-Southern Oscillation. Variance analysis showed that the interannual variations in salt flux were mainly determined by the variations in the current, and the spatial distribution was modulated by temporal mean salinity. Composite strong interannual events showed interannual variations in current, and so the salt flux was driven by the interannual anomaly of the wind field and sea surface temperature associated with the Indian Ocean Dipole. [ABSTRACT FROM AUTHOR]