Climate-driven extreme sea level events along the Indonesian coast during recent decades
Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Forum
Using a 27-yr satellite altimeter record and sea surface temperature data since 1993, combined with in situ observations and climate-model experiments, we show that the number of events with monthly mean SSH anomalies (SSHA) >0.25m have evidently increased in the past decade during May-Oct Indonesia dry season, with concurred marine heatwaves for all super events with SSHA >0.3m. The strongest event occurred in 2016, with SSHA > 0.4m and sea surface temperature increase >2C. The height-heat-surges are primarily driven by the varying surface winds remotely from the equator and locally near the shore. While winds associated with negative Indian Ocean Dipole - a coupled ocean-atmosphere mode of climate variability at interannual timescale – explain over half of the extreme sea level magnitudes, surface winds associated with the Interdecadal Pacific Oscillation and decadal variability of Asian-Australian monsoon cause the accelerated sea level rise in the past decade. Together with the climate-change induced global sea level rise and contribution from seasonal cycle, they account for over 40% of the extreme sea level amplitudes. Surface winds associated with atmospheric intraseasonal oscillations (ISOs) can add >0.12m to the extreme sea level magnitude, bring the surge to over 0.5 meter, which is comparable to the extreme sea level surges due to high tide and storms in this region. We conclude and emphasize that (1) satellite altimeter SSHA agree well with tide gauge data near the Indonesian coast, and can be used to identify sea level surges in this region where large-scale ocean circulation dominate the SSHA; (2) when climate variability modes on different timescales superimpose constructively, they can cause extreme height-heat-surges that devastate Indonesia.