We examine observational data to clarify impacts of three major climate modes on Sea Surface Height Anomaly (SSHA) of the Indian Ocean during 1993-2016: The El Niño and Southern Oscillation (ENSO), the Indian Ocean Dipole mode (IOD) and the Asian summer monsoon. ENSO and IOD dominantly control the SSHA in the eastern tropical area and in the western tropical and northwestern areas of the Indian Ocean, respectively, while the monsoon contributes to local SSHA.

For all climate modes, SSHA is primarily linked to the wind-forced ocean upwelling. In particular, the trade-wind and alongshore-wind changes associated with ENSO- and IOD-related atmospheric convection clearly control the equatorial and coastal upwelling of the tropical areas. The net heat flux anomaly at the sea surface always works to damp the tropical SSHAs. In the northwestern areas, on the other hand, it can contribute to enhancing the SSHAs relevant to IOD and monsoon.