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You can’t make a glacier lie.- Dr Andrew Lorrey; NIWA (Video 1)
Glaciers grow when more snow accumulates than melts. Conversely, they shrink when more snow melts than accumulates. Since 1976 Earth’s glaciers have lost 9000 billion tonnes of water, contributing ~26mm to global sea-level rise. Over 40% of this loss happened between 2015-2024, with 6% lost in 2023 alone.
Aoteaora has around 3,000 glaciers, most in the Southern Alps. NIWA began surveying them in 1977, and has carried out aerial surveys of over 50 of the South Island’s glaciers every year since.
Sometimes weather patterns like El Niño/La Nina can lead to temporarily warmer weather, which is what happened in 2018. And there’s usually a lag time between the loss and the glacier retreating. So how do we know if the decline of New Zealand’s glaciers isn’t just a temporary or localised change?
The 2018 end-of-summer glacier survey (Video 1) was carried out after New Zealand’s hottest summer on record to date. A team from Antarctic Research Centre, Victoria University of Wellington and Monash University in Australia factored in known natural climate forcings and compared them to human climate forcings. The results conservatively estimated that man-made climate change made the extreme ice loss in 2011 at least six times more likely, and overall ice loss in 2018 at least 10 times more likely. The mass loss recorded from just Brewster’s glacier alone in 2018 was up to 350 times more likely by climate change.
The rate of melt in New Zealand is increasing, faster than glaciers in any other region around the world. – Dr Lauren Vargo video presentation 2021 at COP26
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In 2005 my son (pictured throughout) was 9 years old. – Sonny Whitelaw
In 2019-20 an extreme drought in Australia led to extreme bushfires and scouring winds over the desert. Westerly winds send plumes of smoke and desert dust across the Tasman. Dust reduces the glaciers’ albedo (Figs. 2 & 3) so that they absorb more heat, increasing the rate of melting.
Contrary to media reports, the glacier discoloration was caused by a desert dust storm and specific meteorological conditions that transported approximately 4,500 ± 500 tons of southeastern Australian dust across the Tasman Sea to permanent snow and ice of the Southern Alps….Personal observations, time lapse camera and satellite imagery confirm that the bulk of the impurities were deposited around 29 November 2019 and persisted for 2 weeks when they were buried by fresh snowfall. Patches of impurities reemerged after fresh snow disappeared and were still visible at the end of February 2020 and again in February 2023 with long lasting and multi-year impacts on albedo. …Glacier mass has declined over the past few decades in New Zealand and climate conditions conducive to large Australian bushfires and dust storm events are predicted to strengthen with compounding consequences on New Zealand glacial environments. – Winton et al 2024
Fig. 2: Franz Josef glacier cirque 2019 | Twitter/ @Rachelhatesit
New Zealand’s estimated ice volume in 2020 has reduced to 34.60 km3, which is 65% of the 1978 volume. – NIWA 2022
The end-of-summer 2023 (Video 2) survey was hotter than 2018 with all glaciers retreating and losing volume. The glaciers were thinning seven times faster than 20 years earlier, with some ‘approaching an extinction horizon’.
If you were on the surface of the [Brewster] glacier eight years ago in 2016, you were a 10-storey building higher than if you were on the surface of the glacier today. – Dr Lauren Vargo 2024
At the current rate of warming, our glaciers are on track to vanish entirely by 2100. The current and future potential impacts and effects include:
- Reduced capacity/ reliability of hydropower generation
- Increased risks of glacial outburst floods. For example see the 2003 Franz Josef outburst flood.
- Increased risk of avalanches as permafrost melts and the winter freeze/summer thaw cycle fractures the predominantly greywacke rock
- Increased risk of floods as precipitation patterns change from less snow to more rain
- Cascading compounding feedback effects of the above. For example:
A West Coast glacier town [Franz Josef] faces a version of the cascading hazard behind this week’s catastrophic floods on the Nepal-Tibet border — a river capable of damming high in the mountains, then unleashing a torrent without warning. – One News 2026
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