Wednesday, 21 March, 2018 - 09:16

University of Canterbury researchers monitoring glacier mass have confirmed that this summer’s extreme heat has been catastrophic for New Zealand’s alpine glaciers.

A team from the University of Canterbury, led by glaciologist and Geography senior lecturer Dr Heather Purdie, hiked into the Rolleston Glacier in Arthurs Pass National Park for their annual end-of-summer glacier survey.

The UC researchers found that as a consequence of this summer’s extreme heat, the Rolleston Glacier has lost nearly all of the snow that accumulated on the glacier during the previous year.

"This is likely the most negative mass balance year ever recorded on this glacier," Dr Purdie says.

"Glaciers are great indicators of climate change. This summer was very warm and as a consequence New Zealand alpine glaciers are in very bad shape - they have lost a huge amount of snow and ice to melting over the summer."

Dr Purdie and adjunct geography academic Dr Tim Kerr, with the help of volunteers, have regularly measured the Rolleston Glacier since 2010. Each year they hike into the glacier at the end of winter and again at the end of summer to dig snow-pits, measure snow depth, and install stakes that measure how much snow and ice melts off the glacier during the summer.

This year the survey revealed that nearly all of the previous season’s snow had melted off the glacier. The team also recovered monitoring stakes that had been buried in the glacier back in 2014.

"This was significant as it indicates that during this summer not only has the glacier lost all of last winter’s snow, but also snow that had accumulated on the glacier in previous years," Dr Purdie says.

"The only snow left on the Rolleston Glacier was snow that had avalanched down onto the glacier from the surrounding mountain peaks. Without this avalanche input, the glacier would have had no snow left at all."

Although New Zealand has over 3000 glaciers, only two glaciers have ongoing monitoring programmes where the mass balance, or health of the glacier, is directly measured. Data from this monitoring programme contributes to the World Glacier Monitoring Database - a global data base of glacier mass balance.

Climate change and glacier retreat

Glaciers are important fresh water stores. They are also provide a direct measure of climate change, growing and shrinking in response to cooling and warming. The importance of avalanche processes to the overall health of the glacier is something that Dr Purdie continues to research.

Glaciers react quickly to changes in climate by adjusting the volume of fresh water they store as snow and ice. Globally, glaciers are retreating and research has shown that New Zealand glaciers are particularly sensitive to temperature.