Glacier’s astonishing ice loss
A single glacier in the Southern Alps lost roughly enough ice over three years to supply drinking water to all New Zealanders over the same period, Niwa scientists have calculated.
Two marine heatwaves in a row and record-hot air temperatures saw Brewster Glacier in Mt Aspiring National Park lose an estimated 13 million cubic metres of ice from March 2016 to March 2019. The glacier's surveyors calculated the volume was not far off the basic drinking requirements of the country's population.
Niwa's Andrew Lorrey, Ben Noll and Victoria University's Lauren Vargo say the ice lost from Brewster Glacier is only a small part of the Southern Alps ice storage, which has been declining since annual monitoring of the glaciers began in the late 1970s.
Aerial surveys each March have tracked the loss of about 30 per cent of the Southern Alps' ice volume over the past four decades, the equivalent of about 16 trillion litres of water, they said.
This year's survey found the situation looking a little better, with more snow on the South Island glaciers than the previous two years. But Lorrey warned a few ‘‘good snow years'' could not be considered any kind of recovery against an overall trend of increasingly warm temperatures, saying it would take 20-30 years like this to start to reverse the damage. Lorrey said the damage sustained by some small glaciers between 2018 and 2019 had put them on a path to extinction.
Lorrey says the thousands of photos taken of glaciers during each annual survey are growing more important because of climate change and the role the glaciers play in New Zealand's water cycle.
‘‘Our observations of extreme and variable conditions highlight strong impacts on water – which is arguably our most precious natural resource,'' he said.