ICE: MOUNTAINEERING IN A WARMING WORLD

open and tricky to cross, but on this trip it presented no problem as it was still full of snow from the winter. We crossed and started up the final slope towards the summit. I had hoped the mist might clear as we got higher, but not that day. I was just starting to ponder whether or not the top portion of the slope seemed a little steeper than last time—I didn’t remember the climb being this hard—when ‘twang!’ my ice axe punched through the ice and bounced on the rock below.

I had a definitive answer to my question now—the ice cloaking the mountain was definitely thinner this time around, and the route was indeed becoming steeper. Thinning ice can make a climb more difficult over time. While I was experienced enough to navigate the climb, it was a reminder that the mountains are becoming less predictable.

These days, my research into glaciers and the changing alpine environment focuses largely on glacier mass balance, including the feedbacks or flow-on effects of climate change on glacier health. And the ability of my ice axe to penetrate right through to the underlying rock was a clear sign that the glacier was losing mass.

My research comes very much at the intersection of work and play. For me, the mountains are not just about work; they are where I grew up. Climbing brings a sense of connectedness to the environment; you become very tuned in to the weather and the snow conditions, you feel the crispness of the air, and the screech of the kea.

When I started to hear talk in the mountaineering community about climbing routes becoming ‘cut-off’ as glaciers ‘break up earlier’ or become ‘more convoluted’ as glaciers respond to climate warming, I wanted to investigate. Such anecdotes, coupled with my own experiences and observations, inspired myself and a friend and colleague, Tim, to explore what changes could be detected on the main climbing route on Aoraki (Mount Cook), the Linda Glacier route. Tim and I had both climbed the route on separate occasions in the past, and both enjoyed delving into photographs and archives of early mountaineering history.

WHO KNEW THEN THAT 30 YEARS LATER I WOULD BE STANDING ON THE SAME MORAINE EXPLAINING TO A GROUP OF UNIVERSITY STUDENTS WHY THE AREA I HAD ONCE WALKED ON, AND WHERE MY SISTER AND I HAD SAT AS CHILDREN, WAS NOW A LAKE MORE THAN SIX KILOMETRES LONG.

We combined measured physical data with conversations with guides and recreational climbers. We found that at lower elevations, glacier retreat was clearly evident and impacting people’s access to the climb. The thinning or ‘downwasting’ of the Tasman Glacier has resulted in very large moraine walls—steep unstable slopes that can be difficult to descend, making foot access to the route more time-consuming and challenging.

High up the mountain, climate change was not so obvious and measurable. However, climbers talked about their experiences with crevasse exposure, slope steepening and rock exposure. Some people noted that rock was exposed in places that ‘didn’t exist on early summits’.

The large year-to-year variability in snowfall received in the New Zealand Southern Alps makes it hard to quantify changes in snow frequency and volume over time. But after completing the Aoraki climbing project, the conversations I had with climbers still lingered; there was much left unanswered.

These unanswered questions formed the foundation of my latest research programme. When the crevasses are exposed at the surface they increase surface roughness, and trap solar radiation; my research hypothesis is that the models we currently use to estimate melt rates on glaciers will be underestimating snow melt in the accumulation area.

So, for the last two summers, I have been leading a team at the top of the Tasman Glacier, where we install temperature sensors inside crevasses and use drones to map the surface of the glacier with thermal imaging. Crevasses are formed as the ice moves. In the winter they are usually covered with snow, then as the summer progresses the snow melts and they are exposed at the surface.

There is still a lot to do, but our preliminary results show that at times crevasses can be surprisingly warm. Previous work on air temperature in crevasses was only done in polar environments, so there is limited information on air temperatures in crevasses in maritime environments, like New Zealand. What we have found so far is that at times the air in a crevasse is even warmer than the air on the surface of the glacier, meaning melt could occur even faster than previously thought.

One thing that strikes me in my work on climate change is that people are more likely to care about climate change if they can feel and experience a real connection to the environment—it makes it more real. It is this sense of connection to the environment that I try to instil in my students. After all, they are the ones inheriting Earth, so we need them to care, to learn how it works and try to find some solutions to the mess humans are making.

But getting people to care about change can be challenging, especially when the glacier they have come to visit is no longer accessible by foot, and nor is it the majestic glistening feature they expected. Rather it has transformed into a small, dirty mass of ice, viewable only from a distance or from a helicopter. On the Tasman Glacier it can be challenging for visitors these days to actually see the thickness of the ice, and because it’s so far away and covered in debris, visitors can be a bit underwhelmed.

As highlighted on our climb of the Nuns Veil, when glaciers are receding they are not only getting shorter, but they are also getting thinner. This thinning of the ice mass contributes to several flow-on effects beyond the glacier just getting shorter. In particular, as the surface of the ice thins, it exposes rock at the valley sides.

This rock is often loose and crumbly and cascades down the slope onto the ice surface below. Rockfall is clearly a hazard for those walking on the glacier. Anywhere where the ice mass is thinning and disappearing, it will be exposing rock underneath, creating new hazards for anyone