Royal Society of New Zealand Manhire Prize for Creative Science Writing

Non-Fiction winner for 2007

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Touchstones

by Alison Ballance

I hold a personal map of the Southern Alps in my head, one whose landmarks are moments of memory. Two kinds of memories stand out: those to do with birds, and those to do with glaciers. And those memories cluster into two timeframes: twenty years ago when, as a young adult, I first discovered the mountains of the South Island, and more recently, when I have rediscovered them. During that time both the mountains and I have changed, and contrary to what I expected, it is the mountain environment that has changed the most. I always imagined that the mountain world was one of permanence, of immutability, but just as Charles Darwin and his scientific successors discovered that species change, often very rapidly, I have realised that massive landmarks can change dramatically in very short periods of time; and for a bird, having survived more than 60 million tumultuous years in New Zealand is no guarantee of surviving the next hundred.

My first glacier memory is of the Dart Glacier, in Mount Aspiring National Park. A student friend was measuring the thickness of its ice for his thesis project, and I had offered my services as unpaid field assistant. One way of measuring ice thickness is to send shockwaves through the ice, and determine when the shock waves bounce off basement rocks and gravels. My job was to generate the shock waves. This was field science on the cheap, with few resources and no electricity. To begin, I found the largest rock I could carry from the moraine rubble at the side of the glacier, and then lugged it a predetermined distance across the ice. Then I’d hit the rock with a very large sledgehammer, which was connected by a data cable back to my friend, who was measuring the exact moment of impact, and the journey of the shockwave. Invariably my rock shattered into small pieces, and I had to carefully walk back across the slippery ice, find another rock and repeat the process, again and again. It was frustrating hard work, but my friend was good company, and as well as collecting serious data we had a lot of fun. Intellectually it was a total revelation; I’m not a glaciologist and until then I had no idea that glaciers were made of such thick ice, nor that they gouged out deep channels into solid bedrock. If you had asked me to guess, I’d have eyed up the surface of the glacier, looked at how it sat in relation to the land around, and suggested perhaps twenty or thirty metres thick. It turned out that the ice was several hundred metres thick. I was determined to learn more.

My early bird memories come from much further north, in northwest Nelson. I was involved in the study of a small population of rock wrens above the Cobb Valley. Two of us were dropped in by helicopter to spend several weeks catching and banding rock wrens, to start a long-term population study; we also ran a trap line, to see if there were any rats or stoats in the area. I fell in love with the rock wrens, which an early New Zealand climber described as ‘looking for all the world like boiled potatoes with their jackets on, set up on hairpins and let loose on the rocks.’ I nicknamed every bird in our study area Bob, for their endearing habit of constant bobbing, and I kept my ears tuned for their high-pitched calls which my male colleague found hard to hear. The two of us marvelled at how such tiny birds could survive year-round in the alpine zone, and speculated about how they must spend the winter, sheltered within stable piles of rubble and bushes, foraging for food on fine days, and perhaps dropping into a state of torpor on very cold days. We checked the trap line each day, but the traps remained blessedly empty.

I wanted, also, to love the curious kea which haunted our campsite, but ours was a love-hate relationship: I hated that they loved investigating my tent, usually at night when I was trying to sleep. They quickly learnt to play the guy ropes as if plucking a double bass, and they tweaked the stitching and thin nylon fabric. By the time I fought my way past the zips to hurl something harder than abuse, they had safely retreated beyond the reach of my throwing arm. By the end of our time there my tent was in tatters, my colleague’s tent was inexplicably untouched, and I had a new-found respect for the kea’s questioning intelligence and resourcefulness. I was honoured to have spent time with two true mountain birds, both of which have amongst the oldest lineages of any species in New Zealand, their presence here dating back to the time these islands were part of the great Gondwana continent.

The mid-1980s were a time when scientists were just beginning to talk about the prospect of global warming, and speculate on how it might affect life as we know it. Glaciologists warned of melting glaciers, and biologists worried that rats would move up into the alpine zone. The public remained for the most part unaware of the debate, and when the media bothered to investigate the issue the handful of vociferous climate change sceptics were given equal airtime, which effectively masked a much more unanimous opinion held by the scientific community. I was aware of global warming, but like most people I wasn’t giving it much thought.

