25 Oct 2015

NZ's glaciers have shrunk by a third - report

6:19 am on 25 October 2015

A major state-of-the-environment report shows the country's glaciers have shrunk by more than a third in the past 30 years, and a glacier scientist says it is likely humans have helped that to happen.

The government report released on Wednesday says the volume of glacier ice has dropped by 36 percent since 1978 because of rising temperatures.

Andrew Mackintosh of Victoria University's Antarctic Research Centre said globally there was no doubt that human influences had caused glaciers to retreat.

He said it has yet to be scientifically demonstrated in New Zealand, but it was very likely humans have played a part.

"There's no doubt that New Zealand glaciers have lost a lot of ice during that period, especially since 2008 we've seen a rapid loss of ice in the Southern Alps and iconic glaciers like Franz Josef and Fox have retreated dramatically."

Franz Josef glacier.

Franz Josef glacier. Photo: Supplied

Dr Mackintosh said regional climatic variations had also had an effect on the glaciers.

"There's some combination of climate forcing and other processes that are at play here that cause glaciers to retreat."

Dr Mackintosh said the glacial melt would also have an impact on the country's water resources, and the ability to generate electricity through hydro power and the ability to irrigate land.

"It's not completely clear yet how that's going to pan out because you could imagine as glaciers melt more they'll actually give us more water in the short term, but eventually there will be enough ice lost that that water reservoir will be gone, so at some point in the future that extra stored water that we have in the mountains will disappear."

Dr Mackintosh said that the glacial volume loss was still an estimate because it was incredibly difficult to measure a glacier, but scientists in New Zealand are working hard to improve the estimates of volume change.

He said modelling of glaciers and the climate was underway to understand the detailed relationship between climate change and glacier change.

Senior research fellow at Victoria University's Antarctic Research Centre Brian Anderson used a fixed timelapse camera at four glaciers in the Southern Alps to monitor the rapid change in the glaciers.

Dr Mackintosh said the retreat at Fox Glacier during 2014 as captured by his colleague was unprecedented in the modern era.