Nanyang Technological University, Singapore (NTU, Singapore) climate scientists have extended the known record of Singapore’s sea level to almost 10,000 years ago, giving a more solid dataset to improve future sea-level rise projections.

This more refined sea-level record also has wider implications. For instance, it would lead to more robust and accurate local projection of sea-level rise, offering a strategic guide for Singapore as it moves to adapt to climate change.

– Dr Stephen Chua, Lead Author

Stephen added by dating the Singapore sea-level record to 10,000 years ago, they retrieved crucial new information from the early Holocene period. This is a time of rapid sea-level rise that has remained poorly understood – until now. Furthermore, reconstructing its history over thousands of years is one of the most difficult aspects of studying climate change. To have a better understanding of the possible causes and repercussions of future developments, scientists must study and comprehend the past.

An international team led by NTU researchers extracted ancient sediments from up to 40 m underground at a site in Singapore’s Marina South. The samples were then subjected to rigorous laboratory methods such as identifying microfossils like foraminifera and statistical analysis to reconstruct Singapore’s sea-level history.

The longer the sea-level record goes back in time, the clearer the picture becomes for future predictions, according to climate scientists. The Holocene transition (10,000-7,000 years ago) was the last major episode of natural global warming in Earth’s history, with melting ice sheets and rising oceans resulting in a 20-meter rise in sea level. Before the recent increase in the twentieth century due to climate change, the sea level in Singapore has been constant for the last 3,000 years.

Researchers believed that this is the type of crucial information needed to effectively plan adaptation measures in the face of ongoing sea-level rise due to global warming. The team chose the Marina South investigations. Sediment extraction from an ‘ideal’ site with deposits like marine mud and mangrove peats was required to create an accurate ancient sea-level record.

Sea-level rise is a potentially disastrous outcome of climate change, as rising temperatures melt ice sheets and warm ocean waters. Scenarios of future rise are dependent upon understanding the response of sea level to climate changes. Accurate estimates of past sea-level variability in Singapore provide a context for such projections.

– Professor Benjamin Horton, Co-author & Director, Earth Observatory of Singapore

Singapore’s coastal defence plan against rising sea levels will benefit from the findings. The study also discovered the first clear evidence that mangroves only existed for roughly 300 years in the Marina South area before succumbing to flooding caused by rising sea levels at the time.

Researchers discovered abundant mangrove pollen at a depth of 20 metres below contemporary sea level, indicating that a mangrove shoreline existed in southern Singapore nearly 10,000 years ago. According to the findings of the NTU, sea-level rise during that time was as much as 10 – 15 mm per year, which likely contributed to the extinction of the mangrove.

The findings are useful for present and future adaptation strategies in Singapore, as the island nation seeks to move beyond engineering solutions and use natural approaches to protect its shoreline.

Despite their adaptability and usefulness as coastal defence, mangroves have limitations in the event of a fast sea-level rise, according to the study. This research backs up a previous study co-authored by NTU that found mangroves will perish if sea levels rise faster than 7 mm per year under a high carbon emissions scenario.

The sea-level change was modelled without deglaciation, meltwater discharge, and other considerations. This important systematic contribution from Singapore and the vicinity spans the post-glacial Holocene period, allowing a broad sea-level change pattern to be formed.

The Earth Observatory of Singapore (EOS) will lead the collaboration between the Nanyang Technological University (NTU Singapore) and Singapore Land Authority (SLA) in using Global Navigation Satellite System (GNSS) data for scientific studies.

The EOS, as the NTU Singapore Research Centre of Excellence, provides researchers with access to GNSS data collected by SLA’s Singapore Satellite Positioning Reference Network (SiReNT), as well as to its archived historical data.

Leveraging NTU’s strengths in areas such as sustainability and earth sciences, this collaboration also provides us with valuable data to contextualise more accurate projections to augment Singapore’s climate change response.

– Associate Professor Emma Hill, Acting Chair, Asian School of the Environment and Principal Investigator, Earth Observatory of Singapore

Hill ackownledged that Singapore’s GNSS data from the past is very important for understanding how the land and coast have changed over time. Using precise positioning technology like SLA’s SiReNT can help with more than just positioning and mapping. It can also open a lot of new ways to deal with the increasingly complicated problems caused by climate and environmental changes.

With the combined knowledge of SLA and EOS, they want to use the rich historical data to co-create solutions for a new era of predicting and preparing for coastal and land changes to help Singapore deal with and lessen the effects of climate change.

The collaboration between NTU and SLA supports the university’s NTU 2025 strategic plan, which aspires to address humanity’s great issues on sustainability and speed the translation of academic discoveries into solutions that lessen the human effect on the environment.

Together with EOS’s development of new coastal GNSS reference stations in Singapore, this will enable research into more accurate methods of measuring land height and sea-level changes around the country, as well as the effect of the atmosphere on the weather and climate on the island nation.

GNSS refers to various satellite navigation systems, including the well-known Global Positioning System (GPS), which can be used by systems such as SLA’s SiReNT to produce precise positioning data with a 3 cm accuracy.

The NTU-SLA agreement will establish four-year cooperation that will contribute to the Centre for Climate Research Singapore’s National Sea Level Programme (NSLP), which is supported by the National Research Foundation and the National Environment Agency.

Furthermore, during the duration of the collaboration, EOS will analyse previous GNSS data provided by SLA in order to determine how certain places’ land height has changed. This would increase the accuracy of elevation measurements generated from Interferometric Synthetic Aperture Radar (InSAR), the technique currently employed by NTU to map ground deformation over Singapore and other cities in the region.

In Singapore, EOS and SLA will deploy up to four additional coastal GNSS stations for data gathering to develop innovative approaches for monitoring both land height and sea-level changes. Additionally, they will be incorporated into the SiReNT infrastructure and services to maximise resource utilisation. Also, the existing SiReNT station data will be incorporated to assist this goal.

Simultaneously, EOS will study unique ways to use data from existing GNSS, such as investigating the amount of water vapour in the atmosphere. By characterising the atmospheric processes that impact Singapore at different timeframes, scientists may determine where and when localised weather systems are likely to cause heavy precipitation.

EOS researchers will also attempt to employ GNSS data in regional meteorological studies. By comparing and analysing GNSS and meteorological data in detail, the scientists hope to gain a deeper understanding of precipitation and extreme weather events.