Twenty years later, it’s recreation and pleasure that brings me back to the mountains. I was ski touring on the Tasman Glacier recently when my brain, full of random pieces of information read in books and magazines, or heard on the radio, made connections between many things and a puzzle clicked into place for me. On one particular day we were nearly back at the hut when it began to snow. The first flakes were gentle, tentative. A single flake landed on the back of my right glove, teetered briefly, and disappeared. I paused, and as I tilted my face towards the swirling flakes gathering momentum above me, delicate cold kisses caressed my cheeks and my eyelashes. I realised that, on its own, each snowflake is fleeting and insubstantial, yet en masse snow combines with mountains to create glaciers; and in glaciers, great mountains have met their match. But I was also aware of a growing menace hanging over this ancient relationship.

I had watched all day as the weather and the mountains had been locked in fierce battle. In the morning, as we skied down the Tasman Glacier, the gusting winds and streaks of thin cloud high above spoke of a change in the weather. By late afternoon, as we trudged back up the glacier, the clouds had become dark and weighty snowflake factories, unable to contain the turbulent blizzard of ice crystals and snowflakes that they contained. I wondered what the future held for nature’s miniature art works, millions of which were beginning to collect on the glacier surface around me. Some, no doubt, melted or evaporated on the next warm day, but others were blown by the wind or crushed by the weight of snow above to become one of the indistinguishable granules of ice that become the very fabric of the glacier. Each winter, ten or so metres of snow falls here at the head of the Tasman Glacier. The snow beneath my feet was hundreds of metres thick, a liquorice allsort of accumulated layers of annual snow, mixed in with dust blown from as far away as Australia.

It seems so solid, so permanent, but that is far from the case. Far and away New Zealand’s largest glacier, the Tasman Glacier is a grand old dame, a great river of ice that flows down-valley for 29 kilometres. From the moment it lands at the head of the glacier, a single snowflake is on a journey that might take five to seven hundred years to reach the toe. The snowflake masses with others to become a grinding machine, more than 700 metres thick in places, which gathers up rocks and debris, and rasps its way through solid rock. All around are signs that this glacier has been much larger in the past; the valley sides are smooth and polished for hundreds of metres above the present glacier surface. The Mackenzie Basin is full of steps and terraces, created from moraine gravels left by earlier enormous ice sheets, and Lake Pukaki was created when a previous glacier melted.

A hundred or so years ago, when climbers and scientists first began regularly visiting the Mount Cook area and observing the Tasman Glacier they reported that the ice was so thick it was bulging over the high moraine ridges running alongside the glacier, like a baking cake exuberantly rising over the edges of the cake tin. Today, the surface of the glacier lies a hundred or more metres below these same moraine ridges.  But although everyone expects glaciers to respond to changing climate, the Tasman Glacier is actually the worst barometer to use; by virtue of its enormous size, and the sheer volume of ice it contains, it is out of step with today’s climate. It is a lumbering oil tanker, exceptionally slow to turn or stop. On the western side of the mountains, however, the Fox and Franz Josef glaciers are the nimble tugboats of the mountain world. They respond to the slightest changes in temperature and related changes in precipitation, by rapidly dodging up and down their steep narrow valleys at sometimes alarming speeds. If more, or less, snow falls in their head basins, within five to seven years their snouts will be racing forward or shrinking back, moving up to seven metres a day. Within the span of my twenty year experience in the mountains these two glaciers have retreated, advanced and then retreated again. This is just one of the many counter-intuitive results of rising temperatures, which makes it hard to predict what we should expect. This is why glaciologists will tell you that it is never as simple as ‘the glaciers are melting because it’s getting warmer’. But while the Fox and Franz Josef glaciers seem indecisive about how to respond, other glaciers have been giving much clearer signals – my old friend, the Dart Glacier, is now much thinner, and much shorter, and many smaller glaciers have disappeared completely.

Is New Zealand’s largest glacier immune to the effects of rising temperatures? Sadly, it seems not. I recently heard someone use the analogy of defrosting a domestic freezer to describe how global warming will proceed, not in subtle increments, but in catastrophic fits and starts. When you switch the power off, and leave the icy freezer alone the defrosting begins as a slow thaw, drip by drip. But it doesn’t continue that way – at some point, hunks of ice begin to fall of the walls. That is exactly what happened with the Tasman Glacier. After stubbornly remaining 29 kilometres long, less than 20 years ago a lake suddenly formed at the glacier’s snout. For a few years, meltwater ponds on the surface of the glacier had been slowly growing in size, and then suddenly, catastrophically, huge chunks of ice collapsed; what were once ponds were suddenly a small lake filled with icebergs. It didn’t take long for the lake to deserve a name, and Tasman Lake is now more than two kilometres long, and growing rapidly. It has become the beast that will devour the country’s largest glacier. And it is a beast that we humans have unwittingly unleashed. Glaciers may have the power to bring mountains to their knees, but, in their turn, they may have met their match.

