Sea levels have been rising longer and faster than we realized

Sea levels in the Indian Ocean started rising faster much earlier than scientists had assumed. And the proof isn’t buried in computer models or satellite data – it’s recorded in the skeletons of living coral.

Marine scientists have pieced together a 100-year record of ocean change by studying coral samples from the Maldives.

The team behind the research comes from the National University of Singapore (NUS) and Nanyang Technological University (NTU). Their work sheds new light on how quickly the ocean has responded to global warming.

A time machine in the Indian Ocean

By analyzing coral cores – essentially cross-sections of coral that grow year by year like tree rings – the team was able to push the sea-level timeline for the Indian Ocean back by another 60 years, reaching all the way to the early 1900s.

This extended record doesn’t just fill in historical blanks. It changes our understanding of how quickly human-driven climate change has impacted the sea.

Clear fingerprint of human activity

The research produced two key findings. First, sea-level rise in the Indian Ocean began accelerating around 1959. That’s decades earlier than satellite data or tide gauge records suggested.

The timing tracks closely with global temperature increases and rapid glacial melt – both driven by human activity.

“What we’re seeing is a clear fingerprint of human-driven climate change etched into the skeletons of corals. The early acceleration in sea-level rise is a warning sign that the ocean has been responding to global warming far earlier and more strongly than we thought,” said Professor Paul Kench.

The second key finding is that since the mid-20th century, the Indian Ocean has risen about 30 centimeters. That’s a dramatic shift in a body of water that covers nearly 30% of the world’s ocean area and supports around 30% of the global population.

Rising sea levels in the Indian Ocean

This rise isn’t just a number – it’s a direct threat. For millions living in low-lying coastal areas, higher seas mean more flooding, more erosion, more saltwater creeping into freshwater supplies, and more damage to critical ecosystems like mangroves and coral reefs.

The Indian Ocean’s changes also affect regions far beyond Asia. Shifts in sea level here influence weather, water resources, food security, and disaster risk around the world.

For Singapore and its Southeast Asian neighbors, this kind of long-term record is a game-changer. It gives climate scientists more accurate data to feed into models. That means better predictions – and better preparation.

The findings can support existing efforts like Singapore’s Coastal-Inland Flood Model and Climate Impact Science Research Programme. With more precise projections, planners can build smarter defenses against rising seas.

Corals are reliable record-keepers

What makes this study especially powerful is how clearly it confirms that corals are reliable record-keepers.

As corals grow, they build up layers that capture the chemical and physical traits of the surrounding water – temperature, salinity, and sea level. To confirm the accuracy of the records, the team compared coral data with readings from tide gauges and satellites. They found a close match.

Looking ahead, this validation positions coral as a powerful tool for climate science – not only for measuring sea-level change, but also for tracking extreme events such as heatwaves, cooling periods, and droughts.

“These findings have far-reaching implications for climate adaptation planning globally, especially for low-lying and densely populated coastal regions. We hope this work contributes meaningfully to the global dialogue on resilience and preparedness,” said Professor Kench.

Protecting vulnerable coastal communities

This research gives us more than numbers. It offers perspective. Sea levels have been rising longer and faster than we realized. That knowledge gives us a better shot at facing what’s coming next.

For the scientists behind this work, corals aren’t just marine life. They’re storytellers – quietly recording history one layer at a time.

In this case, corals have compensated for the absence of extended historical records of sea level changes in the central Indian Ocean.

“Such data is critical in the region given the abundance of low-lying coastal areas, and islands, and heightened vulnerability of coastal communities and coastal ecosystems in the Indian Ocean,” wrote the researchers.

The full study was published in the journal Nature Communications.

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