For mountain guide Jane Morris, glacier retreat has already had more serious consequences than inconvenient crevasses. Never more so, perhaps, than when she was guiding a climb in Aoraki/Mount Cook National Park. She had kicked early-morning steps across the Grand Plateau, checking out the first part of the route up to Syme Ridge in preparation for a climb up the North Shoulder of Mt Tasman the next day. The small icefall was passable and the final snow slope wasn’t littered with pockets of falling rock. When Morris left Plateau Hut again at midnight, she felt good: the weather was stable and the freezing level was low.
A couple of hours later, Morris and her client were almost at the end of their previous day’s steps, and she thought about turning around to her client to suggest a break for a drink and a snack in the bergschrund. That’s when it hit her: a mug-sized piece of rock that whizzed noiselessly down, from a cliff freed of ice by the last couple of decades of warming. The rock slammed into Morris’ upper arm with such force that she initially thought it had been blown away. But her arm was still dangling on. Morris crawled to the bergschrund and sheltered with her client, while the Westpac Rescue Helicopter looked fruitlessly for a break in the cloud. After dawn, the skies finally cleared and the local crew flew in to the rescue. Surgery to put a shield and 10 screws in her arm enabled Morris to mend. But more rocks, set free of ice in recent decades, continue to fall.
"The glaciers and the permanent snow and icefields are the glue that hold the mountains together," said Morris. "Guides that have been in the hills for 40 or 50 years are just astounded at the amount of rockfall around, and all the guides have a near-miss story to tell." This shattering landscape is almost more of a problem for mountaineers than issues on the ice itself. But these issues are cropping up in no uncertain terms too. A year before her accident below Syme Ridge, Morris had travelled with a buddy up the Hooker Glacier, to climb a route on the South Face of Aoraki/Mt Cook. It has always been a little tricky getting up the Hooker Glacier — back in 1890, Arthur Harper had to crawl across snow bridges above huge crevasses on the first exploration to the valley’s head.
Morris was familiar with the usual difficulty of getting to Pudding Rock, a huge protrusion about halfway up the glacier that used to be the site of Gardiner Hut. A huge rock avalanche down the Noeline Glacier partially engulfed the hut in 2014, and it was later removed. But on Morris’ trip, well below Pudding Rock and early in the season when crevasses aren’t usually so open, she found herself faced with a nearly impassable sea of crevasses. "It was almost unrecognisable," she said.
"The rate of change has been quite phenomenal in the last 10-20 years, and that doesn’t seem to be slowing down at all," said Morris. Up on the Grand Plateau, new climbers are often taken on an ascent of the small ice-capped Glacier Dome. In the last few years, it no longer suits its name; the peak now has a small rock outcrop poking up through the topmost ice.
"Glaciers are nature’s highways," said Morris. "They act like escalators: that’s what gets you to the peaks that you’re going to climb." As the glaciers disappear, so too does access to the peaks. Lower down this is already clear; up high, there will be more changes to come. The most often climbed route on Aoraki/Mt Cook is still that pioneered by Green in 1882, up the Linda Glacier. One recent study looked at historical photographs and interviewed professional mountain guides about changes to the route. There is so much variability from year to year that the photographs didn’t show clear changes. But anecdotally, guides were seeing steepening slopes and new rock exposure. To Morris, it’s looking like Swiss cheese: "In 20 years there will be a small window of opportunity to get through."
THE ICE RELINQUISHES
The world is already committed to losing ice for several centuries to come, because some glaciers take so long to reach equilibrium. But the situation could get much worse unless there are massive and immediate cuts to greenhouse gas emissions.
In the first 20 years of the twenty-first century, satellite data show that glacier mass loss has accelerated, worldwide. New Zealand’s ice loss was nearly seven times greater in 2015-19 compared with 2000-04. We’ve lost a glacier access road, mountain huts, a range of routes and a number of actual (albeit tiny and mostly unnamed) glaciers. It’s getting hard to keep up — science seems slower than glaciers, and politics, which can be so mercurial, has been glacial at effecting change.
Politically, if the world had managed to keep to a very stringent emissions pathway that would have seen emissions declining from 2020, glacier loss could likely have been limited to 11-25 percent of current ice volume by 2100. However, if emissions continue to rise through the twenty-first century, that loss could likely be 26-47 percent.
However, the way this plays out across different regions will vary widely. In high latitudes like the Arctic and Antarctic, melting will take longer. In the Himalaya Mountains, where glaciers are critical water resources for nearly 2 billion people, ice volume could decrease to 30-100 percent of its 2020 volume by 2100, taking into account all emissions scenarios and uncertainties.
New Zealand’s prospects are almost as bad. The large grid squares in global climate models mean they don’t really register the mountains of our Southern Alps/Kā Tiritiri o te Moana. But regional modelling that does take them into account, downscaled from the global scenarios, gives a wide range of possible futures up to 2100.
In addition to more than 1degC of warming that humans have already caused since pre-industrial times, our main mountain range can expect about 1degC of additional warming if there is a substantial fall in greenhouse gas emissions. If emissions remain high or accelerate, however, that additional warming will be more like 4degC.
This contrast for New Zealand’s glaciers is stark. Modelling suggests that additional warming of 1degC to 2100 will cause the Franz Josef Glacier/Kā Roimata o Hine Hukatere to retreat to somewhere below the current neve, with a glacier that is 5.5-7.6 kilometres long. The glacier would be only around two-thirds of its current length, but it would still be a glacier. But with 4degC of additional warming, the glacier will be only 0.3-1.8 kilometres long, reduced to remnant ice patches in part of the current neve.
