Hot weather having massive impact on New Zealand's 'water tower' glaciers

Wednesday, 31 January 2018

The Gardens of Eden and Allah, on the Southern Alps, where snow levels are already lower than they were in March last year.

Two little-known glaciers on the Southern Alps are disappearing thanks to a 'massive melt-off of snow'.

Snow levels were already lower in the Garden of Eden and Garden of Allah than they were last March, researchers say.

Dr Pascal Sirguey, of the University of Otago's Surveying School, says 'a massive melt-off of snow' is happening at New Zealand's second largest ice cap.

With at least two more warm months to come, the melt-off was expected to get worse – which could affect water supplies to Canterbury and West Coast rivers, they say.

Dr Pascal Sirguey and Dr Nicolas Cullen, of the University of Otago's surveying and geography departments, have been studying the ice fields, which cover 36 square kilometres, for two years.

The research team at the Gardens of Eden and Allah at the weekend, including Dr Nicolas Cullen, centre, and Dr Pascal Sirguey, right.

During a visit at the weekend they discovered 'striking' changes, Sirguey said.

'What we're seeing from these current high temperatures is a massive melt-off of snow . . . This year may end up being a year where we lose a lot of ice in New Zealand.

Associate Professor Dr Nicolas Cullen, of the University of Otago Geography Department, says there is urgency to determine theevolving processes at play in these alpine areas.

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'The one thing that's really preserved the glacier from melting when summer comes is what snow is left . . . this glacier will experience a very potent effect of temperature and sunshine for another big chunk of summer.'

The little-known area formed New Zealand's second largest ice cap, Sirguey said. Determining the effect of the melt on the glaciers was urgent.

Cullen said the massive 'water towers' helped to sustain flow to some major rivers – the Rakaia and Rangitata in Canterbury and Wanganui on the West Coast – when rainfall was scarce. Glacial retreat was 'definitely linked to climate change'.

'Air temperature is a governing factor in the health of ice fields and glaciers as it controls melt and whether it rains or snows,' Cullen said.

'As such, the changes in both the timing and volume of runoff from glaciers and seasonal snow will affect New Zealand's hydropower generation, irrigation, and agriculture in the future . . . water availability is set to become a major issue.'

Sirguey said 'very little data' had been collected on the ice cap in the past, so he and Cullen would use satellite imagery provided by the French National Centre for Space Studies to investigate how the glaciers had changed over the past 20 to 30 years.

'These [satellite images] will allow us to reconstruct the gardens and compute an estimate of how much this ice body has lost.

'We may find out as the future unfolds whether or not this summer is exceptional, but right now we're on a track that may really make it a summer of big loss for the glaciers of New Zealand.'

Sirguey said the melt-off was linked with thousands of tonnes of rock falling from mountains in the Mt Cook area, resulting from a particularly warm and dry summer.