More snow on glaciers but no good news, say scientists
Scientists have recorded more snow on the South Island glaciers this year, but they warn it is simply a temporary break rather than any good news on the climate change front.
NIWA and Victoria University of Wellington scientists completed the annual end-of -summer snowline survey of 50 South Island glaciers yesterday, taking thousands of photographs to evaluate the snowline altitude and build 3D models of the glaciers. These will be used to assess how much of the previous winter’s snow has remained covering each glacier to contribute toward long-term glacial ice accumulation.
The scientists also documented widespread ash coverage on the glaciers as a result of the Australian bushfires.
The snowline survey began in 1977 and provides an incredibly valuable long-term record of how New Zealand’s glaciers have retreated over time due to climate change. Scientists estimate about 30 per cent of New Zealand’s ice that was catalogued in the late 1970s has been lost in the past 40 years.
The past two years of the snowline survey have seen the impact of particularly harsh conditions imposed on our glaciers, with marine heatwaves and record temperatures taking their toll.
NIWA climate scientist Dr Andrew Lorrey says while the glaciers looked a lot better this year than the past two years, it could not be considered any kind of recovery.
“You would need to see 20 to 30 years like this one to even start to consider whether the recent damage that has been done can be reversed to any degree. Glaciers can take a very long time to grow. I am not at all heartened by what looks like a decent snowline this year – it is part of climate variability, and some good years are to be expected."
“Every now and then you will get a year that reminds you of how things used to be, but the overall trend is towards more frequent hotter years, which are hugely detrimental to glaciers.”
Yesterday ash from the Australian bushfires was still highly visible across most of the glaciers since it first settled there in early January.
Dr Lorrey says the ash has coloured many glaciers light orange and may have contributed to the annual melt process.
"At this stage it is difficult to characterise exactly how much the ash has added to the ablation of snow and ice, but there should be some immediate negative effect.”
Victoria University of Wellington’s Dr Lauren Vargo will use the photographs from the survey to construct 3D models of the glaciers in a process called structure from motion photogrammetry.The methods being pioneered by Dr Vargo will assist year-on-year comparisons and allow accurate calculations of how recent seasonal snow and older ice are changing. “What we are seeing is a clear trend now - retreating glaciers and a steady loss of ice.”
The scientific results from this year’s survey will be known later this year.