Jamie Morton is the NZ Herald's science reporter.

Are islands more resilient to sea level rise?

Scientists have created a miniature replica of Fatato Island, a coral reef island in Tuvalu, around 3000km north of New Zealand, to model the impacts of sea level rise. Photo / Supplied
Scientists have created a miniature replica of Fatato Island, a coral reef island in Tuvalu, around 3000km north of New Zealand, to model the impacts of sea level rise. Photo / Supplied

Scientists have created a replica of a coral reef island to reveal what a metre of sea level rise would mean for communities in low-lying spots.

Remote island nations in the Pacific and Indian Oceans have for many years been considered extremely vulnerable to the effects of climate change and, in particular, rising sea levels.

Many have gone so far to predict they could even be completely submerged within the next century as sea level rises, forcing their populations to flee and become among the first climate refugees.

However, new research by the University of Auckland and University of Plymouth is seeking to demonstrate that islands formed on coral reefs are in fact more resilient than has perhaps been suggested in the past.

Scientists simulate sea level rise against a replica basin reef created in a UK lab. Photo / Supplied
Scientists simulate sea level rise against a replica basin reef created in a UK lab. Photo / Supplied

It is seeking to support previous field studies conducted by scientists in Auckland, which have suggested that rather than being submerged by sea water, the islands may adapt with the sand and gravel around their coastlines shifting to form a new and higher barrier against the rising sea level.

Coral reef islands are low-lying islands that sit on top of coral reef surfaces and provide the only habitable land in mid-ocean atolls.

Professor Paul Kench, head of the University of Auckland's School of Environment, has spent more than two decades monitoring environmental changes to islands and atolls in the Pacific and Indian Oceans.

"Over recent decades, it has become a commonly held belief that nations such as the Maldives, Chagos or Marshall islands are simply going to vanish as sea levels rise," he said.

Scientists prepare a replica basin reef in a UK lab to simulate sea level rise. Photo / Supplied
Scientists prepare a replica basin reef in a UK lab to simulate sea level rise. Photo / Supplied

"But our research would suggest it is in fact a commonly held misconception, and what we actually believe will happen is that as sand and gravel shift it will form a natural barrier against the sea.

"This is the first time we have been able to test that theory in a laboratory facility, and by replicating the conditions these remote nations face we hope to demonstrate the resilience of the islands but also enable them to appropriately prepare for the future challenges they may face."

Uncertainty around ice melt projections has made it difficult for scientists to put a precise figure on how much sea level rise can be expected to affect island communities under climate change, but Kench said one metre was a good base level to work from.

The research collaboration was supported with funding by the Royal Society of New Zealand Catalyst Fund, and a 1:50 scale replica of a coral reef island in Tuvalu - around 3000km north of New Zealand - which has been constructed in the coastal basin of Plymouth's COAST laboratory.

Scientists prepare a replica basin reef in a UK lab to simulate sea level rise. Photo / Supplied
Scientists prepare a replica basin reef in a UK lab to simulate sea level rise. Photo / Supplied

The model will be subjected to rising sea level and increased wave activity, with sensors recording data which will be correlated against previous field measurements taken over the past two decades and also with a numerical model.

"This is giving us an opportunity to firstly manipulate sea level more cleanly and see what the precise effect if sea level change will do to the island.

"Then, alongside that, we are coding up the computer model to replicate this, which will then allow us to explore the effects of higher sea level."

Scientists hope this will provide an accurate picture of the current state of affairs, but also enable them to assess how future sea level rise will affect this and other nations.

The University of Plymouth's Professor Gerd Masselink said work already carried out has shown that these islands did move and change, but the direction of the global debate was not allowing their populations to adapt and plan for the future using this knowledge and understanding.

Meanwhile, in another Marsden Fund-supported study, Kench and colleagues have been collecting coral samples from across the Pacific Ocean.

Scientists have created a miniature replica of Fatato Island, a coral reef island in Tuvalu, around 3000km north of New Zealand, to model the impacts of sea level rise. Photo / Supplied
Scientists have created a miniature replica of Fatato Island, a coral reef island in Tuvalu, around 3000km north of New Zealand, to model the impacts of sea level rise. Photo / Supplied

Chemical signatures retained by the calcium carbonate in these long-lived corals will allow them to reconstruct pH levels and other factors in the ocean, and build a comprehensive record stretching back thousands of years.

By gaining a deeper knowledge of ocean dynamics like acidity, scientists will better understand natural variations in and between ocean basins, which could give better context to climate models that have shown worryingly rapid changes over recent decades.

New Zealand and climate change

• Under present projections, the sea level around New Zealand is expected to rise between 50cm and 100cm this century, while temperatures could also increase by several degrees by 2100.

• Climate change would bring more floods (about two-thirds of Kiwis live in areas prone to flooding); make our freshwater problems worse and put more pressure on rivers and lakes; acidify our oceans; put even more species at risk and bring problems from the rest of the world.

• Climate change is also expected to result in more large storms compounding the effects of sea level rise.

• New Zealand, which reported a 23 per cent increase in greenhouse gas emissions between 1990 and 2014, has pledged to slash its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030.

- NZ Herald

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