[A-OS19] Sea level rise under global warming and its impact on coastal areas

[AOS19-05] Long-term Trend and Seasonal Variability of Sea Level in the Maritime Continent

*Randi Firdaus^1,2, Toshio Suga^1,3 (1.Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan, 2.Indonesian Agency for Meteorology Climatology and Geophysics (BMKG), Jakarta, Indonesia, 3.Advanced Institute for Marine Ecosystem Change (WPI-AIMEC), Tohoku University, Sendai, Japan)

Keywords:Sea level rise, Trend, Seasonal variability, Steric, Manometric, Tropical region

The observed sea level change is attributed to density (steric) and mass (manometric) contribution. Recent observations show a significant sea level rise (SLR), impacting human and socio-ecological aspects in low-lying islands such as the Indonesian Maritime Continent, a geographically unique and vital region. Besides the long-term trend, seasonal sea level change is a major factor contributing to extreme sea-level events such as coastal flooding, especially in the tropics. This research aims to quantify the seasonal variation and long-term trend of sea level and its steric and manometric components. A thirty-year (1993-2022) monthly 0.25^o GIA-corrected gridded sea level anomaly, 3-D temperature-salinity, and the independent GRACE observation are used to estimate the long-term trend and seasonal change of sea level and its component (steric and manometric). The average sea level trend in the MC is 4.52±0.24 mm/yr (much higher than the global average), consisting of the contribution of the manometric component 2.56±0.06 mm/yr dominantly in the shallow water region and the steric component that is responsible for 1.68±0.18 mm/yr appears dominantly in the open ocean region and deep basin of interior MC. The least-square estimation showed a remarkably high annual amplitude of up to 0.32 m in the continental shelf region. The positive (negative) anomaly occurs during the northwest (southeast) monsoon season in the interior MC, with the manometric contribution dominant in the shallow water region, while the steric component in the deep basin, as confirmed independently by the GRACE datasets. Semiannual variation with an amplitude of 0.1 m was detected in the coastal Kelvin wave propagation region in the west of Sumatra and south of Java, reflected in the steric contribution. The wind-driven Ekman transport and divergence can only explain the seasonal sea level variability to some extent, suggesting the sea level variability in this region is much more complex.