Extending instrumental sea-level records using coral microatolls, an example from Southeast Asia

The small number of reliable long-term (i.e., >50 yrs) tide gauges in tropical locations is a major source of uncertainty in modern sea-level change. Coral microatolls record relative sea-level (RSL) change over their lifetimes and have the potential to extend the instrumental record. Here, we examined a 20th and 21st century RSL record from two living coral microatolls from Mapur Island, Indonesia, which produced 16 sea-level index points. We validated and combined the living coral microatoll data with tide gauge data to show RSL at Mapur Island was 0.0 ± 1.6 mm/yr (2σ) from 1915 to 1990 and 1.0 ± 2.1 mm/yr (2σ) from 1990 to 2019. Through the addition of microatoll RSL data we extended the record of modern sea-level change by over 50 years and reduced its uncertainty by ∼50%.Ministry of Education (MOE)National Research Foundation (NRF)Published versionThe research was supported by the National Research Foundation (NRF) Singapore under its NRF Fellowship scheme (Awards NRF-RF2010-04 to ADS and NRF-NRFF11-2019-0008 to AJM), the Singapore Ministry of Education (Awards RGC4/14 to ADS and MOE2019-T3-1-004 to BPH), and the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative. This research is also supported by the RIE2020 National Sea Level Programme Funding Initiative (Award USS-IF-2020-1), administered by the National Environment Agency, Singapore and supported by the National Research Foundation, Singapore. This paper results from joint-research activities between the Earth Observatory of Singapore– Nanyang Technological University and the Research Center for Geotechnology LIPI

Holocene relative sea-level records from coral microatolls in Western Borneo, South China Sea

The spatial variability of Holocene relative sea level (RSL) in the South China Sea is unknown, with data restricted to Thailand, the Malay Peninsula, and a few other isolated sites. In this study, we present new continuous RSL records for Borneo using surveyed and U–Th dated coral microatolls from four sites in western Sarawak. The record spans 450 years of RSL from 7450 to 7000 yr BP. Our data suggest that RSL was higher than present and rapid RSL rise had ceased by 7450 yr BP. We compare these RSL reconstructions with a regional model of glacial-isostatic adjustment (GIA). The RSL reconstructions from three sites off the coast of Sarawak show a spatial gradient opposite to that predicted by the GIA model. This disagreement can best be explained by tectonic deformation since 7000 yr BP, which was previously unrecognized. We propose vertical land motion of 0.7–1.45 m due to slip on the Serabang fault, which runs between our four sites. This slip may have occurred in response to the loading of the Sunda Shelf by rising sea level.NRF (Natl Research Foundation, S’pore)Published versio