Sea-Level Science in Singapore and Southeast Asia

Sea-level rise in Singapore and Southeast Asia differs from the global average due to various regional and local processes, such as land uplift and subsidence, ocean and atmospheric circulation, and the gravitational effects from melting ice sheets. The current scarcity of sea-level data in Southeast Asia, however, limits our ability to understand the regional and local processes needed to generate more accurate sea-level rise projections. We therefore realize there is a crucial need to produce more sea-level data within Southeast Asia and develop sea-level models that can effectively inform adaptation strategies for rising sea levels.

Using case studies from the Southeast Asia Sea Level (SEA2) program from Singapore and Southeast Asia, we illustrate how historical and geological data can constrain future projections, and how sea-level projections can motivate the development of new sea-level research questions to mitigate and adapt to climate change.

• We showed that rapid sea-level rise driven by ice melting ~14,500 and ~11,500 years ago signi­ficantly reduced land area and forced early human migration across Southeast Asia[1]. During these periods, thresholds of coastal habitat survival were also surpassed resulting in large-scale coastal wetland retreat.
• Glacial Isostatic Adjustment (GIA) model predictions suggest Southeast Asia experienced sea levels higher than present between 7,000 and 4,000 years ago, producing a mid-Holocene highstand[2]. Variability in the highstand magnitude is controlled by solid Earth parameters while the highstand timing is controlled by ice sheet melting history.
• We introduced a new fusion method for quantifying a best-estimate of sea-level rise uncertainty to support decision-making[3]. We estimate that by 2100, global sea levels will likely rise between 0.3-1.0 m under low emission and 0.5-1.9 m under high emission scenarios.
• We demonstrate the implications of rising sea levels to coastal ecosystems. With 3°C of warming, nearly all mangrove forests and coral reef islands would be beyond their sea-level rise tipping point for survival[4].

[1] Kim, H.L., Li, T., et al. 2023. Commun Biol 6, 150. https://doi.org/10.1038/s42003-023-04510-0

[2] Li, T., et al. 2023. Quat Sci Rev 319, 108332. https://doi.org/10.1016/j.quascirev.2023.108332

[3] Grandey, B.S., Dauwels, J., Koh, Z.Y., Horton, B., et al. 2024. Earth’s Future. https://doi.org/10.21203/rs.3.rs-2922142/v3

[4] Saintilan, N., Horton, B., et al. 2023. Nature 621, 112–119. https://doi.org/10.1038/s41586-023-06448-z