Mount loses bit off top
Aoraki/Mt Cook has shrunk 30 metres as the summit reshapes after the massive rock-ice collapse in 1991.
Work to measure the height of the mountain was done by an Otago-led climbing expeditionlast November and analysis of high accuracy GPS data obtained during the climb has confirmed the new height.
The readings reinforce new aerial photography-based calculations by Otago National School of Surveying researcher Pascal Sirguey and Masters student Sebastion Vivero, with support from GNS Science and New Zealand Aerial Mapping.
Dr Sirguey says the discrepancy between the old height of 3754m (estimated from aerial photography immediately following a massive rock-ice collapse on December 14, 1991) and the new height of 3724m can be explained by a two-decades long reshaping process affecting the remnant of the originally thick ice cap.
"By carefully studying photos taken after the collapse, it appears that there was still a relatively thick ice cap, which was most likely out of balance with the new shape of the summit ridge," he says.
"As a result, the ice cap has been subject to erosion over the past 20 years.
"While the effects of climate change may spring to mind as an explanation, it is probably a case of a simple change in the geomorphology of the mountain."
The four-person Otago expedition was led by Nicolas Cullen, a senior lecturer in the Department of Geography at Otago. He was accompanied by Jim Anderson of Survey Waitaki and the pair were guided by Geoff Wayatt and Brian Weedon of Mountain Recreation Ltd.
The November 27 expedition was the 27th ascent of the mountain for 68-year-old Mr Wayatt, who first climbed Mt Cook as a 21-year-old.
"It was fascinating to see the team together with all their skills focusing on getting the job done," he said. "I especially admire Nicolas Cullen who said the No 1 priority was to make sure we were all safe. If there was any risk, we would come down."
Mr Wayatt climbed Aoraki/Mt Cook just days before the mountain lost 30 metres in 1991.