You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Another hot summer has them worried about what they might find.
Following New Zealand's hottest summer on record last year, the South Island's glaciers looked ''sad and dirty''.
The annual long-term aerial Snowline Survey records the snowline altitude of up to 50 glaciers across the South Island, using specialised cameras from a light aircraft.
Thousands of photos are taken from different angles to build 3-D models of glaciers that can be compared year on year, to give an accurate depiction of how much of the previous winter's snow remains to contribute to long-term glacial ice accumulation.
The information gathered over the past four decades has produced a unique and incredibly valuable data set that provides an independent measure of how climate change and variability are affecting New Zealand's water resources.
Niwa climate scientist and project leader Andrew Lorrey said 2018 was the second-hottest year on record and the survey showed a significant recession of the glaciers.
''Every year is different, but with some sort of elements of a marine heatwave still existing in and around the country this year, it's a bit concerning.''
Dr Lorrey said temperatures, wind directions, and the amount of precipitation and snowfall over the previous months, could all have an effect on the glaciers.
''I'm always concerned about what we'll find.
''Last year we saw some really big impacts, and how much of that balance has regressed by this past winter, or if it has regressed at all, remains to be seen.
''I'm anticipating what we're going to see this year and I'm not terribly hopeful.
''So we're going to get up there, do our survey and find out.''
He said flights could begin as early as March 1, weather permitting.