Mt Cook: An Icy recession

Glacial recession may be a worldwide phenomenon but New Zealand’s ice retreats are the fastest and thus most alarming. MEENAKSHI RAO reports about the worrying ice dwindle from the Aoraki/Mt Cook region that houses the island nation’s largest glacier, which is thinning down fast enough to vanish by 2100

Deep turquoise, still and mirror clean, this 7-km-long wonder lake adjoining the grime covered face of the Tasman Glacier is breathtakingly beautiful, what with some blue, some white, some small, some big icebergs dotting its ethereal expanse. You feel blessed to be floating over its icy waters, surrounded by imposing peaks of the stunning Aoraki/Mt Cook region. But wait! This celestial Tasman Lake is not good news. In 1973, it was not even a puddle at the foot of the mighty Tasman Glacier. Today, in 2017, it is more than 7 km long, 2 km wide and carries the depth of the nearby river-fed, 18-km-long Pukaki Lake.

The fast expanding lake is the direct result of New Zealand’s biggest, 23.5-km-long glacier — the Tasman Glacier —retreating in an inordinate hurry since 2008. It has been shrinking around 180 metres every year for the past 27 years, which even the most liberal of glaciologists in New Zealand concede is more than alarming. At this rate, 2050 is being talked about as the year that this glacier will recede so far behind that it will become dangerous to tread on, inaccessible and a fraction of its usual self. Consequently, the lake will expand to become larger than life and the trails to and over the glacier will have to be stopped for your own good.

Simply put, the lake, which has warmer temperatures than the glacier which it laps, holds the Tasman ice cover to ransom — the warmer it gets, the more the glacier will melt with not much to arrest its disappearance. That’s why you need to put the Aoraki/Mt Cook region on your bucket list of must-visit places before it is too late. For, the Mt Cook area, besides being the backbone of the Southern Alps, is endowed with innate natural beauty, easy accessibility to glaciers, trekking havens, a captivating dark sky reserve and stunning valley trails even as the peaks stand over you in ovation.

The Tasman and most of the 3,000 glaciers in NZ are constantly dwindling mainly due to rising global temperatures and also episodic calamities like the 2011 Christchurch earthquake. When the 6.3 flattener struck, two guides and 16 tourists were boating on the Tasman Lake, 201 km away from Christchurch. Before they could figure out, a huge chunk of the Tasman Glacier caved in and fell into the lake, triggering a massive tsunami.

Though there were no casualties, the skilled guides had to navigate a retreat, battling half an hour of 3.5-metre-high waves hitting them from all sides. That was because 30 million tonnes of ice from the glacier calved and fell into the lake due to the quake’s impact. This measured around 1,200 metres across the face, 30 metres above the lake, and more than

250 metres below the surface to the bottom of the lake. The local office of the Department of Conservation tagged this as the third biggest event in Tasman Lake’s history. In April 2017, one could see the remnants of this big chunk sitting as a glorious centerpiece of the lake.

But it is the global warming that glaciologists like Dr Brian Anderson are most worried about, mainly because New Zealand’s glaciers are extra sensitive to temperature. “According to a conservative estimate, the central Southern Alps area has lost 24 per cent of its ice since 2008 and stands to lose another 50 to 60 per cent by 2100 due to rising temperatures,” he tells The Pioneer. That’s almost as spectacular as the beauty of the glacier, which is thinning down on ice and losing several kilometres of territory to the lake.

A recent Sustainable Summits conference held in the heart of the Mt Cook region, attended by top conservation and glacier experts, discussed the impact of New Zealand’s worrying retreat of national treasure on its economy and tourism, even though experts say that the retreating rate of the glaciers, like the Tasman, has far transcended the smaller concern of tourism and one should now worry more about somehow conserving the nation’s dwindling ice asset, much like its birds which vanished from the island 1,500 years ago and are now a part of the world’s biggest conservation project.

However, as Dr Anderson says, conserving the ice cover of New Zealand is a different thing altogether as there is little one can do to control rising global temperatures. “Ultimately, the retreat of these glaciers will be controlled only by how we, as a society, respond to the challenges of climate change. The changes to the glaciers in this century are starkly different, depending on whether we make significant cuts to greenhouse gas emissions, or continue on our current trajectory of emissions,” he adds.

