Glaciers continue to shrink this year: New Zealand scientists

The annual end-of-summer snowline survey of more than 50 New Zealand South Island glaciers has revealed continued loss of snow and ice.

Last week, scientists from the National Institute of Water and Atmospheric Research (NIWA), Victoria University of Wellington, and Department of Conservation took thousands of aerial photographs of glaciers. Some of them are used to build 3D models that track ice volume changes.

Each year, the NIWA monitoring program evaluates many glaciers and the altitude of the snowline to see how much of the previous winter's snow has remained covering each glacier. The long-term aerial survey provides a valuable evidence timeline, stretching back to 1977, and visually shows how much glaciers have retreated.

Since the snowline survey began, the global climate has warmed by around 1.1 degrees Celsius, said NIWA Principal Scientist Andrew Lorrey who leads the project, adding many of New Zealand's glaciers are suffering due to exceedingly warm summer temperatures, exacerbated by a marine heatwave.

Glacier snowline altitudes, also known as equilibrium line altitudes (ELAs), help scientists directly evaluate annual glacier health. If a glacier has decreased in size, the ELA is higher because less winter snow remains. If the glacier increases, the ELA is lower because more winter snow has remained, Lorrey said.

Lauren Vargo from Victoria University of Wellington said the retreat is due to the majority of New Zealand's glaciers losing mass most years over the past decade.

NIWA's work estimates that more than a third of the ice volume has been lost from the Southern Alps since the survey began.

The receding glaciers will have far reaching impacts, such as altering the beautiful landscape, affecting the livelihoods of people who rely on these natural wonders for tourism, and flow on effects from decreased meltwater during periods of drought, Lorrey said, adding it also emphasizes the urgency of slowing climate change because the impacts are going to become increasingly costly and hard to avoid.