On a still and sunny December day when most Kiwis were looking longingly towards the beach, two NIWA researchers had their eyes firmly on the Southern Alps.

Adrian Aarsen and James Townshend jumped on board a helicopter from Queenstown to complete a last-minute piece of work before the Christmas break - servicing NIWA's Mt. Larkins snow and ice monitoring station.

As far as an end-of-year job goes - working at 1915m altitude on a bluebird day - the Mt. Larkins work is pretty good.

The Mt Larkins station is part of a network of 11 NIWA snow and ice stations across New Zealand creating a valuable long-term record of alpine weather and snow measurements, like depth and density.

NIWA hydrologist Dr Christian Zammit, who manages the research programme, says the network was set up for two main reasons: to measure how much water was being stored as snow, and to detect climate change impacts.

Work on the network began in 2008.

By 2013, 11 snow and ice monitoring stations had been set up, representing a range of distinct high-altitude areas of the country between 800 and 2200 metres above sea-level including Aoraki-Mt. Cook, Mt. Aspiring, Arthur's Pass, Tongariro and Fiordland.

The stations measure the depth, density and temperature of snow, as well as a range of other climate measurements such as precipitation, wind speed, temperature and humidity.

He says snow is a valuable economic resource for New Zealand, so understanding the amount, seasonal nature and long-term changes to snow and ice is hugely important - especially with a warming climate.

Snow melt contributes to as much as 30% of water that flows into major South Island hydro-electricity lakes.

Large areas of the South Island rely directly on water from snow melt for irrigation and the ski industry cannot exist without snow. In 2019 alone, there were 1.7 million visits to ski fields in New Zealand.

Dr Zammit says climate change will impact both the amount and seasonality of snowfall in New Zealand.

"We expect the snowline to increase in altitude with time and there is an expectation that there will be less snow. However, with climate change, extremes get more extreme. So, you could have less snow days, but you could have a larger amount of snow falling during storm events."

He says because the network has only been operating for seven years, more years of data will need to be collected to before researchers can confidently say how climate change is impacting our snow season, though NIWA's end of summer snowline survey has documented a long-term decrease in glacier coverage on the Southern Alps over the last 43 years.

As well as a need for long-term information, Dr Zammit says several organisations use real-time data from the network.

The Avalanche forecasting service generated by Mountain Safety Council is one of them.

"Data from the network is the only information they use to predict the state of the snowpack, both in and outside of the ski domain. Their daily avalanche risk forecasts are based on this information, their knowledge of the domain and access to weather forecast information."

Other main users of the network are hydro-electricity generators who use the data to estimate the volume and seasonality of snow and ice melt flowing down rivers. The information informs decision-making about when dams should be opened to generate electricity, as well as how electricity is stored and transported.

NIWA field researchers visit each snow and ice station twice a year.

At the Mt. Larkins station in December, there is some snow high on the alps.

Dr Zammit describes 2020's snow season as being "on the lower side" - winter was warm with little snowfall until a few big dumps late in the snow season.

For safety reasons, the stations are only visited on calm, sunny days. Mr. Aarsen says they waited a month for good weather to visit the Mt. Larkins site in December.

After a 15-minute flight, the researchers have three hours to complete the work needed before the helicopter returns to collect them.

The purpose of the visit is to replace fuel and antifreeze, collect snow samples, empty the snow collector measuring snow fall and make sure the equipment is recording accurate data.

Mr Aarsen says despite the sturdy design and build of the stations, lightning, extreme weather and the pesky destructive kea means the technicians also have to fix any issues that might have sprung up since the last visit - in this case some damage caused by a snow storm.

"You're putting in these instruments and you're thinking 'man, I hope this equipment will survive the elements'. The intensity of what the stations withstand is amazing.

"Kea will come and pick at anything they can. Especially the wind sensors, they love picking them apart. We've had a lot of equipment ruined by kea-. Once they get into something, they get into it pretty hard."

While the researchers work in t-shirts in December, Mr Aarsen says working in minus zero conditions during winter is a different story.

"The cold and snow make everything harder. It makes moving around or trying to undo screws really tricky when it's freezing and you're wearing a lot of layers. There can be up to a metre and a half of snow at Larkins."

As a safety precaution, the researchers bring up a survival bag that contains a tent, gas-cooker, food, sleeping bags and extra layers if a freak shift in the weather meant a helicopter couldn't safely collect the workers.

Despite the "10-out-of-10 view" from the top of the monitoring station, Mr Aarsen says looking out across the Main Divide isn't the highlight of the trip.

"The chopper ride is definitely the highlight... it's got to be, doesn't it?"