Southern Alps glaciers growing

By SIMON COLLINS science reporter

Glaciers in the Southern Alps have grown slightly bigger in the past year.

An aerial survey of the range's 48 glaciers by the National Institute of Water and Atmospheric Research (NIwa) in March recorded the seventh-biggest increase in ice mass since the annual survey started in 1977.

Bit Niwa scientist Dr Jim Salinger said it was only a "blip" in a long-term trend that was likely to see many glaciers retreat for 20 years.

The ice expansion - ironic in a year when southern hydro lakes are low - is the delayed effect of a wet winter last year.

"This is probably because snowfalls in the Southern Alps last winter were above-average as a result of more wet westerly and southwesterly winds," he said.

"Furthermore, cold southwesterlies in spring kept snow precipitation slightly above average, and a cooler-than-normal summer resulted in less snowmelt."

Much of this year's expanded ice is likely to melt a few months too late to be of use for the power shortage.

Niwa's surveys showed an increase in ice almost every year from 1979 to 1997. Since then, the ice has shrunk every year except for 2001 - the last power crisis - and this year.

Longer-term records show that Westland's Franz Josef Glacier retreated about 2.8km between 1935 and 1983, advanced about 1.3km up to 1997, but has now begun retreating again.

The turning points coincide with changes in the Inter-decadal Pacific Oscillation (IPO), which are believed to be caused by a long 20- to 30-year cycle of water movements in the Pacific Ocean.

In an IPO cool cycle, El Nino weather patterns bring cool, dry weather.

An IPO warm cycle brings more La Nina patterns. The present one is believed to have started in 1998 and is possible worsened by global warming.

Said Dr Salinger: "Given another temperature increase and a reduction in snowfall precipitation, we'd expect quite a dramatic retreat over the next 20 years."

NIWA Climate change and global warming