It’s not just the Tasman; many other glaciers are also facing this irreparable damage. The popular tourist haunt of the Franz Josef Glacier on the West Coast has recorded the fastest melt rates in the world, having retreated 1.4 km since 2008. So has the nearby Fox Glacier, which is expected to retreat as much as 5 km and lose nearly 40 per cent of its mass in the coming years. Pedestrian traffic to the Franz Josef and Fox was banned last year because they had receded too far to be accessed safely on foot. They can now be visited only by helicopter.

Dr Trevor Chinn, who has been documenting NZ’s glaciers and photographing them for decades, says: “I started measuring glaciers in 1965 with snow surveys of the Tasman Glacier. In 1968, we chose a small cirque glacier, the Ivory, for New Zealand’s contribution to the International Hydrological Decade. We worked on this glacier until 1975, that is when it developed a lake and collapsed in size. Only glaciers which carve deep hollows under their trunks can shrink back into a lake. Because they stay at the same glacier area while the surface melts down to lake level, they have a period of ‘no retreat’ that leads to a sudden rapid retreat as the lake grows.”

The 2008 to now phase has been a very difficult one. But before that, between 1983 and 2008, very strangely, most of NZ’s glaciers advanced (Franz Josef advanced nearly 4.3 km in 25 years) even when all others around the world were retreating. Call this an unusual Kiwi trait but since 2008, the island nation’s ice cover has been in the severe recessive stage that will last pretty long.

As the glaciers here are dynamic, there might be years in which they advance, but the long-term trend will be of severe retreat as even two to four degrees of warming expected by the end of the century has potential to make these glaciers disappear. “Advance years will happen in the next century, but the overall picture will be of more and more retreat,” Dr Anderson predicts.Dr Anderson was part of a research study led by lead author Associate Professor Andrew Mackintosh of the Victoria University of Auckland and published in the latest edition of the prestigious science journal, Nature Communication.

The research shows that it was regional climate variability that caused an “unusual” period in which some of New Zealand’s glaciers grew bigger, while glaciers worldwide shrank. At least 58 New Zealand glaciers advanced between 1983 and 2008, with Franz Josef Glacier advancing continuously during this time.

Advancing glaciers is a very unusual concept, especially in a period of global warming. The research found that lower temperatures caused the glaciers to advance, rather than increase precipitation as previously thought. These periods of reduced temperature affected the entire New Zealand region, and they were significant for the glaciers to re-advance in spite of human-induced climate change. However, Prof Mackintosh said the climate variability, which includes the cooler years, still reflected a climate that’s been modified by humans.

“It may seem unusual — this regional cooling during a period of overall global warming — but it’s still consistent with human-induced climate change. The temperature changes were a result of variability in the climate system that’s specific to New Zealand. New Zealand sits in a region where there’s significant variability in the oceans and the atmosphere, much more than many parts of the world. The climate variability that we identified was also responsible for changes in the Antarctic ice sheet and sea ice during this period,” he said.

The Franz Josef Glacier actually regained almost half of the total length it had lost in the 20th century. However, the Tasman Glacier, which holds about a third of all of New Zealand’s ice volume, continued to retreat. Because of that, New Zealand glaciers lost mass overall over this period, the study explained.

“The glacier’s moving, it’s retreating, the hillside’s coming down, but at the same time these things are happening, there’s hundreds of people visiting. It’s actually a real struggle to manage these sites safely, with a lot of visitors and very real hazards. We’re now putting 30,000 helicopter landings a year into Westland Tai Poutini National Park,” DOC director general Lou Sanson told the Sustainability Summit. “We’ve got to allow more glacier landings, we’ve got to do it in the park planning process, and we’ve got to do it without annoying climbers who also value the space. These are tricky decisions that we constantly have to work through,” he told the delegates.

Indeed, so! A whopping 40,000 tourists visited Lake Tasman in 2016 and another 4.5 million international tourists will be coming by 2022, half a million of them heading straight to the Aoraki/Mt Cook region. So, where are you this season?

