Mount Footstool 'completely bare of snow' and that's causing aggressive rockfall

Monday, 29 January 2018

Loss of rock and snow has been particularly noticeable on Mount Footstool, experts say.

Thousands of tonnes of rock are coming off mountains in the Mount Cook alpine region, local guides say.

Department of Conservation (DOC) ranger Ray Bellringer said the area's iconic Mount Footstool was 'completely bare of snow', which was abnormal for this time of year. Rockfall events of this degree normally occur around late-February.

Mount Footstool in December 2016. There was more snow then, but the 2017-2018 summer went through more late season weather events.

'This is really unusual for here,' Bellringer said.

'It is quite dramatic. It is definitely to do with the weather.'

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Chief guide at Alpine Guides (Aoraki) Ltd, Dave McKinley, said Mount Footstool was not the only mountain affected by New Zealand's particularly warm and dry summer, but the loss of rock was particularly noticeable because the mountain was the most visible from Mount Cook Village.

Although it was not unusual for the mountains to have loose rock and rockfall events over summer, McKinley said it was particularly pronounced this year.

'Basically the glaciers are shrinking - as they always do in summer, but this is a particularly aggressive downwasting [the thinning of a glacier due to the melting of ice] event,' he said.

'It's because of the extraordinary summer we're having.'

On January 12, McKinley heard continuous rockfall for two hours while he made his way through a whiteout.

'I couldn't see 20 metres in front of my face, but I could hear it. Obviously something was coming down.'

WHY THE LOSS OF SNOW?

The area endured a particularly dry spring and summer, which would likely mean recovery of lost glacier ice could take years, McKinley said.

Bellringer said the 2017 rainfall in the area was two-thirds what it should have been.

'We only had 2800mm of rain in 2017, and we would normally get 4000mm on average. So that's a longer term issue. The rainfall is way down and you can see that very clearly in Lake Pukaki and Lake Tekapo,' he said.

Summer temperatures in Tekapo would normally be around 25C, but Bellringer said the area had been dealing with consistent temperatures of about 30C over the past few days.

'These are the kind of temperatures you would see in Central Otago or Twizel, but not here,' he said.

'That's going to do massive things to the glacial snowpack. The glaciers are dropping and losing snow quite rapidly.

'The height of the snow is dropping so it's exposing the rock, which we've never seen before. It's the whole issue around climate change and how much human impact there's been. There's definitely strong evidence of climate change. It's quite profound.'