Climate Change: The Future of Snow
On the morning of 18 July 2022, Aoraki/Mt Cook avalanche forecaster Taichiro Naka was in his room in the Alpine Guides’ staff accommodation building at Mount Cook village. It was pouring, and unseasonably warm; a storm had rolled in from the northwest over the Tasman Sea. Naka knew it was probably raining higher up in the mountains, too, and on a larger-than-usual snowpack—the second biggest for midwinter since snow-depth records started at Mueller Hut in 2010.
The day before, Naka had issued a warning via the NZ Avalanche Advisory (NZAA), the country’s official backcountry avalanche forecasting service provided by NZ Mountain Safety Council (MSC). “Very dangerous avalanche conditions,” he’d written. “All ingredients for destructive wet avalanches are here. Travel in avalanche terrain is NOT recommended.”
Now, as he listened to the rain drumming down on the corrugated iron roof, he could hear something else, too: a deep, continual rumbling, like the world’s longest thunderclap. When the roar was over, Naka grabbed his binoculars, camera, telephoto lens, raincoat and gumboots, and jumped into his car.
One minute later, he reached Hooker Valley Road. The clouds lifted, and he could see a massive avalanche sprawling down Kitchener Creek—a river of rubbly ice and snow muddied at the end with dirt, sticks and even small shrubs the monster had scraped off the valley floor as it charged down the mountain.
The rock berm built by the Department of Conservation just 4 years earlier to protect Mount Cook village against a 1-in-100-year avalanche had worked perfectly, diverting the flow of snow safely away from the town.
“Money well spent,” says Naka.
Wild Storms and Weak Layers
The 2022 storm brought 550 mm of snow and rain to the Southern Alps in just over 72 hours—an “unprecedented winter rainfall" event in this location, according to paper published in the Geophysical Research Letters science journal in 2023. Since 1928, only three other storms have produced more rainfall, but they all happened in summer.
The warmer-than-usual winter temperatures meant it rained rather than snowed, even at high elevations. Water saturating the deep snowpack caused the Kitchener avalanche—the largest there since 1986, running nearly 2 km and destroying almost a hectare of forest—as well as numerous other avalanches and debris flows elsewhere in the mountains.
The winter of 2023, by contrast, featured a completely different climate problem—but one that also caused widespread avalanches. Snow fell at the start of the season, and then there was a long dry spell. That caused the surface of the snow to harden, with sugar-like crystals then growing on top. When snow eventually fell, it didn’t bond properly to the hard layer beneath causing a persistent weak layer.
“We had a persistent weak layer pretty much everywhere in the Southern Alps,” says Kevin Boekholt, a director of Alpine Guides and an NZAA forecasting coordinator based in Methven.
That meant any travel in the mountainous backcountry, including mountaineering, skiing or boarding, risked triggering a slab avalanche—even at a distance. “Somebody can be skiing down on a relatively flat area of terrain, and they can send a wave of energy through the snowpack and trigger an avalanche on an adjacent slope.”
That’s exactly what happened in 2023: we saw some of the biggest natural and human-triggered avalanches possible in New Zealand, says MSC Operations Manager Nathan Watson. There were several close calls, but no-one was killed. That year, the NZAA frequently warned of the dangerous conditions caused by the persistent weak layer.
People changed their plans accordingly, says Boekholt, cancelling trips or heading to the West Coast or upper Haupapa/Tasman Glacier where conditions were safer. “It significantly affected the whole backcountry industry.”
There was less demand for his company’s helicopter service, and backcountry huts, such as those in the Cass Valley, had cancellations for months. “People were well aware that conditions in the backcountry weren't safe. They really took heed of the avalanche advisory last year, and as a result of that there weren't a lot of people in the mountains.”
Boekholt has worked as an alpine guide in the Southern Alps for 40 years. While there’s always been variability, winters used to be more predictable, he says. “There’s no normalised pattern anymore.”
These swings between extremes are expected to become more common as the climate warms—so what does the future hold for our snow and the rivers the meltwater feeds?
The Science of Snow
Dr Todd Redpath grew up in Southland and spent high school and university going snowboarding at every opportunity. “I used to spend all winter just trying to figure out how to get up the mountain at the weekend, and it hasn’t really left me... It’s a big motivator.”
Redpath, who is now a scientist, has spent years trying to answer what sounds like a simple question: what will climate change mean for recreation in the snow in New Zealand? “Are we still going to be able to go snowboarding or skiing in 10 years? Fifty years? A hundred years, if I live that long?”
That question is surprisingly difficult to answer. In other parts of the world, like the American Rockies, South American Andes and European Alps, there’s a clear link between global warming and rising snowlines, shorter ski seasons, and less snow in fewer places. Here, the likely impacts are a little more complex to tease out, Redpath explains.
