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Summary
You can’t make a glacier lie.- Dr Andrew Lorrey; NIWA (Video 1)
- The planet has already warmed more than 1.3°C since pre-industrial times and this has led to a long term trend in glaciers all over the world shrinking, with many disappearing.
- Glaciers grow when more snow accumulates than melts. Conversely, they shrink when more snow melts than accumulates. Sometimes weather patterns like El Niño/La Nina can lead to warmer weather, 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?
- Aoteaora has around 3,000 glaciers, most in the Southern Alps (Fig. 3). NIWA started surveying them glaciers in 1977, and has carried out aerial surveys of over 50 of the South Island’s glaciers every year for more than 40 years.
- The surveys show that by 2023, 29.3% of the total glacial mass had been lost, and all glaciers had retreated and lost volume. Our glaciers are thinning seven times faster now than 20 years ago.
The rate of melt in New Zealand is increasing, faster than glaciers in any other region around the world. – Dr Lauren Vargo, COP26 presentation, 2021
New Zealand’s estimated ice volume in 2020 has reduced to 34.60 km3, which is 65% of the 1978 volume. – NIWA, 2022
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
- The exceptionally large losses since then have been directly attributed to climate change. At the current rate of warming, our glaciers are on track to vanish entirely by 2100.
- The 2019-20 Australian bush fires dumped ash on our glaciers, reducing albedo and exacerbating melting.
- Glacial lakes form when glaciers retreat; the Tasman glacial lake (photo top of page) didn’t exist before 1973.
- Globally, since 1976, Earth’s glaciers have lost 9000 billion tonnes of water, contributing 25mm to global sea-level rise. Over 40% of this loss has happened in the last decade and 6% occurred in 2023 alone. – Earth System Science Data, May 2025
In spite of 2018 being a very weak El Niño year, New Zealand experienced its hottest year on record:
During austral [southern hemisphere] summer 2017/18, the New Zealand region experienced an unprecedented coupled ocean-atmosphere heatwave, covering an area of 4 million km2. Regional average air temperature anomalies over land were +2.2 °C, and sea surface temperature anomalies reached +3.7 °C in the eastern Tasman Sea… The event persisted for the entire austral summer resulting in a 3.8 ± 0.6 km3 loss of glacier ice in the Southern Alps (the largest annual loss in records back to 1962)… The best match suggests this extreme summer may be typical of average New Zealand summer climate for 2081–2100, under the RCP4.5 or RCP6.0 scenario. – Salinger et al 2019
This has profound implications for New Zealand as we depend on glaciers for renewable energy (hydropower) and irrigation.
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. Their results conservatively estimate that man-made climate change made the extreme ice loss seen in 2011 at least six times more likely, and the ice loss seen in 2018 at least 10 times more likely. The mass loss recorded from just Brewster’s glacier in 2018 was up to 350 times more likely by climate change.
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