Ganmmeng Zhang (ESST, Kyushu University, Japan)

Variations of sea level difference over the Makassar Strait drive changes of currents in the strait, a major part of the Indonesian throughflow, but sea surface height (SSH) variations within the strait have not been fully studied. By applying a coastal retracker to Jason-2 waveform data, we determine local SSH variations at 1 deg-S within the strait from June 2008 to September 2016. For long-term variations, the local SSH varies with the same phase with a Pacific side of the large-scale sea level difference, but seasonal local SSH variations are rather independent. Comparing with the local SSH in the strait, SSH variations in the Celebes Sea to the north of the strait are smaller and nearly sinusoidal, which suggests presence of local dynamics within the strait that dominate local asymmetric seasonal SSH changes, such as convergence of weakened wind-driven flows over a shallow area near the southern boundary of the strait. Both long-term and seasonal SSH variations are not in phase with sea surface temperature (SST) variations, implying steric height changes are negligible. However, for residual component, phases of SSH and SST variations agree in some periods, suggesting presence of baroclinic response, such as internal Kelvin waves.