RETREAT OF GLACIERS

India’s Gangotri Glacier retreated 1,147 m between 1936 and 1996 with 850 m of the retreat occurring in 20th century’s last quarter. The glacier is still over 30 km long. In Sikkim, 26 glaciers retreated at an average rate of 13.02 m a year between 1976 and 2005. Overall, glaciers in the Greater Himalayan region are retreating at an average of between 18 and 20 m annually

NZ’s glaciers have lost significant ice volume after a golden advance period between 1983 and 2008. The loss in Southern Alps’ total ice volume from 1976 to 2014 is 34 per cent of the total. The fastest receding glaciers are Franz Josepf, Fox, and Tasman. Their retreat has been marked by expanding glacial lakes and terminus region thinning

Cutting gases

• NZ tourism industry has overtaken its No 1 earning sector — dairy farming
• The country makes most of its money by showcasing its ice cover and glacial lakes; it also follows strict environmental laws
• Is part of a team of 170 nations pledged to phase out the dangerous greenhouse gas HFC, used for refrigeration and ACs
• By 2036, NZ aims to cut the use of HFC and CFC by 80 per cent
• These gases are up to 15,000 times more potent global warmers than carbon dioxide
• Cutting their use globally could reduce global temperature rise by 0.5 degrees Celsius by the end of the century

Dr Brian Anderson, Senior Research Fellow at the Antarctic Research Centre with the Victoria University of Auckland, tells MEENAKSHI RAO about New Zealand’s ice plummet. Excerpts:

New Zealand has a unique process of advancing and retreating cycles when it comes to its glaciers. What is the phase now?

There was a remarkable period from 1983 to 2008 when some of the glaciers in New Zealand advanced — the Franz Josef Glacier advanced 1.4 km during this time. But even during that time, the largest glaciers, such as the Tasman, continued to retreat because they respond to climatic variations very slowly, and they lose ice by calving icebergs into their lakes. Since 2008, all of the monitored glaciers have retreated, but some have recently stopped retreating.

The Tasman glacier is fast retreating. How bad is the situation and is there anything that can be done to arrest its retreat?

Since the lake formed at the Tasman Glacier in the 1980s, the glacier has been destined to retreat. Because the retreat is now largely controlled by this lake-calving process, it cannot be arrested without a decades-long cooling, and its continued retreat is largely controlled by the shape of the bed under the glacier.

2050 is being talked about as the dreadful year by which the Tasman Glacier will disappear. How serious is the situation?

Tasman Glacier will not disappear by 2050 — the truth is that the lake-calving process is not fully understood and we don’t have enough information on the shape of the glacier bed to make any firm predictions. What we can be sure of is that the ice that feeds the Tasman Glacier comes from the highest peaks in New Zealand, including Aoraki/Mt Cook, and this high-altitude ice will continue to feed the glacier, albeit at reduced rates, even as the climate warms. However, mathematical models indicate that if we get extreme warming, such as 4°C by 2100, even this source of ice will disconnect from the Tasman Glacier. We also know that the covering of rock and debris on parts of the glacier will protect it from melting for decades.

But by 2050, the glacier will be very different — the lake will be much larger, more of the glacier will be covered in rock debris and lower elevation snow accumulation areas of the glacier will no longer be connected to the main trunk.

What measures are and can be taken to save this region in the face of climate issues like global warming?

New Zealand glaciers are extremely sensitive to temperature. So the glaciers will retreat in the face of global warming. Most of the response has been around adaptation and different ways of accessing the glaciers that could once be simply walked onto (and are now mostly visited by boat and helicopter). Ultimately, the retreat of these glaciers will be controlled by how we, as a society, respond to the challenges of climate change. The changes to the glaciers in this century are starkly different, depending on whether we make significant cuts to greenhouse gas emissions, or continue on our current trajectory of emissions.

The Southern Alps are the backbone of New Zealand. Is the Mt Cook area of the Tasman Glacier the worst affected or are there regions which have already vanished as far as the ice reserve is concerned?

There are many small, low altitude glaciers which have retreated and are disappearing as they no longer accumulate snow through the year. In many ways, the Aoraki/Mt Cook area is the most resilient because it collects snow at high elevations.

Franz Josef has borne the maximum retreat. Has the glacier receded completely? The trek to this glacier here has been stopped. Can you please elaborate on this?

Franz Josef is still a steep and spectacular glacier. It has retreated 1.43 km since 2008 and this has made it too dangerous to walk onto, although you can still view it from the valley below. But glacier guiding continues there and remains very popular. All the guided groups are now being flown onto the glacier by helicopter.

What is the percentage by which New Zealand’s ice cover has shrunk and in which period has it been the fastest?

We don’t have good enough records to exactly answer that question, but recent work on a new inventory of glaciers in New Zealand by Sabine Baumann has shown that between 1978 and 2016, the glaciers lost 24 per cent of their area in the Aoraki/Mt Cook area.

Source: Sunday Pioneer, 21 May, 2017