Glaciers in New Zealand's Southern Alps more than half-gone

Since the Industrial Revolution, glaciers across New Zealand's Southern Alps have lost more ice than they have remaining, according to a study published Friday in the journal Scientific Reports.

Glacial volume and extent in the Southern Alps peaked during the Little Ice Age, 400 years ago. Since then, the glaciers have been in decline. According to the new study, the glaciers have lost upwards of 77 percent of their volume over the last four centuries.

The analysis suggests the glaciers have been melting at a more rapid clip over the last century.

For the study, researchers examined historical records of glacier outlines and surveyed glacier-caused geological features, including moraines and trimlines. The observations helped scientists reconstruct historic volume changes for 400 mountain glaciers.

The data suggests ice loss rates have doubled over the last 400 years, with the pronounced ice losses occurring over the last four decades.

"These findings quantify a trend in New Zealand's ice loss," lead study author Jonathan Carrivick said in a news release.

"The acceleration in the rate of ice mass loss may only get worse as not only climate but also other local effects become more pronounced, such as more debris accumulating on glaciers surfaces and lakes at the bottom of glaciers swell, exacerbating melt," said Carrivick, a senior lecturer in geomorphology at the University of Leeds in Britain.

The research demonstrates the significant impact of climate change on glaciers all over the world. Previous studies have documented accelerated ice loss rates across the European Alps, as well as Asia's Himalayas.

The latest findings also have implications for those that live beneath the peaks of the Southern Alps.

"Our results suggest that the Southern Alps has probably already passed the time of 'peak water,' or the tipping point of glacier melt supply," Carrivick said. "Looking forwards, planning must be made for mitigating the decreased runoff to glacier-fed rivers because that affects local water availability, landscape stability and aquatic ecosystems."

The steady retreat of glaciers in the Southern Alps has been documented by photographers for several decades. Now, scientists have numbers to go with the photos. Both the data and imagery present an alarming picture.

"Our findings provide a conservative baseline for rates of Southern Alps ice volume change since pre-industrial times," said study co-author Andrew Lorrey.

"They agree with palaeoclimate reconstructions, early historic evidence and instrumental records that show our ice is shrinking from a warming climate," said Lorrey, principal scientist with the National Institute of Water and Atmospheric Research in New Zealand.

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