ON THIN ICE: MOUNTAINEERING IN A WARMING WORLD

WHEN in these environments. This is exacerbated by the fact that freezing and thawing of ice breaks apart the rocks, so they are already very fractured. And so, monitoring the rate at which ice masses are thinning is also important for understanding how such hazards evolve over time.

As well as this, as the ice melts, fragments of rock, eroded and transported down the valley by the glacier, are left behind on the ice surface, adding to the volume of rock that also accumulates from the valley sides. A very thin layer of debris on the ice surface can speed up the rate at which the ice melts, as the darker coloured debris absorbs more heat from the sun, and transfers that heat into the ice.

However, once that accumulation of rock starts to exceed two to three centimetres in thickness, the rock begins acting as a protecting cover, slowing down the rate at which the ice melts. It’s hard to say how effectively and how long this could preserve a glacier; we’re talking about decades not centuries though.

From a global water perspective, melting all of New Zealand’s glaciers would not change sea level very much, because despite having more than 2,900 glaciers in New Zealand, the total volume of ice is small compared to locations like Antarctica or Alaska. However, glaciers in the Southern Alps are great natural laboratories because due to New Zealand’s maritime location the glaciers here are very sensitive to climate change. They exist in a marginal environment, very close to freezing point, which means that even a small shift in temperature can have a big impact on glacier mass balance.

Globally though, glaciers are important not just for the volume of water they store, but the way they deliver that water into rivers. Glaciers at the top of a catchment store the rain that falls as snow during winter, and then release it at the hottest time of year when water is most needed. This is not such a big deal in New Zealand as we have a lot of water. But in other parts of the world like South America and the Himalayas, communities and crops are entirely dependent on glaciers to supply water during the summers.

Earth is not just the home of people, it is also the home for millions of plants and animals, and is composed of an incredible array of landscape features. If we want the snow and ice to remain on the mountains, feeding the rivers that sustain us, Earth has to come first.

When our crevasse-team returned from the field work on Tasman Glacier in early 2020 the world had changed. Countries including New Zealand were heading into lockdowns in response to the global pandemic. As people adjusted how they went about daily life, global green-house gas emissions plummeted; so it can be done, we can live more lightly on Earth.

As I stood on the summit of the Nuns Veil the second time around, maybe it was a good thing Jason and I were engulfed in cloud and not able to see the ever increasing evidence of climate change in the surrounding landscape; the lakes, the newly exposed rock faces, and the diminishing snow and ice. What will it all look like if I return to the Nuns Veil again in future? Will I be climbing on snow and ice, or will I be scrambling over loose, broken rock?

From the Frontiers of Climate Change, 2023, edited by Wendy Bruere, published by Woodslane Press with support from Paddy Pallin.

Bringing together science and adventure, the anthology features 15 stories by scientists from around the world. With tales of falling into crevasses, facing sharks, surviving cyclones, chasing pirates on the high seas, and more, the contributors explore the science behind exactly what is happening as the world warms.

Available from Paddy Pallin, Australian and NZ bookstores and online at Woodslane Press or via the Adventure Entertainment shop.