New Zealand's glaciers are continuing to shrink and are showing the lowest total ice mass on record.
The National Institute of Water and Atmospheric Research (Niwa) said the Southern Alps glaciers had lost 2.2 billion tonnes of permanent ice from April 2007 to March this year, the fourth-highest annual loss since monitoring started.
Niwa has been surveying 50 glaciers in the Southern Alps for the past 32 years to record the height of the snow line at the end of summer.
Niwa principal scientist Jim Salinger said that because of the La Nina weather system over New Zealand, more easterly winds and warmer than normal temperatures during the period, there was less snow in the Southern Alps and more snowmelt.
Snow fed the glaciers, he said.
"The higher the snow line, the more snow is lost to feed the glacier. On average, the snow line this year was about 130m above where it would need to be to keep the ice mass constant," Dr Salinger said.
He said that worldwide, most glaciers were retreating.
Dr Salinger said global warming was one of the main reasons for the shrinking.
Glaciers were sensitive to changes in wind and precipitation as well as temperature.
Dr Salinger said the glaciers would not disappear entirely, as that would require a temperature rise of 7degC and no snow even at the top of our highest mountain, Mt Cook.
However, they would continue to retreat, he said.