“We can't really say with a lot of confidence that we're going to see the snow season reduced by X percent or snow depth decreased by Y percent. That's still relatively tricky, and there just hasn't been a lot of research done in that space.”
There are two main reasons it’s tricky. Firstly, our records aren’t very good. Snow cover at the national scale is easiest to measure from space, and we only have reliable, regular satellite data for the last quarter-century, from 2000.
The first attempt to scientifically model the potential impacts of climate change on snow across New Zealand was done by NIWA researchers in 2012; the results suggested we’ll see much less snow at low elevations on average over the 21st century, and possibly marginally more at the highest elevations (above 2900 m.)
The other factor, though, is the dramatic variability in climate conditions from year to year—making it difficult to both untangle what role global warming is playing and to predict exactly how that warming might play out in the mountains.
Snow requires both cold and precipitation. Climate change is set to bring warmer temperatures, Redpath says, but also more precipitation in some places, especially the Southern Alps. When, where, and exactly how that precipitation will fall—as snow or rain—is frustratingly hard to predict.
Because of our location in the South Pacific, New Zealand is buffeted by a set of complex and interacting climate patterns, Redpath explains. Wind direction, timing, and a few degrees of variation in temperature can dictate when and where it snows. “Quite subtle differences can play quite a big role here,” he says.
“A lot of our snowfall that does occur, occurs within quite a narrow range of temperatures close to zero degrees. So, any particular snow event in New Zealand can be really sensitive to exactly what orientation that air mass takes—is it a little bit warmer or a little bit cooler than normal? That can tip the balance quite quickly between a big snowfall event or a rain event in the middle of winter.”
In August 2020, for instance, warm winds and rain on snow closed Wānaka’s Treble Cone for nearly a week—the snowpack literally sliding off the mountain in some places. Masters student Anita Bentley, who Todd co-supervised, consulted three decades of ski patrollers' observations from the Craigieburn club ski field in Canterbury from 1991 to 2019. She identified a gradual decline in snow depth over that period—but also, that around half of the winter snow accumulation comes from snowfall events where you get more than 15 cm dumped at once. For ski fields, “a few of these big snowfall events through the winter are really important”, says Redpath.
In general, climate change is likely to bring more weather extremes—meaning the swings between storms and droughts seen in the South Island in 2022 and 2023 may become a feature of our future, he says.
Raging Rivers, Simulating Snowmelt
The kind of heavy rain on snow seen in 2022 has downstream implications, too, for people spending time in the outdoors well below the snowline. When rain melts snow, it can supercharge floodwaters, making rivers more dangerous and damaging infrastructure and homes. The July 2022 downpour took out an entire bridge on Ohau Road near Twizel, cutting off the nearby village and Lake Ohau Lodge, and caused the Omarama stream to jump its usual course.
Similarly, in March 2019, snow- and ice-melt added 400 mm of runoff, increasing river flow in the Waiho catchment by 20% and destroying the state highway bridge at Franz Josef Village.
“If you're someone that's thinking about the flood hazard downstream, you're not just considering the 150 mm of rain in the forecast, you also have to think—how much snow is there? How much of that snow might melt, and what does that add to the runoff?” says Redpath. “That hasn't really been thought of explicitly in New Zealand before.”
But it is now. Hydrological forecasting scientist Dr Jono Conway from NIWA is leading a team of scientists working on exactly this question. They’re working on a 3-year project to develop a modelling system to accurately simulate snowmelt, which should help to predict flooding up to 5 days into the future. MSC is a project partner and will help to test the models, with the hope that this leads to improved safety information for public use.
If it’s funded long-term, in a few years' time people planning a walk or tramp may be able to check not only the weather forecast on MSC's trip planning tool Plan My Walk and avalanche forecast on the NZAA, but the snow-melt runoff predictions too, before heading out, he says.
“It will be another tool in the toolbox,” says Conway—a way for people to visualise the risks. “So, you don't look at a weather map and think, ‘Oh, it's a sunny day, the rivers are going to be low’, when actually, because of heavy rainfall and snow melt the day before, there may still be high river flows.”
Surviving Via Snowmaking
In a related paper, the authors of the 2012 NIWA snow study predicted that under most likely future scenarios, the number of snow-days at commercial ski fields will fall as the century progresses, as will possible snow-making hours—a reduction of 40% percent by 2090. The snow cover is set to thin by then, too. By how much is uncertain, but somewhere between 48% and 9% of current maximum snow depths, on average.
However, the paper also suggested that ski areas may be able to offset much of the natural snow losses with snowmaking. More research needs to be done, Redpath says, but in the meantime, ski field operators are investing heavily in state-of-the-art snowmaking equipment.
