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A bird's eye view of changing glaciers
11 June 2018, by Andrew Lorrey, Andrew Mackintosh, Brian Anderson
New Zealand's glaciers is clear and irreversible, at
least within our lifetimes. Many glaciers we survey
now will simply vanish in the coming decades.
Glaciers are a beautiful part of New Zealand's
landscape, and important to tourism, but they may
not be as prominent in the future. This stored
component of the freshwater resource makes
contributions to rivers that are used for recreation
and irrigation of farm land.
Meltwater flowing from glaciers around Aoraki/Mt
Cook into the Mackenzie Basin feeds important
national hydroelectricity power schemes. Seasonal
meltwater from glaciers can partially mitigate the
Small aircraft carry scientists high above the Southern impacts of summer drought. This buffering capacity
Alps to survey glacier changes. Credit: Hamish may become more crucial if the eastern side of
McCormick/NIWA, CC BY-SA New Zealand's mountains become drier in a
changing climate.
Pioneering glacier monitoring
Every March, glacier "watchers" take to the skies
to photograph snow and ice clinging to high peaks When Trevor Chinn began studying New Zealand's
along the length of New Zealand's Southern Alps. 3,000 or so glaciers in the 1960s, he realised
monitoring all of them was impossible. He searched
This flight needs to happen on cloud-free and for cost-effective ways to learn as much as he
windless days at the end of summer before new could. This resulted in comprehensive glacier
snow paints the glaciers white, obscuring their mapping and new snow and ice observations when
surface features. similar work was dying out elsewhere. Mapping of
all of the world's glaciers – nearly 198,000 in total –
Summer of records was only completed in 2012, yet Trevor had already
mapped New Zealand's ice 30 years earlier.
The summer of 2017-18 was New Zealand's
warmest on record and the Tasman Sea In addition, he wanted to understand how snow and
experienced a marine heat wave, with ice changed from year to year. Trevor decided to
temperatures up to six degrees above normal for do annual glacier photographic flights, looking for
several weeks. the end-of-summer snowlines – a feature about half
way between the terminus and the top of a glacier
The loss of seasonal snow cover and older ice where hard, blue, crevassed glacier ice usually
during this extreme summer brings the issue of gives way to the previous winter's snow. The
human-induced climate change into tight focus. altitude of this transition is an indicator of the
The annual flights have been taking place for four annual health of a glacier.
decades and the data on end-of-summer
snowlines provide crucial evidence. It was a visionary approach that provided a
powerful and unique archive of climate variability
The disappearance of snow and ice for some of and change in a remote South Pacific region, far
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removed from well-known European and North and Atmospheric Research, is a remarkable long-
American glaciers. But what was hidden at the time term record. Our colleagues Lauren Vargo and
was that New Zealand glaciers were about to Huw Horgan are leading the effort to harness this
undergo significant changes. resource with photogrammetry to deliver precise
(metre-scale) three-dimensional models of glacier
changes since 1978, building directly on Trevor
Chinn's work.
Octogenarian Trevor Chinn still participates in the
snowline flights every year to support younger scientists.
Credit: Dave Allen/NIWA, CC BY-SA
Glaciers respond to natural variability and human-
induced changes, and we suspect the latter has
become more dominant for our region. During the
The Franz Josef glacier advanced during the 1980s and 1980s and 1990s, while glaciers were largely
1990s but is now retreating. Credit: Andrew Lorrey/NIWA, retreating in other parts of the world, many in New
CC BY-SA Zealand were advancing. Our recent research
shows this anomaly was caused by several
concentrated cooler-than-average periods, with
Southern Alps air temperature linked to Tasman
Trevor Chinn took part in this summer's flight and Sea temperatures directly upwind.
said: "This year is the worst we've ever seen. There
was so much melt over the summer that more than The situation changed after the early 2000s, and
half the glaciers have lost all the snow they had we postulated whether more frequent high
gained last winter, plus some from the winter snowlines and acceleration of ice loss would occur.
before, and there's rocks sticking out everywhere. Since 2010, multiple high snowline years have
The melt-back is phenomenal." been observed. In 2011, the iconic Fox Glacier (Te
Moeka o Tuawe) and Franz Josef Glacier (K?
New insights from old observations Roimata o Hine Hukatere) started a dramatic
retreat – losing all of the ground that they regained
The Southern Alps end-of-summer snowline photo in the 1990s and more.
archive, produced by the National Institute of Water
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Looking ahead by examining the past
How New Zealand's glaciers will respond to human-
induced climate change is an important question,
but the answer is complicated. A recent study
suggests human-induced climate warming since
about 1990 has been the largest factor driving
global glacier decline. For New Zealand, which is
significantly influenced by regional variability of the
surrounding oceans and atmosphere, the picture is
less clear.
To assess how human-induced climate influences
and natural variability affect New Zealand glaciers
requires the use of climate models, snowline
observations and other datasets. Our research
team, with support from international colleagues,
are doing just that to see how Southern Alps ice will
respond to a range of future scenarios.
Continuing the snowline photograph work will allow
us to better identify climate change tipping points
and warning signs for our water resources – and
therefore better prepare New Zealand for an
uncertain future.
Provided by The Conversation
APA citation: A bird's eye view of changing glaciers (2018, June 11) retrieved 5 July 2022 from
https://phys.org/news/2018-06-bird-eye-view-glaciers.html
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