Wellington: New Zealand's glaciers are melting away, according to an annual survey of the snowline on 50 glaciers in the South Island, the National Institute of Water and Atmospheric Research (NIWA) announced on Monday.

They have lost half of their snow and ice over the last 30 years, scientist Jordy Hendrikx said, confirming that the glaciers again lost much more ice than they gained in the 12 months ending March at the end of the Southern Hemisphere summer.

He said this was mainly due to above-normal temperatures and average rainfall over the Southern Alps during the previous winter combined with above-normal sunshine and well below normal precipitation during late summer.

Hendrikx said that, on average, the snowline during the year was about 95 metres above where it would need to be to keep the ice mass constant.

This indicated that the loss of glacier mass observed in 2007-08 had continued, he said.

Last year's survey showed that the glaciers had lost 2.2 billion tons of permanent ice in the previous 12 months and shrunk to their smallest size since records began in 1977.

Prime Minister John Key told his weekly news conference: "It certainly demonstrates that we need to take this issue of climate change very seriously."

Key does not plan to go to the United Nations conference on climate change in Copenhagen next month, but he said it would be on the agenda of this week's British Commonwealth Heads of Government meeting in Trinidad and Tobago.

After releasing the report, Hendrikx told the TV3 channel: "It's undeniable that we have altered the atmosphere." IANS