“Snowmakers are very much a necessary part of our industry now, and will be into the future as well,” says Mt Hutt Ski Area Manager James McKenzie.
The new electric machines are more energy-efficient and power up automatically when on-board temperature monitors tell them conditions are right for making good quality snow, says McKenzie, saving electricity, water, and money. “Our windows for snowmaking are getting shorter and shorter, so we need to start up and shut down much more quickly than we used to,” he says.
There’s also the option of additives that help catalyse the creation of snow crystals and reduce evaporation—a costly solution, but one that might need to be used more often as snowmaking weather-windows narrow.
Whakapapa ski field on Mt Ruapehu, on the other hand, has installed a “Snowfactory” which can spit out snow even when the mercury hits 20 degrees. But scientists point out that the warmer and wetter the weather, the more energy and water is required to make snow. According to some estimates, running a Snowfactory for two days uses as much electricity as a typical NZ house does in a year.
More frequent wild weather is another emerging issue, says Ewan Mackie,Treble Cone’s Ski Area Manager and RealNZ Sustainability Lead. “At some point the snow will run out, but that is relatively distant. The challenge now is the extreme weather…that interrupts our ability to operate safely and reliably.”
Winters have always been variable in New Zealand, but commercial operators are preparing for the unpredictability to increase. At the same time, that variation does mean ski fields may continue to have some good years for a long time yet, says McKenzie.
“It just takes one snow event to set us up for the start of winter. Even in a cold winter you could end up with a pretty bad snow year—and vice versa.
“We’ve just got to be ready for whatever Mother Nature throws at us. That’s always been the case, we know it’s just going to get harder—which is why we’re [investing] to help us do things more quickly and more efficiently.”
Backcountry Boom
For two decades, backcountry skier, outdoor enthusiast and emergency doctor Marc Gutenstein and his group of mostly-medical friends have looked forward to their annual week off-piste together—old mates catching up in the backcountry for a mountain fix.
As they haul their skis up the lift-less slopes, they sometimes worry about their personal responsibility when it comes to the environment. “If we drive around New Zealand chasing the snow, or occasionally ride in a helicopter if we’re feeling extravagant, you can’t deny that you’re contributing carbon to the atmosphere, which is driving climate change. We’ve been through stages, some winters, of feeling like—how can we do this anymore?”
At the same time, Gutenstein says, he knows addressing global warming requires collective and institutional action, and his individual contribution, while real, is small. Ultimately, he’s decided he has to live with the contradictions, use his carbon on skiing—his passion—and sacrifice in other ways. He worries that when his own young children are grown, skiing may become too technically difficult, inaccessible or unaffordable. “Will it just become a boutique activity? I kind of think they won’t be skiing in New Zealand.”
Back in the day, Gutenstein and his mates often had slopes to themselves, but backcountry skiing has become a lot more mainstream, he says, partly due to improved and more affordable gear. But climate change may be playing a role, too—as glaciers retreat and snowlines rise, more people are crowding into fewer accessible places.
MSC anticipates backcountry recreation will continue to grow in popularity, says Operations Manager Nathan Watson. “We expect to see more and more people looking towards the backcountry as a place to get their snow fix.”
Snowmaking aside, most ski fields are already utilising all the easily accessible skiable terrain—there’s little room for them to chase retreating snowlines higher up the mountain. And club fields, like Tukino, Temple Basin or Craigieburn don’t currently have snowmakers; they're entirely dependent on natural snow, in a bad year, they’ll simply have to close, says Watson.
“A backcountry skier or boarder can choose to go anywhere they like to find snow, so the opportunities and possibilities are near limitless compared to a ski area. In the backcountry, you can often go higher. The natural snow is there if you want to work for it, even in lean years like the current one.”
For beginners, there are clear safety implications, he says, as the backcountry differs significantly from the controlled ski areas. "An influx of people without the proper training, equipment and skills to manage their own safety risks, increasing injuries and accidents.”
Gutenstein says skiers and boarders need to be ready for a wide range of snow conditions if they plan to tackle the backcountry. “You’re going to get ice conditions, you’re going to get crusty conditions, your skis are going to get ruined. You just have to be okay with skiing in extremely variable conditions. It’s always been that way—but it’s going to get worse.”
Climate change might make it harder to get the “powder shots”, and require more careful attention to slope stability, weather and avalanche danger, “but I just love being out there,” he says.
“We live in this completely glorious country. If it's crusty, if it's icy, if it's powdery, if it’s rocky—whatever! We're out there, we're doing it... I’m in it for the whole experience.”
This story was funded by NZ Mountain Safety Council and published exclusively by Adventure magazine in June 2025.
PHOTO CREDIT | Taichiro Naka | Avalanche, Aoraki/Mount Cook