Climate scientists at Nanyang Technological University, Singapore (NTU, Singapore) have extended the known record of sea level in Singapore to nearly 10,000 years ago, providing a more robust data set to improve future sea level rise projections.
This refined record of sea level also has broader implications. For example, this would lead to more robust and accurate local projections of sea level rise and provide Singapore with strategic guidance on climate change adaptation.
– dr Stephen Chua, lead author
Stephen added that by dating the Singapore sea level record to 10,000 years ago, they gained important new information from the early Holocene period. This is a time of rapid sea level rise that was poorly understood — until now. In addition, reconstructing its history over thousands of years is one of the most difficult aspects of studying climate change. In order to better understand the possible causes and effects of future developments, scientists need to study and understand the past.
An international team led by NTU researchers extracted ancient sediments from up to 40m underground at a site in Singapore’s Marina South. The samples were then subjected to rigorous laboratory methods such as identification of microfossils such as 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, climate scientists say. The Holocene Transition (10,000 to 7,000 years ago) was the last major episode of natural global warming in Earth’s history, with melting ice sheets and rising oceans causing sea levels to rise by 20 meters. Before the recent rise in the 20th century due to climate change, sea levels in Singapore had been constant for the past 3,000 years.
The researchers believed that this is the type of critical information needed for effective planning of adaptation responses to continued sea-level rise due to global warming. The team chose to investigate Marina South. Sediment extraction at an “ideal” site with deposits such as sea mud and mangrove peat was required to produce an accurate sea level record.
Sea level rise is a potentially catastrophic consequence of climate change as rising temperatures melt ice sheets and warm ocean water. Future rise scenarios depend on understanding how sea levels respond to climate change. Accurate estimates of past sea level fluctuations in Singapore provide context for such projections.
– Professor Benjamin Horton, Co-Author and Director, Earth Observatory of Singapore
Singapore’s coastal protection plan against rising sea levels will benefit from the results. The study also discovered the first clear evidence that mangroves in the Marina South area only existed for about 300 years before falling victim to flooding caused by then-rising sea levels.
Researchers discovered abundant mangrove pollen at a depth of 20 meters below present sea level, suggesting that a mangrove coast existed in southern Singapore almost 10,000 years ago. According to the NTU, the sea level rose by 10-15 mm per year during this period, which probably contributed to the extinction of the mangroves.
Findings are useful for current and future adaptation strategies in Singapore as the island nation seeks to go beyond engineered solutions and utilize natural approaches to protect its shoreline.
Despite their adaptability and usefulness as coastal defenses, mangroves are limited by rapid sea level rise, according to the study. This research supports an earlier study co-authored by NTU which found that mangroves will die if sea level rises faster than 7mm per year under a high carbon emissions scenario.
Sea level change was modeled without melting, meltwater runoff, and other considerations. This important systematic contribution from and around Singapore spans the postglacial Holocene and allows for the formation of a broad pattern of sea level change.