The bobbing rock wrens have also met the beasts that will devour them. Somebody has been re-running the trap lines in our old study area, and rats have indeed begun to invade the alpine zone. Who knows how long the little rock wrens will be able to avoid these voracious predators, against whom they have no defences. They might be able to escape uphill for a short while, but they will quickly run out of mountain. The kea, I’m confident, will fare better – not only are they much larger than the enemy, they are altogether more resourceful, less specialised, better able to look after themselves.

So, what was my revelation that day at the head of the Tasman Glacier? Well, I suppose it was several revelations. Firstly, it was that there is a big difference between the potential effects of global warming on rock wrens and glaciers. The worst case scenario is that both will disappear, but the similarity ends there. The rock wrens are irreplaceable – they will join four other ancient New Zealand wrens in the ranks of the extinct. Glaciers are made, not of flesh and blood, but of frozen water; if the world cools, they have the ability to rise from the dead.

My second flash of insight was that we humans don’t usually care about things until they affect us personally. That was the moment when I decided that it mattered to me whether we still had glaciers and rock wrens, when they became my personal touchstones against which to measure global warming. Other people will need to find their own reasons to care. The farmers in the nearby Mackenzie Basin might not care about the beauty of the glaciers – but they might well care, when they realise that the glaciers of the Southern Alps are enormous machines that drip-feed water year-round to the plains below. The glaciers didn’t just supply the gravels that built the great outwash plains – they keep the rivers and aquifers well-watered. Similarly, people who live at the coast may not be interested in the mountains, but they will probably protest when rising sea levels, caused by melting ice, start lapping at their doorstep.

Do we need to be concerned? Scientists say we should be. The world naturally fluctuates between cold ice ages and warmer interglacial periods, but what is different this time is the speed of warming. Yes, there have been equally rapid changes in the past: nearly 13,000 years ago North America and Europe were plunged into a sudden ice age known as the Younger Dryas. Within just 10 years temperatures dropped by up to 10° Celsius and more than 40 species of giant creatures such as the woolly mammoths became extinct. But the cause of this sudden freeze was literally out of this world: a new theory suggests it was the result of a comet exploding above a large ice cap covering what is now Canada, and intriguingly leaving no impact crater to mark its catastrophic arrival. This time round the equally catastrophic warming has, as the modern equivalent of the comet, the explosion of industrialised human society.

My third revelation insinuated itself as subtly as the snowflake whose melting briefly cooled the tip of my nose. Just as billions of tiny snowflakes can build something as monumental as the Tasman Glacier, who knows how powerful the combined effect of six billion tiny actions might be. That’s just one for every person on the planet - it doesn’t seem too much to ask.

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BIBLIOGRAPHY

Chinn, T.J., New Zealand glacier responses to climate change of the past century, New Zealand Journal of Geology and Geophysics, 39: 415-428, 1996.

Fitzharris, Blair; Lawson, Wendy and Owens, Ian, Research on glaciers and snow in New Zealand, Progress in Physical Geography23(4): 469–500, 1999.

Gibbs, George Ghosts of Gondwana: the history of life in New Zealand. Craig Potton Publishing, Nelson 2006.

Hochstein, M.P.; Claridge, D.; Henrys, S.A.; Pyne, A.; Nobes, D.C. and Leary, S.F., Downwasting of the Tasman Glacier, South Island, New Zealand: changes in the terminus region between 1971 and 1993, New Zealand Journal of Geology and Geophysics, 38: 1-16, 1995.

Mannering, George Edward With axe and rope in the New ZealandAlps. Longmans Green & Co, London 1891.

Nicol, Scott A geophysical investigation of the Dart Glacier, South Island, New Zealand thesis submitted for the degree of Master of Science (geophysics) at the University of Otago, 1987.

Perkins, Sid Ice Age ends smashingly: did a comet blow up over eastern Canada? Link 3 June 2007.

Petyt, Chris The vanishing rock wren Forest and Bird 310: 22-25, November 2003.

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