The National Institute of Water and Atmospheric Research (NIWA) says the 13 million cubic metres of ice lost from just one of New Zealand's glaciers over the past three years is roughly equal to the amount of water the New Zealand population drank over that time.
New research from Dr Lauren Vargo, a researcher based at Victoria University Wellington, used photogrammetry to map out changes to the Brewster Glacier in Mount Aspiring National Park between 2016 and 2019.
Ms Vargo said the volume of water lost from Bewster Glacier is only a small part of the total ice lost from Southern Alps glaciers over the past four decades.
While more snow had been recorded on the South Island glaciers this year, compared with the previous two years, NIWA climate scientist Dr Andrew Lorrey warned that could not be considered to be any kind of recovery.
Mr Lorrey noted that the past two years had produced "particularly harsh conditions" for the glaciers, with marine heatwaves and record high temperatures taking their toll and pushing snowlines upwards.
He said that damage sustained by some of the smaller glaciers in 2018 and 2019 had already put them "on a path to extinction".
Ash from the Australian bushfires was also a contributing factor, as a layer had been deposited on the glaciers within the past year, which has led them to retain more energy from the sun, rather than reflecting it, and sped up the melting.