Glaciers a third smaller over past four decades

AUCKLAND: New Zealand’s glaciers have shrunk in area by onethird since over the past four decades — an astonishing loss scientists have partly attributed to climate change.

The new figures, just presented to an international conference, come as a glaciologist has warned an abnormally hot summer could mean trouble for the South Island’s ice giants.

Dr Sabine Baumann, of the Technical University of Munich, recently completed the first complete stocktake of New Zealand’s glacier cover since Dr Trevor Chinn made an aerial survey in 1978.

The work drew on remote sensing technology, along with field work that helped distinguish the glaciers’ physical area size, which could be camouflaged to satellite imag ing by heavy debris cover.

Her results, reported to the American Geophysical Union, revealed how the total glacier area had shrunk from 1240sq km to 857sq km — a decrease of 31% since the late 1970s, or just under 1% of loss each year.

The number of glaciers also fell slightly from 3283 to 3180, while mean altitude climbed from 1859m to 1939m above sea level.

Those figures followed a 2014 analysis by Dr Chinn and other scientists which showed ice volume in the Southern Alps had shrunk by 18.4cu km or 34% since the 1970s, and ice losses had been accelerating rapidly since the turn of the new century.

Victoria University glaciologist Dr Brian Anderson said glaciers responded to climate over a variety of time scales — anywhere between a few years and centuries.

‘‘So most of the glaciers are still retreating because of warming during the 20th century, and particularly since 2007,’’ he said.

‘‘But some of our most responsive glaciers are actually advancing, likely a response to slightly positive mass balances measured from 2013 to 2015.’’

Franz Josef Glacier, after retreating 1.43km between 2008 and December 2016, had advanced around 50m.

However, a La Ninaflavoured summer bringing consistently hot weather and warm sea surface temperatures in the Tasman Sea could have significant impacts.

‘‘If the projections are correct, and we are in for a long, hot La Nina summer, then it will certainly be a year where the glaciers lose a lot of mass.’’ — NZME