Vanishing taonga: How climate change is melting our glaciers

New Zealand's cherished glaciers are melting at a frightening rate, with warmer temperatures over recent decades stripping them of a third of their total volume.

As our third consecutive La Niña bodes another dire summer for these icy wonders, a glaciologist is launching a major new effort teasing out the precise hand of human-driven climate change in their decline.

While melting glaciers are often seen as global warming's coalmine canaries, Victoria University's Dr Lauren Vargo said scientists still couldn't say exactly how much of this melt owed to climate change alone – particularly for individual glaciers and years.

But the signal was likely significant.

In one disastrous melt year – New Zealand's record-warm summer of 2017-18 – Vargo and colleagues estimated global warming made the extreme ice loss at least 10 times more likely.

That study, focused on specific South Island glaciers for which scientists had detailed records of mass change, happened to be only the second to link greenhouse gas emissions with high annual ice loss.

In her latest project, just awarded a three-year grant through the Marsden Fund, Vargo planned to apply the same modelling methods to around 230 glaciers.

"I will ask, for the highest melt years for each glacier, what is the increase in likelihood of melt with climate change, and the increase in the amount of melt with climate change?" she said.

"We'll also assess future glacier melt, and ask, how much might the highest melt years for glaciers increase in likelihood and severity as temperatures rise to 1.5C and 2C?"

One major study published this year, and which Vargo co-led, found that if contemporary decadal trends continued, the Southern Alps' average snowline elevation would be displaced at least 200m higher than normal, as early as 2025 to 2034.

This graph shows how the average snowline of the Southern Alps has risen over time. Image / Drew Lorrey, Niwa

On current trajectories, 11 of 50 annually-checked "index glaciers" selected in the late 1970s to track change were expected to disappear by the middle of next decade, with another 10 swiftly approaching a similar fate.

"I'm interested in these questions because billions of people worldwide rely on glacier melt for water, power generation, and agriculture, and declining water availability in glaciated regions is already contributing to human migration," Vargo said.

"This study will help us to better understand the effects of climate change on glacier melt."

Victoria University glaciologist Dr Lauren Vargo is leading a new Marsden Fund-supported study. Photo / Hannah Perrine Mode

She hoped the research would also help fill in knowledge gaps around the world, where a third glacier ice has vanished over two decades and 0.5C of temperature rise.

That connection was tragically highlighted in Pakistan this year, where heavy monsoon rains, heatwaves and melting glaciers led to devastating floods that killed more than 1700 people.

Here in New Zealand, Vargo expected another dominant La Niña climate system – something that's traditionally coincided with glacier loss – combined with background warming would likely spell another high melt year.

Why is pounamu so tough?

Vargo's programme is among 113 projects just allocated a total $77.3m through the Marsden Fund, the country's premier pool for investigator-led research.

They spanned a broad range of disciplines and topics: among them, countering antibiotic resistance, understanding the drivers of solar cell adoption and uncovering the cultural history of the taniwha.

One study, led by GNS Science, will look at why pounamu - Aotearoa's own nephrite jade – is so tough.

Project co-leader Dr Simon Cox said the project had been built on over nearly two decades of pounamu research together with Ngāi Tahu.

The prized taonga was renowned for its extreme toughness compared to other rocks, which was why it was historically revered so highly as a tool that holds a sharp edge.

"It also makes it very suitable for artisanal work such as carving and shaping," Cox said.

"We all have a lot of theories to explain its special properties, but this gives us the platform to explore it further using state-of-the-art materials science and iwi cultural knowledge to form a larger picture of pounamu use over time."

He said the project would bring together scientists unfamiliar with the carving properties or history of various samples and pounamu artisans who had yet to include physical science data in their work.

"Ngāi Tahu's kaupapa and tikanga around their tino tāonga, as well as mātauranga on pounamu, are integral to research success and two-way knowledge transfer."

It was hoped the research would be useful in informing the selection and cutting process of high-quality pounamu for carving and illuminate future development of super-tough synthetic materials.

GNS Science geologists Dr Nick Mortimer and Dr Simon Cox. Photo / Supplied

"With its cultural, geological, archaeological and materials science significance, this project could rewrite the jade textbooks of the world and lead to better management of this precious resource."

Co-leader and geologist Dr Nick Mortimer said nephrite jade and pounamu were "unusual rocks: in that they had a metal-like toughness, and were very resistant to fracture.

"Why this should be is a scientific mystery. The mineralogical explanation of pounamu's physical toughness remains elusive," he said.

"The minerals in pounamu are all fairly soft yet the rock is tough. This makes it excellent for carving, and for creating objects which keep a sharp edge.

"We think the longstanding explanation - of twisted mineral fibres - is wrong. We will be testing other theories - including ultra-fine grain size and stored strain."

Marsden Fund Council Chair Professor David Bilkey said Māori research and mātauranga Māori had been particularly recognised across the projects, with one in 10 investigators identifying as Māori.