The 23-kilometre (14.3 mile) long glacier in the South Island's Southern Alps is likely to shrink at a rate of between 500 and 820 metres a year, said Martin Brook, a physical geography lecturer at Massey University.

"In the last 10 years the glacier has receded a hell of a lot," Brook said on the university website.

"It's just too warm for a glacier to be sustained at such a low altitude -- 730 metres above sea level -- so it melts rapidly and it is going to disappear altogether."

The rapid melting has seen a lake seven kilometres long and two kilometres wide form at the base of the glacier. Thirty-five years ago, the lake did not exist.

"The last major survey was in the 1990s and since then the glacier has retreated back 180 metres a year on average," Brook said.

The lake at the foot of the glacier is speeding up the melting as more ice is submerged under the surface of the water.

A study last year by the National Institute of Water and Atmospheric Research found the volume of ice in the Southern Alps had shrunk almost 11 percent in the past 30 years.

More than 90 percent of this loss was due to the melting of the 12 largest glaciers in the mountain range due to rising temperatures, the university report said.

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