A bird's eye view of changing glaciers - Phys.org

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A bird's eye view of changing glaciers - Phys.org
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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A bird's eye view of changing glaciers - Phys.org
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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A bird's eye view of changing glaciers - Phys.org
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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