Ash from the Australian bushfires is still visible on many of the South Island’s glaciers, according to NIWA scientists.

NIWA and Victoria University of Wellington scientists completed their annual post-summer snowline survey of 50 South Island glaciers in early March.

The survey discovered widespread ash coverage on the majority of glaciers surveyed, which may be contributing to glacial melt, NIWA climate scientist Dr Andrew Lorrey said.

“At this stage, it’s difficult to characterise exactly how much the ash has added to the ablation of snow and ice, but there should be some immediate negative effect,” he said.

In 2019, the South Island glaciers enjoyed the best snow dump in three years.

“Every now and then you will get a year that reminds you of how things used to be,” said Lorrey. “But the overall trend is towards more frequent hotter years, which are hugely detrimental to glaciers.

“You would need to see 20 to 30 years like this one to even start to consider whether the recent damage that has been done can be reversed to any degree. Glaciers can take a very long time to grow.”

The annual survey sees scientists take thousands of aerial photographs of the glaciers to evaluate the snowline and build 3D models. The findings are used to assess how much of the year’s fresh snow contributes to glacial ice accumulation.

The snowline survey has been documenting glaciers since 1977, and results from this year’s survey will be known later this year.