New analysis charts historical loss of New Zealand’s glaciers

The West Coast's famous Fox Glacier. A new analysis has put the worsening decline of New Zealand’s postcard glaciers into bleak historical context. Photo / Miles Holden

• An analysis highlights the tragic loss of New Zealand’s postcard glaciers back to the late 19th century.
• It suggests that ice volume has shrunk by 80% in 130 years: with climate change ramping up the rate of loss.
• It comes after another team of scientists recently estimated our glaciers had lost a third of their volume within just the last 24 years.

A new analysis has put the worsening decline of New Zealand’s postcard glaciers into bleak historical context: suggesting they’ve lost 80% of their ice since 1895.

Half of that loss had come over the past 75 years, with a combination of climate heating and other drivers taking increasingly large bites of the ice over recent decades, the new study showed.

Successive studies have painted a stark picture of our glaciers’ future: last month, scientists reported they’d shed around a third of their volume within the last 24 years.

New Zealand already boasts one of the longest continuous records of glacier loss, thanks to end-of-summer snowline altitude measurements that have been carried out since 1977.

The latest analysis, led by veteran climate scientists Professor Jim Salinger and Emeritus Professor Blair Fitzharris, offered an even longer view by extending the glacier volume back to the end of the 19th century.

The research reconstructed ice volume changes for more than 3000 small and medium-sized glaciers and the 12 largest glaciers in the Southern Alps region.

Along with the data from the annual snowline survey, it drew on historical climate data and statistical modelling methods.

“The broader data set also allows us to identify the rate of ice loss,” Salinger said.

“This is important as it shows the impacts of regional climate warming in New Zealand over the last 130 years.”

For the entire period, on an annual basis, the rate was 0.82cu km per year – but it was the past 15 years that had seen the starkest decline.

“This has been a product of an acceleration of global warming and marked changes in atmospheric circulation,” Fitzharris said.

Between 1895 and 1949, ice volume declined steadily as temperatures rose by 0.5C.

Since 1949, temperatures had increased by a further 1.3C, accelerating the loss dramatically.

“From 1895 to 1949, temperatures warmed by 0.5C, leading to a decrease in ice volume to 40% of its original size,” Salinger said.

“The further decrease to only 20% of this volume occurred with a total warming of 1.8C since 1895.”

In all, the scientists found glacier volume had shrunk from 134 cu km in 1895, to about 27 cu km today.

Climate change was the stand-out driver of ice loss: especially in recent decades.

But the study also highlighted the role of major climate drivers such as the Southern Annular Mode (SAM) and the Interdecadal Pacific Oscillation (IPO) in glacier retreat.

The mode, which had been trending more positive over the past 130 years, brought higher air pressure and warmer conditions, exacerbating ice loss.

The IPO’s multi-decade oscillations influenced regional climate patterns, with its current negative phase since 1998 promoting warmer temperatures and increased glacial melt.

“The results show that after regional warming, the most important climate drivers are firstly the SAM and then the IPO,” Salinger said.

“A positive SAM phase tends to bring relatively light winds, tranquil weather, and above-average temperatures, while the IPO influences climate variability over the Pacific Basin, including New Zealand.”

Looking to the future, the study suggests that continued warming could reduce the Southern Alps’ ice volume to just a fraction of 1900s levels.

“Modelling of current warming from Nationally Determined Contributions to the Paris climate agreement goals suggests warming of 2C to 3C by 2100, which could reduce ice volume to between 5-10 cu km,” Salinger said.

“Aotearoa [land of the long white cloud] could certainly become Aoteapoto: land of the short white cloud.”

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.

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