Glacier melt most recorded

Scientists from the University of Otago at the Mt Brewster weather station, which is being used...
Scientists from the University of Otago at the Mt Brewster weather station, which is being used as part of a study on ice loss in the Southern Alps. PHOTO:SUPPLIED
Scientists measuring snow and ice in the Southern Alps say glaciers are losing ice at the highest rate ever recorded.

Associate Prof Nicolas Cullen of the University of Otago School of Geography has been recording ice melt from the university’s weather station on the Mt Brewster glacier in Mount Aspiring National Park since 2004.

"From the start of the programme we have been watching the glacier retreat, but ice being lost on our glaciers presently is unprecedented and has never been higher," he said.

Since 2016 Otago University researcher Dr Todd Redpath has been using data from the university’s Pisa Range weather station to record the depth and variation of seasonal snow cover and the impact of climate change.

"Pisa Range is interesting because it is east of the Main Divide of the Southern Alps, so the atmospheric processes and the climate are different from Mt Brewster.

"Having weather stations in different environments give us a better understanding and can produce models that better represent what is happening in the mountains, he said.

Niwa had 13 alpine and subalpine weather stations across New Zealand but more weather stations would make their forecasts more robust, Dr Redpath said.

"If we wanted to have the same geographic coverage of high-altitude weather stations as Switzerland we would have to have 248 weather stations.

"We are not covering all of the mountains in New Zealand as well as we might like and there are lots of regions where we don’t have any stations, but there are earth observation satellites operating continuously orbiting around 500 to 600 kilometres above the earth surface providing high to medium spatial resolution data," Mr Redpath said.

In 2010 the Mt Brewster weather station was upgraded and high-quality radiation instruments were installed to carefully measure radiation from the sun and earth, which could tell us a lot about the variability in clouds in the Southern Alps, Dr Redpath said.

Prof Cullen said he expected in the future there would be a shift away from spending a lot of money on one or two sites towards having many more low-cost instruments at different locations.

"If we have a lot more observations, even if they are not of the highest quality, it would be a game changer."

One of the biggest challenges was understanding how air temperature changed with altitude.

"If we could have more observations on the valley floors and leading up to the highest points or peaks in the Upper Clutha catchment or elsewhere it would allow us to determine more accurately when it is going to snow, versus when it is going to rain.

"You would get a much better sense of where the rain-snow threshold is, which is really important for everyone in the ski industry," Prof Cullen said.

The Mt Brewster weather station and the Mt Pisa station had recorded a lot of variability from year to year in terms of where snow was on the mountains and how long it lasted, he said.

Dr Redpath said "the ski areas have worked with this for a long time and are getting very good at dealing with variable conditions by investing in grooming and snow-making technologies, but the bigger question is how different will things be in the future and what the range of our current snow variability will look like in 50 years or 100 years.

"We are on the way to understanding it better but there is still a lot of work to do."

Both scientists are core members of Otago University’s Mountain Research Centre established last year to provide research expertise on mountain environments for government, industry and recreationists.

Prof Cullen is also leading a $733,000 project to improve the modelling of seasonal snow and catchment processes, which is being funded by the Deep South National Science Challenge: Changing with our Climate.

kerrie.waterworth@odt.co.nz

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