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Evidence & Impacts: Our vanishing glaciers

Tasman glacier lake image: Kuno Shweitzwer

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Our vanishing glaciers

Summary

“You can’t make a glacier lie.”- Dr Andrew Lorrey; NIWA (Video 1)

  • The planet has already warmed more around 1.2°C since pre-industrial times (Fig. 1), and this has led to a long term trend in glaciers all over the world shrinking or even 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. 2). 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 2017, 30% 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.

“When I started  in 1977, we had 53 cubic kilometres of ice. Today (2017) we have 30% less… The glacier is the best climate indicator you can use.” – Dr. Trevor Chinn | NIWA (Video 1).

“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

Home > Climate wiki > Evidence > New Zealand’s disappearing glaciers

Summary

“You can’t make a glacier lie.”- Dr Andrew Lorrey; NIWA (Video 1)

  • The planet has already warmed more around 1.2°C since pre-industrial times (Fig. 1), and this has led to a long term trend in glaciers all over the world shrinking or even 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. 2). 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 2017, 30% 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.

“When I started  in 1977, we had 53 cubic kilometres of ice. Today (2017) we have 30% less… The glacier is the best climate indicator you can use.” – Dr. Trevor Chinn | NIWA (Video 1).

“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

Video 1: The 2018 survey was carried out after New Zealand’s hottest summer on record.

Fig. 1: Instructions for this interactive graph (Credit: The Institute.)

  • Mouse over anywhere on the graph to see the changes in global temperatures over the last thousand years.
  • To see details for time periods of your choice, hold your mouse button down on one section then drag the mouse across a few years, and release it.
  • To see how this compares to the past 771,000 years, click on the ‘time’ icon on the top left.
  • Compare this to rising global temperatures by clicking the planet/thermometer icon at the top left corner.
  • To return the graph to its original position, double-click the time icon to the left of the thermometer/planet icon

Temperatures were warmer 120,000 years ago, however the amount of carbon dioxide in the atmosphere today is much higher. There is a lag time between carbon dioxide concentrations and temperature, so higher temperatures are ‘locked in’ over the coming decades.

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.

Fig. 2: The main glaciers in the South Island (Image: Chinn et al.)
Fig: 4: Nine-year close to the glacier terminus. (Image: S. Whitelaw)
Fig: 4: Nine-year close to the glacier terminus. (Image: S. Whitelaw)
Fig: 5: Nineteen-year-old (same person) a decade later. (Image: S. Whitelaw)
Fig: 5: Nineteen-year-old (same person) a decade later. (Image: S. Whitelaw)
Fig. 3: Changes in ocean temperatures around New Zealand 2010 – 2019 (Image: NIWA). Warmer oceans means there’s more water vapour over the water. And warmer air can carry more moisture. This also powers tropical cyclones, so they may reach New Zealand more often, bringing greater risks of destructive winds and flooding.

Marine heatwaves occurred again in 2020 and 2021. 

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