An international group of researchers, including a UNSW Canberra PhD graduate and Emeritus Professor, have mapped the rise and fall of sea levels in the central Indian Ocean over the last 2000 years, providing a glimpse of what can be expected in the future.

Published by Nature Geoscience, the research demonstrates that sea levels in the Indian Ocean have risen by close to a metre in the last two centuries.

This rise has long been considered unprecedented. However, an examination of coral in the Maldives shows that a rise of this magnitude has been observed on two occasions in the last two millennia.

“The world is a rather dynamic place,” co-author and UNSW Canberra Emeritus Professor Roger McLean said.

“Most people thought of sea levels continuously rising over the last 4000 to 6000 years without any changes. What we have found are very significant changes, particularly between 500 and 800 AD, as well as 1500 and 1800 AD.”

The research was led by Professor Paul Kench, a UNSW Canberra PhD graduate who is now the Dean of Science at Simon Fraser University in Canada. Professor McLean was his PhD supervisor in the early ‘90s.

Professor Kench and Professor McLean in the field at Muhutigalla Island, Southern Maldives.

While the current rate of sea-level acceleration has previously been observed, the paper notes that the Indian Ocean will exceed its highest sea levels on record if it continues along this trajectory.

Professor McLean, a lead author on four Intergovernmental Panel on Climate Change (IPCC) Reports, said understanding where sea levels have been historically and what happens when they rise provides insights into how small islands and coral reefs may respond to future changes in sea levels.

He said the research also opens up new avenues to explore human adaptation to changing sea levels.

“People on these islands would have had to respond to the sea levels rising before,” Professor McLean said.

“It would be very interesting to find out how traditional communities adapted to those two sea level rises.”

The researchers sample a fosil coral micratoll in Mahutigalla.

The data obtained in the recent fieldwork identifies time periods that researchers could examine.

“This gives people a time to focus on – to look at what was happening on these islands between 1500 and 1800, when temperatures were lower and when the sea surface temperature was lower.”

Climate forced sea-level lowstands in the Indian Ocean during the last two millenniais the latest instalment in Professor McLean’s extensive biography of more than 150 papers. Beginning with his first paper Marine Geology in 1967, his work has greatly contributed to an enhanced understanding of the impacts, vulnerability and adaptation to climate change and sea-level rise.