The summer heatwave has massively affected New Zealand's glaciers, resulting in the largest annual ice loss on record.

Photo: 123RF

The meltback was observed by the annual Glacier Snowline Survey, a collaboration between NIWA and Victoria University.

Survey founder Trevor Chinn said it was one of the largest glacier meltbacks since he began the survey in 1977.

"A glacier is the best climate change indicator you can use," he said.

New Zealand glaciers have lost 30 percent of their ice, in the 40 years that the annual snowline survey has been running.

Whether these dramatic results could be directly attributed to climate change "is the $64,000 question", Niwa climate scientist Andrew Lorrey said.

Niwa said it was embarking on formal testing in collaboration with Victoria University and the University of Melbourne to see if a definitive correlation could be found.

"Can you actually get a natural event like this, or is it something where climate change has loaded the dice and it's pushed us over some sort of threshold?" Dr Lorrey said.

"Those are the questions we're looking to answer."