Scientists are measuring New Zealand's glaciers after record-breaking heat this summer.
Climate scientists and glaciologists are taking to the skies to record the snowline altitude of up to 50 glaciers across the South Island.
NIWA's annual long-term aerial snowline survey marks its 40th anniversary this year and is undertaken every March at the end of summer.
The survey reveals how much of the previous winter's snow remains to contribute to long-term glacial ice accumulation.
NIWA climate scientist Dr Andrew Lorrey says they look at the surface of each glacier and the line of demarcation where there is snow from the previous winter above, and exposed bare ice below - that line can tell you about the amount of snow gained versus the amount lost since the start of the glacier year in April.
Dr Lorrey expects this year's survey to reveal some "pretty pathetic" glaciers, following New Zealand's hottest summer on record.
"At this time of year we can see the effects of the summer melt but following such an extreme summer the layers really start to peel back and you can see how harsh the effect has been on the glaciers."
Meanwhile, the heatwave this year also saw temperatures up to 6degC higher in some parts of the Tasman Sea, which will mean scientists are expecting to see a much higher snow line.
The scientists begin this year's aerial snowline survey on Saturday.